The volume Bragg grating (VBG) recorded in photo-thermo-refractive (PTR) glass is used as longitudinal mode selection element,and use the narrow filter which consists of transmitting and reflecting gratings to select longitudinal mode. We have obtained 1053 nm single frequency mode with 100% single longitudinal mode rate,2 mJ pulse energy in Nd:YLF laser. The experimental results show that the volume Bragg gratings work as both mode selector and output coupler,therefore simplify the structure of the cavity structure and improve the anti-interference ability. The laser also has the potential of high-power output.

Research on intra-cavity second harmonic generation using periodically poled stoichiometric LiTaO3 (PPSLT) based on quasi phase matching (QPM) is reported. Periodically poled crystals with different lengths (3.5 mm,5 mm,10 mm) are compared and examined. For the 3.5 mm PPSLT,1445 mW fundamental wave of 1064 nm could be achieved in condition of 2500 mW pump of 808 nm,then 760 mW green light of 532 nm could be achieved through second harmonic generation (SHG). Problems on system temperature control that affect SHG efficiency are also analyzed.

A novel ultraviolet (UV) femtosecond laser source is experimentally studied based on the large-mode-area photonic crystal fiber femtosecond laser system. Walk-off effecting due to the group velocities mismatch between the fundamental wave and the second harmonic is analyzed theoretically. The average power and the conversion efficiency of second harmonic generation with different crystal length are compared experimentally. Second harmonic generation (SHG) and fourth harmonic generation (FHG) of 1040 nm fundamental wave are demonstrated,and high power UV femtosecond laser is obtained out of cavity at the repetition rate of 50 MHz by using two pieces of Type-Ⅰ BBO crystal,length of which is 5 mm and 0.18 mm respectively. The fundamental wave is generated from the photonic crystal fiber amplifier with pulses duration of 110 fs. At the average power of 20 W,8.88 W frequency doubled green laser wave is obtained with the conversion efficiency up to 44.4%,and 656 mW FHG UV laser is also achieved with a single pulse energy of 13 nJ. The conversion efficiency from the second harmonic (SH) to the fourth harmonic (FH) is up to 7.39% at the maximum power.

A watt-level Yb-doped ps fiber laser in tri-stage master oscillator power amplifier (MOPA) configuration is investigated. The first stage is a semiconduttor saturable absorption mirror (SESAM) passively mode locked fiber laser with a low average output power of 9.2 mW. A fiber Bragg grating (FBG) is utilized as the output laser cavity mirror. The second stage is an Yb-doped single mode fiber amplifier with a moderate average output power of 108 mW. The last stage is a double clad Yb-doped power amplifier which increases the average output power to 1.9 W. The center wavelength of the mode locked pulse is 1064 nm with a pulse width of 36 ps. The pulse repetition rate,the peak power and the energy of a single pulse is 29.6 MHz,1.8 kW and 61 nJ,respectively. A small dip located at the center laser wavelength is observed on the output spectrum,which is considered to be caused by the high reflectivity and the narrow bandwidth of the FBG.

Temperature and thermal stress of high-power photonic crystal fiber (PCF) lasers were numerically simulated and analyzed. Equivalent thermal conductivity was introduced to simplify the structure of photonic crystal fiber,and then three dimensional temperature field model of photonic crystal fiber laser was established. By using the finite element method,the distributions of the temperature in fiber and the thermal stress in end-surface of fiber were numerically simulated and analyzed with natural and forced convection heat transfer,respectively. The results show that the selected PCF can support the pumped power of 1000 W under forced convection heat transfer,but improving the parameters of fiber is required to further enhance the output power by supporting higher pump power.

A rapid optimization algorithm to determine the selective value area of input mirror reflectivity and output mirror reflectivity for the optimum of high power fiber lasers is proposed. Under slope efficiency optimization selection criterion,taking Yb3+-doped fiber lasers as examples,the numerical simulation results indicate that computing time using the rapid optimization algorithm of reflectivity in high power fiber lasers is less than 8% of time using traditional algorithm,ladder errors are well avoided and improvement of precision is obtained. The numerical simulation results also indicate that under the conditions,the selective area of mirror reflectivity of fiber lasers with forward pumping is largest,the selective area of mirror reflectivity of fiber lasers with bidirectional pumping takes second place and the selective area of mirror reflectivity of fiber lasers with backward pumping is smallest.

A ring-shaped all fiber tunable Yb-doped fiber laser with tuning range over 20 nm is demonstrated by using a fiber Mach-Zenhder interferometer as an intra-cavity filter which is constructed with two 3-dB optical couplers. The method for fabricating the fiber Mach-Zenhder interferometer is detailed. The fiber laser has a moderate milli-Watt level output power over the whole tuning range from 1050 to 1071 nm,a side-band suppression ratio greater than 45 dB,and a bandwidth less than 0.1 nm.

The choice of doping radius is the key of ensuring the part-doped fibers to play an effective role in mode selections. This paper begins with the normalized mode distributions. By comparing the intensity distributions of different fiber modes,the use of smaller or larger doping radius is deemed not to be conducive to the fundamental mode selection. And then from the views of saturation gain and mode power allocation,the influences of doping changes on the mode ability to gain access and the ability to power extraction are analyzed in detail. The varying of doping radius changes the interaction opportunities between the mode field and the population inversion,and then changes the mode ability to gain access as well as its mode power output. When the gain doping optimally overlaps with the fundamental mode distribution,and the fundamental mode intensity gets the advantage over other modes,the access gain of the fundamental mode will exceed any other mode,and its power will reach the maximum value. Some quantitative results have indicated that selecting about 0.6 relative doping radius for step-index fiber can help us to efficiently extract the fundamental mode power.

Based on the Fabry-Perot (F-P) cavity model with three mirrors,the theoretical model of the triple feedback effect of non-alignment cavity was established,numerically simulated and experimentally validated. The factors affecting the power turning properties of the self-mixing interference were analyzed under three conditions:1) double and triple feedback effect of alignment cavity;2) double and triple feedback effect of non-alignment cavity;3) the feedback effects when a λ/4 plate was inserted into the external cavity. The experimental results are in good agreement with theoretical analysis. It is shown that,the resolution of the self-mixing interference system can be up to λ/6;the self-mixing interference signal is related with the reflectance of the cavity mirror,the alignment of the cavity mirror and other plates in the external cavity;the self-mixing interference signal in condition (3) is similar to that of the non-alignment cavity;the information of the displacement direction of the reflector is contained in the self-mixing interference signal of double and triple feedback,so it could be easily distinguished.

Theory simulation and experiment was carried out for thermal recovery of the multi-segment amplifiers (MSA). New design of time delayed water cooling was developed isolate the heat transferred from flashlamp to Nd glass which contributes more than half of the unwanted heat of Nd glass.The delayed time of 4×2×3 amplifiers is about 10 minites.

We investigate two important aspects of the terahertz imaging technology. They are the pulsed terahertz spectral imaging and the continuous wave terahertz imaging. Experimentally,we obtain terahertz images by these two imaging systems. We compared many aspects between the pulsed imaging system and the continuous wave imaging system,such as imaging mechanism,system resolution,system noise,imaging speed,information capacity,price,complexity,portability and their applications. Experimental results show that the pulsed imaging system has an obvious advantage that it can get more spectral information,on the other hand the continuous wave imaging system is simple and compact. The two systems have their own strong points,and are complementary to each other. In addition,we present an identification method based on the terahertz multi-spectral imaging technology.

The electron acceleration mechanism in a wake of the plasma with a variety of adiabatically attenuating density modes is checked by numerical simulation. The simulation results prove that the new electron acceleration mechanism owing to the density attenuating is operated well,and the properly choice of the density attenuating mode can greatly improve the quality of accelerated electrons beam. And the results indicate that the efficiency of the electron acceleration mechanism in a wake of the plasma with a variety of adiabatically attenuating density modes is not dependent on the very high intensity of the laser. Experimental verification is convenient.

Based on the principle of the photoelectron angular distribution imaging spectrometry,the photoelectron image is investigated by using single-photon resonance and three-photo ionization. The physics sense of the angular distribution of the photoelectron is analyzed. The impact of the photoelectron interference effect in the process of multi-channel ionization on imaging spectrometry is emphasized,the relation between the information of the atomic states and the photoelectron angular distributions is discussed in detail.

A method for fabrication of microlens arrays using soft lithography is reported. The master of the microlens array is fabricated by traditional thermal reflow technology. The microlens array is first transferred on an elastomeric mold using replica molding method,and then the elastomeric mold with microlens structure on its surface is imprinted on the glass substrate with ultraviolet (UV) curable polymer on it. After the UV glue was fully solidified,the final microlens array is formed on the UV curable polymer of glass substrate. The microlens array is tested and it is found that it has uniform focusing function. This technology has great potential application for fabrication of polymer microlens array with low cost and high throughput.

Based on the laser gyro digital integration circuit,the coefficients between the null shift and current discharge difference,current discharge sum,beam intensity difference are got by precision controlling the parameters changing. Through long time tests to laser gyro,the infection,caused by the precision of these parameters,is got by calculating. In order to make the conclusion validly,the two laser gyros which are different in precision are selected to be tested. The resucts show that the digital integration circuit which is working under now mode infects the precision of laser gyro no more than 1%.

Potassian vapor was irradiated in a glass fluorescence cell with pulses of radiation from a optic parametric oscillator (OPO) laser ,populatingK2(1Λg) state by two-photon absorption. Energy transfer in K2(1Λg)+K collision is studied by using molecular fluorescence. The K number density was determined by the optical absorption measurement. The decay signal of time-resolved fluorescence from 1Λg→11Σ+u transition was monitored. The effective lifetimes of the 1Λg state can be resolved. The plot of reciprocal of effective lifetimes of the 1Λg state against K densities yielded the slope that indicated the total cross section for deactivation and the intercept that provided the radiative lifetime of the state. The radiative lifetime 20±2 ns is obtained. The cross section for deactivation of the K2(1Λg)molecules by collisions with K is 2.5±0.3×10-14 cm 2. At the different K densities ,the time resolved and the time-integrated intensities of the resulting K23Λg→13Σ+u line were measured. The absolute values for K2(1Λg)+K→K2(3Λg) +K collisional transfer cross section has been obtained. The cross section is1.1±0.3×10-14 cm2.

The life of laser-induced plasma is usually in the μs region,and it is necessary to study the temporal evolution of the plasma in order to optimize the signal detection. Calibration curve is the basis of quantitative analysis,which closely relates to the sensitivity and accuracy. The plasmas were induced by a focused,pulsed laser. The emission spectra of plasmas were then dispersed by an Echelle spectrograph and detected by an intensified charge-coupled device (ICCD). Graphite was the major constituent of the sample,and Ca,Al,Na,K elements were added to pellet the sample respectively. The spectra including the emission lines of Ca,Al,Na,K elements were presented. The temporal evolution curves of the plasmas were obtained via the experimental system of using the gating periods of 100 ns of ICCD. The calibration curves of the lines intensities were obtained. The calibration curves were also analyzed,whose slope are different for the spectra line of the same element of the sample at different wavelength.

Besides a channeling radiation there is an undulator radiation in an periodic bent crystal. A sine-squared potential is introduced to describe the motion behaviours of the particle in the system,the particle motion equation is reduced to the pendulum equation with a dampping and a force terms in the classical mechanics frame and the dipole approximation. The bifurcation and the chaotic behaviours of a separatrix orbit with the Smale horseshoe are analysed by Melnikov method. The critical condition of system through to a chaos is found. It shown that the critical condition of the system entered in a chaos is related to its parameters,provided regulating a parameters of the system,the chaos can be avoided or controlled in principle. Thus the effective export of X-laser or γ-laser can be assured furtherlly.

The intensity correlated quantum imaging experiment and application with thermal light restricted by the high bright thermal light to some extent. The coherence time is shorter,and the number of photons in a coherent cellular is smaller because of true thermal light,so true thermal light is replaced by pseudo-thermal light,which can be obtained by a laser transmitting through rotary ground glass. When a nanosecond laser is used,the source simulates the intensity fluctuation of true thermal light extremely,and obeys to Gauss statistical distribution property. In addition,the important property is that the measurement to intensity fluctuation isn’t limited by finite pass band of the photo-detector. Even in the case of slower response detector,the intensity fluctuation can be recorded accurately,and the light field is cross-spectrally pure.

The control of fusion splicing energy and heating time is a key to avoid air-hole shrinkage in fusion splicing process for photonic crystal fibers (PCFs). A mathematic model of mechanics characteristic in fusion splicing process for PCFs is developed from classical mechanics theory. Furthermore,the distortion of air-hole and fusion splicing loss are analyzed. Experiments and analysis show that distortion of air-hole may be controlled by adjusting fusion splicing energy and heating time. According to theory analysis results,fusion splicing experiment is carried out. The experiment result shows a good consistency with the analyses result.

Dynamical simulation on coherent beam combining of multiple fiber amplifiers based on stochastic parallel gradient descent (SPGD) algorithm is carried out. The influence of phase noise with different amplitude and frequency on the control bandwidth is computed,and the relationship between control bandwidth and laser numbers and iteration rates of the algorithm is analyzed. The results show that the control bandwidth decrease as an increase in the amplitude or frequency of the phase noise,the value is in proportional to N-4/3 and iteration rate,where N is the laser numbers. The computing results present a reference for scaling coherent beam combining based on SPGD algorithm to high-power,large-number of laser beams.

Infrared femtosecond laser has highly spatial coherence,and order walk-off will happen behind the phase mask. In this paper,the interference patterns in the core are modeled by using two beam interference theory,and fiber Bragg gratings are fabricated in the unphotosensitive Tm-doped fibers using 800 nm femtosecond radiation. In the end,the simulative results are compared with the experimental results.

An experiment study on the bottle beam which are produced by the interfering of the two Bessel beams generated from the axicons is proposed. Based on the “bottle beam with Talbot effect generated by interfering Bessel beam”,the three-dimensional optical intensity distribution of the superimposed optical field along the propagation distance and the intensity evolution of the bottle beams in a complete period are simulated numerically. In the experiment,the bottle beam is generated by two interfering Bessel beams with different radial wave vector. Our result fits well with theoretical calculation and numerical simulation.

Based on the Fresnel diffraction integral,the intensity distribution of Laguerre-Gaussian beam transmitted through a single-slit has been investigated. It is found that the diffraction fringes of vortex beams will dislocation and shift in the diffraction field,and the direction and the amplitude of the shifts is closely related with the topological charge. These results have been demonstrated experimentally in this paper. In addition,the spiral spectral of vortex beams transmitted through the single-slit has also been discussed. It is shown that the spiral spectrum will be broadened due to the limit of the single-slit,and the broadening depends on the topological charge,the beam size,and the width of the single-slit.

The influence of dispersive magnetic permeability on spatiotemporal instability (STI) in metamaterials is identified based on the Drude model. In the case of co-existence of cubic nonlinearity,pseudo-fifth-order nonlinearity and self-steepening,a generic expression for instability growth rate is derived. It is found that in the negative-index region,the pseudo-fifth-order nonlinearity increases the range of spectrum and the gain value of STI for the case of self-focusing material while it do opposite for the case of self-defocusing material,which are different from the results in ordinary materials,in the negative-index region,the pseudo-fifth-order nonlinearity will suppress the emergence of STI for the case of self-focusing material,which exhibits the same features for the case of ordinary material. In any way the self-steepening in metamaterials always tends to suppresses appearance of STI regardless of its sign.

By using the theory of partially coherent light and the basis set of biorthogonal elegant Hermite-Gaussian (EHG) modes,the analytical expressions for the mode coherence coefficients (MCCs) and M2-factor of laser light have been derived. The relation between the coherent-mode representation of laser beams in terms of EHG modes and that in terms of corresponding standard Hermite-Gaussian (SHG) modes has been built up. Furthermore,two typical application examples have been discussed. It can be shown that the MCCs in EHG coherent-mode representation can be obtained by use of the MCCs in SHG coherent-mode representation;for the case of the modes with the same orders having the same weight factors,the beam quality of the laser beams that are made up of a superposition of mutually uncorrelated EHG modes is better than that of mutually uncorrelated SHG modes.

For beam passing through cavity mirror twice in multi-pass amplifier laser facility,deformable mirror is often applied at location of cavity mirror for the goal of improving correction range. However,multi-pass amplifier with U-turn for improving optical quality has its own feature different from other facilities. Beam has 90° rotation and size change between 1-2 pass and 3-4 pass propagation. A new mathematical method is described to prove the solution existence of cavity deformable mirror and the application of cavity deformable mirror is verified in Xingguang-Petawatt (XG-PW),facility with U-turn reverser. The results are important for the adaptive optics system design of succeeding large-scale laser facility.

The process of the bottle beam generated from an axicon-lens system is described by a novel method based on the ray-tracing. The intensity distribution of the bottle beam in propagation is analyzed. Using ray-tracing,the influence of the focal length of the lens on the sizes of bottle beam is analyzed. The result shows that the sizes of bottle beams increase with the increasing of the focal length of the lens. Experimentally the bottle beams are generated by using an axicon-lens system. The beam patterns are captured in different propagation position,and the evolution and transversal intensity distribution of bottle beam is analyzed. The experimental results fit well with the theoretical simulation. Therefore,we can choose right size bottle beam to manipulate different particles.

This study designed to establish a complete transaction of dorsal corticospinal tract SD rat model and discuss about the effect of low power laser irradiation on neuron regeneration after acute spinal cord jury. 30 SD rats were equally and randomly divided into two groups. Complete transaction of dorsal corticospinal tract was done to each rat. Then,irradiation group was undertaken local consecutive low power laser irradiation 15min after surgery and lasted for 14 days. Compared to irradiation group,there was no postoperative irradiation after surgery in control group. After infusion,1 cm length of spinal cord,which was above and below T8 level,were extracted on the 3rd,7th and 14th day after surgery. Hematoxylin and eosin stain and immunofluorescence stain were use for evaluation. At two weeks after surgery,the value of gial scar area was less than that of control group with statistically significant differences. There was intensive expression of glial fibrillary acidic protein (GFAP) and Chondroitin Sulfate (CS56) around the injury area in control while sparsate distribution of GFAP and CS56 was found in irradiation group. An amount of fibriform Neurofilament (NF) expression associated with regularly Growth Associated Protein 43 (GAP43) expression were located around the injury area,However,scrambled and slight GAP43 and NF expression were found in control. The result of our study showed that low power laser irradiation can improve regenerate of axon and decrease formation of gial scar area during the acute stage of spinal cord injury.

To solve hyperspectral image′s problems of the high dimensionality,the huge amount of data,and the real-time solution and so on,a real-time hyperspectral dimensionality reduction method is brought forward. Based on singular value decomposition (SVD) method,hyperspectral dimensionality is reduction,and finish the design of the chip system with top-down method. The chip system is divided into autocorrelation module,SVD module,feature extraction module and dimensionality reduction module. It completes the design,simulation and verification of these modules. The results indicate that the hyperspectral image reduced to 1/3,classification error is only 0.2109 percent after the dimensionality reduction. All of this show,the SVD method for hyperspectral dimensionality reduction is effective.

Four derivatives-based autofocus criteria functions are proposed through bringing several applicable computational methods of derivatives into the study of autofocus algorithms for the digital holographic imaging. By analyzing the transfer of noise produced during recording in phase shifting digital holography,the impact of noise on the derivatives-based autofocus algorithms is investigated. The results from the simulation and experiment indicate Prewitt gradient (PRG) and Tenebaum gradient (TEG) criteria functions,together with the angular spectrum reconstruction routine can form two types of efficient and reliable autofocus algorithms.

The volume holographic correlator (VHC) can perform multi-channel inner products calculation. By encoding the input function and two-dimensional Walsh functions into input image and stored images respectively,a method that using volume holographic correlator to perform two-dimensional discrete Walsh transform (DWT) is proposed. This method has a potential to approach a high processing speed. By use of speckle modulation and interleaving method,the calculation accuracy can be improved. An experiment is carried out,and the correspondency between experimental results and theoretical ones proves the effectiveness of the method.

In order to resolve the problem that the silicon wafer cannot be divided after laser cutting for heat effect,water is used as assistant material to cut the silicon wafer. The influence of laser and water parameters are analyzed. The technique can avoid the influence of water wave. The results of experiment show that the usage of the water as the assistant material can achieve the purpose perfectly for the cool and insulation effect of water.

Ultra-low carbon bainitic (ULCB) steel plates with 12 mm thickness were welded by using CO2 laser-gas metal arc (GMA) paraxial hybrid process and multipass technique. The experimental results indicated that the good weld can be obtained by controlling the change of heat input on each pass when adopting three passes welding. In hybrid welding process,the focal point position is very important for the first filling pass and should be in the scale of the rootface. For the other filling passes the focal point position could be changed in a large scale. At the same time,in order to increase the utilization of laser energy,the higher wire feeding rate was used. Furthermore,the mechanical property tests showed that the tensile strength of weld in laser-GMA hybrid welding was over 95% as much as that of the base metal,and even to exceed partially the tensile strength of base metal. The tensile strength of the joint is 829.5 MPa when the specimens were failed in base metal. When the specimens were failed in welds,the defects led the specimens to fracture mainly.

A component is fabricated with Fe314 alloy powders on the substrate of 45# steels. The interlaminar distributing structures,the microstructure in different regions and mechanical properties of components are investigated. It is indicated that forming layers are stacked up like ladder shapes in aspect of microstructures which are mainly constituted of tiny compact equiaxed grains with distribution of some flat grains and columnar grains on the substrate. Furthermore,the hardness of components is low accompanied with high plasticity and ductility in aspect of mechanical properties because of the composing phases of austenite. There is no appearance of cracks under 690 MPa maximum residual stress,which has shown a high crack resistance is obtained through laser rapid forming (LRF) with Fe314 alloy powders.

Brazing diamond grits to steel substrate using Ni-based filler alloy was carried out via laser in an argon atmosphere. The brazed diamond grits were detected by scanning electron microscopes (SEM),X-ray diffractomer (XRD) and X-ray energy dispersive spectroscopy (EDS). The formation mechanism of carbide layers was discussed. All the results indicate that high strength bonding between diamond grits and the steel substrate has been successfully realized because the chromium in the Ni-based alloy segregated preferentially to the surface of the diamond to form a chromium-rich reaction product Cr3C2,and the bond between the alloy and the diamond is established through the reaction product.

We performe dynamics and thermodynamics analysis on the formation of nanodiamonds (NDs) produced by pulsed-laser ablation (PLA). The analysis on physical and chemical difference arise from two PLA processes based on laser parameters and synthesize methods are carried out,and the equilibrium size is also discussed upon thermodynamics factor as well as the growth velocity,growth time,and the final size of NDs are calculated using the Wilson-Frenkel growth law. The result shows that the radius and density of plasma plume determine the cooling velocity,and the growth time correlates with the cooling velocity when the temperature and pressure are high enough to meet the conditions of the stable growth of NDs. The calculation on the lowest free energy also indicates the formation of NDs is reasonable. Theoretical calculations are in good agreement with experiment results and give a well explanation on the formation of ultrafine NDs.

Ablated particles and ambient gas atoms are assumed to be rigidity-spheres. In order to investigate the influence of substrate on the density-reversion time of environment,the propagation of Si particles generated by single pulsed laser ablation through ambient He gas with 1000 Pa is simulated via Monte Carlo method. The results show that the density-reversion time of the environment is 1713.2 μs and 1663.2 μs respectively when the Si particles are absorbed and rebounded completely by substrate. With increasing critical adsorbing velocities of the substrate,the density-reversion time firstly increases and then decreases.

A testing device of laser-induced damage threshold (LIDT) with the combined irradiation of different wavelength pulse was built. The damage morphology and the laser-induced damage threshold of 1064 nm and 532 nm anti-reflection film (ARF) were researched by 1064 nm pulse only,532 nm pulse only and 1064 nm with 532 nm pulse combined irradiation. The result showed that the damage morphology of samples caused by 1064 nm and 532 nm pulse combined irradiation was similar with which of the 532 nm pulse,and the 532 nm pulse plays a leading role in the factors that induce damage. The LIDT of 1064 nm pulse is higher than one of 532 nm pulse,that of 1064 nm and 532 nm pulse combined irradiation is in the range between 1064 nm pulse only and 532 nm pulse only.

Laser damage threshold and damage morphology at the wavelength of 1064 nm are tested in vacuum,air,O2,N2,He2 environments by using 1-on-1 testing method. The results show that compared to normal atmospheric conditions,anti-reflection films(ARF) have a decreasing laser induced damage threshold under vacuum environments. The morphology of the damaged sites showed a particular difference under two conditions. In vacuum environment with a few O2,N2,He2,laser induced damage threshold of anti-reflection films increased. Different gas environments and gas pressure result in different laser induced damage thresholds and damage morphology.

To study the influence of film on the characteristics of subwavelength grating,the growth of 100 nm Au film on the surface of subwavelength grating with sine groove shape and 80 nm groove depth was investigated. It was shown that the growth was profiling copy,the sine groove and periodic were keep unchanged almost. When sine duty cycle increased,the groove depth reduced and uniformity of groove depth got worse. The shadow effect generated by the microstructure of grating was proposed to explain these variations. The effect of sine duty cycle increasing on the spectrum of guided mode resonant filters was investigated too.

It is important to decrease the statistical error for improving the measurement precision of Raman lidar for the large statistical error of the Raman backscattering signals. An adaptive filter signal processing technique is applied to the Raman lidar for atmospheric CO2 measurement by subsection,and the result of the statistical error of the atmospheric CO2 mixing ratio changes little with detecting range in each subsection. After signal processing by the technique,we obtained the high precision of Raman lidar measurement of atmospheric CO2 concentration at night in Hefei. The maximum statistical error of atmospheric CO2 concentration was 2.5% from 1.5 to 5 km,5% form 5 to 8 km,and 10% from 8 to 10 km. The technique also can be used to determine the number of laser shots necessary for a desired statistical accuracy and spatial resolution.

According to thermal expansion principle,a novel real-time method is proposed in this paper for determining the glass transition temperature (Tg) of thin polymer films based on the attenuated total reflection technique. The method is that the changing values of the refractive index and the thickness of the polymer film can be determined with the ascending temperature using the real-time system. Experimental results definitely show that curves of temperature dependence of the thermal expansion coefficient (β) and the refractive index (dn/dT) change discontinuously and exist a same intersection point. The temperature of intersection point is the polymericTg. With host-guest DR1/PMMA,the measurement procedures and experimental results are given. The repeatability and reliability of measuring Tg of polymer by this method are examined.

A novel approach and system for measurement of bidirectional reflectance distribution function (BRDF) based on optical fiber array in hemispheric space are proposed. With a fiber array composed of numerous multimode fibers located uniformly in a hemisphere,the angular distribution of surface optical reflectance in tri-dimensional space is transformed into a two-dimensional planar image. By collecting the image using a CCD camera and going though a corresponding data processing,a fast measurement of BRDF can be realized. Furthermore,the laser beam is transmitted and guided by fibers to irradiate the sample surface in various incidence angles. Primary measurements and analysis of surface reflectance of varied substance along with various machining process are carried out with this system. The results indicate that,comparing with conventional measurement systems,this novel one can avoid the measuring errors generated by the fluctuation of laser power and the sensitivity of the detector,as well as dramatically shorten the acquisition time. In addition,a compact configuration eases the measurement procedure consumedly.

A novel method based on the scanning spectrum system is proposed to calibrate the compensator. One multiple-order half wave plate is added to be used as a benchmark of the retardation. Any retardation between 0 and λ can be measured in high precision. The method can avoid errors caused by the light intensity measuring method,and moreover it can measure the zero-order retardation which the scanning spectrum method hardly accomplished. In the experiment,a compensator is calibrated based on a multiple-order wave plate at 633 nm. It is demonstrated that the retardation measuring precision is 0.45 nm in 0 and λ while the maximum error is less than 3.2 nm between the two positions.

A Rayleigh-Raman-Mie lidar (RRML) signal detection and optical receiver unit is constructed,the principle of lidar design is emphatically introduced,the design is based on the simulated calculation on atmosphere backscatter signal. The purpose of the signal detection unit is to improve the signal to noise ratio (SNR) of the lidar signal. By rational design the signal detection and optical receiver unit,use extremely sensitive R4632 photomultiplier tube (PMT) and photo counting method,a good SNR of Raman and Rayleigh signal could received. Through construct the PMT gating control and signal attenuation unit,a linear detection of aerosol and cirrus signal is received. Finally,the experimental result shows the rationality of the signal detection and optical receiver unit design method.

This paper studied the diffuser panel used for onboard calibration for satellite optical sensors. In order to investigate it’s stability and the adaptability under spatial environment,a series of environment simulation tests such as vibration and shock,temperature cyclic,vacuum bakeout and UV/VUV were planed and implemented. The diffuser’s optical properties were retentive after tests. The difference of reflectance at 350nm before and after UV/VUV test is within 3%. Analysis shows that some degradation of optical properties under UV radiation has been linked to degradation of contaminants,which can be prevented by improvement of production protocol and environment control. At the same time,the diffuser panel goes though space level mechanical environment tests. So,the space stability of the diffuser panel used for onboard calibration can satisfy the spatial application demand.

Thermal lens effects are severe for Nd:GdVO4 laser crystals with a end-pumping scheme. A 532 nm laser is used as a probe beam in experiments. By detection of the far-field image of the probe beam,the thermal effect could be measured. A model is presented using beam interference theory. Based on this model,the phenomenon at far-field is explained and a new formula for calculating the thermal focal length is formed. Thermal lens measurements are also performed using a resonator stability method. The results agree well with the beam interference model and the thermal focal length formula.

A precise pose monitor is required for high precision target positioning in inertial-confinement-fusion (ICF) experiments. Conventional visual monitoring methods are sensitive to illumination and target pose and often need artificial judgment. This paper introduces seale invariant feature transform (SIFT) algorithm into ICF target monitoring domain and implements an on-line target monitoring method based on SIFT features matching. The experimental results of an on-line setting demonstrate that the translational and angle accuracy are better than 6 μm and 0.5′,respectively.

The present optical circulator has a variety of defects,such as,the angle errors among constituent components,its failing to eliminate the optical axis orientation errors of half-wave plate,and its complexity in installation and debugging. In order to overcome these shortcomings,we devise a dual-wave plate axis asymmetric structure which can reduce or even eliminates errors. Further,we design an error self-healing high-isolation quasi-four-port optical circulator based on the strucutre. Through theoretical analysis,Jones matrix calculation and MATLAB simulation,we find its insertion loss is minimum among existing optical circulators,and the isolation can increase 5-8 dB.

Free-space optical communication (FSOC),which features the large capacity,high data transmission rate,high anti-EM interference capability,good security,low power consumption,small dimension and simple structure,is the tendency of the communication between ships in the future. This paper studies the simulated moving platform of the ship-borne laser communications system,which mainly consists of four parts:a horizontal,a vertical,a rotating and a swing moving platforms,simulating ship′s four swaying motions in wave:surge,heave,roll and yaw respectively. According to the ship motion equations,we mainly discuss the motion law of the ship in the wind waves by using linear system theory. These four movements can be used to synthesize ship′s complex movements in waves,and thus could simulate ship′s movements in various sea conditions in laboratory,providing a simulation experimental environment for studying the ship-borne laser communications system. The manipulation and control of the platform are realized through computer.

The match between optical pulse source and en/decoders is an important issue in optical code dirision multiple access (OCDMA) system design. Half band application for equivalent phase shift superstructured fiber Bragg grating (EPS-SSFBG) en/decoder is proposed in this paper. The decode performance is fairly well when the source spectrum just cover half of the encode band which is decided by the SSFBG structure. The possibility of half band application is testified by both simulation and experiment.

A new method is proposed to realize millimeter-wave sub-carrier generation at central station by using a double-uniform fiber Bragg grating filter (UFBG) scheme. Two optical waves with a spectrum of a millimeter-wave sub-carrier distance heterodyne after detector at base station then we can get the wanted millimeter-wave signal. The advantages of this new method of millimeter-wave sub-carrier generation are analyzed by designing a radio over fiber (ROF) downlink system,and the eye diagrams after detection and interference demodulation in 0 km,10 km,30 km,40 km transmission distance are also analyzed. Moreover,performance of this radio over fiber downlink system could be improved by reducing the bandwidth of band-pass filter of millimeter-wave sub-carrier generator. The proposed scheme may be taken as one of the candidates for the next generation high-speed and large-capability radio over fiber system.

We have theoretically and experimentally investigated all optical wavelength conversion based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). Pump and signal lightwaves are generated from two different distributed feedback laser diodes (DFB-LDs). 2 Gbit/s orthogonal frequency division multiplexing (OFDM) is used to modulate directly on the signal CW lightwave. The modulated signal lightwave and pump are coupled and then amplified before they are injected into the SOA for wavelength conversion based on four wave mixing effect. Experimental result shows that the newly converted wavelength signals copy the original OFDM signals and its conversion efficiency of the converted signals are proportional to the amplitudes of the input signal and the pumps under the condition of SOA non-saturation. The polarization angle between the pump and signal lightwave affects the optical power of the converted OFDM signal. The bit error rate (BER) curves and receive constellation are also measured.

Large-aperture receiving is one of the effective approaches to overcome the impact of turbulence on atmospheric optical communications. Based on the irradiance fluctuation theory for finite apertures,the relationship between the average signal-to-noise ratio and the quantities of the signal-to-noise ratio without turbulence,the aperture averaging factor and the irradiance fluctuation variance was mathematically modeled,and the formula of bit error rate (BER) was derived. The curves of relationship between the aperture diameter and the signal-to-noise ratio without turbulence at a given BER with various turbulence parameters were obtained numerically.

A multi-channel all-optical modulation format converter from non-return-to-zero (NRZ) to return-to-zero (RZ) is reported based on the fiber optical parametric amplifier (FOPA). In this scheme,the NRZ data together with a synchronized pump clock are injected into the highly non-linear fiber (HNLF). The FOPA consisting of HNLF converts the NRZ signal to RZ signal,and the wavelength of the signal is preserved. The multi-channel operation at 10 Gb/s is demonstrated experimentally. The sigal to noise ratio (SNR) of the converted RZ signals is no less than 7.6 dB with 3 dB enhancement of extinction ratio (ER). The pulse-width of the obtained RZ signal is around 30 ps. According to the operating principle of the multi-channel code converter,the converter is considered to be proper for the multi-channel operation at 40 Gb/s or even higher bit-rates.

The high energy laser system architecture based on coherent beam combining has been an important research field for high energy laser technology. The recent experimental results of coherent beam combining of multiple fiber amplifiers and fiber-slab compound amplifiers using active phase controlling and self-organization are presented in detail.

Laser processing robot is to be toward 21st advanced manufacturing technology in the world. The princeples,constructions,kinds and applications of the robot are comprehensively summarized. Some key techniques for laser robot are focussed on fiber transferable lasers,robot body,online and offline programming,robot intelligence and networking and three-dimensional (3D) reconstruction of repair area by inverse engineering. Laser robot development trends of remote processing,machine vision and hearing,robot intelligence and networking are presented.

Intranasal low intensity laser therapy (ILILT) was the clinical applications of intranasal low intensity laser irradiation in internal medicine. ILILT may be mediated through three pathways,blood,meridians and autonomic nervous system,one of which is at least far from its function-specific homeostasis. Blood pathway was directly supported by its improving blood lipid and hemorheologic behavior of patients with vascular diseases. The meridian mediated ILILT hypothesis was supported by the comparative studies of therapeutic effects of acupuncture and ILILT. The rehabilitation of ILILT might be mediated by increasing the promotion of the sirtuin.