Visibility was regarded as one of the most important meteorological complications affecting the safety in the field of aviation and navigation. The alignment status of transmittance meter has played an important influence on the accuracy of visibility measurement in the course of installation and application. A measuring light path alignment method based on scanning mode was proposed and the automatic alignment system was designed based on this method. The system drove the probe beam and received field of view scanning in two vertical directions by electric machinery, then the azimuth angle of the transmitter and the receiver was calculated, and the alignment of the optical path was realized. System test shows that the system could realize the automatic alignment of the optical path of the transmittance meter, the maximum error of azimuth position is 66 ?滋rad, alignment time is less than 10 min. The system has the characteristics of high collimation precision, process automation, easy installation and so on.

Aiming at the problem that the calibration result of two-step calibration method for star sensor optical error depends on the initial value too much, a modified calibration method was proposed based on particle swarm optimization (PSO) algorithm. Taking advantage of the global searching ability of PSO algorithm, a set of suboptimal initial value for two-step calibration of optical errors was provided via optimization. In sequence, the two-step calibration method was utilized to obtain the final calibration result. Numerical simulations demonstrate the effectiveness of the proposed method in overcoming the shortages that two-step calibration method is heavily influenced by initial values as well as the improvement of the stability of the calibration.

For resolving the problems including shadowing, poor secrecy, expensive consumption, and excessive interference in visible light indoor dynamic target positioning method with improving accuracy, an indoor walking target 3D positioning method was proposed based on white light LED. According to the walking characteristic, the model was established with fixed ommateum receivers, SiO2 transparent floor, and beam displacement(BD). Then the virtual direct transform(VDT) was actualized with two optimum ommateum lenses for 3D position. Indeed, the proposed method used only one LED emitter for saving energy. Also, it obtained the shorter beam propagation distance, improved optical power, and better confidentiality and generalization. Experiment shows that with the proposed method the error rate can be limited within 3.5%. And more than 5 targets can be most effectively positioned, while the distance between adjacent receivers is equal to the coverage radius from each one.

The whole Stokes measurement instrument based on aperture segmentation can obtain all polarization information of the target, but the polarization detector system has an effect on the measurement results. So it is necessary to analyze the measurement error of the Stokes vector [S0,S1,S2,S3]. First, the theory of Stokes vector was researched; next, the working and measuring principle of the full Stokes measuring instrument were introduced; then, the error sources were analyzed; last, the influences of the error sources were simulated. The final simulation results show that, the relative error of polarization and elliptical angle are 1.16% and 4.55% when the phase retardation is ±5°, the relative error of azimuth angle is 7.68% when the fast axis direction of the wave plate is ±2° with respect to the x axis, and the relative error of polarization degree, elliptical angle and azimuth angle is about 1% when the signal-to-noise ratio of CCD detector is 40 dB. The analytical results provide reference for the selection of the component parameters of the experimental device, and support for the full Stokes measuring instrument based on aperture division.

In order to realize the real-time pose determination of the flotation experiment platform, a pose measurement method based on monocular vision was proposed. Firstly, an easily identifiable circular cooperative target was designed, which was invariant to the rotation, translation and scaling. Then, combining the size, shape and installation location, the cooperative target could be detected fast based on Blob analysis which could ensure the accuracy of the point extraction. Next, a method was proposed to extract the object circle centers fast and robustly by scanning the connected domains to be recognized. Finally, the actual pose of the flotation experiment platform could be calculated by the circle centers in the computer image coordinate system and the relations of coordinate transformation of the vision-based pose measurement system. The results showed that the proposed method had high accuracy and strong anti-noise capability, and the average period of processing the image of 1 600 pixel×1 600 pixel was 53.086 ms (about 19 frames per second). The method can realize the real-time, accurate and robust measurement of the pose of the flotation experiment platform.

Based on the measuring benchmark of higher precision, the inner orientation elements of star tracker were modeled and optimized. Because of the fact that the error of the optical system with large FOV is not ideally axial symmetry, a calibration model based on net zone-division field of view and the corresponding optimization method was proposed to calculate inner orientation elements of star tracker. Firstly, the principle point and focal length were resolved based on pinhole model after the compensation of initial alignment error. Then, the polynomial combined with bilinear interpolation was used to correct the optical distortion under the guidance of zone-division modeling theory. Finally, measurement angle error was applied to the accuracy evaluation of calibration. A calibration experiment in lab and a real sky test validated the proposed method with the residual error of x axis decreased by 35% and y axis decreased by 20%.

In order to get accurate time information, the GPS was always used. But GPS can not be used in outdoors due to the complicated environment. Digital zenith camera is a kind of high-precision astronomical positioning instrument. The study about time calibration based on digital zenith camera was rather little. Considering that the orientation result can be influenced by star apparent position and time. Firstly, the influence of time error and star catalogue on star apparent position was analyzed respectively. Then, the influence of star apparent position on the orientation result was analyzed. One new method of time calibration based on digital zenith camera was proposed. The precision of time calibration was 0.025 s. The analysis of experimental data shows that the time calibration method is feasibility.

The absolute measurement of thermal X-ray flux from a hohlraum is essential to get the radiation temperature and the laser-hohlraum coupling efficiency in the experiments of indirect-driven inertial confinement fusion (ICF), which can be measured by a flat response X-ray detector. The configuration parameters of flat-response compound filters were optimized to enhance the performance of flat-response X-ray detectors. The effects of thin layer thickness, thick layer thickness and hole area ratio on response flatness of detectors were investigated. The calculated results agree well with the calibrated data. From the results, it can be found that the thin layer thickness plays a primary role in performance of detectors while thick layer thickness and hole area ration take a minor role. Besides, the detectors show a best response flatness less than 5% which reaches the limit value of theory as the thin layer thickness, thick layer thickness and hole area ratio are 50 nm, 380 nm and 1:6.1.

To prepare a low-residual-stress laser cladding coating, Fe-Mn-Si shape memory alloy(SMA) coating was prepared on the surface of the AISI 304 stainless steel. And the ANSYS finite element software was used to simulate its stress field, meanwhile the residual stress distribution of the cladding specimens was measured by the mechanical hole-drilling method under the same process to verify the correctness of simulation. What′s more, the mechanism of low residual stress inside Fe-Mn-Si SMA coating was analyzed by XRD. The results show that the stress caused by laser cladding induces the γ→ε martensite phase transition inside the coating to get a low residual stress coating. And the coating alternately bears the thermal stress of tensile-pressure-tensile during laser spot getting closer and further to the coating center. And the thermal stress was inversely proportional to the distance between the simulating nodes and the center of laser heat source. When the specimen was completely cooled to the room temperature, the residual stress inside coating presented tensile stress, and its maximum value happened at the junction between the substrate and the coating. In the directions of parallel and vertical to the laser scanning, stress value was relatively small in the middle region, but large in two sides. And from the coating peak to the fusion line in the thickness direction, the residual stress was tensile stress and the extreme value of stress was locating at the center of the coating. Far away from the fusion line, the substrate bore pressure stress and levels off to zero-stress state.

A sub-pixel center extraction algorithm based on hierarchical processing was proposed for the implementation of laser stripe processing in the large aerospace parts measurement with high speed and precision. Firstly, the high-resolution image was compressed into low-resolution image with structural invariance. Then, the normal vector of the center of laser stripe was calculated by using quadratic curve fitting in the low-resolution image. The normal vector in the low-resolution image was reproduced to the high-resolution image based on the theory of normal regression. The judgment of gray center on normal direction was established to determine calculated pixels. The sub-pixel center of calculated pixels on the normal direction was accurately calculated by the gray weighted centroid method. Finally, the presented method was utilized to measure a composite material standard part and complex aviation parts in the laboratory and assembly testing machine, respectively. Experimental results show that the precision of the reconstruction of a single stripe on the surface of object is 0.269 mm and the precision of three-dimension surface measurement is 0.268 mm. It indicates that the proposed method can improve the speed and precision of the engineering measurement of large part. Moreover, the method can satisfy the requirements of the in-site measurement of large aerial parts.

The uniformity and orthogonality are important technical indicators of photoelectric incremental encoders′ performance. The precision measuring of incremental encoders is an important link in development and manufacture of encoders. Traditional measurement of signal quality is based on time position and varied from the uniformity of rotating speed. The dynamic performance testing is incorrect with high speed and variable speed rotation. A testing method based on angle was proposed and corresponding system was established. The measured incremental encoder and a high-precision angular impulse generator were installed and rotated synchronously with a brushless DC motor; when measured incremental encoder output a signal edge, collected the data of the high precision angular generator and calculated the error. The detection error of the proposed system caused by uneven shaft rotating speed of the encoder shaft was greatly reduced. Measurements were carried out through encoders with periodical impulse output number 32 400, and was contrasted to the experiment based on time. The experimental results show that the system is free of the impacts of varying speed of driving motor, and is capable of improving the accuracy and efficiency of the incremental encoders testing. It was the proposed system that brings the batch production with great convenience.

The non-linearity caused by the detector of the Fourier transform spectrometer was studied, and the influence of non-linearity on the spectrum was discussed. The quadratic non-linearity correction methods were also discussed: convolution method and iterative method. Then the two methods were used to correct the nonlinear data. A new method which is more suitable for practical data was proposed based on both convolution method and iterative method. Finally, the three methods were used to correct the non-linearity of the simulated data and the actual data. The experimental data shows that the nonlinear performance of the data after correction was restrained. And it was found that compared with the other two methods, the new method has better accuracy and faster speed.

A convenient and rapid, sensitive and accurate, and non-destructive method was established to analyze rubber sole. It provides clues, indicates investigation direction for the detection, and provides the scientific basis for proving the crime. Rubber sole samples was tested by using X-ray energy dispersive spectroscopy (EDS) to provide scientific basis for verifying crime. The test parameters were set as the following: voltage was 45 kV, test current was 40 μA, power was 1.8 kW, the size of sample was 1.5 cm×1.5 cm, and testing time was set as 60 s. The qualitative and semi-quantitative analysis of inorganic elements in 40 different rubber sole samples of different brands and different types was carried out, and the reproducibility of the method was examined. At the same time, the rubber sole samples were classified using SPSS clustering analysis-center of gravity method as definition of distance between the classes. Consequently, the method has the characteristics of accurate and reliable result, good reproducibility, no need for sample preparation and non-destructive testing. It can be used for public security organs to resolve the cases.

Based on Monte-Carlo simulation, the achievable information rate of the Q-ary pulse-position modulation and avalanche photodiode (APD)-based deep-space optical uplink channel was investigated for the beam wander and intensity fluctuation model. The results indicate that unlike the downlink channel, when the beam wander effect is taken into account, optimum divergence angle can be selected to achieve the maximum achievable information rate for the uplink channel. Besides, with respect to achievable information rate, the optimum divergence angle dependence on the transmitted beam number, the zenith angle, thermal noise and transmitted beam width have been evaluated. This work can be helpful for the uplink laser communication system design.Key words:

As beaconless acquisition tracking and pointing (ATP) uses the same laser beam with communication, and needs no more extra laser equipment, it has advantages in inter-satellite optical communication application which limits weight and power consumption of laser communication terminals. For scenario of low earth orbit inter-satellite optical communication, beaconless ATP of small optical terminals based on intensity modulation and direct detection was studied. The link budget was calculated, and the ATP procedure was designed. The effect of boresight vibration on acquisition time and acquisition probability was analyzed, and the method of residual uncertainty cone calculation was presented. It shows that the maximum laser transmitting power required is 0.135 W, and beaconless acquisition time is 30 s with acquisition probability of 95%, which can meet requirements of low earth orbit inter-satellite optical communication links.

Due to the advantages on small size, light-weight, compact structure, immunity electronmagetic interference and high sensitivity, fiber Mach-Zehnder interferometer has been considered in various applications. However, the abilization of the fiber Mach Zehnder interferometer has recently become the most important problem to the measurement and communication system with higher accuracy and performance, because its non balanced parallel structure. A stability control system of the fiber Mach- Zehnder interferometer was introduced,which was based on 3dB optical coupler. It was realize the stability control by bias control, the output signal of microwave photonic link feedback to one of the fiber Mach Zehnder interferometer arms. This simple method was effective to overcome the unstably problem of the fiber Mach-Zehnder interferometer which composed of 3dB fiber coupler.

In order to have an accurate measure about modulation transmission rate of UAV′s optical communication tasks to ground in the current conditions, a channel model which is suitable for airborne atmospheric optical communication needs to be established. Firstly, the airspace range was divised, the influencing factors was limited in the troposphere. Then the comprehensive influence model was established based on tropospheric typical atmospheric effect, and further the channel transmission model was established under UAV′s optical communication to ground. Parameters setting about UAV was made under the existing conditions, and total amount of effective information was simulated under UAV′s optical communication to ground on different heights, the best height for carrying out optical communication tasks was obtained which was about 2 600 m. At this altitude, the channel transmission model was simulated by selecting appropriate modulation rate points. Combined with the critical effective total information′s setting and the simulation results of channel model, on the basis that the needs for feedback test about optical communication system was met, the critical modulation rate needs of UAV′s optical communication was locked in 1.12 Gbps. The result provides the evaluation standard for the design of the optical modulation system under existing conditions and it has a strong guiding significance.

The received constellation effect of QPSK subcarrier modulation by multiplicative noise and additive noise was studied. A theoretical model of laser communication system was constructed, the received constellation of the system under multiple noise and additive noise was derived. The constellation distribution and the power spectral density of the receiver were calculated under mixed noise environment. The influence of system bit error rate in different visibilities and transmission was analyzed in detail under mixed noise environment. The results show that with the change of turbulence intensity, the receiver power spectrum has obvious broadening. When the visibility is less than the transmission distance, the atmospheric aerosol scattering is the main factor affecting the communication under different additive noise conditions; when visibility is 0.5 km to 1.5 km, the passenger noise will affect the reception light and increase the system error rate under different multiplicative noise conditions. The proposed works are very important for reducing the bit error rate of laser communication and improving the communication quality in the real environment.

Large scale and high integration of IRFPA device is the core of high spatial resolution infrared imaging. With the development of the high integration IRFPA technology, a 640×512 readout integrated circuit(ROIC) of IRFPA with 15 μm pixel pitch was presented. In order to improve SNR and integration time, one technology method of 2 by 2 pixels sharing an integration capacitor was proposed and the DI architecture was chosen as the input stage, thus the maximum effective charge capacity can reach 20 Me-/pixel. And two levels of charge capacity can be chosen for the readout of different photocurrents.Moreover, current bias circuits were designed for the analog signal chain ciruit to lower the noise and improve the bias current accuracy for buffers. According to the simulation results, the circuit achieves 108 Hz frame rate, less than 110 mW and 99.99% linearity. The circuit was taped out by CSMC 0.18 μm 1P4M 3.3 V CMOS process. The preliminary test results under room temperature show that the working current is normal and the bias switches can be adjusted and the circuit can work normally.

Operating distance of Rosette scan infrared detection system is hard to be estimated by infrared detector operating distance formula in complex background. So correlated to the operating distance model of Rosette scan infrared detection system, the model working in complex background was developed. Using the algorithms that calculates the Rosette scan infrared detection system responses pluses characteristics via gray scale of background collected by infrared thermal imager and verified by field tests, the result shows that the improved model can estimate the operating distance of Rosette scan infrared detection system under complex background more efficiently.

The operating range model of the infrared polarization imaging system was established based on the minimum resolvable temperature difference(MRTD) between the target and the background. The impact of the background clutter on the operating range was also analyzed. Simulation results show that the operating range is concurrently dependent on the target/background polarization characteristics, atmospheric transmission and the observation geometry. Among these factors, the background clutter greatly affects the operating range of infrared polarization imaging system. Besides, polarization imaging mode and intensity imaging mode may have different advantages compared with each other under different imaging conditions.

The traditional univariate calibration method used in measuring infrared sky brightness is confronted with many issues, and two main issues are the insufficient dynamic response of the measuring instruments as well as the influence of the ambient temperature on the measurement result. In order to extend the dynamic response of the measuring instruments, a bivariate calibration model at the constant temperature was demonstrated in the paper, and its independent variables were radiance and exposure time. Then with the experiment data acquired in many temperatures, the variation of the bivariate calibration model in different temperature was analyzed. Thus trivariate calibration model was presented at the last part, and the goodness of the fit of the model and the experiment data was best. R-square is 1.000, and the relevant uncertainties in 95% confidence degree of a, b and d, parameters of the trivariate calibration model, were all less than 0.82%, trivariate model can be degraded to bivariate at some certain temperature, the deviation of all of parameters of degraded model were less than 0.6%; Finally, with the outfield experiment of infrared sky brightness, bivariate and trivariate calibration model were validated and compared. The benefit of this trivariate calibration model is that it can extend the dynamic response of the measuring instruments, and the precision of its measuring result is not affected by the variation of ambient temperature. Hence this model can be widely used and can achieve high-precision and high-efficiency measurement without in-situ calibration.

An infrared thermal wave radar imaging system was set up to detect the internal CFRP laminate defects. Two novel kinds of signal extraction algorithms named Chirp lock-in algorithm and HT algorithm based on Hilbert transform and Fractional Fourier transform were developed in order to obtain the characteristic information of thermal wave radar signal. The defect size distribution range and criteria of defect judgment were designed reasonably. The influence of signal extraction algorithms on the probability of detection was studied by means of Hit/miss analysis methodology. The POD curves obtained by the proposed algorithms at the designed testing parameters and thresholds were given. According to the probability analysis of detection, the probability level of CFRP laminate defects detection using infrared thermal wave radar imaging system were identified.

Satellite Laser Altimeter multiple mode waveforms are composed of sub-pulses generated from several targets. According to the spatial distribution characteristics of multiple mode targets, the geometric modeling of the sub-target was realized by using the parameters such as the slope angle, the area, the center position and the height. Combined with the basic definition of the target response function, the expression of the sub-target response function was built up by using the line integral method. Meanwhile, the mathematical models of laser ranging and its corrected value for sub-target were derived on the basis of the first order moment theory. Using some parameters of Geoscience Laser Altimeter System(GLAS) as input, the influence of slope angle, area and the center position on the shape of received pulse waveforms and the corrected value of laser ranging was simulated by numerical simulation method. The results show that the corrected value of laser ranging becomes larger with the increase of the slope angle, the area and the center position of sub-target. As for the sub-target with low relief, moderate relief and high relief, the corrected value of laser ranging can be reached at 1.33 m, 4.98 m and 12.07 m, respectively, which exerts a tremendous influence. In term of the regularities distribution of the corrected value of laser ranging, its theoretical expression is described with linear functions by using slope angle, area and the center deviation distance as variables. The conclusion has important guiding effect for the improvement of laser ranging accuracy for multiple mode targets.

Underground metal mines cavities were serious threats to mineral resources exploitation and the surrounding environment of mines. Useful points′ spatial information about cavity shape could be gotten from 3D laser scanning detection precisely, which had become the main method of cavity accuracy detection. Traditional 3D laser equiangular scanning has its disadvantages of uneven spatial resolution and low efficiency. With the analysis of the irregular characteristics of mined-area, a 3D laser spatial resolution enhancement method was proposed. The formula of calculating the distance between the spiral line and the scanning trajectory was derived. The experimental result of points cloud verifies the efficiency of the new method, which improves the spatial resolution of the 3D laser scanning, and provides a solution for the high accuracy acquisition of 3D shape in the mined-area.

In order to improve the resolution further, the laser probe optical system was redesigned and optimized. The ultimate resolution of the laser probe based on far-field optics was studied. Using the reflex objective (N.A=0.4) to focus the incident 532 nm laser beam, under the condition of appropriate energy, the resolution of 2.26 μm and 1.87 μm on pure Al and Fe samples surface was obtained, respectively. Under this system, the effective Al and Fe atomic spectrum can be acquired with intensity three times of the background noise, respectively. A set of coaxial confocal imaging system with coaxial illumination was designed and realized, the field magnification is 24.7. The results showed that the coaxial illumination system can improve the sharpness and identification of the graphics with resolution not less than 228 lines per millimeter. A coaxial spectral collection system with indicator was invented, which can maintain the alignment error within 10 μm between the plasma and the coaxial collection system. In the coaxial monitoring area and combining with an X-Y axis scanning system, a spectra matrix with 63 points on the plasma surface can be acquired, which the images of plasma spatial resolution could be obtained.

By using 6-axis robot and inside laser powder feeding technology to form the arcuate cantilevered entity part, and a way of variable posture and radial overlap laser cladding was proposed. This experiment discussed the cladding nozzle self-healing effect and deduced the quantitative relation between the single track height and the laser defocus when the defocusing amount ranged from -5.5 mm to -1.5 mm, and verified it by experimrent. The experiment result shows that the surface of formed part is flat and smooth without staircase effect; the thickness and length of formed part are uniform under different angle, and all the dimension precision meet the requirements of modeling, different angle almost has the same microstructure.The hardness keeps the same change rule with microstructure by testing the forming part hardness.

Fano resonance is a special effect which can greatly enhance the intensity of the local electric field. For a nanostructure, if the hot spots of different wavelengths are in the same spatial position and the scattering spectrum has a Fano lineshape, the enhancement factor of surface enhanced coherent anti-Stokes Raman scattering can be hugely increased. The Fano resonance effect of a symmetric cross bowtie Au nanostructure was studied by FDTD software, the electric field of the "hot spots" near the middle of the structure was greatly enhanced. In surface enhanced coherent anti-Stokes Raman scattering, this structure can make the enhancement factor to be as high as 1013, enabling the detection of single molecules.

The vertical distribution of the atmospheric temperature in the troposphere is directly related to the meteorological phenomena and the diffusion of atmospheric pollutants. It has been the major parameters observed by the meteorological department and the environment sector. The lidar technology has become an effective method to detect the vertical distribution and time variation of the atmospheric temperature in the troposphere. Lower tropospheric temperature profile measured by lidar using the Rayleigh and vibrational Raman scattering can′t be obtained accurately due to the abundant aerosols. Using N2 and O2 molecular pure rotational Raman scattering signal, the lower tropospheric temperature profile can be obtained without the influence of lower tropospheric aerosol theoretically. The main difficulty of the rotational Raman lidar is design and mechanics of the receiving spectroscopic system. In domestic research, most of the lidar systems use the spectroscopic technique based on double grating spectrometer. The technique based on the interference filters was introduced in this paper and used in our lidar system for observation of the tropospheric temperature. This technique had more efficiency and suppression in separation of the pure Raman signals from Mie signals. Furthermore, the system′s sensitivity can be optimized by selecting the tilting angle of the filters. The experiment was based on the project of "Formation Mechanism and Control Strategies of Haze in China" carried out by the research groups of the Chinese Academy of Sciences. Our lidar system was moved to the super atmospheric observatory in University of Chinese Academy of Sciences on November 2014 and the experiment were taken during the APEC conference. The energy of laser in ultraviolet was about 200 mJ, the frequency was 20 Hz, the laser pulse number was 5 000, the spatial resolution was 7.5 m. The experimental result shows that the statistical error between lidar and radiosonde are less than 1.5 K with the range up to 10 km and the statistical error of less than 1 K is obtained up to 7.5 km height in the clean night. Larger differences of about 3 K at the region above the thin cloud may be caused by the strong elastic backscatter signal and the statistical error of less than 1 K is obtained up to 4.8 km height.

Backscattering lidar is a powerful tool for atmospheric aerosol detection, but it can not receive the full signals in lower hundreds of meters, and has an assumption of lidar ratio for aerosol backscattering coefficient reversion. One wavelength emission and five channel receivers lidar system based on backscatter, side-scatter, and Raman scatter technique overcomes the above shortcomings. The system can detect aerosol depolarization ratio profile, water vapor mixing ratio profile, backscattering coefficient profile and aerosol extinction coefficient profile. Aerosol backscattering coefficient and extinction coefficient profile were from the ground to the tropopause, aerosol depolarization ratio profile was in troposphere, and water vapor mixing ratio was in planetary boundary layer. The signal to noise ratios of all channel and relative errors of detected results were analyzed based on the system hardware. Case study indicates that the data of this system are reliable, and detection ranges are rather wide. The system can be used for studying the spatio-temporal distribution of atmospheric aerosol extinction coefficient, water vapor and their relationship.

Traditional backscattering lidar has complex system and requirement to correct the geometrical factor. Using imaging lidar can overcome these drawbacks and this lidar can work all the day. It adopted the weighted fitting method, slope method and modified iteration algorithm that combined Klett backward integration method and Genetic Algorithm(GA) method based on the distribution of extinction to deal with the image data. Taking the data from four different weathers, the atmospheric visibility of these days was obtained. Then, it was made a confrontation with the America Belfort model 6230A visibility meter. It can achieve from this process that the differences of visibility between two facilities were on the small side and had the high correlation coefficients over 0.67. Finally, it can reach a conclusion that this imaging lidar system can be a new instrument to measure the atmospheric visibility.

Based on two independent physical phenomena: laser induced fluorescence(LIF) and depolarization resulting from elastic scattering on non-spherical particles, a short range lidar system for real-time standoff detection of bio-agents was developed. The lidar system included three laser sources, two receiving telescopes, one depolarization component and fluorescence spectral signature analyzing spectrograph. It was designed to provide the stand-off detection capability at ranges from 200 m up to several kilometers. For fluorescence excitation, 3rd (355 nm) and 4th (266 nm) harmonics of Nd:YAG pulsed lasers were used. They emitted short (about 6 ns) pulses with the repetition frequency of 20 Hz. Collecting optical system for fluorescence echo detection and spectral content analysis included 25.0 mm diameter f/4 Newton telescope, Czerny Turner spectrograph and a 32-channel PMT. The depolarization and Mie echo signal were collected by a Cassegrain telescope with an aperture diameter of 12.5 mm. Through the simulative calculation of SNR of fluorescence measurement, it was found that, with the minimum detectable SNR value of 10 as reference, the bio-agent cloud with concentration of 10 000ACPLA at the distance of 1 km could not be detected in daytime, while a rather good signal intensity could be obtained in nighttime. The preliminary analysis to the depolarization measurement results indicated that:(1) the depolarization ratios were wavelength-dependent; (2) depolarization measurement using multiple wavelengths could increase discrimination efficiency significantly.

To raise the alarm rate of small scale and low-level turbulence detected by lidar, an alerting algorithm based on the combination of glide-path scanning and transverse velocity structure function was presented in this paper. Firstly, the scanning sector of the glide-path was divided into several overlapping subsectors, and the transverse structure function of each subsector was calculated by using the spatial fluctuation method. Secondly, the structure function was fitted with that predicted by the theoreitical Von Karman model to give eddy dissipation rate, and the results on provisions of the International Civil Aviation Organization′s turbulence threshold was compared to come to the conclusion. The performance of the proposed method was verified through the lidar collecting data of Hong Kong International Airport installed by Hong Kong Observatory. The results show that the proposed algorithm detects the small scale turbulence which longitudinal velocity structure function fails to detect. The new proposed method is effective, it is significant to raise the alarm rate.

An high efficient actively Q-switched Nd:YVO4 self-Raman laser based on in-band pumped at 914 nm was reported. Particles from thermally excited Stark leveled in the ground-state were pumped to the upper lasing level directly, the Stokes factor loss was reduced to a minimum and the quantum efficiency loss was eliminated. This alleviated the thermal effect of the laser and consequently realized better performance. The effect of pump absorption on conversion efficiency was investigated experimentally in detail with the in-band pumping. Using two Nd:YVO4 crystals with different doping concentration, 1.51 W(1.0-at.%, 20 ℃) and 2.11 W(2.0-at.%, 20 ℃) output power were obtained respectively, corresponding to the conversion efficiency of 42.7%(1.0-at.%) and 39.0%(2.0-at.%) and the optical efficiency of 28.5%(1.0-at.%) and 35.2%(2.0-at.%).

The sensing system and demodulation algorithm of laser array based on REC technology were analyzed and put forward. REC process met the low-cost mass production of laser array, and had the advantages of small size, and a greater practical value in the field of sensing in future. An efficient algorithm for laser scanning was proposed to measure the displacement of fiber Bragg grating (FBG) due to external stress. The system was unique in that accurate demodulation can be achieved by scanning only 0.4 nm bandwidth FBG spectrum instead of relying on scanning FBG main power peak and the algorithm can be applied in any FBG band, which enable using of wavelength-division multiplexing(WDM) for FBG sensing network. In the experiment, the single-channel and four-channel can accurately search the displacement of FBG reflection spectrum. Preliminary experiments demonstrate the effectiveness and feasibility of the proposed method, results show that the error of single-channel is less than 5 pm, four-channel′s is below 2 pm, stress and algorithm results show good linearity. It has certain reference value for the multi-channel laser array sensing.

With the increase in output power of high power semiconductor lasers(HPSLs), thermal management is one of the critical bottlenecks affecting the optical-electrical performance and reliability of HPSLs. Thermal characteristics of a kW-level conduction cooled semiconductor laser array were analyzed based on numerical simulations and experiments. Firstly, transient thermal behavior was studied using finite element method (FEM). There is significant "thermal crosstalk" behavior among the semiconductor laser bars with pulse width greater than 250 μs. It shows thermal resistances along horizontal and vertical directions are 64.7% and 35.3%, respectively, indicating that heat mainly dissipates along horizontal direction. 74.9% of thermal resistance along horizontal direction and 66.5% of thermal resistance along vertical direction origin from CuW layer, which shows that CuW is the most significant factor affecting the efficiency of thermal dissipation. Based on accumulated average temperature method, the simulated temperature differences are 2.13, 1.47, 0.75 ℃ at the repetition frequencies of 20, 30 and 40 Hz compared with that at the frequency of 50 Hz. Average junction temperature rises at different repetition frequency have been measured using spectral method, and the temperature differences at the repetition frequencies of 20, 30 and 40 Hz are 2.33, 1.56, 0.78 ℃, respectively. The average error is less than 6.85% between experiment results and numerical simulation. It shows that the simulated transient thermal resistance is coincident with the experimental result.

An all-polarization-maintaining erbium-doped fiber laser mode-locked by graphene saturable absorber mirror was reported. The laser with monolayer and ten-layer graphene as saturable absorbers devices avoided the influence of environment on the intracavity polarization and generates high stability, high degree of polarization and self starting mode-locked pulse output with pulse width of 697 fs and 502 fs. Compared to single layer graphene, the ten layers graphene can obtain shorter pulse width, higher peak power and better mode locking effect. While the pump power increases, a two harmonic mode-locked pulse with 62.94 MHz repetition frequency can be generated. The mechanism of harmonic mode locking was analyzed by nonlinear Schrodinger equation. The mode-locking laser cavity based on the reflection mirror was expected to be the excellent single polarization femtosecond fiber laser source which can be switched between the fundamental frequency and the two harmonic.

In order to realize the output of high power semiconductor laser with uniform brightness, symmetrical shape and high symmetrical beam quality, a high power fiber-coupled diode laser system based on mini-bar was proposed, and Zemax was used to simulate a 500 W-output fiber-coupled diode laser system with a fiber of 200 μm core diameter and 0.22 numerical aperture. In the system, mirror-stripe mirror system was put forward to compress the beam size in the fast axis of diode array in terrace structure, and polarization multiplexing was used to double the output power without changing the beam parameter product. Then, a beam expander system was taken to reduce the residual angle in slow axis, and an aspherical lens was used to coupled the shaping beam into the fiber. Based on the existing condition, 4 diode laser arrays (each contains 5 mini-bar) in terrace structure were used to validate the design. The output power of the fiber-coupled diode laser system can achieve 506 W, and the brightness is 10.3 MW/(cm2·sr), while the E-O efficiency is 43.0% at operation current of 37 A. Design and experiment all show the fiber-coupled diode laser system can work steadily with output power over 500 W. This module can be used in material processing and many other areas.

In order to realize a highly stable and tunable laser output, an Er3+-doped fiber laser based on Mach-Zehnder filter structure and grating array made by femtosecond laser was proposed, and an optical delay line(ODL) was set into one interference arm to tune the interference interval flexibly. In the designed configuration, one 976 nm laser diode (LD) was used for pumping; an Er3+-doped fiber (EDF) of 6 m length was selected as the gain medium; The grating array will selete the femtosecond light reflection loop cavity specific wavelength oscillation form; the M-Z structure, which was used as comb filter, was adopted to select the wavelength reflected by the grating array; Tuning laser output can be realized by adjusting the ODL. In the experiment, when the pump power was 100 mW, a stable and tunable single, dual and triple wavelength output laser was observed. The single wavelength tunable interval was 2 nm within 1 570-1 596 nm, and the side-mode suppression ratios (SMSRs) of all were more than 50 dB.

The mid infrared region covers the extraordinarily important atmospheric windows and has a wide range of molecular fingerprints, which has made the MIR laser based on chalcogenide glass attract considerable interest. In the development of infrared ultrashort laser, the solution of laser pulse broadening in chalcogenide glass fiber is critical, due to the high nonlinearity and dispersion properties of chalcogenide glass(ChG). In the paper, in order to settle the broadening of laser pulse, the chirped fiber grating was designed to compensate dispersion stretching of Gaussian pulse lasers due to transmitting in the fiber. The study shows that the dispersion caused by pulse broadening can be well compensated by chirped fiber grating. Further investigation suggests that the chirped fiber grating are optimized by using Gaussian apodization function to improve dispersion compensation and realize complete compensation to dispersion broadening. The research is a beneficial exploration to the design of high-quality chalcogenide mid-infrared fiber lasers and of theoretical significance.

In the field of biological medicine and clinical medicine, the diagnosis and treatment of many diseases almost rely on the identification of cell morphology. Different cells have different shape which would lead to the change of the light propagation characteristics among biological tissues. What′s more, it affects the light scattering properties of cells. At present, the theory of dynamic light scattering is the optimal way to dynamically identify the distribution of the size and the shape which related to the cell. Cells are mainly composed of cytoplasm, nucleus and mitochondria. Therefore, analyzing their optical properties have great significance for optical diagnostic and treatment. Experiments were designed to obtain the light scattering properties of lung cancer cells and Polystyrene microspheres which contained cytoplasm, nucleus and mitochondria. The models of cytoplasm were built with finite different time domain(FDTD) algorithm to simulate the light scattering properties. The light scattering properties of lung cancer cells demonstrate that mitochondria make a contribution to forward scattering (0°-20°) and backward scattering (160°-180°), nucleus make a big difference to side scattering (80°-100°), cytoplasm have an effect on any angle. The result of the simulation testified that the experimental results are correct.

By the way of 1-on-1, the FT50M FT-CCD working on the evaluation kit is irradiated by the 1 064 nm pulse laser with 8 ns pulse width. The experiment shows that, along with the increase of laser pulse energy density, the damage phenomena of unilateral black line, white spot and bilateral white line from the position irradiated by laser successively appear in the output image of FT-CCD. This process distinguishes obviously from the IT-CCD, which presents successively the white spot and bilateral white line in the similar experiments. Comparing the structures of FT-CCD and IT-CCD, and combing the damage mechanism of IT-CCD, it is thought that the first occurrence of unilateral black line damage phenomenon indicate a FT-CCD damage mode of the poly-silicon electrode being damaged earlier than the Si substrate. This study enriches the knowledge of laser damaging CCD image sensor, and provides a new clue for deep searching the mechanism of laser damage CCD.

Experimental research on pulsed nanosecond laser irradiation on Charged Coupled Devie was carried out to understand the damage and blindness mechanism of multiple pulses interaction with EO systems. The results showed two distinctive damage effects and mechanisms. It exhibited damage and blindness accumulation effects and damage threshold reducing outcomes with multiple pulses arriving at the same spot on CCD, including point-to-line damage and line-to-full frame blindness. The threshold reducing outcomes is closely related with pulse number and laser fluence with the same mechanism as single short blindness. However, the damage mechanism for multiple-pulse damage to different pixels is obviously different, which attributes to a multiple vertical line damage superposed effect without electrical disorder. The functional blindness threshold is indentified with line damage threshold 660 mJ/cm2, and evidently less than that of single-pulse blindness threshold 1 500-2 200 mJ/cm2.(GKCP2016004)

The response law of output signal for irradiated and unirradiated pixel in PV-type HgCdTe linear array infrared detector was researched when energy density of nanosecond pulse laser, less than destroyed threshold, was increased. The features of two-stage response of base signal and six-stage response of optical signal were pointed out, the energy density threshold range of each response phase was also given; some abnormal response phenomena such as zero voltage output of base signal integral jumping, sag output-recovery-convex of optical response signal were discovered. Based on the above results, from the point of view of readout circuit and thermo-induced electrodynamic force, the mechanism of abnormal response was revealed. We hope to strengthen the deep understanding of the photoresponse characteristics of HgCdTe array infrared detector, and provide inspiration for the technical innovation of this kind of device.

The multi-group circular fringes on the optoelectric detector were observed in the experiment of laser disturbing optoelectric imaging systems. The method of disassembly, measurement, modeling and ray tracing of optical system was used to investigate the formation mechanism of multi-group circular fringes. First of all, the radius of curvature, thickness, pupil of every lens were measured and the model of optical system in TRACEPRO software was built. Based on the model, large number of random rays to propagate in the optical system were traced secondly and the energy distribution on the optoelectric detector was obtained. By analyzing the origin of every energy component, it was found out that the multi-group circular fringes were caused by interference effect of the different energy component on the optoelectric detector. The research results can provide the technical support for evaluating laser disturbing effect on optoelectric imaging systems.

To study the influence of laser radiation on the performance of an image intensifier, the irradiation experiment of CW laser on the image intensifier was carried out and the effect of laser irradiation on its gain characteristics was analyzed. Experimental results show that no pixel crosstalk phenomenon is found as the increase of the laser power until the light illumination arrives 8×104 times of the illumination for point saturation, meaning that the gain of the image intensifier is saturated and the output light intensity of image intensifier will not increase indefinitely. The equivalent circuit model of the microchannel plate of the image intensifier was established and its gain characteristic was analyzed. The maximum current for linear gain, got from this model, was approximately 1.64×10-10 A, which was very close to experimental data, indicating that the charge extracted from the microchannel wall cannot be replenished in time is the main reason of gain saturation.

In order to study the effects of single-junction GaAs photovoltaic cell irradiated by 808 nm continuous wave laser, a physical model was established by software COMSOL and MATLAB. The voltage-current characteristics, open circuit voltage, short circuit current, photoelectric conversion efficiency, fill factor and heat steady temperature of cell were simulated, and the influence of the power densities, equivalent series, parallel resistance and antireflection coating were also discussed. The results shows that open circuit voltage and short circuit current increases with the increase of laser power density, while conversion efficiency and fill factor have maximum value. Reducing equivalent series resistance and increasing equivalent parallel resistance are an effective method to improve the output performance of cell. It was significant to improve the efficiency of cell with adding antireflection coating, however making the cell temperature higher at heat steady. The conversion efficiency of cell reaches to maximum value of 50.13% under 62.4 mW/cm2 at heat steady. The simulation result is basically consistent with relevant experiments, which can provide theoretical reference for output characteristics study of photovoltaic cell by continuous wave laser irradiation at some extent.