The propagation of Laguerre-Gaussian beam in intermediate fluctuation turbulent atmosphere is studied. Using the split-step Fourier method and the phase screen method, the intensity distribution, phase distribution and the spectrum distribution of LG beam are simulated in the case of up-downlink communications path and level communication path respectively. It is found that the atmospheric turbulence will induce the spread of the spiral spectrum. With the increase of the topological charge and refractive index structure constant, the spectrum spread becomes more serious. It is also concluded that the influence of the atmospheric turbulence on the Laguerre-Gaussian beams is smaller in up-downlink communication path than in level communication path.

Cirrus has the effect of radiative forcing which is influenced by the microphysical properties of cirrus. An algorithm for retrieving the microphysical properties of cirrus based on micro-pulse lidar and millimeter wave radar is presented. In the algorithm, lidar extinction coefficient retrieved from backscatter signal intensity and water equivalent radar reflectivity factor are combined to obtain cirrus-cloud ice water content (IWC) and general effective size (GES). A cirrus case in Shouxian is analyzed using the proposed algorithm and the data from micro-pulse lidar and millimeter wave radar. The results show that the IWC and GES are 10-3~10-1 g/m3 and 1~200 μm, respectively, which are consistent with the empirical values. The changes of IWC and GES with time are in accordance with the evolutions of cirrus. The analysis results imply the feasibility of retrieving microphysical properties of cirrus from micro-pulse lidar and millimeter wave radar data.

With the development of communication technology and the highly valued position of space area, space optical communication technology has become one of the hot spots in the world. At present, the ground optical communication is developing very fast, and a variety of difficulties has already been broken through for amplification techniques, especially those based on fiber amplifier have been widely used, and the technology is very mature. As the fiber-type devices are very sensitive to the radiation environment of the space, if the external modulation technology which has been successfully used in ground optical communications is used in space environment, we must consider the feasibility of the erbium doped fiber amplifier (EDFA) which is the core device in the external modulation technology and analyze the corresponding anti-radiation technique. This paper analyzes the space radiation environment and its effect on the performance of EDFA. Approaches including fading center anti-radiation technique, pre-radiation and hydrogen loading active anti-radiation technique and fiber manufacturing technology of anti-radiation technique are proposed to improve the space radiation resistant performance of the EDFA systems. A theoretical basis is provided for the application of EDFA in space optical communications. Through the experimental study, it is found that by adopting the above anti-radiation methods, the radiative decay of 1550 nm erbium-doped fiber (EDF) can be reduced by 0.8 dB/km theoretically.

The submicron fiber is fabricated by drawing a single-mode optical fiber through a flame-heated treatment. Gold nanorods (length and middle-section diameter are 80 nm and 20 nm, respectively) are deposited on the designated position of the submicro fiber by the positioning function of optical microscope, and the local surface plasmon resonance (LSPR) of gold nanorods is excited by the evanescent wave around the fiber. When the optical power increases to 30 mW, due to strong plasmon absorption and photothermal conversion, a microbubble forms at the position of the fiber decorated with the gold nanorods. Therefore, the laser light at this position is absorbed by plasmon resonance and scattered by the bubble. Optical transmission is not observed behind the bubble. Polystyrene particles (900 nm in diameter) near the fiber can be trapped by the gradient force, and then delivered along the direction of light propagation due to the scattering force induced by the evanescent wave. Once the particles move to the position of the bubble, they will stop their advancing. This technology can be used for targeted delivery of microparticles.

Numerical simulation of a parabolic-shaped pulse pair propagating in fiber is done based on the nonlinear Schrdinger equation, and the solution of the equation is found with split-step Fourier method. The transmission behaviors of the parabolic-shaped pulse pair in single-mode fiber and dispersion-managed fiber are studied. Simulation results show that there is almost no interaction between the parabolic-shaped pulse pairs transferring in fiber, and the main challenge is to preserve their shape and reduce the interference generated by pulse stretching. The evolution of parabolic-shaped pulses in fiber is affected by dispersion. When the pulses propagate in normal dispersion fiber or dispersion-managed fiber with average normal dispersion, they can maintain the parabolic shape. Especially, the pulses stretch fiercely when propagating in normal dispersion fiber, and taking advantage of the dispersion management methods, the tendency of pulse stretching is suppressed well. This result is of great help in long-haul optical fiber communication without relay.

With the continuous development of computer visualization technology and laser technology, “Digital Forestry” in China is being moved forward steadily. As a new mapping technology, three-dimensional (3D) laser scanning can quickly obtain the 3D model of the target，and therefore it has been initially applied in the survey of forest resources, study on the stand structure and 3D reconstruction of single tree. To explore the accuracy of the technique in forest mensuration, the measurement accuracy of 3D laser scanning technology is analyzed through the experiments in forestry and the factors which affect the scanning accuracy are summarized. The results show that the model constructed by the scanning data has a higher precision: the average error of scanning diameter at breast height (DBH) is -0.16%, the average error of scanning tree height is -0.35%, and the average error of scanning basal area is -0.11%. The errors meet the precision requirements of forestry completely. The technology has the adaptability and application prospects in the field of conservation of old and rare trees, forest resource inventory and forest cutting.

The higher the temperature of a blackbody, and the greater the amount of radiation of the terahertz band, the higher the test signal-to-noise ratio, but at the same time the increase of the amount of infrared radiation is far greater than that of terahertz radiation. The infrared radiation is difficult to filter and the blackbody terahertz radiation test accuracy is reduced. To improve the test accuracy, a suitable temperature range is chosen for the blackbody and the test method is designed for its terahertz radiation. Firstly, the distribution of spectral radiant emittance in the terahertz and infrared wave bands is calculated by Planck′s law for the blackbody at temperatures between 3~600 K. The radiation difference of blackbodies in this two wave bands is analyzed. Then the relative changes of radiation at different terahertz narrow band wavelengths for blackbody at the same temperature are analyzed. The phase-locking test method for blackbody in terahertz band is put forward, with the suitable blackbody temperature range of 223~273 K. The experimental results show that the terahertz test relative deviation is 0.1%～2.0%. The terahertz test curve is consistent with the related theoretical curve for blackbody in 100~3000 μm at this temperature range.

In order to overcome the existing disadvantages of offline laser peening detection methods, the online detection system based on laser plasma shock wave effects is developed. Laser is absorbed by the ablative layer on the surface of the work piece, and plasma of high temperature and pressure is formed under the tamping layer and propagated outward in the form of shock wave. The shock wave in the air is sampled, stored, digitally filtered and analyzed by the system. The system gets the sound pressure level factor to determine the effect of laser peening. The online laser peening detection system is designed and the implementation is performed. The system is very simple and convenient. By comparing the surface residual stress of work piece, the results show that the laser peening online detection system is sensitive and reliable.

In order to research the phenomenon of spontaneous emission in fiber laser, the numerical model of master oscillator power amplifier (MOPA) systerm is established based on the energy-level structure and rate equation of Yb3+-doped fiber. The analysis results by numerical calculation show that the system energy storage and amplified spontaneous emission (ASE) of amplifier are influenced by the pump power and particle population. The ASE is extremely serious in amplifying process with a low repetition rate. To reduce the ASE, continuous pump is changed to pulse pump, which means that a period of pump pulse that recovers the upper-level population adequately is set before the signal pulse. The ASE existing continuously in continuous pump system could be reduced obviously without influencing the signal pulse amplification. Numerical simulation shows that this method is feasible with a suitable pulse width and pump power, furthermore, the result of corresponding experiment agrees well with the calculation result.

This paper reports the cavity-dumped mode-locked picosecond laser with single pulse energy greater than 10 μJ for the first time in China, to the best of our knowledge. We complete semiconductor saturable absorption mirror (SESAM) mode-locked high-power picosecond laser oscillator with a fiber-coupled laser diode end-pumped Nd:YVO4 crystal. Then we insert BBO electro-optic crystal to the clamping cavity, realizing the repetition frequency 1 Hz~10 kHz continuously adjustable electro-optical cavity-dumped mode-locked operation. When the pump power is 17.9 W, pulses with single pulse energy of 12.5 μJ and repetition frequency of 10 kHz are obtained, whose pulse width is about 24.7 ps.

In order to measure the longitudinal and lateral speeds of a vehicle simultaneously, a triple-beam laser Doppler velocimeter (TLDV) system based on Janus configuration is presented. The model and the expression of speed measurement are given. According to the analysis and simulation, some results can be obtained as follows: firstly, TLDV is less sensitive to bump and shake; secondly, the relative speed measurement error is affected only by the bump angle and has no relationship with the shake angle; thirdly, the relative error is lower than 0.3% when the bump angle is 10° and the velocity is 0.2 m/s. Last of all, a kind of optimal configuration of TLDV beams is given.

For non-scanning laser three-dimensional (3D) imaging sensors, the imaging resolution is low and the calibration accuracy is not high. In order to solve this problem, a low-resolution sensor calibration method based on bilinear interpolation is proposed．Firstly, a resampling strategy based on the bilinear interpolation algorithm is used to improve the image resolution. Then calibration algorithm based on OpenCV is adopted. Finally the calibration results are compared with those obtained by the traditional calibration method. Experimental results show that the calibration error is reduced by nearly 1/2. The proposed calibration method based on bilinear interpolation algorithm can improve the calibration accuracy of low-resolution sensor.

Using the finite element method (FEM), we analyze the characteristics of the surface plasmon polaritons of an elliptic cylinder metal wire at 0.5 THz. The field has properties of low absorption and low dispersion, which is similar to that of a cylindrical metal wire. The results show that, as the major-to-minor semi-axis ratio of the elliptic cylinder metal wire increases, the fields are gradually separated and concentrated to its tip regions, while the absorption keeps notably reducing, so the propagation length continually increases. Because of these properties, elliptic cylinder metal wire is appropriate for applications such as terahertz waveguide, focusing, and imaging, etc.

A novel sub-wavelength transparent metal structure consisting of with a layer of gold ellipsoid nanoparticles arranged into the hexagonal lattice on the surface of a gold film is proposed. The transmission characteristics of the structure are investigated by using the finite-difference time-domain (FDTD) method. Simulation results show that the structure presents pronounced optical transparent behaviors. With the increase of the ellipsoid aspect ratio or the gold film thickness, obvious blue shift of the narrow resonant peak appears, accompanied by the pronounced change in transmittance. The transmission spectrum with much narrower peak is achieved in the proposed structure as compared to that of the structure with a gold nanosphere array on the thin gold film. In addition, we also find that the transmittance of the structure with the gold ellipsoid array on the top surface of the gold film is larger than that with the gold ellipsoid array on the bottom surface of the gold film.

The power-controlled transformation of Gaussian beams in strongly nonlocal nonlinear media is investigated. Based on the relation between the solution for the free propagation and that for the strongly nonlocal nonlinear propagation, the field at the output plane is obtained, and then the analytical solution for the output Gaussian beam is obtained. With the increase of the input power, the waist is located alternatively at the left- and right-hand side of the output plane; and the waist width varies oscillatorily. Therefore, one can make a continuously steerable transformation on the Gaussian beam if appropriate input power range is chosen.

A method for analyzing the primary mirror deformation of photo-electronic theodolite with Zernike annular polynomials is researched. Firstly, a formula used to convert the finite element method (FEM) analysis results into the data based on the wave-front coordinate is deduced. Then, the deformation of the primary mirror in a photo-electronic theodolite is fitted with Zernike annular polynomials, and the peak-to-valley (PV) value (30.7 nm) and root-mean-square (RMS) value (6.3 nm) of surface error are calculated. Their error are 9.2% and 10.5% compared with actual inspection results. The influence of the primary mirror deformation on the aberration of optical system is obtained based on the relationship between Zernike annular polynomial coefficients and Seidel polynomial coefficients. Importing the Zernike annular polynomials into the Zemax software, a comprehensive analysis of the optical system can be realized. It provides information for optimizing the optical system.

A local optimization method in the design of freeform surface lens based on non-imaging optics to achieve uniform illumination for LED source is proposed. In this design, the regular quadratic curve is adopted to replace the freeform curve of initial model, and the Scheme programming language and the optimization engine in the TracePro software are used in combination. In this way, a uniform illumination of LED is achieved. A Lambert emission of 1 mm×1 mm LED is used as simulation source. It is shown that the illumination efficiency of 80.89% and the uniformity of 95% within a field of view of ±15° are achieved at the target surface 1 m away from the source. Compared with the current global optimization method, the field-of-view and the illumination uniformity are improved significantly by this technique. It also possesses advantages of simplicity in process, less reliability requirement on initial model, and good versatility.

A novel LED-based light source is developed for the photodynamic therapy (PDT) treatment of cells in vitro. According to the characteristics of porphyrin-based photosensitizers for PDT applications, the red LED with emission wavelength of 627 nm is chosen. The arrangement mode and the distance between two LED units are optimized based on the simulation of light distribution for LED array by using TracePro software. Furthermore, the secondary optical design is performed in order to further improve the illumination uniformity. Based on the mathematical simulation, a novel LED-based light source is successfully developed, and the average power density and illumination uniformity are measured to be around 13.7 mW/cm2 and 90%, respectively. The obtained results imply that the LED-based light source is a convenient and promising light source for in vitro PDT studies.

A zoom lens is designed for a specific airborne platform. In order to decrease the axial dimensions, the rear-view mirror group is folded twice. It meets the space requirements since the axial dimension of the optical system is 96 mm. The zoom ratio of lens is 20, and the focal length is 6~120 mm, and the relative aperture is 1/5.6. The lens uses a method of mechanical compensation and a guiding mechanism of carriage. The lens has a small axial size, with high accuracy and a small optical axis shaking. Through the test, the optical axis shaking is found to be no more than 34″ in the process of continuous zoom. Through flight test, it is proved that the zoom lens can search objectives in the short focal length and track the target in the long focal length. In addition, the zoom lens can quickly change the focal length, the obtained image is stable, and the tracking video image is clear.

A tunable polarization filter is proposed based on one-dimensional photonic crystal with nematic liquid crystal defect. Tunable polarization filtering can be realized dynamically by the electrically controlled birefringence of nematic liquid crystal. The transmission spectra of TM mode are numerically calculated using the transfer matrix method. The results show that the filter has good tunablilty and advantages of simple structure, small volume, easy adjustment, low wastage and narrow pass band. The results imply that this filter has potential applications for wavelength division multiplexing and precision optical measurement.

Digital micromirror device (DMD) as an infrared scene generator, which has high frame rate, high spatial frequency, high grayscale, good uniformity and other advantages, is generally concerned in the study of target simulator for infrared imaging guided system. The principle of DMD is analyzed. The composition of target simulator for infrared imaging guided system is proposed. The simulation temperature achieves a high level above 400 ℃, and the grayscale could reach 214. Optical system and gray plate of the lighting system of the target simulator are designed.

The effect of quasi-DC discharge plasma filament on the cavity in a scramjet combustor is numerically investigated based on the dominant thermal mechanism. The electrodes are located near the upper edge of the back-step and at the bottom of the cavity. And plasma filament is formed in pulsed control mode. Change of prformace parameters such as wall pressure, shear layer, cavity drag force and mass ex-change rate under the different pulsed control frequencies is analyzed. Simulation results demonstrate that the first oscillation frequencies of the key points are close to the pulsed control frequencies, and other oscillation frequencies are the multiple of the pulsed control frequencies. The big recirculation zone is destroyed by the plasma filament, yet the cavity is preheated. The drag coefficient drops more apparently with higher control frequency, while the rate of mass exchange increases much more by the plasma, the mass exchange rate is higher under higher control frequency.

The presence of nonlinearity chirp in the transmitted synthetic aperture ladar (SAL) signal badly deteriorates the range resolution. The signal model with nonlinearity chirp is established in this paper, by which the pair-echo effect induced by the nonlinearity term is analyzed. By estimating the nonlinearity chirp using the time-shift characteristic of the Fourier transform, a novel modified frequency scaling algorithm is proposed to correct the ladar nonlinearity based on the residual visual phase filter. Through simulation experiments, the modified algorithm confirms its superiority in terms of resolution and image quality.

This paper described the principle of an all-optical cesium magnetometer based on absorptive detection. In order to reduce transverse relaxation rate and to maximize spin polarization time of the alkali-metal atoms, it is usually to fill the inert gas He and the diatomic molecule N2 which are used as buffer gases into the cell to achieve high measuring sensitivity. Not only the collision probability of polarized atoms with the cell wall but also the radiation trapping can be reduced or avoid by this approach. The relationships between the output signals of this magnetometer with buffer gas pressures were expressed here. After a detail theoretical analysis, it was found that the optimal gas pressure of the buffer gas was about 3.9×104 Pa for helium (He) and 3.6×103 Pa for nitrogen (N2).

Based on the theory of selective absorption of gas in the near-infrared region and the Beer-Lambert law, Raman scattering characteristics of hydrogen sulfide gas are researched. Meanwhile, a broad-band light source is used to detect the concentration of H2S gas. Self-focusing lenses are used as collimating or focusing lens for transmission gas cell. A method using cascaded GRIN lens to increase the optical-path length is presented, and the detection sensitivity of the gas cell is greatly increased by this method. By analyzing the experimental curves of hydrogen sulfide absorption, it is shown that the system sensitivity is 3.672×10-4 μW/(μL/L), and the resolution is 122.5 μL/L.

A quick and accurate detection method which can identify whether the meat contain excessive moisture is proposed. By using near-infrared (NIR) spectroscopy measurement, the meat moisture content model is established. In order to improve the accuracy and sensitivity of NIR spectra measurement, image information and the pH value data are used as assistant parameters of the meat moisture content model. Multi-sensor information fusion is performed on the moisture, image information and pH value. The detection is completed with a support vector machine (SVM) data classifier.

Total volatile basic nitrogen (TVB-N) content is an important index in evaluating the chicken′s freshness. We attempt to use synergy interval partial least square coupled with genetic algorithm to select the best wavelengths. Texture features of gray images of the corresponding wavelengths are extracted. Principal component analysis (PCA) is implemented on these feature variables from image information. We take the best principal component factor numbers as the input layer. And a prediction model of the TVB-N content is developed by the back-propagation artificial neural network (BP-ANN). The results of the model are achieved as root-mean-square error (RMSE) of 6.61 and 9.84, and correlation coefficient r of 0.9054 and 0.8030 in training and prediction sets, respectively. This work demonstrates that hyperspectral imaging technique is a valid means for quick and nondestructive detection of TVB-N content in chicken.

In order to improve detection sensitivity of Cu element in sewage by laser induced breakdown spectroscopy (LIBS). The LIBS test in aqueous solution of cuprum are conducted with a direct blow to the liquid level and the filter paper enriched method, experimental parameters are optimized and results of different methods are discussed. The results show that the best analyzing spectral lines of Cu is 324.7 nm; the optimal delay time is 1400 ns; the optimal pulse laser energy is 100 mJ. Getting the calibration curve of two methods, the correlation coefficients are 0.97047 and 0.99901. The limit of detection are 74 μg/mL and 1.5 μg/mL respectively. The results show that filter paper enrichment method works better. This study indicates that filter paper enriching method can improve the sensitivity of detection and reduce the limit of detection.

In order to realize the ultratrace detection of Hg2+ by optical waveguide spectroscopy, a displacement strategy of gold nanoparticles (Au NPs) for target analysis based on the optical waveguide spectroscopy is designed, which differs from the usual target-induced aggregation effect. The PATP-coupled Au nanoparticle (PATP-Au) multilayer was layer-by-layer assembled on the OWG chip surface and used as the probes to detect Hg2+. OWG spectroscopy can monitor the SPR extinction from Au nanoparticles, which enables to easily capture changes in the probe structure. Because Hg2+ has a higher binding affinity to the thiol group of PATP molecules, the presence of Hg2+ will greatly destroy the probe structure, produce large changes in surface plasmon resonance features of the probes. Our experiments indicated a high selectivity for Hg2+ detection and reached a low detection limit of about 1 nM.

Finite element analysis software ANSYS is used to calculate the stresses in GaN film on sapphire，and the results was proved to be reasonable by theoretical calculation. The stress distribution of GaN film on sapphire is simulated. The dependence of stress on deposition temperature, film thickness and substrate thickness is analyzed. The effect of non-uniform temperature distribution on stresses is also discussed. The results show that a largest thermal stresses appears in the center, a sharp reducing of stress occurs at the film edge and the rest parts are relatively uniform. When the deposition temperature increases, the film thickness reduce or the substrate thickness increases ,thermal stresses will increase. When the radial direction temperature has a non-uniform distribution in the sapphire substrate, the film stress will increase, and the larger difference of temperature is, the larger thermal stress in the film will be.