The optical characteristics and waveguide index profiles of Z-cut LiNbO3 optical waveguides which fabricated by using a new proton source formed by a mixture of adipic and benzoic acids with different values of the adipic-benzoic acid concentration ratio were studied.The experimental results show that the optical waveguides present β4-phase when high concentration ratio, while present β3-phase when relative low concentration ratio under the exchange temperature of 230℃ exchange time of 6 h. The higher the concentration ratio, the greater the surface refractive index change and waveguide depth of the optical waveguides in β4-phase, and the difference of optical properties in β3-phase is not significantly. The optical waveguides fabricated by using single benzoic acid and 60% ratio dilution were analyzed by double crystal X-ray diffraction. The results give useful information in making optical waveguides and to understand the physical mechanism of refractive index change in the LiNbO3 optical waveguides.

It is necessary to study characteristics of axial intensity distributions, such as focal depth and focal shift, which influence the maximum energy efficiency obtained and the assembling error at the receiving plane. The rigorous electromagnetic characteristic must be considered for diffractive optical elements (DOEs) whose features are on the order of or smaller than the wavelength of the incidence illumination. The rigorous electromagnetic analysis of diffractive micro-cylindrical lenses that are finite in extent using a two dimensional finite-difference time-domain (FDTD) method is presented. Compared with the scalar theory, the axial intensity distributions of lenses with different F-numbers are analyzed rigorously, considering different incidence polarizations (transverse electric polarization and transverse magnetic polarization) and different profile structures (continuous profile, 16-level profile and 8-level profile) of lenses, respectively. It is shown that focal shifts calculated by the rigorous method are larger than those made by the scalar theory, and focal depths calculated by these two methods are consistent basically, furthermore, focal depth and focal shift increase when F-number increases for both the rigorous electromagnetic method and the scalar method.

In this paper, based on the wavelet transform′s singularity detection principle, the transform coefficients at different scales were given to examine output I-V curve and compute the threshold current and other correlative parameters, such as the modular max WM2j and junction characteristic parameter m and so on. Making use of the above examined parameters combining with electrical derivative method, the reliability of semiconductor laser and quality of device can be compared directly and evaluated accurately. The theory and the experiment indicate that compared with the other classic methods, this method is distinct.

In this paper, the characteristics of long-period Bragg grating written on panda fiber are presented. Both the strain and temperature responses show a good linear characteristics at the strain range and temperature range investigated. The temperature-tuning characteristics of the long period grating (LPG) by using a thin film metal coating on the nude surface of the fiber as a heater are also demonstrated. In the range of 0～150 mA, the response curve of the LPG has good linearity with the square of the current, while the loss change is less than 0.3 dB.

Resonator fiber optical gyroscope (R-FOG) uses ring resonator to enhance the Sagnac effect, the detecting methods have open-loop and closed-loop, the phase modulator′s controlling signal has analogous and digital in circuit. Compared with analogous modulation, the method of digital closed-loop detection has a big dynamic range and high sensitivity. In resonator fiber optic gyroscopes by digital modulation, imperfect serrodyne′s reset amplitude V2π has influence on the rotation sensing errors and the scale factor non-linearity. The effects of imperfect V2π on the system are analyzed theoretically. If the amplitude is not exactly V2π, two electric fields, Ecross and Ebar cannot result in optimum destructive interference, thus the resulting waveform has errors. Based on the sum of electric fields expression in detector, numerical calculations of rotation sensing errors associated with imperfect serrodyne amplitude are given for resonator fiber optical gyro using two frequencies modulation. At last, some solutions for substantially reducing errors are presented.

The propagation properties of laser beams are of much significance in applications of laser technology. The analytical propagation equation for beams is one of the focuses in laser optics. Starting from the Collins formula, the properties of the off-axis Gaussian beam (OAGB) propagating through a paraxial ABCD optical system with an aperture are studied in detail. Moreover, the analytical equations for the off-axis Gaussian beam propagating through a paraxial ABCD optical system with hard-edged aperture, Gaussian aperture or cosine aperture are derived. The relationship among hard-edged aperture, Gaussian aperture and cosine aperture is discussed. The validity and advantage of results are confirmed and illustrated by numerical calculations. The difficulty of finding the analytical propagation formula of laser beams propagating through a paraxial ABCD optical system with multi-aperture is analyzed. It is shown that the difficulty is due to the existence of an error function in the analytical propagation formula for single-apertured laser beams.

The study on laser transmission and scattering characteristics in complex environments is the basis research of light scattering from target and environment. The severe attenuation caused by laser propagation in sand and dust storms was mainly discussed in this paper. The attenuation characteristic of laser was studied with Mie theory for single scattering of sand and dust particles with special size distribution. Based on Mie theory, the average scattering cross section, albedo, asymmetry factor, and phase function were calculated. The laser multiple scattering and attenuation characteristics of slanting transmission in the layering sand dust atmosphere were studied by using four-flux model method and Monte-Carlo method, and the relationship between attenuation and visibility in difference heights was also given. Finally, after considening of multi-scattering, numerical calculations of specify attenuation were made for laser signal of 1.06 μm in sand and dust atmosphere by using the above two methods respectively, and the results were compared to the condition of single scattering. It is shown that biggish error can be brought in the low visibility take no account of multiple scattering, and that the more layers of the sand and dust atmosphere is divided into for slanting transmission, the more accurate the result is.

Active laser imaging system, which can be of high resolution, anti-interference and three-dimensional (3-D) imaging, has been used widely. But its imagery can be disturbed by speckle and some other Gaussian noises. Speckle noise is a kind of multiplicative noise and the Gaussian noise is additive noise, and which noise on the dominating status is very important for building the model of noise suppression. So, in the paper, the statistic characteristics such as probability curve and gray mean variance ratio etc. in the imagery disturbed by speckle and some other Gaussian noises are analyzed firstly, then the different statistic characteristics effected by the two kinds of noises respectively are found. Based on these characteristics, the images of active laser imaging system are discussed, then the results show that the most imagery noise is speckle. At the same time, the speckle noise variance in this imagery is calculated.

In this paper, a new method of nanoparticle preparation by laser ablation of tiny wire is reported. Moreover, an archetypal equipment is designed and manufactured. In experiments, magnetism γ-Fe2O3 nanoparticles are prepared by laser ablation of 0.5 mm diameter pure iron wire in a mixture of nitrogen and oxygen. The prepared γ-Fe2O3 nanoparticles are basically spherical in shape and form chain-like structure because of their magnetism. Besides, the prepared nanoparticles are uniform in granularity with little agglomeration and the average diameter is about 19 nm. For comparison, preparation of γ-Fe2O3 nanoparticles by laser ablation of Fe bulk material is also conducted under the same condition. Laser ablation of iron wire can realize explosive evaporation of the target, which is different from that laser ablation of bulk iron target in mechanism and may cause the production increase greatly. The production rate of γ-Fe2O3 nanoparticles by laser ablation of iron wire is about 1.8 g/h under 400 W laser output, almost 6 times as much as that by laser ablation of bulk iron target under the same condition.

Layer manufacturing time in laminated object manufacturing (LOM) technology is determined by the cutting speed and cutting path of each layer. When the parameters of cutting process such as cutting power and cutting speed are defined, the manufacturing time of each layer is determined by the cutting (scanning) path. So it is most important to optimize the cutting path in order to improve the manufacturing efficiency. In LOM technology, laser cutting path optimization is in fact vacancy course path optimization. The mathematical model of vacancy course path optimization is set up in this paper. Because of the complexity of solving the model, the two algorithms of grading planning are presented: start points in cutting contour are solved by using an improved nearest neighbor algorithm; when start points are determined, the problem of the path optimization turns into the traveling salesman problem (TSP), which is solved by using an high-efficiency intellectual biological algorithm-the ant colony system algorithm. The results of algorithm show that the algorithm remarkably shortens vacancy course in LOM and the manufacturing efficiency of rapid prototyping is improved.

Laser cladding Co-based alloy coating (Co60) and Co-based alloy composite coating with 25(mass)% Cr3C2 particles (Cr3C2/Co) on low carbon steel substrate were obtained by 5-kW CO2 continuous wave laser. Effects of Cr3C2 particles on microstructure, micro hardness and corrosion-wear resistance of Co-based alloy coating were discussed. The results showed that the good laser cladding coatings were obtained in the test conditions. The Co60 coating is consisted of many γ-Co dendritic solid solution and eutectic structure (γ-Co and (Cr,Fe)7C3) between the dendrites. The Cr3C2/Co coating is consisted of undissolved Cr3C2 particles, many different shape rich-chromium carbides (M7C3,M23C6) and very finer dendrite and eutectic structure between the carbides. Addition of Cr3C2 particles alters the solidification characteristic of the laser cladding coating Co60, transforming the hypo-eutectic crystal mode of Co60 to hyper-eutectic crystal mode of Cr3C2/Co. Cr3C2 particles play a role of non-spontaneity nucleation, and many rich-chromium carbides are formed around Cr3C2 particles, fining the dendrite structure. Micro-hardness and corrosion-wear resistance in different corrosion media of the Cr3C2/Co coatings are obviously higher than those of Co60 coatings.

Composite coatings of Al2O3 nanocrystalline/Ni-based powder produced by transverse flow CO2 laser on Ni-based superalloy were introduced. With Olympus Pme-3 type optical microscope, Philip-XL 30 type scanning electronic microscope (SEM) and energy dispersive X-ray spectroscopy (EDS), the microstructure, chemical composition and distribution of nano particles of the cross-sections of the coatings were analyzed. The results showed that columnar dendrite grew perpendicularly to the interface without nano Al2O3 particles. And the growth morphologies of dendrite transformed from long columnar to short form by adding nano additives. Non-directional dendrite growth at the interface and equaxied dendrite across the section of the clad appeared with the additive amount of Al2O3 particles to 1%. The solidified microstructure was greatly refined because the nano Al2O3 accelerated nucleation ahead of the advancing interface of solid/liquid and held back crystal growth by its concentration. Nano particles prevented the formation of cracks in the coatings.

Based on Maxwell′s equation, spatially coupling wave equation of self-frequency-doubled (SFD) lasers with quasi-there energy levels was derived by virtue of the rate equation of quasi-there energy levels system and the slowly varying envelop approximation, with the situation that the media end pumped. Characterization of SFD Yb:YAB [YAl3(BO3)4] lasers typically pumped by laser diode (LD) was numerically simulated. The simulation showed that intensity of SFD harmonic increased quadratically with the increase of intensity of fundamental harmonic, while intensity of SFD harmonic and fundamental harmonic decreased sharply with the increase of temperature. Within the effective doubled-frequency length, there are different optimal crystal lengths for fundamental and SFD harmonic output being maximum, respectively. Influence of quality of pumping beam on the fundamental and SFD harmonic output of laser was quantificationally evaluated by means of M2 factor.

BIBO (BiB3O6) crystal is a novel nonlinear crystal, which has stable physical and chemical properties, high destroy threshold, and big nonlinear effective coefficient, so BIBO crystal can be used as frequency conversion device to obtain efficient second harmonic wave generation. In this paper, high efficient blue laser at 473 nm was generated by BIBO crystal inserted in a diode-pumped Nd:YAG (Y3Al5O12) laser at 946 nm for intra-cavity frequency doubling. A home made laser diode was used to end pump a piece of 2.2 mm long Nd:YAG crystal dopped with 1.0 at.-%. With 1.6 W pumped laser, 183 mW TEM00 mode stable blue laser output was obtained by a 5 mm long Ⅰ typed BIBO crystal, conversion efficiency up to 11.4%, which was about 45% higher than a 10 mm long Ⅰ typed LBO (LiB2O3) crystal.

The laser diode array (LDA) end-pumped intracavity doubling frequency high power blue laser is reported. Gain medium is composited Nd:YAG crystal, the temperature of which is precisely controlled by thermoelectrically cooled (TEC). The doubling frequency crystal used in the experiment is a LBO (LiB2O3) crystal cut in phase-matching type Ⅰ. The cavity is V type. This cavity is designed based on the facts that the thermal-lensing effect of the rod pumped by high pumped power is serious and the focal length of the thermal lens becomes shorter when the pumped power increases. According to the highest pumped power, the cavity is optimized so that the optimum mode-matched and high conversion efficiency are realized. When absorbed pumped power is 18.5 W, the blue laser output power at 473 nm is 1.38 W and the conversion efficiency of pumped light to doubling frequency light is 7.5%. The laser is simple and stable in structure.

A high pressure, short pulse duration XeCl laser was fabricated, and laser parameters were measured. Aiming at large volume and high gas pressure, the laser system adopted the ultraviolet preionization to produce glow discharge. The result was that the nano-second (ns) discharge pumped 308 nm excimer laser was realized in proportion of HCl:Xe:He=0.1%:1%:98.9% with the output pulse energy of 530 mJ and the minimal pulse duration of 13 ns. The rectangle facula is 2 cm×1 cm, the beam divergence is 3 mrad, and the maximal repetition frequency is 5 Hz.

The essentiality and necessity of pulse shaping to second harmonic generation (SHG) experiment of laser are analyzed. At present, the plasma shutter which has compact structure and good effect on the pulse shaping is a better method by which the high-quality short pulse can be obtained. The plasma shutter in which laser triggering gas breakdown is used to shape the laser pulse is devised. The principle is explained by using reflection and transmission of electromagnetic wave in plasma. Plasma shutter is used to shape the transversely excited atmospheric pressure (TEA) CO2 laser pulse. The TEA CO2 laser pulse with full width at half maximum (FWHM) of 60 ns and the nitrogen tail of several hundred ns is shorten to the pulse with FWHM of 30 ns and free of nitrogen tail. When adding plasma shutter to the SHG experiment using two crystals, the conversion efficiency is 12.9%. This figure is bigger than 2% which is gained without plasma shutter.

Employing an intense laser field coupling to the degenerate two-level system of cesium 62S1/2(F=4)-62P3/2(F′=5) transition in a cesium vapor cell, electromagnetically induced absorption (EIA) has been demonstrated via probe absorption spectra, at the same time, electromagnetically induced transparency (EIT) of V-type three-level scheme has been demonstrated on the F=4-F′=3 and F=4-F′=4 transition frequency. The EIA is affected by the intensity and detuning of the coupling laser. By analyzing the effect of optical pumping between Zeeman sub-levels on the EIA and the coherent interactions between multiple degenerate two-level atoms, it is shown that the optical pumping affects the population of different Zeeman sub-levels and the number of the involved two-level atoms, the coherent time between the sub-levels is then changed and the linewidth and intensity of the EIA are affected accordingly.

The absorption spectra and fluorescent spectra property of Cr3+, Yb3+, Er3+ co-doped phosphate glass were measured. Some basic properties of spectroscopic properties were calculated. The effect of Ce3+ and Cr3+ concentrations on the spectroscopic properties of the phosphate erbium glasses was also discussed. It could be concluded that the co-doped phosphate glasses of 2.8 mol-% CeO4 and 0.08 wt.-% Cr2O3 have the better spectral properties. On the other hand, the spectral properties are also affected by the valence change between the Ce3+ and Ce4+. Ce3+ is more favorable for the absorption of pumped light and energy transfer. The Cr3+, Yb3+, Er3+ co-doped phosphate erbium glass with fluorescent lifetime of 8 ms and stimulated emission cross section of 0.8×10-20 cm2 was achieved in the study. This provided good basis for the next laser experiments.

In order to determine optical constants of azo nickel chelate (Ni(azo)2) thin film, the ellipsometric spectra of Ni(azo)2 thin film, which prepared by spin-coating method on a single-crystal silicon, have been investigated on a scanning ellipsometer with the analyzer and polarizer rotating synchronously. The complex refractive index, complex dielectric function, absorption coefficient and thickness of the film were obtained through drawing up simulation. The absorption spectrum is discussed. These results indicate that the film has a good reflective and absorption characters at the wavelength of 650 nm and is promising for application as recording media for digital versatile disc (DVD-R).

Magnetization transition from in-plane to perpendicular caused by temperature changes was investigated for the magnetostatically coupled multilayer films (GdFeCo/AlN/DyFeCo). The results indicate that the magnetization orientation of the readout layer (GdFeCo) is affected by the saturation magnetization and the effective anisotropy energy, but the transition occurs mainly as a result of the change of the saturation magnetization. At high temperature the saturation magnetization and the demagnetizing energy of the GdFeCo layer decrease, then the transition of the GdFeCo layer from in-plane to perpendicular magnetization occurs due to the magnetostatically coupled interaction. The magnetization direction of the readout layer changes rapidly in a narrow temperature range.

The reception of laser pulses is one of the key technologies in the laser rangefinding. The stable and effective detection and the increased ability of anti-jamming are the main problems to be solved. In this paper, an elementary study on walk error in pulsed laser range finding is carried out. The photodiode response time is affected by the change of depletion layer width, which is caused by the interaction between depletion layer charges and photo-induced carriers. The basic theoretic model is set up to explain this process, and two characteristic parameters unit optical power sensitivity K and unit time jitter Δτp0 are introduced. The approximate relation between the photodiode response time, its jitter and the laser pulse power projected on the detector is obtained respectively, which are successfully employed to explain the walk error phenomena in the self-triggering pulsed time-of-flight laser rangefinding experiment.

A simple method using resonator critical stable point is applied to measure the thermal lens focal length of a flashlamp-pumped continuous wave (CW) Nd:YAG (Nd:Y3Al5O12) laser. By measuring output power at special critical stable point, the laser rod thermal lens focal length can be calculated. The method can also be used to obtain the thermal lens radial and tangent focal length, fr and fθ, respectively. This method is simple and practical, it is applicable especially for the measurement of thermal focal length of high power laser. Because of using the critical point of the resonator with laser on, this method is closer real case than without laser, the measurement is more accurate. The measuring deviation of the method comparing with probe beam method is within the order of ±10%. It is less than that of the unstable-resonator method that is in the order of ±20%.

In this paper a new technique of differential absorption lidar (DIAL) was presented for environmental SO2 measurements. The fourth harmonic of Nd:YAG laser was used to pump CH4 and D2 gas cell, and their first Stokes Raman-shifted wavelengths of 288.38 nm and 289.04 nm were gotten. Laser beam of 289.04 nm is rather strongly absorbed by SO2, but another laser beam of 288.38 nm is weakly absorbed. This wavelength pair of 288.38 nm and 289.04 nm can be used to measure environmental SO2 concentrations. Based on this technique, a SO2 DIAL was constructed. SO2 actual measurements and primary studies were also carried out at lidar located site. Measurement errors were analyzed and evaluated. SO2 concentrations measured by SO2 DIAL are comparable with results obtained by SO2 analyzer.

To essentially eliminate the measurement errors arisen from light source power fluctuation, a measurement method of solution concentration was proposed. The method is based on the relationship between transmission optical spectrum central wavelength of fiber Fabry-Perot (FFP) interferometer and the refractive index of medium in the cavity, as well as the relationship between solution refractive index and its concentration. Such a measurement system was developed. A tunable fiber optical Fabry-Perot (F-P) filter was used to collect the sensing data. Different concentrations of a set of alcohol solution, with the concentration being from 5% to 80%, were measured experimentally. The maximum absolute measurement bias is no more than 0.003%. This measurement system possesses following advantages

Sampled fiber Bragg gratings (FBG) have many applications in wavelength division multiplexed (WDM) systems, and can be filtering or chromatic dispersion compensating simultaneously in multiple channels. Periodic phase-only sampling is a preferable approach to the design of multi-channel FBG, which facilitates the fabrication of multi-channel FBG. However the periodic sampling function replicates a given chromatic dispersion function, as a result, all the channels are identical and the resulting device cannot compensate for the dispersion slope. An optimization method is presented to design weakly aperiodic phase-only sampled gratings, and a set of chirp controlling parameters, which are related to chromatic dispersion in each channel, are introduced to compensate the chromatic dispersion and the dispersion slope simultaneously. By using the simulated annealing method, an optimized set of the relative channel phases can be found to reducing the difference between the minimum and the maximum values of the amplitude modulation of the sampling function. Then, an iterative procedure, called the Gerchberg-Saxton algorithm, is applied to remove the amplitude modulation of the sampling function, and the aperiodic phase-only sampled grating is synthesized successfully. Finally, the complex reflection spectrum of the aperiodic phase-only sampled grating is simulated by using the transfer matrix method. All time delay curves in all channels are overlapped in one figure for a visible comparison of their slope, and the result shows that the dispersion compensation capacity in each channel can match with the dispersion slope of fiber link exactly. However, as a price of the Gerchberg-Saxton algorithm, the additional channels appear at both sides of the reflection spectrum.