The atmospheric boundary layer height has important influence on particulate air pollution. A statistical investigation of atmospheric boundary layer height based on a large amount of Lidar data from multiple sites is used to analysis the characteristic in the Jing-Jin-Ji area. The atmospheric boundary layer height retrieved from the Lidar data is compared with the national weather service national centers for environmental prediction global data assimilation system forecast model result. Statistical results show that the atmospheric boundary layer of the Jing-Jin-Ji area has obvious characteristics of diurnal and seasonal variations, and the atmospheric boundary layer height is higher in the daytime than at night, and the peak value of the atmospheric boundary layer height occurs at 14:00. The atmospheric boundary layer height during the summer and autumn is higher than spring and winter, the atmospheric boundary layer height in winter also has a decreasing tendency. In addition, the statistical result of November 2014 based on all Lidar sites of atmospheric boundary layer height shows that the boundary layer height of the Jing-Jin-Ji area is between 300~900 m and higher in the southeast.

The action range of airborne infrared search and track (IRST) system is affected by the large humidity of atmosphere in low latitude areas. Aiming at this problem, the main factors affecting the atmospheric transmittance are analyzed based on the atmospheric data in low latitude areas in recent years. The mathematical model of atmospheric transmittance is established. The impact of height and oblique distance are also revised. Atmosphere transmittance at the wave band from 3 μm to 5 μm is analyzed by using Matlab under different seasons, weather conditions, pitching angles, heights and distances. Comparing with the simulation results of LOWTRAN7, the error is about 5%, which verifies the effectiveness of the model. The conclusion has significant reference value on guiding the practical operation of IRST system.

To deal with the problem of high current measurement in electrolytic aluminum industry, a portable fiber-optic current transformer (P-FOCT) is proposed on the basis of the traditional optical fiber current transformer (FOCT). Due to that the galvanometer accuracy is affected by the Faraday phase shift errors which are caused by the flexible sensing coil non-closed optical path and conductor eccentric position in the process of P-FOCT design and installation, the influence of sensing coil errors and conductor eccentric positions on P-FOCT are theoretically analyzed and experimentally tested. The results show that the Faraday phase shift relative error increases with the non-closed angle of sensing coil and decreases with the increase of the distance between conductor and the center of the non-closed length. Moreover, the Faraday phase shift relative error can be decreased by increasing the number of sensor head turns, and its accuracy can be improved.

In view of the difficulty of achieving high sensitivity and good stability at the same time for fiber current sensors, mathematical models of straight-through and reflective all-fiber current sensors based on Jones matrix are set up in theory according to Faraday effect. The simulation is conducted by the OptiSystem software, and the linear sensitivities of straight-through and reflective all-fiber current sensors are 0.24 and 0.37. A fiber loop ring-down structure is proposed, and the intensity modulation is converted into the time modulation. The effects of light source and external environment on the performance of system are eliminated, so the system can achieve high sensitivity and good stability at the same time. The scheme is verified in theory and experiment.

The characteristics of high-order Bragg waveguide grating based on phase-mask method are investigated, and the resonant wavelengths of Bragg waveguide grating with different orders all increase with the increasing of saturation coefficient. Influences of the order of grating, diffraction efficiency of phase mask and saturation coefficient on the refractive index modulation of Bragg waveguide grating are taken into consideration synthetically. The largest refractive index modulation amplitude can be acquired when the order of Bragg waveguide grating is 2 and the saturation coefficient is 0.67. In this case, the maximum reflection and the zero bandwidth of Bragg waveguide grating can reach the maximum. The maximum reflection increases and the zero bandwidth decreases with the increasing of grating length. The saturation coefficient of waveguide grating increases with the product of the writing beam intensity and the writing time. The saturation coefficient is 0.67 when the product is equal to 160 s·W/cm2. The optimal saturation coefficient can be acquired by controlling the writing beam intensity and the writing time.

A buried intrusion monitoring system has the characteristics of strong concealment, little affected by natural factors, low false alarm rate and high identify probability, and plays an important role in intrusion monitoring. The main technical scheme for security intrusion monitoring based on fiber sensing is introduced. The working principles of the fiber distributed vibration sensing (DVS) system and the fiber Bragg grating (FBG) vibration sensing system are described. Personnel invasion monitoring experiments for the two systems are carried out. The results demonstrate that the maximum effective detection range of the DVS system is 10-15 m, and the spatial resolution is about 20 m. The maximum effective detection distance of the FBG vibration sensing system is beyond 75 m. The key performances of the two systems are compared and evaluated, and the application of buried fiber intrusion monitoring system is also discussed.

Aimed at the mistiness and color distortion of underwater optical colorful image, an underwater image restoration method based on transmittance optimization and color temperature adjustment is proposed. Dark channel prior algorithm is applied to the underwater optical imaging model to realize the image visualization. Transmittance is improved by guided filter to increase its estimation precision. Then the image should be divided to bright areas and normal areas by setting threshold. Adaptive restored image is got by transmittance optimization. Finally the color of image is restored by adjusting the position of gray axis to rectify color temperature. Experimental result shows that the proposed algorithm can not only improve the clearness of image largely, but also correct the color accurately. Compared to other algorithms, the proposed algorithm have good results and robustness.

For highlighting the infrared targets in the visible image and advancing the quality of infrared and visible fusion images, an image fusion algorithm of infrared and visible images is presented by target extraction. The two binary images are fused to obtain the target image by edge extraction and threshold segmentation on the infrared images. The infrared image, the infrared target image and the value component of visible image turned to hue, saturation, value (HSV) color space are decomposed multi-resolution by Laplace transformation. The high-frequency decomposition coefficients are fused by rules based on calculating the mutual information, matching degree and energy of corresponding region, and the low-frequency coefficients are fused by region information rules combining with the rules based on regional fusing. Lastly the fusion image reconfiguration is realized through Laplace transformation and inverse transformation. Experimental results show that the image fusion algorithm presented highlights the targets of the infrared image as much as possible, and injects details information of the visible image. Fusion image definition and visual effects are better than the traditional algorithms.

Point cloud registration plays an important role in three-dimensional laser scanning technology as it affects modeling quality directly. The iterative closest point (ICP) algorithm is widely used in point cloud registration because it can register the point cloud automatically and accurately. But the ICP algorithm is complex in time and space, slow convergence and easy incorrect matching. The ICP algorithm and the curvature extremum algorithm are combined as a new algorithm to process point clouds with apparent curvature features. Experiments are conducted concerning effect of convergence efficiency, robustness and quality of initial data on the new algorithm, and the results of the classic ICP algorithm and other modified ICP algorithms are compared. The results show that the proposed algorithm has high convergence efficiency for point clouds with apparent curvature features and good convergence stability for worse initial data.

A tandem full-field optical coherence tomography (FF-OCT) system based on compensation interferometer is proposed. The new system consists of a common-path detection interferometer and a double-armed compensation interferometer. The former is used to detect the backscattered light from the sample, and the latter is used to compensate the optical path difference of two arms of the detection interferometer. A broadband halogen light source and a large numerical aperture microscopic objective are used for imaging. When the phase is modulated by a single chip-based control device, en-face tomography images of samples are obtained from the interference images. The experiment of optical tomography imaging for onion cells is conducted to demonstrate the feasibility of the proposed system. The detection interferometer based on the common-path structure has a small size and it is not sensitive to external environment. The handheld detection interferometer can be achieved when we use a fiber to connect two interferometers, and it has great importance in achieving endoscopic probes.

To improve the phase reconstruction accuracy of two-step phase-shifting interferometry measurement method, a phase blind demodulation algorithm based on zoned background estimation is proposed. In the algorithm, a sequence of zero value points in interferograms are picked out as seeds. A Voronoi figure surrounding these seeds is created, and the Voronoi figure segments each interferogram into several zones. The background of all points in these zones is set as the seed background, and a whole background is obtained when we combine these seed backgrounds. Numerical simulation and experimental analysis are conducted. Numerical simulation results show that the root-mean-square error (RMSE) of demodulation phase of the proposed algorithm is close to that of the method with real background. Experimental results show that the demodulation phase RMSE is reduced by 16% compared with the traditional low-pass filtering method.

We propose a new grating model building method by the inverse-deducing method using the coordinate relationship between the reference plane and fringe pattern. The method can make sure the fringe pattern projected to the reference has standard periodicity and can solve the problem of optical distortion in reference plane in traditional phase measurement profilometry produced by divergent illumination. The 3D shape of the tested object can be reconstructed with the help of phase-height mapping algorithm. The proposed method does not need to store the relationship between phase and height as the traditional method. It does not constain the 3D measurement much, simplifies the design of measurement system and has high measuring precision. Computer simulations and experiment results validate the feasibility of this method.

Four-step spatial quasi-phase-shifting technique, an analysis method for phase estimation from a single spatial carrier fringe pattern, is proposed for dynamic optical measurement. Based on the frequency-modulation form of sinusoidal function for the carrier fringe pattern, the phase demodulation formulas are derived with the intra-frame phase shift relations and the integral intensity in four segments. This proposed algorithm has robustness for white Gaussian noise by using the integral intensity for phase estimation, and has high spatial localization for local noise isolation. It can deal with the problem of frequency mismatch in the sub-fringe integration algorithm. Because the local frequency detection process is not necessary, the computation efficiency for the phase estimation is increased. Particularly, it is suitable for dynamic measurement. The simulation and experimental results demonstrate the feasibility and the validity of the proposed algorithm.

A photonic crystal polarizing beam splitter based on directional coupling structure is proposed. The beam splitter consists of two single-mode waveguides. By adjusting the width of the two single-mode waveguides, the coupling length can be changed. The splitter is simulated and analyzed by using finite-difference time-domain method. The results show that at the wavelength of 1550 nm, both TE and TM polarizations achieve mode split. The transmissivities of TE and TM modes both exceed 90% and the extinction ratios reach 22.4 dB and 18.2 dB respectively. The size of the device is only 25.8 μm×13 μm.

Based on the gain theory and the laser dynamic theory of laser, the effects of laser active region size, fiber grating structure, coupling efficiency and injection current on frequency noise and relaxation-oscillation frequency are analyzed, when we combine with the classical laser rate equation. To obtain low frequency noise and high relaxation oscillation frequency, a simulation is conducted. The simulation results show that a small laser active region size, a strong external cavity light feedback and a high injection current are beneficial to the improvement of noise characteristics, and the influence of injection current is especially important. When the injection current is 9 times higher than the threshold current, the frequency noise reduces by 14.7%, and the relaxation oscillation frequency increases about 6.0 GHz.

The parameter control method is utilized to carry out the experimental investigation on laser trepanning of GH4037 superalloy and the trend in the effects of pulse energy, defocusing amount, trepanning velocity, and trepanning times on the hole taper and entry-exit-hole diameter is achieved. The results indicate that the pulse energy and defocusing amount obviously influence the hole diameter and taper angle, while the trepanning velocity and trepanning times mainly influence the hole morphology. The larger the defocusing amount is, the larger the heat-affected zone, entry hole diameter, and taper angle are. Increasing trepanning times and selecting appropriate trepanning velocity (3-6 mm/min) are helpful to improve the hole quality, reduce the accumulations around hole aperture, and improve the hole roundness.

An optimization method of laser quenching process parameters of Cr12MoV die steel is proposed based on the orthogonal experiment and Vague set. The laser power, scanning speed, overlap rate, black paint thickness are taken as optimizing process parameters, while the quenching layer surface hardness after quenching, quenching layer depth, relative wear rate and corrosion rate of quenching layer are taken as integrated process optimization objectives. Orthogonal experiment is first carried out to obtain the data samples, and then the data are analyzed and processed by the Vague set theory to realize the optimization of process parameters. The optimization of single process is first carried out, and then comprehensive process optimization is taken through single process objective weight sum, where the multi-objective optimization problem is transformed into a single objective optimization problem. The optimization results are listed as laser power of 1400 kW, scanning speed of 15 mm/s, lap ratio of 40%, and coating thickness of 60 μm. Test experimental results indicate that the optimization of process parameters make the hardness of quenching layer increase by 1.62%, the relative abrasion value decrease by 9.84%, the corrosion rate decrease by 9.26%, and the quenching layer depth only decrease by 1.33%.

Under different protection conditions of shielding gases composed of pure N2, pure Ar, or N2 /Ar mixing, one experiment of fiber laser welding of 304 austenitic thin plate with a thickness of 2 mm is conducted, and the effects of shielding gas pressure, gas type, and mixing ratio on the weld joint morphology and mechanical property are investigated. The results indicate that the larger the shielding gas pressure is, the larger the weld penetration depth becomes, but the gas pressure has no obvious influence on the weld strength and hardness. When the N2/Ar mixing gas is used as the shielding gas, the larger the N2 content ratio is, the larger the penetration depth becomes, and the tee-heeded weld is kept no matter what the content ratio of shielding gas is. The type and content ratio of shielding gas have no obvious influence on the weld strength and hardness, but the strength and hardness are both larger than those of substrate.

In order to reduce the errors in the formation direction (Z axis) during the process of selective laser melting (SLM) of TC4 titanium alloy, the generation and variation of Z axis errors caused by powder melting during the SLM process are investigated. The mathematical models describing the accumulation and compensation of Z axis errors are established, and one corresponding compensation method is proposed. Formation experiments are conducted to verify the effectiveness of these mathematical models. The experimental results indicate that these models can effectively describe the accumulation and changing trends of Z axis errors. With the proposed compensation method from these models, the Z axis error can be greatly reduced. Compared with the traditional Z axis error analysis method, the new model is more accurate, and it provides a reference for the error control and rapid selection of optimal layer thickness in SLM of metal materials in future.

The tests of laser drilling of 304 stainless steel specimens is conducted, the surface roughness parameter is obtained by the profilometer, and based on the back-propagation artificial neural network, the neural network prediction model based on the relationship between the three process parameters of laser power, pulse frequency, and defocusing amount, and the microporous surface roughness is established. After lots of network trainings with enough test data, it is confirmed that this artificial neural network model possesses a high prediction precision, the predication error is controlled around 6%, and the maximum error is less than 8.08%. This model can precisely predict the surface roughness of laser drilling pore surface, and effectively shorten the preparation period for laser drilling operations.

The energy band structures of Fe-doped, S-doped and Fe-S co-doped ZnO are investigated using first-principles pseudo-potential method based on density functional theory. The density of states and optical properties are compared and analyzed as well. The results indicate that the lattices of ZnO distort after doping. The energy gap of ZnO decreases because of S doping. The several impurity energy levels are introduced after Fe doping and Fe-S co-doping, which lead to the significant increase of photon energy absorption in visible and ultraviolet regions, the expansion of spectral response range and the improvement of ZnO photocatalytic performance. In the Fe-S co-doped ZnO system, the interaction between Fe ions and S ions leads to the decrease of impurity energy levels in the band gap, and the absorption coefficient is between Fe doped and S doped ZnO.

Critical power for small-scale self-focusing (SSSF) of Gaussian beam is studied by both theoretical analysis and numerical simulation. It is found that the initial modulation amplitude affects the critical power for SSSF of Gaussian beam. Generally, critical power of Gaussian beam deviding into filaments decreases with the increase of initial modulation amplitude, and it increases with the decrease of initial modulation amplitude. When the input power of Gaussian beam is higher than the critical power of whole beam self-focusing but lower than the critical power of SSSF, the Gaussian beam collapses into a single spot as the laser beam propagates in nonlinear media. When the initial input power of Gaussian beam is higher than the critical power of SSSF, the Gaussian beam divides into many high strength filaments as the laser beam propagates in nonlinear media. As for the nonlinear propagation process of Gaussian beam, there is a competition between the whole beam self-focusing and SSSF, and the result of the competition is determined by the initial parameters of Gaussian beam.

The light intensity distribution of warning light for the temporary closure of airport runway is critical to the guide of aircraft. In view of the effects of configuration, layout, and other factors of warning lights, one algorithm for calculating the whole luminous distribution of warning light is proposed based on the light intensity distribution model of single lamp. The experimental results indicate that the fitting degree between light intensity distribution obtained by this method and that from the practical measurement is larger than 98%, and the accuracy here is improved by more than 6% compared and with that from the superposition method of single lamp.

A cumulative feedback optimization algorithm based on illumination deviation restrained by energy mapping relationship and easy processability is proposed, and a freeform surface lens with uniform illumination distribution and light emitting diode (LED) of chip on board (COB) as light source is designed. In this approach, the new target light distribution is modified by accumulating the illumination deviation after each iterative feedback optimization between the simulation light distribution and the target light distribution to the presupposed target light distribution. The target light distribution after modification is then used to reconstruct the model of the freeform lens by combining the energy mapping relationship. Meanwhile, to make the designed lens easier to be molded and processed, the structure of the lens is modified by restraining concave plane of the lower half of lens into vertical plane in the feedback optimization progress. With this method, the corresponding freeform lens is designed with Cree CXA1816 COB LED as light source. The results show that the uniform illumination distribution in a circular region with a distance of 1000 mm from light source and a radius of 1480 mm can be achieved after 3 times feedback optimization. Finally, according to the design results, the corresponding lens is fabricated, and the illumination effect is tested. Actual measured illumination of the lens is consistent with the simulation results.

Usually, a lens is used in a large-aperture mirror testing system. The deformation caused by gravity of the lens seriously influences imaging quality, so it is a critical work to reduce deformation of a support system by optimization. We investigated a large-aperture lens with 1.5 meter diameter in a testing system, and the 3D solid model constructed by Solidworks was imported into Ansys software for finite element analysis. The position of support points and support force were optimized with Design-Expert software and OPT workbench of Ansys. The front and rear surfaces of the distorted mirror were simulated with Zernike polynomial. The root mean square (RMS) values of the two surfaces′ deformation are 1.85 nm and 3.28 nm, Peak to valley (PV) values are 9.4 nm and 24.4 nm. Meanwhile the RMS wavefront error is 0.998 nm, which meets the technical requirements.

An iris recognition lens composed of three plastic aspheric lens for mobile phone application is designed. The pixel size of focal-plan array detector complementary metal oxide semiconductor (CMOS) chip is 1.12 μm. The F number of the designed lens is 2.0, the field of view is 32.6°, and the total length is 4.0 mm. At the optimal work distance of 320 mm, the modulation transfer functions (MTF) of all fields at 1/2 Nyquist frequency are larger than 0.45, the optical distortion is less than 1.2%, and the relative illumination is higher than 87%. The optical system has the advantages of simple structure, small volume and excellent image quality.

Compared with the traditional lighting, intelligent lighting systems which use light emitting diode (LED) as the light source are efficient, comfortable and environmentally friendly. Real-time acquisition and dynamic feedback for environmental data are the research focus for LED intelligent lighting systems. Based on the modular design mentality, an integrated LED intelligent lighting system is proposed, and the mapping relationship among environmental parameters, human comfort index and output parameters of light source is established. The multi-channel integrated module is used to monitor the change of environmental parameters in real time, and the optical properties of the light source can be adjusted automatically to satisfy the requirement of human comfort. The established system can synchronously collect and feed back the sound, temperature, humidity and illumination in the space environment. By analyzing the changes of luminous flux, color temperature, spectrum and color rendering index in real time, we demonstrate the validity of the established system. The proposed system achieves the synergy fusion of automatic control and green lighting, and it is a kind of generalized, low-cost and humanized lighting control system. The system will has a broad application prospect in the field of lighting and display.

We report a process for the functionalization of graphene prepared by chemical vapor deposition with plasma treatment. A pH sensor is prepared by the treated graphene. The micro-structure of graphene before and after plasma treatment is investigated by contact angle meter, Raman spectrometer, X-ray photoelectron spectroscope and atomic force microscope. With plasma treatment time increased, the contact angle with water droplet is gradually reduced. Raman spectroscope result indicates the D and D′ defect peaks start to merge and 2D peak is suppressed and broadened. In the X-ray photoelectron spectroscopy, plasma treatment leads to the oxygenated functional groups on the graphene surface. It is found that surface roughness of graphene is increased after plasma treatment. Under the optimized conditions, the sensitivity of graphene pH sensor with plasma treatment can be improved by 3 times.

At terahertz frequencies, three types of Bessel resonators, namely, a stable Bessel-Gauss resonator, a Bessel resonator, and an unstable Bessel-Gauss resonator, are built based on quasi-optical theory and technology. To strictly analyze the diffraction field distribution characteristics of the cavity, the boundary element method is used to calculate the iterative dyadic Green′s functions (IDGF), whose algorithm is then used to calculate the three-dimensional self-reconstructing model of the cavity. The zero order model and high order model of three types of Bessel resonators are compared and the results are given. The Bessel beam or Bessel-Gauss beam generated are expected be used in such fields as communications, measurement and imaging in quasi-optical or terahertz spectrum.

To figure out the effect of rainfall on the free space quantum communication, the effect of rainfall intensity on extinction coefficient is discussed based on the theory of the distribution of raindrops and the Mie scattering theory. The relationship between photon attenuation, channel capacity and rainfall intensity is proposed. The calculation model of channel survival function and transmission distance is established. And the performance parameters of the system are simulated. Simulation results show that, without considering the effect of atmospheric aerosol particles and other circumstances, when the rainfall intensity is 1.46 mm/h, the transmission distance is 3 km, the initial energy of the photon decreases to 50%, the channel capacity is 0.2702, the channel value of the survival function is 0.9122 and the error rate of channel is 1.8×10-8. Thus, the rainfall has different influences on the performance of free space quantum communication, including the cavity of the channel, the survival function and the error rate. Therefore, the parameters should be adjusted adaptively based on the rainfall intensity to improve the reliability of free space quantum communication.

To make up the shortcomings that data redundancy is large and the fusion result is not ideal when pyramid transform algorithm decomposes, a new algorithm of remote sensing image fusion optimized by pyramid transform algorithm is proposed. The proposed algorithm uses pyramid decomposition to build pyramid sequence. According to the relevant weight coefficient given by prior knowledge, the remote sensing image is reconstructed by iterating. Then through optimization selection of Baldwinian clonal selection algorithm, within the acceptable scope of iteration, the weight coefficient is adaptively modified and chose, and the suitable fusion parameter is sought and estimated to optimize fusion effects so as to avoid empirical selection of pyramid transform algorithm. In order to highlight the algorithmic merits, experiment applies pyramid transform optimization, pyramid transform optimization via genetic algorithm, and pyramid transform optimization via particle swarm optimization algorithm to make a comparison. Fusion quality is analyzed and evaluated from the two aspects of visual effect and mathematical statistics. Experimental result indicates that this arithmetic fusion result by the proposed method is consistent with human visual perception, and conducive to image analysis and information extraction.

Logarithmic ratio k of aerosol backscatter-to-extinction is usually as an assumed value in solving lidar equation. The relationship expression among value k, wavelength exponent, measurement wavelength and aerosol extinction coefficient is derived. A new method to determine value k is put forward. The value of k under different weather conditions is initially analyzed by using the data of 532 nm Rayleigh-Raman-Mie lidar and micro pulse lidar and combining CE-318 sun-photometer data. To verify this method, the visibility is brought to estimate the actual condition of aerosol extinction coefficient. It shows that under better air condition, aerosol extinction coefficient is closer to the result estimated by visibility only in k=1.0, and under foggy weather, when the value of k calculated by this method changes from 0.7 to 0.9, the relative error between aerosol extinction coefficient and result estimated by visibility reaches the minimum. It shows that the calculating value of k using this method has certain reliability.

Optical turbulence forecast involves many subjects such as atmospheric science, computational mathematics and optical engineering and many technologies such as computer technology and turbulence measurement technology. It is urgently needed to improve the capability of atmospheric optical turbulence forecast in low stratosphere. The reason why the mesoscale meteorological model is chosen for forecasting optical turbulence, the characteristics of representative mesoscale meteorological model, optical turbulence parameterization, current situation and challenges of optical turbulence forecasting are discussed. The prospect of future development in this field is discussed. The outer scale parameterization formula in accordance with the regional climatic characteristics of China, the nesting of mesoscale and microscale models, and the non-Kolmogorov turbulence statistical characteristic and the new method for the atmospheric optical turbulence parametrization under low stratosphere are studied. The study will has an important significance in spatial resolution and forecast accuracy of optical turbulence forecast.

Generally, laser amplification systems can be divided into two types, high peak power laser systems and high average power laser systems. In recent years, there are more and more applications which need the characteristics of the above two systems at the same time. That is to say, the system is required to be able to output high peak power laser and to work efficiently with high repetition frequency, as well as with high energy conversion efficiency. According to the increasing application demand, the coherent amplification network (ICAN) plan solves the key problems limiting power increase, such as nonlinear damage of high power laser pulse in fiber, based on chirped pulse amplification, fiber beam splitting, fiber amplification and coherent beam combination techniques. The waveform distortion caused by the nonlinear effect in fiber is avoided, while the higher energy and peak power are obtained. It offers a solution to break through some key barriers which limit the development of high peak power, high repetition frequency pulse laser system. The scaling amplification characteristics of fiber amplification network provide solutions for many new applications, such as laser-based particle accelerator, laser-driven spent fuel transmutation, orbital debris removal, laser-driven fusion energy and so on.

Based on the generation, harmfulness and solution of thermal effects of lasers, different kinds of lasers are illustrated in detail from the perspective of their principle and recent progress on high power, including thin disk lasers, heat capacity lasers, slab lasers and fiber lasers. As practical application on laser weapons, projects and progresses of laser weapons are classified. The development trend of high power solid-state lasers is proposed, which is low cost for operation and maintenance, compact structure and unmanned aerial vehicle (UAV) loading. Furthermore, the development advantage and the tendency of composite lasers are addressed.

Picosecond laser has picosecond (10-12 s) pulse width, which is the same as the electro-optical relaxation time (10-6-10-12 s) or even shorter. When picosecond laser interacts with materials, there is no enough time for electron to transfer the energy to crystal lattice. Therefore, there's little heating effect during fabrication, which is called cold ablation. This technology is widely used for precision machining in astronautics, national defense, materials, medical science, biological science and so on. The technique of micro-nano fabrication by picosecond lasers is introduced and the precision drilling on high hardness metal, the hard and brittle materials cutting and the selective surface removal with picosecond lasers are summarized. The challenges and future trends of micro-nano fabrication by picosecond lasers are pointed out.

Laser Doppler electrophoretic light scattering is one of the standard methods for measuring the zeta potential of nanoparticles. However, the signal is usually mixed with the low frequency noises and the deviation from mathematical model of autocorrelation function. We introduced the Hilbert-Huang transform into the data analysis of the measurement in order to improve the measurement accuracy. After decomposing the original signal into several intrinsic modes, we found that by eliminating the low frequency noises and the deviation from mathematical model of autocorrelation function, the reconstructed signal was greatly improved. The simulated and experimental results demonstrate the feasibility and validity of this method.

The analysis of the sampled fiber Bragg grating reflection spectrum usually obtained with so much noise. Levenberg-Marquardt (LM) algorithm is used to optimize the Gaussian curve fitting coefficient and the optimized Gaussian-LM algorithm is used for fiber Bragg grating spectrum peak detection. The comparison of the peak search results proves that the Gaussian-LM algorithm is important for optimizing the Gaussian curve coefficient. Research shows that Gaussian-LM peak detection algorithm can effectively reduce the peak error. It also improves stability of central wavelength detection and accuracy in fiber Bragg grating sensor system based on wavelength demodulation system.

(Bi,Er)2Ti2O7 dielectric thin films are synthesized on indium-tin-oxide (ITO) glass substrates by the pulse laser deposition method. The pure Bi2Ti2O7 thin films can be obtained when the deposition temperature is controlled in the range of 500～600 ℃. The range of dielectric constant of (Bi,Er)2Ti2O7 thin film is 166～178 and the dielectric loss is less than 0.05 at room temperature. When the frequency and the temperature are changing, the dielectric constant remains stable. The spectral analysis shows that the up-conversion luminescence spectra of thin films contain two green light emission bands centered at 527 nm and 548 nm and a red light emission band centered at 660 nm. These emission bands correspond to the transition of Er3+ from 2H11/2, 4S3/2 and 4F9/2 levels to the ground level 4I15/2. (Bi,Er)2Ti2O7 thin films can be considered as a kind of multifunctional material, which will be widely applied to transparent optoelectronic devices in the future.

Indium-tin oxide (ITO) thin films are deposited by electron beam evaporation and treated by rapid thermal annealing (RTA) under nitrogen. The influences of RTA treatment on crystal orientation, microstructure, composition and photoelectric properties of ITO thin films are measured by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), visible spectrophotometer and four-probe meter. The analysis results show that the rise of annealing temperature is helpful for Sn to release electrons on the 5s orbit, and Sn4+ to replace In3+ to form a new chemical bond. Moreover, the binding energy of In and Sn elements is increased, their degree of oxidation is changed, and the electron carrier concentration and mobility are increased. Besides, the crystal lattice distortion of ITO thin films, the defect density and compactness are ameliorated, and the recovery of the lattice mismatch is promoted. In the experience of 450 ℃ RTA, preferable photoelectric properties of ITO thin films can be obtained.