In this paper, by using the Ebppler effect between atom beam and laser beam in optically pumped cesium beam frequency standard to select and apply slow atoms in thermal atomic beam, the Ramsey line-width has been narrowed. In order to maximize the tube merit factor, the selected atom velocity should be 153 m/s by theoretical calculation, when the oven temperature of atom beam is 100 ℃.
Using SDCH, a one-dimensional Lagrangian magneto hydrodynamics code, the simulation results of discharge-pumped 2p53p→2p53s transition 46. 9 nm laser line in Ne-like Ar are preseted. Energy structures and atomic process parameters are calculated, and the possibility of population inversion in the plasma produced by capillary discharge is discussed systematically.
Based on an approximative Fokker-Planck equation for a system driven by a multiplicative colored noise and an additive colored noise that are cross-correlated, the stationary probability distribution (SPD) of the single-mcxle laser cubic model with correlated pump colored noise and quantum colored noise is derived. Morever, the influence of cross-correlation, correlation-time and net gain on the SPD, and the influence of multiplicative noise on the normalized variance with the different correlation-time are also studied.
The cavity field spectra of a Λ-type three-level atom interacting with a two mode quantum cavity under the largepdetuning condition are investigated. The results for the initial field in two-mode Squeezing vacuum field are obtained. The influence of AC-Stark shift on the spectra is discussed.
An optically thin gaseous mixture of Κ and low-density He is excited by 570 nm~600 nm of the cw dye laser. The excited K-He molecule is dissociated into the K(4P1/2) or K(4P3/2). The branching ratio is defined as I(D1)/I(D2) where I(D1) and I(D2) are measured intensities of the atomic Κ D1 and D2 lines respectively. The branching ratio is determined in the He density range of (2~8)×10^{23} m^{-3}. The ratio of dissociation rates and the fine structure changing cross section are obtained. The ratio of the dissociation rates approaches 0. 6 as a limit which is independent of the laser frequency.
Bloch's theorem is the foundation of plane wave method and transfer matrix method in the theory of photonic crystals. In this chapter, the theory about operator in quantum mechanics is generalized to vector field and Bloch's theorem with vector is given. This is the direct conclusion of the spatial translational symmetry of dielectric materials.
The distribution of the small signal gain of the combustion-driven gas-dynamic CO2 lawer along the gas active medium flow direction is calculated numerically when the temperature, pressure and compositions fraction ratio of the combustion cabin are different. The calculation results show that the small signal gain distribution of the combustion-driven gas-dynamic CO2 laser changes slowly, and the higher temperature and pressure and lower fraction ratio of the H2O can produce the high gain.
The Nuclear Reactor Pumped Lasing Model (NRPLM) He-Ar-Xe was proposed and the power efficiency function was derived in the present work. Tlie power efficiency was built as a function of gas temperature (energy deposition), cell pressure, xenon concentration, He and Ar fractions. The influence of energy deposition on efficiency were also explored. And the laser output was also extimated. The present work will benefit the future experimental design.
In this paper, a new idea is proposed, using two driven laser beams combined one beam in prime frequency with another beam in double frequency to shot on target obliquely. According to theoretical calculation, not only energy loss due to the double frequency can be avoid but also a higher gain coefficient can be achieved, comparing to use two driven laser beams in double frequency with same power in the prime frequency. A design of long distance four targets series coupling is also presented, the X-ray laser produced by former two targets is collected by a pair of junction mirrors with grazing incidence, then amplified by latter two targets. The theoretical research predicts that, taking advantage of this method, saturated gain of X-ray laser at spectral "water window" can be got by Shen-Guang II facility.
Using the phase operator, the expression of the phase of Bose-Einstein condensate is obtained, which associates with time, initial phase, non-interaction energy and the atom number. Further, the interference condition of two condensates is given after calculating the relative phase of two condensates with interaction. Finally, it is found that the phase of condensate is mainly determined by the potential well for a finite atom number with the TF approximation, which is similar to the cavity of optical laser.
A one-dimensional array of three spatially coupled solid state lasers is investigated. It is shown that the periodic synchronization, chaotic synchronization and loss of synchronization in laser intensities occur when the coupling between lasers is changed. Meanwhile, the laser light is changed from partially coherent, perfect coherent, to partially coherent again and finally incoherent. The phase differences between lasers show generalized synchronization and loss of synchrOriization as the coupling is changed.
The effect of quantum colored noise on single-mode laser gain model is studied. The analytical expressions of the time-dependent moments, the correlation function and power spectrum of the laser intensity are derived by means of linear approximation method. It is shown that the statistical properties of the laser intensity are mainly decided by quantum colored noise when the laser is operating near the threshold. The conclution is that the initial plateau of the intensity correlation function observed by experiment is due to the “color” of the noises and predict that the intensity variance will also exhibit initial plateau.
The load resistance can impact the propagation of a Gaussian beam in a biased photovotaic-photorefractive crystal. The results show that, changing the load resistance can change the bias field intensity, and make a Gaussian beam evolve into a stable bright soli ton when propagating in a biased photovotaic-photorefractive crystal.
The transfer matrix of an optical resonator is obtained based on Frensnel-Kirchhoff diffracted integral equation by dividing the mirror into finite grids. The eigenvalue calculation and iteration of the transfer matrix will lead to the mode and far-field beam characterization of the resonator. An example is illustrated: confocal unstable resonator.
The self-starting dynamics of the Kerr-leiis mode-locking (KLM) in a Ti. sapphire laser using an intracavity broadband semiconductor saturable absorber mirror (SESAM) was investigated experimentally. The mechanism of the self-starting KLM using a SESAM was investigated and discussed.
The paper presents an advanced technique, SHG-FROG (second harmonic generation frequency-resolved optical gating) to measure an ultrashort laser pulse. The computer is programed lo retrieve the amplitude and phase of the pulse. The retrieved results got by the program and the development of the traditional algorithm and experience and rule to use the algorithm practically are given. Not only was the FROG method tested to be easily built up but also the algorithm is handy and quick.
Base on the "thick-lens" model, the KLM Ti:sapphire laser operation point is selected near the upper edge of the HMS stable region, so that the effects of intracavity gain saturation and frequency dependent mode size are reduced. As a result, the pulse bandwidth broadening is enhanced significantly. Pulses with bandwidth of 144 nm have been generated from this laser. As short as 8. 5 fs pulses are obtained at wavelength centered at 710 nm.
This paper analyzes the mechanism of Cr4+:YAG passive mode-locking as a saturable absorber of 1064 nm laser. A suitable folding-cavity was adopted to achieve the mode-locking and the intracavity frequency doubling of a Nd:YAG/KTP/Cr4+:YAG laser pumped by a flash-lamp. The picosecond green pulse train with output energy of 12 mJ was obtained.
In this paper, flashlamp-pumped Cr:LiSAF laser systems with a prism splitter to obtain tunable dual pulse and dual wavelength fundamental laser output and with bean) adjustable structure and BBO crystals to obtain tunable dual pulse and dual wavelength harmonic laser output have been designed. The relation of laser output behaviors with input energy is studied experimentally.
The non-linear optical properties of InP/SiO2 nanogranular films fabricated by radio frequency magnetron co-sputtering technique have been investigated by z-scan technique using a single Gaussian beam of pulse dye laser. Results of the investigations show that the magnitude of the nonlinear refractive index y for the film annealed at 310 ℃ at wavelength of 585 nm (non-resonant) is the order of 10^{-11} m2/W, which is 5 orders of magnitude as large as those of bulk InP. The optical nonlinearity of the films is quite sensitive to the annealing temperature. The enhancement of optical nonlinearity of the films results from strong quantum confinement of the photo induced carriers and the enhancement of the oscillator strength of the localized states.
Frequency doubling is experimentally fulfilled in tunable mini-TEA CQ laser with home made AgGaSe: crystal, with the dimension of 7 mm×8 mm×12 mm. 21 doubled lines generated from CO2 spectrum region 10.6 μm~9.6 μm were obtained at the same time. The maximum output was found to be 1.32 mJ [ 10P(16)]. And, in 10P(18) line, the maximum energy conversion was efficiency 4%.
Type I/Type II angle-detuning tripling frequency scheme of KDP crystal was chose for triple harmonic conversion with large aperture and high power. Based on three-wave mixing nonlinear coupling equation, wrote a two. dimension program for numerical simulation triple harmonic conversion by introducing discrete Fourier transform and a fourth-order Runge-Kutta integrating method. With the code, conversion features and efficiencies of second and third harmonics were calculated with different thickness of crystal and different angle-detuning. The tripling frequency system is also optimized assuming the intensity distribution of 1ω is super Gaussian distribution with sixth-order. The results showed that the system has both broad dynamic range and more high conversion efficiency.
Deposition of Langmuir-BIodgett, spectra and second order nonlinear optical properties of Asymmetric Substituted naphthalocyanine derivatives were investigated by using linear absorption and second harmonic generation (SHG) technique. The results showed that the substituent had a significant influence on the second order nonlinear optical properties of naphthalocyanine derivatives. The second order nonlinear optical susceptibility χ(2) of tri-tert-butyl-cyan naphthalocyanine was about 3.7×10^{-8} esu, which was 37 times more than that of tri-tert-butyl naphthalocyanine.
According to Fast-Fourier-Transformation method, the amplitude regions for each order soliton are numerically investigated in nonlinearity-saturation LSSM optical fibers different from Kerr fibers. Interaction properties of the first order solitons are analysized.
This paper reports the experimental study on the pulse duration stability of stimulated Brillouin scattering in methanol pumped with XeCl eximer laser. While the pulse compression ratio is 1.95, the pulse duration stability of stimulated Brillouin scattering with 8.26% is obtained, which is close to the pulse duration stability of the pump beam.
A physical model that describes the gain performance of high power solid state laser amplifier has been presented. The model is time-and spectrum-related and consists in four key factors that describes the energy conversion of amplifier, i.e., (1) pump source, (2) cavity transfer, (3) gain medium, and (4) gain performance and energy storage efficiency. With this model, the parameters of pumping sources and gain medium for 4×2×3 amplifier have investigated in detail. The calculation results indicate that the small signal gain coefficient and energy storage efficiency are about 5.0% cm-1 and 3.0%, respectively, which meet design performance requirement.
A LD pumped intracavity frequency tripled all-solid-state Nd:YAG laser is reported in this paper. The CW laser output power of 3 mW at 355 nm is obtained with 8 W LD pumping power. Under the condition of AO Q-switch operation, the average output power at 355 nm is about >50 mW.
Considering the thermal effect of KTP crystal in high power LD pumped frequency doubled YAG laser, the optimum phase matching angle of θ=90°,φ=23.27+0.7° was given. 40 watts green laser output from the acoustic-optic Q-switched intra-cavity frequency doubled laser was abtained.
A intracavity frequency-doubled diode side. pumped Q-switched Nd:YAG laser was developed. Green power of 40 W was generated at 13 kHz repetition rate. The electrical-tooptical conversion efficiency is 3%.
Using laser diode (LD) as pumping source, CW Yb:YAG laser output was obtained at room temperature. The pumping threshold of Yb:YAG is as low as 2.2 W, the maximum output power of 5.2 W was attained with the pumping power of 18 W, and slope efficiency is as high as 33%. At the same time there is no saturation in laser experiments, so the high power output of Yb. YAG laser can be obtained with high power diode laser pumping source. This research will be beneficial to the development of high power Yb:YAG lasers.
The temperature characteristics of LD pumped Nd:YAG laser slab are investigated through experiment. The temperature distribution photograph of YAG slab are taken by an IR camera under different LD pump current. A primary qualitative analysis is given to explain experimental results. It demonstrates that using an IR camera is a liable method to reflect the actual cooling effect.
Ail efficient red light generation in a periodically poled LiTaQ (PPLT) by extracavity single-pass frequency doubling of a diode-pumped Nd:YVO4 laser at 1342 nm is reported. The sample used in the experiment is 20 mm in length and 14. 77 μm in period. The maximum output power of the 671 nm red laser is 840 mW, when the pump power of 808 nm is 12.3 W. The overall optical-to-optical efficiency is 6.8%. An internal conversion efficiency of 63% is obtained when fundamental power of 1342 nm is 647 mW. The measured effective nonlinear coefficient under the CW mode of the sample is ~4.6 pm/V.
The relationship between gain profile and pump cavity structure was studied for LD side-pumped Nd:YAG laser, the conversion efficiency and beam quality were improved by use of an advanced cavity configuration. A maximum green power of 68W was generated at 10-kHz repetition rate when the two Nd:YAG rods were pumped by total 600 W power of laser diodes, leading to 11.3% optical-tooptical conversion efficiency and 5% electrical-to-optical conversion efficiency.
In this paper a kind of laser-diode pumped and frequency doubled Nd:YAG/LBO blue laser is reported. It utilizes a folded Semi-monolithic cavity and archives high output operation. The blue light output reaches 42 mW and its conversion efficiency is 4.2 %.
A CW Nd:YAG intracavity frequency-doubled red laser is reported in this paper. With a flat-flat laser cavity, 2 Kr-lamps pumping, KTP crystal and AO Q-switch, 2 W output power at 660 nm laser is obtained. The relationship between laser cavity length and output power is analyzed.
A new method of optical pre-pumping was proposed for active Q-switched lasers. With the optical pre-pumping the stability of Q-switched lasers would be improved effectively by squeezing intermediate frequency noise. Experiments showed that the stability of Q-switched output pulses would be increased by 4% in the system of LD pumped acoustic-optical Q-switched Nd:YAG. At the repetition of 50 Hz, 45 μJ output energy with single fundamental mode and ±0.8% instability were achieved.
This paper has designed a high effecient uniformly pumping and cooling reflector; Using dual YAG rods having consistent optical properties into which a 90° rotator is inserted, and special output mirror having a variable reflectivity coating forming an unstable resonator with a total reflection mirror, the output beam from resonator with near diffraction limit under high pulse energy is got; the amplifier also uses dual YAG rods into which a 90° rotator is inserted for decreasing thermal depolarization, by amplifying, optical isolating, beam expanding and phase matching, a high repetition frequency, high beam quality and high peek power is achieved. The following are details: 1) pulse peek power: λ1=1064 nm,P1=388 MW/p, λ2=532 nm, P2=158 MW/p; 2) pulse width: τ1=8 ns(λ1=1064 nm), τ2=6.8 ns(λ2=532nm); 3) beam quality: M2=1.62; 4) pulse repetition frequency: τ=61 Hz;5) continuous work time: t=20 min.
In this paper, high average power Nd:YAG laser have been investigated experimentally. The components (LD, Q-switch etc.) are all made in our country. With AO Q-switch, the output average powers of as much as 130 W, optical-to-optical conversion efficiency 26% and M2 parameter of 10 were obtained. The power change less than 3% after the laser running 8 hours.
In this paper, Nd:YAG laser side-pumptxl by diode-arrays is introduced, which applies multi-path folded scheme and solve the contradiction between high output power and good beam quality. Output power is 10. 3 W, with optoto-opto efficiency 20.6% and M2<1.5.
High power quasi-CW diode-pumped high repetition rate E-O Q-switched three wavelengths Nd:YAG laser is experimentally studied. The lasers with the pulse output of 8.5 mJ and the narrowest pulse duration of 20 ns for 1064 nm, 2.9 mJ for 532 nm using KTP double frequency crystal, 1.5 mJ for 355 nm using BBO triple frequency crystal at pulse repetition rate of 100 Hz are obtained. The highest repetition rate is 500 Hz.
A compact, no water cooled Er-doped YAG laser with the central wavelength of 2.94 μm was developed and fabricated. The output characteristics were studied.
The output of flashlamp-pumped Nd:YAG single-pass laser amplifiers has been studied in theory and experiment. Design criteria are outlined. The results obtained with an oscillator/amplifier Nd:YAG laser system are presented.
The thermal effect of diode laser pumped solid-state slab laser is studied at the high repetition rates. Gaussian beam side-pumped modules is setup in the numerical calculation. The experimental data are consistent with the numerical calculation results.
This paper discusses the design the crystal structure, pump cavity, and laser resonator of high average power solid-state slab geometry laser. A laser with a output power of 1028 W at 100 Hz, and with a beam quality of M2x=—2.386 and M2y=2.528 has been developed. The instability of output power is less than 2.1% with in 0.5 h, and a pulse width is 0.238 ms.
Cr4+:YAG crystal was used as a saturable absorber in an active-passive mode-locked Nd:YAG laser. The stable and complete mode-locked pulse train was achieved at 1064 nm. The duration of a single pulse from ~0.8 ns to 2.4 ns was obtained by using Cr4+:YAG crystals with the different initial transmissions, and there was a shortest pulse width. The mode-locking dynamic process of Cr4+: YAG crystal was discussed to explain the experimental result, and the effect of excited-state absorption was considered.
Generations of efficient blue light at 447 nm and red light at 671 nm were achieved by frequency doubling and tripling of a diode-pumped, Q-switched 1342 nm Nd:YVO4 laser with a periodically-poled LiTaO3 (PPLT). The first-order and third-order vector reciprocals of the PPLT compensated the phase mismatches of second-harmonic and sum-frequency processes, respectively. The resulting averaged blue light power of 51 mW and red light power of 207 mW under the averaged fundamental power of 500 mW indicate that the PPLT may be used to construct an all-solid-state blue and red dual wavelength laser.
A new LD pumped non-planar unidirectional ring resonator is presented in this paper. A corner cube prism and a porro prism form the resonator. More than 1 watt of single frequency output power was obtained from the resonator when the pumping power is 4.5 watts. Optical-optical efficiency is about 23%.
High power laser diode arrays pumped Nd:YLF laser amplifier system with abaxial double-pass was studied. A single laser head gain is 2.66, another laser head gain is 3.01. The system wastage is 34.7%, with the injected energy of 137.4 μJ, the output energy is 100 mJ and net gain is 1115.
By using a new mutually pumped phase-conjugation setup consisting of two photorefractive crystals, a broad-area three-stripe diode laser is locked to a single-mode diode laser at a drive current up to 2.25 times the threshold current. The bandwidth is narrowed from about 2 nm to 0.034 nm, with an available output power of 1.5 W.
In this paper, the current modulation characteristics of a high power GaAs/GaAlAs quantum well laser in low frequencies (100 Hz~20 kHz) were experimentally investigated. The laser characteristics, such as the laser power, the open delay time, the threshold current, the positive duty cycle, in dependent on the modulation frequency and the modulation current were measured.
The experimental results of a Nd:YAG laser side-pumped by two laser diodes are reported. The "light-to-light" conversion efficiency is about 30%. A pulse energy of 30 mJ at the wavelength of 1064 nm under a pump pulse energy of 96 mJ is obtained. The maximum pulse repetition rate is 1000 Hz.
The convention theory of the diverging angle of the semiconductor laser and the coupling of the laser and multimode fiber is introduced. By using a fiber micro lens, the coupling efficiency is increased up to 80%.
The threshold current density, temperature dependence and gain spectra of InGaAs/AlGaAs single quantum well (SQW) laser grown by MOCVD were studied. A low threshold current density of 200 A/cm2 for a 2000 μm long stripe laser was achieved. The laser showed good thermal stability with a characteristic temperature T0 of 179 K. In low temperature region of 160~220 Κ the threshold current density of InGaAs/AlGaAs SQW laser decreased with temperature, indicating a negative characteristic temperature.
As a new type of semiconductor lasers, VCSELs have had great influence upon many fields, such as computation, network, sensing, and so on. This papers made some discussions about the performance of VCSELs, applied in optical communication, under high-frequency modulation. A practicable model of its equivalent circuit was brought forward. The authors simulated VCSELs modulating characteristic with PSPICE, the general circuit simulator, and got its characteristic curves at high bit rate by experiment. Those are helpful for optimizing the performance of VCSEL-based data communication networking.
A intelligence control model of HF-excited Laser has been put forward in this paper. The method and theory of building this model is discussed in brief.
An electrically excited CQz laser with gasdynamic cooling has been developed. The structure, technical features and experimental results of the laser are reported. When the total injecting power is 2.7 kW, the power output is 195 W and the electro-optic conversicai efficiency is higher than 12%.
In this paper an experimental study of automatic tuning system of miniature TEA CO2 laser is presented. By oontrolling of monolithic microprooessca. and programming the laser system is realized to rapid tuning. By monitoring infrared photodectric transducers, system can fix initial pusition of gration accurately. Sin^e-hranch emissicn at two different wavdoigths with time interval ≤10 ms has been obtained. Reappearance of laser wavelength is within 0.1 nm~0.5 nm.
A Series of new development in pulsed discharge metal vapor laser are introduced, which are stimulated by two different mechanism, self-terminating transition and plasma recombination transition individually. A sort of metal vapor laser with new pattern has been discovered. On the basis of self-terminating transition laser, a new classification of pulsed discharge metal vapor lasers was suggested.
The electro-optics pulse waveforms and dynamic plasma resistances are measured and ccmpared with and without hydrogai additive. It is found that the peak of the discharge voltage increased about 34% and the amplitude of pulse current reduced approximately 23%, meanwhile the dynamic plasma resistance increased about 2 times with 2% hydrogen additive in Ne buffer gas. The reason for this phenomena and mechanism with hydrogen additive are discussed and presented.
Program and method for simulating the three-dimensional flowfields of HYLTE nozzle and cavity, which governed by the compressible full Navier-Stokes equations with Realizable k-e turbulent model, has been upbuilt by using an coupled implicit FVM method based on efficient grid for complicated gecmetry. The HYLTE nozzle and cavity have been simulated as a integrative for considering non-uniform flowfield parameters of secondary nozzle exit. Cold flowfield parameters and mixing mechanism of reactant streams have been studied detailedly. Results show that mixing process is accelerated by two ways: reacting surface strentching and streamwise vortices. Furthermore,the cold result can be as the initial value of the reacting flowfields. The program can be modified to simulated overtone HF chemical lases and other kind of chemical lasers for studying the SSG coefficient and output power & chemical efficiency of FP reasonator.
A six-beam multiplexing master-oscillator-power-amplifier (ΜΟΡΑ) high power KrF excimer laser system has been built, the energy on the target has reached 120 J, and the focal intensity on the target can be up to 1013 W/cm2. The researches for ion flight time measurement, plasmas temperature measurement and other plasma physics study are being carried out. A Ti:sapphire/KrF hybrid UV ultrashort pulse laser has been also built, it can produce 50 mJ/220 fs/ 248 nm laser pulse, the intensity on the target exceeds 1017 W/cm2. The hot electron spectrum from the solid target has been studied.
A theoretical model of capacitively coupled radio frequency discharge for ion lasers is developed by using a two-electron group method. The relationship between discharge current and applied voltage is obtained and the role of various ionization mechanisms on the transition of operating mode is investigated. The study has shown that the high current mode of a RF discharge with narrow gap of electrodes is much like the case of a hollow cathode discharge.
An experimental study has been performed on a double-sided transversely pumped dye laser amplifier. The output power of the amplifier has arrived 34 watts, and the amplifier extraction efficiency up to 37% has been obtained. Furthermore, the analytic expressions of the efficiency and output power related to the dye solution concentration, laser wavelength and input dye laser power have been given.
In ion-ripple wiggler, with changing the direction of the injected electron beam, the longitudinal component of the ion-ripple electric field equals to zero, thereby, the harmful influence of longitudinal electric field of an ion-ripple wiggler can be eliminated. Under the condition of small amplitude, the operating equations of the wiggler are given, and then, the trajectories of the beam electrons, the angular spectrum of spontaneous emission and small signal gain are derived.
A cladding pumped Yb3+-doped fiber laser operating in a hybrid Q-switched regime with a tunable repetition rate is described. By exploiting fiber nonlinearity-stimulated Brillouin scattering (SBS) process in the laser cavity, the pulses with duration of 4. 8 ns and the peak power of 8. 3 kW have been achieved. The repetition rate was stable and adjustable by the pump source.
Dependence between the output properties and device parameters of FRSLs (fiber ring semiconductor lasers), including on splitting ratio and coupling coefficient, was investigated using the rate equations. An analytical expression for position-dependent photon flux in FRSLs is deduced. The experimental results are compared with theoretical simulations, in order to select and configure an appropriate splitting ratio. The analysis confirms that there is an optimum splitting ratio to trade off between the threshold current and output power. As the results well show, the excellent agreoiient between simulation and experiment was obtained.
A new structure of the annular waveguide COs laser is presented in this paper. A positive lens is used as the output mirror of the resonator. The plane-parallel resonator is formed by a ail-reflected plane mirror and the bottom planar surface of the positive tapered lens. The delivering light spots are variable between the annular profile and the solid profile as the negative tapered lens.
The design and performances of a multi-wavelength simultaneous output laser system are presented in this paper. The laser system has been used in the L625 lidar, and the profiles of the atmospheric aerosol, ozone, water vapor and temperature over Hefei area have been obtained by this system.
According to the asymmetrical distribution of high-power laser beam, the idea of rotating crystal window is put forward to successfully solve the problem of airproof. Experiment on a 2 kW CO2 laser system proves that it works weil. The result indicates that this structure can make the heat stress distribution of the window to homogenize.
Basing on the theory of frustrated total internal reflection, an optical modulator is designed. The experimental results of the optical modulator are reported. By putting the modulator in the laser cavity, there is no additional loss in the cavity and the peak power of the laser pulse is increased. The phenomenon is analyzed in the paper. The optical modulator can also be used as a Q-switch.
The diode bar soldering technics and copper micro-channels cooler technique for high power diode laser package have been investigated. To meet the application needs, two different kind of stack package structure with back surface cooling and the micro-channels cooling have been designed. The package experiments of linear array and stack array were carried out and the experimental results were presented.
Plasma-electrode electro-optic switch is one of key technologies for largely aperture high power solid laser. A metallic chamber plasma-electrode electro-optic switch with clearly aperture of 240 mm by 240 mm with a KDP crystal slab which is 15 mm thickness. Its switch efficiency is larger than 98%. Comparing to the other switch, the compounding model has better performance.
Based on design principle of thin-film optics, to the special needs for output spectrum shape and gain characteristics in the process of femtosecond laser pulse amplification, a type of femtosecond laser spectrum filter is designed through optimum calculation to thin-film system. The filter can control intensity of laser spectrum and distribution of laser frequencies for a special purpose, and acquire the special femtosecond laser spectrum shape which is needed. Our results show that the femtosecond laser spectrum filter can be used in the femtosecond laser chirp pulse amplification system.
This paper reports an innovative structure of laser reflecting mirror cooled by phase-change. Cooling channels are built up in reflecting mirror of positive-branch virtually-confocal unstable resonator, stuffed solid-liquid phase-change materials for maintaining mirror's temperature at a comparatively constant point. This mirror, whose structure is simplistic, could be united with crystal output window, neglecting 45° plate scraper for output coupling, and then high quality output beam is available.
Using an Anti-resonant Ring (ARR) in the Nd:YAG laser, and inserting the BDN dye film and LiF:F-2 color center crystal into the center of ARR, a high stability and high energy single Q-switched laser pulses with output energy of 98.3 nij and 82. 5n\J, and energy fluctuation of 1. 44% and 0. 88% meanwhile, the experiments in the plane-plane resonator were compared and results were analyzed.
A solid-state laser system with short pulse width, including an oscillator and an amplifier, was implemented. In the oscillator a classical E-O Q-switch method was used. The maximal output frequency is 20 Hz. In-depth discussion and analysis were focused on the phenomena that the laser beam with a quite high energy was reflected from the side of polarizer. And the cause of this phenomena was pointed out. It has been discussed that how to make use of this phenomena to guide the debugging of this kind of laser.
A spontaneous Ranuin imaging system has been described that can monitor the absolute concentrations of major species in low pressure flow. The concentrations of the species in the air and mixed gas were measured. The error is less than 8%. The measurement precision of O2(a1Δ) concentration will be improved largely when this technique is applied to monitor the singlet oxygen generator performance of chemical oxygen-iodine laser.
The characteristics of ccnipasite quarter-wave plate were iinalyzed based on the Jones matrix theory in this paper. It is found that a composite quarter-wave plate and an aissemblage of a rotator and a quarter-wave plate were equivalent. The rotation angle of equivalent rotator and azimuth angle of equivalent single quarter-wave plate were derived.
According to the requirement to the coherent laser radar, a coherent laser radar antenna system was simplified by using a binary optics element with planar substrate to correct aberration. Only one large aperture spherical lens and one small aperture spherical lens as well as one small aperture binary optical corrector with planar substrate were used in the system. The designing parameters are, as a transmitting system, the objective field of view 2ω=10°, the aperture of the exit pupil Φ=100 mm, the reducing times of the angle of the diverging beam β=5×, the wavelength of the laser source λ=10.6 μm. The designing result is that the imaging quality of the optical antenna system reaches the diffraction limit.
The power spectral density (PSD) is employed as a parameter to specify the large aperture optical elements' surface manufacture quality. According to the different kinds of modulation of the wavefront, the PSD calculation results have been given. The variation of the PSD curves with different depth and frequency of the modulation has been shown. The results show that the PSD curve can describe the modulation information of the optical elements surface clearly.
By utilizing of 2 kW CQ2 laser as a laser source, a Twyman-Green's interferometer, CCD photography technology, and a computer data collection and procession system, the thermal deformations of two types of mirrors have been measured, respectively. The experimental results show that the thermal deformations of the phase-change-cooled mirrors are smaller than those of general silicon mirrors, and that the initial thermal distortions of the mirror surface increase greatly with increasing of laser irradiation time; after about two seconds, the thermal distortions increase slowly. The thermal deformation interferogranis of the mirrors at different times are obtained.
A methodology for monitoring extrusion process using in-line fiber-optic near-infrared spectroscopy is introduced in this paper. Fiber-optic sensor and sensing system are also designed. Predictive calibration models of NIR spectra are developed for monitoring of polymer composition and concentration by using multiple linear regression techniques and artificial neural networks.
7 types of volume absorption laser energy meters for accurately measuring the output multi-wavelength high power energy from SG-Π are developed. The technical parameters including sensitivity, homogeneity and stability etc, are better than the original designing objectives via the calibration and testing by Chinese Metrology Academy. These devices satisfy requirements of multi wavelength high power laser energy measurement for SG-Π. The sampling modes and measuring accuracy of the laser energy measurement at 3 kinds of wavelengths at SG-Π facility are also analyzed in this paper.
Temperature dependence of two-beam coupling gain coefficient Γ, the effective trap density Neff and intensity dependent factor η(I) are studied theoretically for the two-centre photorefractive crystals. The results show that Νeff, η(I) and Γ has more complicated temperature dependence behaviors in two-centre crystals, which are related to the density of shallow level.
For the symmetric near-axial optical system that can be described by using 2×2 matrix, Collins had derived the calculating formula of diffraction field of the coherent light passing through the optical system, which is related to element ABCD of optical matrix. The formula is able to simplify effectively the diffraction calculation and widely used in the research field of laser transmission. In this paper, three methods are developed to calculate Collins formula and verified by the experimental data.
A new 4×4 complex curvature tensor Μ-1 is introduced to describe partially coherent anisotropic Gaussian-Schell model beams (GSM). The propagation law of Μ-1 is also derived which may be called partially coherent tensor ABCD law. The focusing properties of GSM beam focused by a thin lens using the derived tensor ABCD law of partially coherent are calculated and analyzed. The result shows that the focusing properties of partially coherent GSM beam are closely related to the coherence length and phase front curvature. For the case of partially coherent anisotropic GSM beam, its focusing properties are also related to the twist factor.
Results are described of recent contributions to the problem of laser atmospheric scintillation in space laser communication in this paper. The effects of laser atmospheric scintillation on the space laser communication are presented. The reduction in scintillation with different number of transmit apertures, different distance between two transmit apertures and different size of receive aperture is introduced. The method of using adaptive optics to reduce intensity scintillation is also given. A way to solve the problem of laser atmospheric scintillation in space laser communication is introduced at last.
In the investigation of the temporal feature for a laser beam propagating through a turbulent atmosphere, in general, the Gaussian beam wave can not be treated simply as a plane or a spherical wave. The high-frequency spectrum (HPS) is affected by the receiver aperture, the turbulence spectrum in the dissipation range, and the Gaussian beam type. The HFS departs from the ordinary behavior in a deeper tendency with the increase of the receiver aperture. For a plane or a spherical wave, the HFS departs from the 一 8/3 power law and trends to a — 11/3 power law when the aperture is as large as the Fresnel length. With the increase of the turbulence inner scale and the wind speed the HFS departs from the ordinary power law in a deeper tendency. When the Gaussian beam can not be treated as a plane or a spherical wave the HFS presents a — 8/3 and a — 14/3 power-law dependence in two regions or a unique — 14/3 power-law dependence. The results are verified by experimental data.
In this paper, power spectrum density (PSD) for laser beam wavefront is described and wavefront retrieved algorithm based on PSD is presented for the simulation of laser propagation. The effect of middle and high frequency distorted wavefront on intensity distribution of sidelobe of focal spot is also discussed.
The high-resolution absorption spectra of real atmosphere near the 1.315 μm wavelength were recorded accurately using an experimental system. The system includes a tunable narrow-line-width pulsed ΟΡΟ laser, a multipass absorption cell of the White-type with total optical length as long as 1097 m, and a single time-division multiplexing fast-response detector system. It is verified from the spectra that water vapor is the main absorption gas in the wavelength band. The absorption cross-section of atmospheric absorption molecule at the wavelength of iodine laser (7603.14 cm-1) was gotten from the measurement data which is (1.05±0.09)×10^{-24} cm2 (at the standard atmospheric condition). And the parameters of atmospheric absorption lines were also obtained around the wavelength of 1. 315 μm from the measured spectra. The absorption cross — sections of atmospheric absorption molecule near the wavelength of iodine laser were also calculated from the measurement parameters.
Laser illumination is an effective technology for the imaging and tracking to the far dim objects in the air. The laser intensity spatial distribution on the target plane fluctuates usually remarkably, which will decrease image resolution and tracking accuracy in optical system. In this paper the parameters for evaluating illumination effect have been discussed, and power spectral density (PSD) of the illumination laser intensity fluctuation on the target plane is adopted to evaluate the intensity uniformity. A model of illumination laser propagating in atmosphere has been built, numeric simulation for laser illumination to air objects has been carried out and the illumination intensity fluctuant power spectral density and object image have been obtained. Being contrasted with experiment result shows that the simulation is reasonable.
The branch point problem was computed by four-dimension code of laser propagating in atmosphere and compensation of adaptive optics in this paper. The relation of density of branch point with atmospheric turbulence and propagating range was analyzed. The problem of branch point of various beacon and its effect on compensation of adaptive optics were analyzed too. These computational results showed that the compensative effect of adaptive optics is not characterized completely by coherence length and frequency bandwidth of adaptive-optics system. The effect of scintillation needs to be considered in compensation of adaptive optics when a laser beam propagated over a long distance through even weak atmospheric turbulence.
It is carried out a series of synchronous measurnients of the irradiance scintillation and the extiction of a He-Ne laser beam propagating through a real turbulent atmosphere over complex terrain. The relationship between the statistical properties of the irradiance scintillation, such as the scintillation index, the probability distribution and the power spectrum, and the extinction was analysed. There is certain relationship between laser irradiance scintillation and irradiance extinction in a real atmosphere.
This paper studied the working process of the DIRCM system. Theoretical analysis and computation have been made for the three important courses i.e. atmospheric transmission of laser radiation, laser interfere on IR sensors, reflectance of the IR imaging guider projected by detecting laser. Then they are programmed into several simulating modules carrying out corresponding tasks. Finally they are integrated into one friendly interface simulating system. This work is very essential for the fixing of the parameters of the DIRCM system.
When optical beam passes through a turbulent, a medium of varying index of refraction, its optical wavefront emerges aberrated. The interaction of light with the fluid is termed aero-optics. This paper gives a brief reviewing of the aero-optics reach methods and the applications in the high power laser.
The rigorous couple-wave method is comprehensively applied in the analysis of frequency-separation gratings used for inertial confinement fusion system, some result is abtained.
This paper discussed the design, configuration and experiments of a high accuracy laser beam parameter (M2-factor) measurement system. The system utilizes a cooled digital CCD array as the detector and has the functions of background subtraction, noise determination, 2D and 3D energy distribution display, image histogram, beam width, divergence and M2-factor determinations. For testing the reliability of the above system a LD. pumped mode generator which can generate Hermite-Gaussian modes from TEM0.0 to TEM35.0 was developed. The M2-factor of different transverse modes were experimentally measured and the results agree with the theoretical estimation.
The mode field distributions of higher order mode of planar optical waveguide are analyzed by using the Finite-Difference Time. Domain (FD-TD) method. In this paper, the mode field distributions of TE, niode is analysed by using the vector FD-TD method at first; Then the mode field distributions of TE2 mode is analysed by using the scalar FD-TD method. The figures of mode field distributions calculated by conputer are identical to the conclusion discussed by else methods.
By using the generalized truncated second-order moments method, the closed-form expression for the M2-factor of Hemiite-Gaussian beams with hard-edge aperture is derived, which is written in terms of the incomplete Gamare function and dependent on the beam order n and trancation parameter α. Numerical calculations are performed and analyzed. Furthermore, some special cases oi our analytical expression are discussed.
A kind of wide-band scanning rotating mirror of high power laser is discussed in detail by using scalar diffraction theory in this paper. The transient power distribution of laser in any observed region has been derived for the arbitrary laser beam passing through the optical system. Given the translation velocity and laser absorptivity of workpiece in the laser treatment, the distribution of energy absorbed by the surface of workpiece in given time interval is investigated and the calculating example has been finished.
By YG algorithm, the diffraction of a 16-levels BOE is calculated for converting a He-Ne laser single-mode into TEM10 intensity distribution in one-dimensional case. The simulation results show that the relative average deviation of the designed intensity from the desired intensity is less than 1.0% when the input beam-waist deviation is not more than 0.03 mm.
The equivalent beam qualities of GaInP/AlGaInP strained multiple quantum well laser are measured by transforming nonparaxial semiconductor laser beam into paraxial one non-trunctatedly. The beam quality factor in the direction perpendicular to the junction plane is shown to be smaller than unity. Based on the waveguiding mode and nonparaxial vectorial moment theory, the beam qualities are analysed and calculated, which are basically coincided with the experimental results.
In the paper, the phase conjugation effect and the threshold effect of SBS inducing the reducing of the divergence angles of back-SBS were discussed in the theory. In the experiment, the wave-front aberration was compensated, the beam quality was improved, and the divergence angles were compressed by using the SBS PCM in the Nd:YAG laser. The pumping energy, lens focal length and SBS medium affecting the beam quality of the amplifying back-SBS were studied, the beam quality was improved in evidence by using SBS system to replace the general holophote.
Based on the treatment that the rectangular function can be expanded into an approximate sum of complex Gaussian functions with finite numbers, the analytical expression for the focusing intensity distribution of a partially coherent Gaussian Schell-model (GSM) beam through an aperture lens was derived. The typical numerical examples were given and were compared to those obtained from numerically integral calculation. The results have shown that the method can significantly improve the numerical calculation efficiency.
Distorted wavefront of the free-vortex aerodynamic windows (FADW) is measured using the method of the lateral shearing interferometry (LSI). And the optical quality factor, i. e., STREHL ratio, is calculated from the reconstructed wavefront. This paper measures the optical quality degradation introduced by the supersonic free-vortex jet of FADW running under the different conditions first. And then it measures the variety of the optical quality with the running time.
Initial laser intensity distribution characteristics will affect energy concentration in the far field under some certain conditions. The intensity distribution characteristics of annular beam in the far field is studied. Intensity nonunifomiity factor UE is put forward to describe the initial random intensity distribution. For high power laser, the intensity nonuniformity will cause the deflection of the beam in the far field while no wind.
Based on the united idea of geometry optics and phase modulation of binary optics, a prism array is used to change four incident beams, which have 45 degree gradient with horizontal axes, into parallel beams, and then the beams transit the two-dimension pure phase element which is designed by couterchanged two one-dimension phase. Through the lens, the uniform irradiance on the ICF targets which are superposed by four beams is achieved.
This paper discusses the coupling technique of optical fiber for narrow-pulse high power laser. Solid cone of light which can reduce the power density of converged laser because of its function of converging light energy is adopted. Correlative parameters of solid cone of light are calculated.
The laser beam automatic control system is applied in the beam collimation of the laser fusion facility of "SG-II. It can be inferred from the optical analysis of Fourier, the image noise of the near and far-field caused by diffraction is the least when the near and far-field which are to detect the location of the laser beams are on the image-relay plane of the spatial filter. When correcting the beams automatically, the correlation of the near and far-field is also the least so that they can be adjusted independently. The image processing makes the automatic alignment realized with the computer and CCD camera. It can be shown from the error analysis and the experiment of automatic alignment of the system that the precision of the beam position is less than 1".
A design method used in large-caliber pure phase element for quasi-annular beam shaping of "SG II" laser driver is presented in this paper. The adaptability of the pure phase element in the practical system is studied and the beam qualities in different situations are calculated.
The theoretical model for erbium-dc^ed phosphate glass waveguide amplifiers pumped at 980 nm wavelength is studied in this paper. This model is usually simplified as two models with upconversion and without upconversion. The comparison study of the two simplified models is carried out by the effect of erbium-doped concentration on amplifier gain. Numerical results demonstrate that when the erbium-doped concentration is less than 10^{26} m-3 the upconversion may be neglected or upconversion may be considered.
Based on signal radiation characteristic, the problem of designing a planar array is discussed. An array of tapered waveguides is used by optical communicated in wavelength multiplexer. A design procedure for optimizing the array is described. Optimum conditions, structure parameter and transmission efficiency are calculated by simulation. Theoretical analysis is concided with the simulation result.
As the technology of WDM is practicality, the wavelength tunable laser becomes the key component of WDM. Then it is important to optimize its property and simplify its structure. In this paper, a new type of laser structure by using EDFA (Er3+-Doped Fiber amplifier) and AOTF (acousto-optical tunable filter) is demonstrated. Theorilly, the output characteristic of such laser is analyzed, as the same time, the factor which effect the output characteristic of laser is also analyzed. Base on the analysis, some method to improve the properly of laser are proposed.
CMOS-SEED integrated chip with input/output optical windows combine the advantages of electrical logic processing and optical interconnection. The layout of CMOS integrated circuit is designed. The chip is fabricated with 0.35 μm processing technique in HP Company and flip-chip bonded SEED device is performed by Bell Lab.. The CMOS-SEED integrated chip with input/output optical windows is developed successfully. A 16×16 free-space crossbar photonic switching module with CMOS-SEED integrated chip is designed and fabricated. The functions of 16×16 crossbar photonic switching are implemented.
A theoretical model about the relationship of misalignment and coupling efficiency is set up by using method of transfer matrix and Gaussian optics. Numerical analysis shows that excess loss is sensitive to the angular tilt and the lateral offset. The measured results offer reasonable agreement with the analysis presented in this paper.
Nowadays the channel spacing of DWDM systems is becoming more and more dense to accommodate the exploded traffic demand. Interleaver, which separates the incoming spectra of the optical signals into two compleraeiuary sets of periodic spectra, could provide a solution for DWDM devices and systems. In this paper an interleaver based on crystal waveplate (Yttrium Vanadate) is introduced. The performance of the output spectra is optimizing by use of Fourier expansion. Experimental results give excellent agreements with the theoretical analysis.
The expressions for transmission power, dropping power and free spectral range of a microsphere-taper fiber coupling system are derived using the coupling equations for the field transfer and characteristics of the WGM in the sphere. The optimal conditions for filtering are discussed. The results could be important for the design of channel dropping filters.
Fiber-optic Mech-Zehnder interferometer can be used to multiplex and demultiplex wavelengths. The ΔL and Δφ directly influence the properties of M-Z. Through lengthening the ΔL, the density of wavelength dividing can be improved. The longer the ΔL, the more sensitive to temperature the M-Z. The method for making the M-Z work stably is explored. The wavelength separation is 0.8 nm, and the extinction raio is high.
Arrays of five FBGs, with a reflective peak wavelength separation of 1 nm, were written into the same fiber and in different positions utilizing the same phase mask through the stretch and UV writing technique.
A brief review on the history, fabrication and application of Yb3+-doped double-cladding fiber is given. Several factors affecting the properties of Yb3+-doped double-cladding fiber are discussed.
Erbium-doped waveguide amplifiers (EDWA's) operating at 1.5 μm wavelength have the characteristics of higher gain, lower pump threshold, smaller dimaision and apt for integration. They have wide application in integrated optical communication system. At present, Materials for EDWA's are oxide film, organic mixture, silica and glass.
It is studied that the soliton amplitude varies with respect to the distance z of soliton transmission, when there is loss in optical fiber. The result is that the soliton amplitude declines exponently to the distance z.
A novel configuration design of two path optical Add/Drop OADM multiplexer used in DWDM all-optical communication network is presented in this paper. It composes of polarization beamsplitter, λ/4 waveplate, right-angle prisni, total reflection mirror, and polarization light modulator. One path or two path different wavelength signals can be added or droped from the main optical path by division and recxxnbination of the p- and s-polarization components of the optical signals under the oontrol of polarization light modulator. It has the features of flexibility, polarization indeoendent, less optical elements, compact constitution, and easy to packaging.
The crosstalk-to signal ratio and the power penalty caused by double Rayleigh scattering of different fiber Raman amplifiers are investigated. Under the same pump power, the gain of dispersion shifting fiber Raman amplifier is the highest, and its crosstalk-to signal ratio and power penalty are also the highest. The double Rayleigh scattering noise performance of fiber Raman amplifier decreases rapidly as the pump power increases.
In this paper the inverse iteration method was introduced to analyze the guided mode of integrated optical waveguide devices. A three-dimension rectangular waveguide was also calculated by this method. And the result was analyzed by the finite difference time domain (FDTD) method. From these results it is concluded that the inverse iteration method is a relatively useful method to analyze the guided mode of integrated optical waveguide.
A kind of 3-D free-space optical interconnect integrated module with Mesh network topological configuration is presented in this paper. The highlight is laid on the optical design of the light transceiver lens array of the system module on the basis of the image aberrations. Two different design methods are compared. The results show that the method of slantwise incidence through the center of the lens directly has an output signal spot size of 0.4630 μm. It is the better method to meet the demands of 3-D free-space optical Mesh interconnect integrated module.
The reflectivity of DBR is calculated through equivalent F-P cavity. Then the far-field distribution of a vertical cavity surface emitting laser (VCSEL) is equated through numerical method. Based on this, the coupling mechanism on two VCSELs in optical interconnection are studied emphatically.
By simulating an AWG of 16-channels, the impact of the width of waveguides, pitches of the arrayed waveguides and pitches of the output waveguide of the Rowland circle on the crosstalk is studied.
The paper introduce a new interleaver/de interleaver technique used in WDM network. The principle and simple structure of a de interleaver based on polarization interference theory are discussed. According to the theory analysis and experiment conducted by the author, a means is brought forward to widen the bandwidth of output. Some other interleaver techniques are also referred in terms of their advantages and disadvantages. At last the author prospect the potential application and market of interleaver techniques.
The novel two pump configuration of the two-step cascaded Raman fiber amplifiers are numerically simulated. On the basis of simulations, the gain and noise characteristics of two-step cascaded Raman fiber amplifiers of different pump configurations under the same pump powers are analyzed and compared. And the pump powers distribution of the two pump configurations with the same gain are also supplied.
The photoresist is very important in fabrication of Binary Optical Elements (BOE). In this paper, different photoresist are used and compared in the photolithography and etching process of fabricating BOE. By adjusting the type of photoresist according to various patterns, BOE with good performance have been accomplished.
A kind of novel material of holographically polymer-dispersed liquid crystal (HPDLC) is reported. The hologram can be recorded due to the diameter of LC droplet, which is far shorter than light wavelength. Moreover, the diffraction efficiency can be modulated by the application of electric field. In this paper, the theory of HPDLC formation is analyzed in detail, the composition of the material and the way of preparation are given, and the diffraction efficiency and the morphology observed by SEM are studied. The HPDLC is compared with traditional PDLC. This material has the potential and broad application in the field of optical communication and information storing.
A novel DVD/CD-R compatible integrated optical-pickup is proposed. In this device, the beam follows a zigzag optical path inside a planar glass substrate. A transmission planar combiner & splitter, an achromatic waveplate and a color separation grating were integrated on a glass substrate. With these elements, the system has the functions of combining and splitting the two wavelength beams, rotating their polarizations. Such a planar integrated optical-pickup is compact and lightweight with high energy usage ratio.
A technique of measuring laser mirror thermal distortion and a method of mathematical morphology used to process interference patterns of thermal distortion are presented. The practicability of technique in this paper is proved by the results of experiments.
In this paper, a PVK-based polymer composite doped with DR1, PBA & TNF is described. By the ameliorated two beam coupling experiment, its photorefractive properties have been investigated and the dynamic process of the index grating in the sample has been watched. The two-beam coupling gain coefficient as higher as 137 cm-1 was measured at poling DC electric field of 28 V/μm.
For the ultra-high-density photon data storage, a new type of optical head scheme is presented. A miniatured and integrated recording-and-readout optical head system is designed by the micro-optic technology. It can achieve multichannel and multi-layer rapid storage, and increase the recording and readout speed. In addition, the optical structure is simplified and the weight of the optical head is lightened.
A novel double-wavelength single-beam two-photon bit-by-bit recording scheme that employs a special optical wavelength-division aperture in its beam focusing system is proposed. The simulation results show that, by properly selecting the configuration of a wavelength-division aperture and the power ratio of the two laser beams, our new scheme can achieve a much smaller recorded bit than a conventional single-beam two-photon recording scheme, especially in the longitudinal direction. It means that our new approach improves the two-photon recorded data density on a large scale.
It was realized that the erasable holographic storage in the visible range for the thin layers of PMMA matrices doped with N-salicylideneaniline material. An argon laser beam of 488.0 nm and a He-Ne laser beam of 632. 8 nm were used as writing and reading light, respectively. The intensity of the diffraction signal increased with the increase of writing time, then it decreased with the increase of writing time. In the grating growing and dropping process, the relation between erasing time and grating diffraction signal was studied. For the former, the diffraction signal increased firstly, then decreased with the increase of the erasing time; for the latter, a decrease in the intensity of the diffraction signal was observed. A possible explanation is that pressure-driven mass transport induced from photoisomerization which causes a change on the surface to form a surface-relief grating. However the surface-relief grating partly counteracts the phase-grating because of the two gratings with a phase difference of π.
Nd:GdxLa1-xVO4(x=0.8,0.6,0.45) series crystals were grown by the Czochralski method, and some factors influencing the quality of crystal were also discussed. The lattice constants of three kind crystals were measured. The absorption and fluorescence spectra at room temperature were measured. The laser output of Nd:Gd0.8La0.2VO4 crystal at 1.06 μm and 1.34 μm were demonstrated when the crystal was pumped by a LD.
Using CW-Ti: sapphire laser as pumping source, the self-Q-switched Cr, Yb:YAG laser has been demonstrated at room temperature. An average output power as much as 75 mW at 1.03 μm with a pulse width (FWHM) as short as 0.4 μs was attained. The laser experiment demonstrated that the Cr,Yb:YAG crystal exactly combines the Cr4+ saturable absorber and Yb3+ gain medium into one. And Cr,Yb:YAG crystal can be a most promising self-Q-switched laser crystal for compact, efficient solid-state lasers.
In this paper, the new development of the laser heated pedestal growth (LHPG) technique is introduced. The diameter of the crystal grown by LHPG has been increaseed to 2~3 mm. The growth speed of LHPG has been increased to 150 mm/h. Lead-containing ferroelectric single crystals have been grown by LHPG successfully. Fiber crystals of eutectic ccanposition MgTiO3-CaTiO3 system have also been obtained.
The spectroscopic and upconversion properties of Er3+-doped aluminosilciate and phosphate glasses were studied in this work. High erbium ion concentration ranging from (1.5~3.6)×10^{20} cm-3 was used in these two glasses. Yb3+[(0~3.6)×10^{20} cm-3] ions were codoped in these glasses. It is found that the emission properties of Er3+-doped aluminosilicate glass is greatly affected by OH group at high erbium concentration. More than 6ms fluorescent lifetime can be achieved in Ef3f-doped aluminosilicate glass at 3.6×10^{20} cm-3 Er3+ ion concentration after water removing process, and as broad as 60 nm FWHM can be achieved in this glass. Intensities of emission and upconversion fluorescence of both glasses increase with the increase of Yb3+ ion concentrations. Compared with Er3+-doped aluminosilicate glass, doped phosphate glass has higher emission cross section and narrow FWHM (35~40 nm), long fluorescent lifetime (7 ms) and low upconversion fluorescent intensity. With the increase of Yb3+ concentration, 2H11/2→4I15/2 (525 nm) fluorescent intensity becomes stronger, 4S3/2→4I15/2 (545 nm) emission weakens in either of the glasses.
The influence of growth conditions (such as growth pressure and the flux ratio of group ID precursor) and the widths of SiO2 mask upon the thickness enhancement factors of selectively grown InGaAsP were studied in this paper. The growth rate decreased and the selectivity increased with the increasing of the growth pressure; the growth rate increased and the selectivity decreased with the increasing of the flux ratio of group III precursor. The InGaAsP bulk material with high thickness enhancement factor was grown by selective MOVPE.
The attribute of spatial soliton in a series photorefractive crystal circuit has been investigated. There are screening and screening-photovoltaic dark solitons in the dark-dark soliton pair; there are only the photovoltaic bright solitons in bright-bright soliton pair; and there are screening-photovoltaic and photovoltaic bright solitons and screening-photovoltaic dark solitons in dark-dark soliton pair.
Reflectance properties of silicon mirrors with TiO2/SiO2, Ta2O5/SiO2, and Si/SiO2 film systems at 1315 nm are numerically analyzed, and discussed under conditions of normal and 45° tilt angle incidence, respectively. The results show that reflectance properties of TiO2/SiO2 and Ta2O5/SiO2 are similar; theoretical reflectivity is less than 99.95% for 1315 nm laser wavelength. Theoretical reflectivity of Si(c)/SiO2 stack can be more than 99.99%.
Ion-assisted bombardment is an effective method to improve a-C film. a-C films were deposited on Si (100) by pulse laser (532 nm, 3. 5×108 W/cm2) ablating graphite target with Ar+ bombarding growing films simultaneously. Scanning electrical microscope and Raman spectra were applied to analysis film structure. As a result, lower working pressure and higher RF power is helpful to prepare a-C film, meanwhile, laser repetition has evident influence on film s growth.
The morphologies of hafnia/silica surface defects, such as nodular, bottom pit and crack were studied using Normaski at atomic force microscopy. The laser damage experiment was carried out using 1064 nm pulse laser with 10 ns duration. The relations between the damage threshold and various defects, the character difference of laser damage between AR, HR coatings and polarizer were investigated.
In this paper, the coating samples are deposited by reactive electron-beam deposition using the materials of HfO2/SiO2, ZrO2/SiO2, (ZrO2+Y2O3)/SiO2 and Ta2O5/SiO2 respectively, for high power laser, the study of laser conditioning effect of oxide multilayer mirror was taken by using N-on-1 mode. The experiment results show that the different materials mirror have different laser conditioning effect. The HfO2/SiO2 coating is best for improvement of damage threshold, up to 3 times. The ZrO2/SiO2 and (Ζr?2+Y2O3)/SiO2 is better, up to 1.5 times. But for Ta2O5/SiO2, the laser conditioning has almostly not effect on threshold improvement. Especially for HfO2/SiO2 mirror laser conditioning, the mechanisms are found to be two kinds of situation (state), laser annealing and laser clean of coating. The experiment of damage size and degree influencing on its spectrum shows that the damage of scald less than 200 μm and pit have almostly not influence on their reflectivity, for the damage diameter larger than 500 μm scald and delaminate, the reflectivity of coating drop less than 10%, so for HR coating it is better that the damage threshold is determined by practical application, not only by laser damage simply.
A new method to over ccmie defects of optical coatings was introduced. It was found that the micrographs of the laser induced damage of the coatings were different to each other when using different testing methods, and some damage sites were stable at repetitive shots. The experimental results show that damage threshold of optical coatings can be improved by laser conditioning.
In this paper, the function, structure and principle of the expert system for pulsed laser deposition are introduced. The design thought of the expert system is presented. The condition, application and further development of the expert system are also discussed.
By using ZnS/YbF3 five-layer coatings, wide-band infrared antireflective coatings on CaF2 window in the range of 3.4~4.2 μm has been fabricated. The tested spectral results have shown that the average transmittance is above 99%. The wide-band infrared antireflective coatings on CaF2 window can endure the output laser with 200 kW.
By the means of ion sputtering, the optical anti-reflective thin films are deposited. Through the measurement of these thin films, the characteristics such as surface morphology, refraction index, weak absorption, structure, etc., have been analyzed. And the feature of ion sputtering and its adaptation is pointed out.
Pyroelectric polymer films have been prepared using spin-casting method. IR spectrum and XRD of the samples have been analyzed. Pyroelectric properties of the films have been studied, too. The results show that pyroelectric response sensitivity of the film samples prepared using spin-casting method is higher and more suitable for infrared detectors than other methods.
In this paper, high quality nanocrystalline ZnO film has been prepared by using thermal oxidation of ZnS thin film, which was grown on a Si substrate by the low pressure metalorganic chemical vapor deposition (LP-MOCVD) technique. The X-ray diffraction (XRD) patterns show that ZnO thin film has a hexagonal wurtzite structure with preferred (002) orientation. In photoluminescence (PL) measurements, a strong PL with a full width at half maximum (FWHM) of 10 nm (88 meV) around 380 nm at room temperature was observed from the samples annealed at 900 ℃. The PL intensity ratio of the UV emission to the deep-level emission is 28 at room temperature, providing evidence of the high quality of the nanocrystalline ZnO films.
The properties of polyimide film were greatly influenced by the thermal treatment temperature. Laser-induced periodic surface structure (LIPSS) on PI films were studied at different temperatures ranging frcxn 100 ℃ to 270 ℃. The ripples were obtained on PI films under irradiation of linearly polarized UV laser with a wavelength of 355 nm. The effects thermal treatment temperatures on formation process and the configuration of LIPSS were investegated.
Considering the birefringence character, an anti-reflect ion films coated on quartz plates were prepared by changing the coating technique, such as optimizing thin film design, selecting coating material etc.
A new method of turn-point-value monitoring is provided in this paper. Deposition is stopped at a point which is senstative to film depth variation by designing and modulating monitoring wavelength. This method can be used to improve deposition monitoring accuracy.
TiN films coated on glass by D. C. reactive magnetron sputtering of a titanium target were deposited using the variation of the deposition conditions such as total pressure and the ratio of N2 to Ar. The preferred orientation and N/Ti ratio of TiN films were investigated by measuring the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The results of the XRD show that the XRD intensity ratio (R) of (200) to (111) gradually decreased with the increase of the total pressure. When the total pressure is approximately 1.0 Pa, the value of the R is approximately 1. When the total pressure is not changed, the R is increased with the increase of the N2. The results of the XPS show that the atomic ratio of Ν to Ti is larger than 1 for all the TiN films when the ratio of N2 to Ar is changed from 1% to 7%.
Zinc oxide quantum dots (QDs) embedded in MgO thin film matrices have been prepared by a simple combination evaporation technique, in which electron beam evaporates MgO crystalline, simultaneously resist thermal evaporates high purity metal zinc in order to embed metal zinc atoms into MgO matrices. Post-annealing process in oxygen ambient at 500, 600, 700, 800, 900 and 1000 ℃ for one hour, respectively, was proceeded in order to transform metal zinc atom into zinc oxide. After the post-annealing process, X-ray diffraction (XRD) spectra were used to identify the formation of ZnO. A strong ultraviolet emission band has been observed at room temperature in the photoluminescence (PL) spectra for the samples annealed at 900 and 1000. The PL spectra measured at 77 Κ to room temperature show little change in the peak intensity and the peak energy, which indicates that ZnO QDs strongly confined by MgO matrices have been fabricated through this simple method. The dependence of photoluminescence properties of ZnO quantum dots on the annealing temperature is discussed.
An improved approach of large area thin film deposition by a hybrid scanning laser ablation is proposed, in which the pulsed laser radiates a target along a specially designed track just like moon circling round sun. The calculation results show that the thickness distribution of films is more homogeneous than that with the simple circle scanning ablation, and an optimum dependence of film thickness homogeneity on such parameters as scanning track, and scanning speed etc. is presented. The tentative experimental study indicates the effectiveness of this method.
In the laser destroying experiment, the mode of laser should be constant, especially of output beam power. The multi-layer mirror is used in order to keep the thermal deformation small. Under the same condition, the deformation of multi-layer is only 1/40 of normal copper mirror's.
A (TiO2+B2O3+Al2Q3+TiB2)/NiCrAl metal-ceramic coating was fabricated on a steel (Chinese brand 40Cr) by laser. TiB2, Al2O3 were introduced by an in-situ reaction of Al, B2O3 and TiO2 during laser cladding process. The microstructure, phase, element distribution and micro-hardness have been analyzed with the aid of microscope, electron probe and micro-hardness tester. The hardness and the boundary strength are significantly enhanced due to the present of ceramic particles (TiB2, Al2O3) in the coating. With the ceramic composition increasing in the range of 5% to 20% the wear resistance is enhanced.
The Ni-based metal-ceramic coatings on the surface of mild steel were cladded by a high power CO2 laser. The effects of rare-earth oxide La2O3 and CeO2 on microstructure and properties of Ni-based metal-ceramic coatings were investigated. The result shows that the microstructure and property of clad coatings with RE-oxide were balanced and better compared with the coatings without RE-oxide, the crackle, hole and entrapment in the coatings were reduced and TiC particles were slippy.
Laser cladding experiment of nickel base alloy and cobalt base alloy on the Q235 steel was done with a 3 kW transversely flow CO2 laser. It was discovered that suitable rare-earth oxide additives promoted size of crystallites in the cladding layer to coarsen obviously, and thermal shock resistance of the layer rose by over 10 times, which is quite important to the application and study of laser cladding technology at high temperature or thermal shock situation. Mechanisms about effect of on the laser cladding layer were discussed in this paper.
The research prospect of temperature field of laser remelting and laser cladding were discussed. Two and three dimensional steady-state and unsteady-state heat transfer model were introduced. The results from these models and the experiments were cxxnpared. Some main factors that influence on the establishment of models were discussed. The research will be helpful to the research of physical process of laser-matter interaction and will supply the theoretical guidance for establishing measures of laser repairing cracks of components.
The plasma produced during deep penetration laser welding decreases the efficiency of laser energy. The difference of thermal movement speed between electrons and ions results in a voltage between the nozzle and the workpiece, and an electric current occurs if the nozzle and the workpiece are short circuited. The current increases with the increase of external voltage. The charged particles can be driven away by electric and magnetic fields if the magnetic field is applied in the direction transversal to the laser beam. In the experiment the nozzle is elevated during welding so that the welding mode changes from deep penetration welding to heat conduction welding. The increment of bead length by applying electric and magnetic fields indicates the improvement of energy efficiency if plasma above the melt pool is driven away. With stronger magnetic field, longer bead length is produced. The length of deep penetration weld reaches largest value at 25 V external voltage and decreases when higher or lower external voltage is adopted.
The hardness and the dimension of micron-grained steel welding joint were studied with different laser energy inputting. The macroscopical configuration, grain size, hardness, and impact toughness of micron-grained steel joint that was acquired by different weld techniques with different energy inputting were investigated and compared. The research shows the micron-grained steel welded by laser has great superiority.
After laser surface treatment of TiAl alloy, superplastic forming/diffusion bonding (SPF/DB) was carried out. The structure transformation of laser surface melted TiAl internietallic alloy and its rule of SPF/DB were discussed. The results show that, during the annealing treatment, the dendritic structure formed by laser surface melting will be transformed into fine-grained structure, which offers a good structural basis to SPF/DB. And the SPF/DB results show that the main bonding parameters influence on bonding effect commonly, thereinto, the choice of fitting temperature plays a key role.
In this paper, Mg-Ni alloy was synthesized by laser induced SHS in a container full of argon. The synthesized samples were analyzed by XRD, SEM and EDX. The result shows that intermetallic compound M&Ni with amount of holes could be produced by laser induced SHS.
Modification of textiles with low-temperature plasma has been studied for a long time. But modification with lasers is a attractive alternative. The properties and mechanisms of the two technologies are compared using poly ethylene terephthalate (PET) textile. Chemical composition changes are measured by FTIR spectrum.
A real-time short-range laser-ranging system has been offered in this paper. It also gives the specific design method of the system.
Primary analyses and discussions on the possibility of launching and pushing lightcraft with lasers were waged in this paper. With a single laser pulse, it is successful in launching a simulate bullet which is about 5.87 g weight to the height about 1.48 m and taking the pictures of pyrotechnic pillar and firelight of the laser-induced plasma spraying and the flying bullet. Its applied foreground is also discussed.
On the basis of analysis on interaction between processing materials and three types of lasers, i. e., free-running, CW-acoustic-optical Q-switched and PW-acoustic-optical Q-switched Nd:YAG laser, the experiments on laser drilling with these lasers were carried out. It was shown from analysis and experiments, PW-acoustic-optical Q-switched Nd:YAG laser can be used in drilling to attain high quality drilling holes with less recast layer and free cracks.
The ablation rates and mechanisms of typical engineering materials such as Ni, W, Ta, Cu, Si and diamond by diode pumped YAG laser were analyzed. It was found that a lot of factors such as the melting point, evaporation point, thermal conductivity and crystal structure have a big effect on the abalation rates. In almost all the cases, the materials are heated up to melting point and the evaporation is the main mechanism for laser ablation.
Thermal cycle greatly influences the microstructures and mechanical properties of laser welded joint. Taking account of the heating effect of plasma on the workpiece and the absorption of heat in the keyhole, a mathematical model, consisted of a point heat source and a line heat source which weakens with the depth, is put forward, and a delamination method is applied for the analysis. The model is used to calculate the thermal field of laser welding of mild steel. The results are compared with that of experiment. The calculation results coincide well with the experiment results.
Compared with the limitation of traditional monitoring methods, the advanced spectral monitoring system is summarized after deeply expound the UV/VIS DOAS system theory. DOAS system model is setup and experiment data which may accurately measure the real polltion is given.
The article summarize the traditional monitoring methods of continuous emission monitoring system (CEMS), and deeply expound the DOAS system theory. This DOAS system model is formed, and special optical fiber system utilized to get accurate SO2 concentration.
The design for optical system of laser trimmer is mainly discussed. The effect of parameters and scanning manner of laser beam on the trimming is analysed in detail. In addition, according to the general needs of the machine, the accurate control of scanning galvanometer and laser source is presented.
The advantages of laser bending over traditional forming processes are being recognized. The greatest difficulty in applying the process currently is the lack of information about process parameters to form predefined final shapes. Numerical simulation can be of significant help in this regard. In this review, several recent mathematical models on laser bending are examined and key areas for the future directions are suggested.
In this paper, the process studying of precision machining ceramics tile and glass tile with KrF (λ= 248 nm) excimer laser were carried out, the effects of processing parameters on quality of precision machining were studied. The effect of laser parameters on surface roughness of workpieces were studied too. The surface topography of machined workpiece was analyzed.
Through the systemic experiments, the relationship between laser cutting factors and surface roughness of metal parts and tool fabricated by LOM (Laminated Object Manufacturing) method and the effect of main laser cutting process parameters on the surface roughness were investigated. The experimental results show that the roughness (Ra) of the cut surface would be less than 0. 7 μm. This result provides a good practical evidence for the laser surface finishing technology of LOM method.
The finite difference method was used to calculate the thermal field induced by laser beam with different power repartitions on the surface of cylindrical body with different radius. It shows that the induced thermal field is related to the laser repartition as well as radius of cylinders. It is important to note that there is a critical radium for a cylinder to be self-quenched by a laser beam. Otherwise, the assisted cooling will be inevitable. For the tubes, the same scene happens when a critical radium and thickness is reached. The experiments were performed to verify the validity of the modelling. Comparison between experiments and theoretical calculation confirms the validity of the finite difference calculations. It is evident that the absorption at the surface is also an important factor in the laser heat treatment. Therefore the appropriate method of modelling as well as the stable absorption is the key to predict the laser induced thermal effects.
In this paper, general laser image engraving arithmetic such as ordered dither and error diffusion was studied. Based on visual grayscale characteristic, a new method of multi-level grayscale module for laser image engraving was proposed. Using this method, a color image was processed through grayscale conversion and color quantization, then engraved with engraving module without digital halftoning process. With lamp pumped Nd:YAG laser and x-y scanners, a 25-level grayscale, 247 dpi laser engraving image system is implemented.
This paper introduces circuit designation of eliminate effect of laser power wave on result of measurement of diameter measure and describes theory of diameter measure with laser scanning and reason of laser power wave. The hardware diagram is also presented.
According to the requirement of excimer laser micromachining, an optical system is designed by studying the beam property of the excimer laser.
On the basis is of Nd:YAG lasers, a set of equipment of machining stencils and correlative software were developed, and were put in use. In this article, the setup and using method were described in detail. What's more, some machining examples were also enumerated.
The pairs of cylinder and piston ring of internal combustion engine made by gray cast and alloyed cast respectively by laser quenching were optimized. Wear experiments with enough lubricates showed that the best pair of laser hardening cylinder and piston ring is cylinder alloyed with phosphor. Chromium and molybdenum with piston ring alloyed with Chromium, molybdenum and copper which has much lower wear velocity than that without laser hardening.
Laser quench and carbon alloying of 40Cr steel (Chinese brand)is performed on the surface. Carbon alloying is accomplished with pre-deposited carbon layer on the surface and scanning with the laser afterwards. The microstructure, micro-hardness as well as the wear properties were tested and compared with those obtained from the ordinary quenched work piece. It shows that: (a) the wear resistance of the laser quenched pieces is always superior than that obtained with ordinary quenched work piece; (b) after the carbon alloying, a thin layer of white iron was obtained which is very hard, but due to the presence of the residual austenite between the white iron layer and substrate, the wear properties of white iron layer is weakened.
Some typical laser post-treatment methods for oriented silicon steel were introduced and compared each other, the effects of laser post-treatment on the oriented silicon steel were analyzed and the mechanism of refining domain structure, hence reducing the total core loss of oriented silicon steel by laser scribing (LS) method and local laser surface alloying(LLSA) method was studied. On the base, a laser nitriding method (LN method) is given. The results show that after laser treatment, domain structure of oriented silicon steel was refined, especially after laser nitriding treatment, not only the domain structure was refined, and the core loss was reduced, but also the aging property was improved and the evenness of oriented silicon steel kept well.
A new on-line real time dynamic identifying and detecting method, which can be used to measure the shapes, states and trends of the line components on the basis of laser scanning and dynamic localization technologies, is reported here. The three-dimensional collection mode and mathematical model is introduced. The laser dynamic identifying system was established.
The methods for monitoring the atmospheric pollution are introduced in this paper.
A new method of real-time measuring technology is presented to research on the thermo-physical process of laser-material interaction during laser non-melting processing. The dynamic micro-deformation of the specimen was studied using laser beam reflex amplifier system. The temperature distribution on the heat zone side was measured with the thermovision Infrared System. The microstructure in the cross section of heated region center was analyzed. Experimental results show that the final deformation is identified to be a result of thermal strain and phase transformation strain and at the same time the temperature distribution on the heat zone side is revealed. The conclusion is helpful to application research of laser non-melting processing further.
A portable colorimeter is developed based on colorimetry. The principle of the instrument, the basic structure and the overall design of hardware and software system are described. The performance of the instrument is tested and compared with the traditional one. The results show that the portable colorimeter achieves the performance of the exact instruments.
Investigation has been carried out into the solidifying like-waste nuclear materials borosilicate by laser glassing. The results showed that laser glassing related to the laser power, scanning speed and laser beam diameter. The quantity variation of vitrification can be described using two parameters of laser power density and scanning speed. For example, when laser power density is the order of 25.48 W/nim2, scanning speed is at 8 mm/s, the volume of laser glassing can be reached the value of 532.0 mm3/s. The microscopical analysis indicated that laser irradiating region consisted of vitreous body, transition zone, sinter and original powder region when powders were put in advance during laser glassing process. The elements Na, B, Si, Ο were homogeneously distributed in vitreous body, and there didn't exist crystal phases.
The CNC laser cutting equipment is integrated of laser, machine tool and CNC. The complete machine has the advantages of high performance, little floor space, convenience to transport and low cost. Based on the research of such machine tool, by using the character-no cutting force an optimum design and theoretical analysis on the machine tool s driving, precision and general planning are given. The key teclmology, runup of the machine tool, portabilities of the focus system and diversification of the Z-float are studied.
In this paper, a mcxle-locked frequency-doubled Nd:YAG laser for the satellite laser ranging is introduced. The influency of the power stability on the ranging accracy is studied.
The boundary of the single and multiple solution is given by solving the phase equation of self-mixing interference system. This can determine choosing rule of the parameters in a stable operating system.
This paper introduces ICCD single pulse imaging for under-water target detection, and makes it clear that this method gain advantages in many aspects. Though the analysis, also bring forward some new techniques in experiments. Experiments results shown in the paper prove the method and testify the techniques.
The practical low measurement precision open-loop FOG uses polarization-maintaining technology, modulated by sine signal added to a PZT. The harmonic components analysis method, Chebyshev filter, self-adapting sample frequency adjustment, FFT and digital correlation are used to process the gyroscope's signal, and finally reach 2 deg/h measurement precision. In this paper, the method to choose and stabilize the action spot of the gyroscope and the method to improve the precision of the gyroscope are mentioned.
Principle of the laser diode (LD) pumped solid state laser gyroscope (LDPSSLG) is introduced, the advantages of the LD pumped solid laser gyro is analyzed, the experimental apparatus of the LDPSSLG is set up and the experiment result is described.
It is reported that the wavefront aberration produced by atmosphere distortion can be cxxnpensated with nonlinear optics phase conjugate technology. And a dosed-loop connection between laser system and moving target can be established. The experiment in principle is completed, which laser trace and aim at moving target in the distance of 18 m with Stimulated Brillouin Scattering phase conjugate technology. The result indicate that the conjugating beam can be focused onto a small district not a large enianative ares like the singal beam.
In this paper, a method of scanning and receiving two beams is theoretically studied. Two laser beams scanning respectively in the top half and the bottom half of the same frame, then separated at the two receivers. With the same imaging distance, the product of pixel and frame frequency can increase by two times; With the same product of pixel and frame frequency, the imaging distance without iuzziness can increase by two times. Therefore detecting two laser beams can increase the imaging performance for laser radar. Receiving the echo signal of two vertical polarized laser beams from the target is experimentally studied.
The dynamic random optical field, which is formed after the laser is scattered by biology tissues, can be regarded as the superposition of two segmental optical fields. For example, the scattering of skin tissues can either be composed of the scattering of epidermis tissues and erythrocytes in endermic capillary, or be composed of the scattering of erythrocytes in artery and the tissues around them. This paper describe how the different proportions of the two segmental optical fields affect the statistic properties of the composed field.
Optical biopsy has the potential to perform noninvasive, real time and in situ diagnosis of tissue pathologies in vivo. The current status and development perspectives, as well as the principle and merits of optical biopsy are presented. Furthermore, the advantages and disadvantages of different techniques among optical biopsy are also analyzed by combined with the recent progress in the world spectrum. Finally, the promises and hopes, as well as the application and industrialization of optical biopsy are briefly discussed.
A novel three-dimensional human body modeling method, on the basis of laser technology and three-dimensional space measurement s principle, is reported. The three-dimensional collection mode of human body, its mathematical model, and the principle of human body feature identifying are introduced. The laser scanning human body three — dimensional modeling system was established.
The effects of several lasers such as Ho:YAG, Nd:YAG frequency-doubled Nd:YAG lasers, on creating transmural channel in isolated swine heart were investigated. Light microscopy was used to assess the histologic characteristics of laser-induced thermal damage and the channels diameter. The pulse number of creating a transmural channel was recorded. The results showed that the frequency-double Nd:YAG laser, as well as Ho: YAG can effectly creat the transmural channel with less thermal damage.
The aim of this study was to investigate the clinical response of laser treatment in case of syringoma. Among 135 cases of syringoma, 116 patients (86%) experiented completely recovery after single treatment. Fourteen percent of patients were partly recovery. It seems that ultrapulse CO2 laser works on the principle of rapid vaporized the target tissue without affecting surrounding tissue. A good success rate has been achieved with no side effects and high safety.
The clinicall response of Hemangioma treated with 585 nm pulsed dye laser and PYM was evaluated. The results as fellow: 100% patients showed treatment effect, and 67.74% patients totally cured.
The CQ laser and Nd:YAG laser therapy for hemangioma of the oral and facial is presented. From the results treating 165 patieats, it is shown that the combination of diagnosing by Color Doppler flow imaging and DSA and treatment by CO2 Laser and Nd:YAG Laser for hemangioma of the oral and facial is a reliable and effective method. It may cure or well control the disease, niay well preserve major functions of the organ while avoid serious complications.
Red blood cell (RBC) deformability plays an important role in angiocardiopathy. In this paper, the Yin and Yang of low intensity laser irradiation (LIL) and RBC were defined according to the time theory of Yin and Yang, and the biological information model of the effect of LIL on RBC deformability was put forward in terms of Yin-Yang parallel principle and cellular collective phototransduction theory as following: For LIL at dose 1, cold color such as green, blue or violet reduces RBC deformability, and hot color such as red, orange or yellow improves RBC deformability; for LIL at dose 2, hot (cold) color reduces (improves) RBC deformability;……; the effects of LIL at dose 2n is the same as the ones at dose 2; the effects of LIL at dose 2n+1 is the same as the ones at dose 1. This model was verified by many experimental data. The initial state effect of RBC on LIL effects and the union effects of LIL and drug on RBC deformability were also discussed in terms of the cellular collective phototransduction theory.
Based on the micron precision manipulation and measurement of the optical tweezers, this new system that can make quantitative measurement of displacement with nanometer resolution. It is an eminent tool for manipulating biological specimens at the macromolecular level. This paper describes its technical properties, design, and does some discussion of these methods.
The dynamic bio-speckle, which is formed after the plant seed is irradiated by laser, carries the biology information of the seed. The statistic properties of biospeckle are related to the physical state of the seed and the illumination conditions, whose varieties will lead to the change of bio-speckle. In this paper, the changes of the plant seed s dynamic biospeckle in various conditions were observed.
This paper discusses multiple methods used to form ring optical trap: extracting high-order diffractive light oomponent, axioons, rotating lens and phase-only mask, compares their characteristics in terms of quasi-parallel ism of the formed ring beam, transfer performance, energy contrast between solid and vacant part of ring beam and the size of the focus after the 40× objective, and point out the rationality of using the method of extracting high-order diffractive light component. Using ring beam makes it possible to form an optical trap through a 40× objective. This is consistent with theoretical calculation.