The problems of the amplitude spatial light modulator(SLM) by electrical addressing in high power laser systems are analyzed. Firstly, the effect of the black gate of the SLM by electrical addressing on the near-field beam shaping is analyzed theoretically. The technical scheme of obtaining the best shaping effect by optimizing the aperture size of the spatial filter is proposed, and the energy efficiency of the filter is calculated. Meanwhile, the effect of liquid crystal SLM′s opening ratio on beam shaping is analyzed. In order to enhance the near-field shaping accuracy, the opening ratio of the SLM should be better than 64%. Finally, the phase distortion introduced by the pure amplitude spatial light modulator is studied. The additional phase is obtained from the theoretical analysis and experimental verification. The calculated maximum additional phase is 0.135λ, which means that the influence on the laser device is within acceptable range.

To find out the role of laser parameters on in-vitro tissue bonding, experiments are designed to study the effect of laser parameters, such as power and scanning mode, on the appearance and tensile strength of in-vitro skin tissue incision, and then the process parameters are optimized. Results show that the appearance and tensile strength of tissue incision is better and greater when we use low laser power with long welding time, and also the irreversible thermal damage decreases. Using interval laser scanning increases the bioactivity closed to the incision and decreases the thermal damage. Experiments are performed to verify the reliability and stability of the optimized parameters, and the tensile strength of incision is tested. Results show that the bonding along the depth of tissue can be realized and no carbide or burning occurs. Compared with that of the continuous laser welding process, the welding time is decreased by 30%-40%, and the tensile strength of incision is 0.38 MPa, which can meet the requirement.

The transmission of orbital angular momentum (OAM) modes in grapefruit-type microstructure fiber(MOF)is studied. The fiber core is surrounded by grapefruit-type air holes with diameter of 3 μm. The refractive index difference between fiber core and air hole is large, so that the transmission light can be concentrated into the core and stable modes can be formed. Based on the finite element method, vector eigenmodes in the fiber are analyzed. The effective refractive indexes and the mode filed distributions of these modes are obtained. The results show that the transmission of ten OAM modes can be supported around the wavelength of 630 nm. The effective refractive index differences among OAM modes are larger than 0.01. The large effective refractive index difference can suppress mutual coupling among different modes, and improve the transmission performance of OAM modes in fiber. In addition, we use the special designed optical vortex Dammann gratings in experiments to detect the OAM1,1 and OAM-1,1 modes after transmitting for 1 m in MOF.

Photon spiking neurons are connected by weighting devices, so the implementation of weighting devices is critical for realizing the large-scale computation of neural networks. Based on the variable optical attenuator (VOA), a weighting device for automatically adjusting photon spiking neuron is developed. The weighting device includes VOA, photoelectric detector, single chip, analog to digital converter, digital to analog converter, amplification module, etc. The weighting device can quickly calculate and look up table, and the attenuation values of VOA can be adjusted online based on the received optical signal. The weighting device has the advantages of high efficiency and easy implementation. When we combine the optical spike-timing-dependent plasticity (STDP) circuits and the proposed weighting device, STDP learning mechanisms for photon spiking neural can be achieved. The weighting device is detected when the height of STDP curve window is 0.2, and four STDP learning curves are obtained. The experimental results are consistent with the theoretical computation results.

An optical multi-beam synthetic system based on differential true time delay network which is with micro-optical array is proposed, and the relationships among the structural parameters and the beam-forming performance of the proposed system are studied. The initial phase and the consistence of amplitude and phase are optimized when we optimize the parameters of differential true time delay network based on micro-optical array. The directional diagrams of antenna elements are optimized when we optimize the structural parameters of antenna elements, and the problems of existing grating lobe and wide beam in beamforming are solved. At last, the grating lobe is suppressed, the extinction ratio of sidelobe is larger than 10 dB, the 3 dB bandwidths are 35° at 3.8 GHz and 29° at 4.9 GHz, the steering error is less than 1.5°, and the frequency covering band is 2-6 GHz. The proposed system has wide application prospects in optically controlled phased array radar.

A diode pump high power and high efficiency Nd∶YAG planar waveguide oscillator at quasi-continuous mode is reported. The 1 mm×10 mm×60 mm planer waveguide is selected as gain medium. The plane-plane cavity is built, and the output properties of the planar waveguide laser under different output mirror transmissions and different pulse repetition rates are studied. Experimental results show that when the output coupler transmission is 79%, an average output power of 441 W for the 1064 nm laser is achieved under the pulse repetition rate of 500 Hz and the drive current of 200 A. Under five different repetition rates, the maximum single pulse energy is 928 mJ, and the effective optical to optical efficiency is 53.2%. The pulse waveform of output laser is consistent with that of the pump laser, and both have a pulse width of 240 μs. The output power of the oscillator can be increased after the system optimization.

The beam quality of no-chain pulsed HF laser cavity is improved by optimizing a positive branch confocal unstable resonator. Cavity structures of five different parameters are designed with different cavity magnifications and laser mode volume diameters. The effect of different cavity structure parameters on laser beam quality and laser pulse energy are studied by using the diffraction limit magnification based on the measuring of the focusing spots. The experimental result shows that diffraction limit magnification of 2.3 can be reached with the cavity magnification larger than 2.5. In order to get a better experimental result, the optimum diameter of mode volume is controlled within 80% of the gain cross section, and a better laser beam quality is obtained under the discharge electrode structure in the experiment.

By detecting and counting the circuit, the photoelectric signal of laser gyro is amplified, shaped and the phase of it is discriminated. The pulse that are signals proportional to the rotating angle of gyro are obtained. Since the output signals of gyro are weak photoelectric ones, and shot noise and thermal noise disturbances exist in the detecting circuit, it is crucial to improve signal-noise ratio to ensure normal function of the counting circuit. To improve the signal-noise ratio of the detecting circuit, we have to guarantee that the output optical power is as large as possible. The optimal transmission of mirror for optimal optical power is derived and calculated according to the power formula of laser gyro, and experiments are followed to verify it. Both theoretical calculation and experimental results prove that, by using optimal transmittance, the output optical power of the mirror can be effectively improved.

A new miniature diode-end-pumped Dy∶YAG yellow laser based on the domestic single crystal is reported. According to the special energy structure of Dy∶YAG laser crystal, the yellow laser of 582.7 nm on the 4F9/2→6H13/2 transition is obtained using laser diode pump at room temperature. In order to matching the pump wavelength with the Dy∶YAG crystal absorption peak, the blue LD is used as the pumping source, and the center wavelength is optimized at 447.3 nm by tuning the LD operative temperature. With a total incident pump power of 1.4 W, the yellow laser maximum output power of 56 mW is achieved. The maximum single pulse energy is up to 1.1 mJ. The optical-to-optical conversion efficiency is 4% and the slope efficiency is 5%.

The output laser pulse cannot sustain a flat-top temporal profile owing to the time domain distortion caused by gain saturation effect in laser amplifiers during the transmission and the amplification of high energy pump laser pulse. Therefore, the pump laser pulse needs to be pre-shaped to compensate the gain saturation in the amplifier. A temporal shaping technology based on optical-optical synchronization amplification is proposed to compensate the time domain distortion caused by gain saturation. The proposed technology is based on the conventional amplification model, and it is not restricted to the width of laser pulse. The proposed technology is simple to operate and costs low. Theoretical simulation results indicate that the effective temporal shaping for the input pulse of laser system can be achieved and the gain saturation can be compensated by the proposed technology, and the output pulse with flat-top shape in time domain can be obtained.

In order to study the laws of single- or double-layer metal/polyimide etched by movable pulse lasers, one general model of movable nanosecond pulse laser etching is built with the finite element method. The influence of laser movement speed on etching depth is discussed, and the law of temperature change of the metal Al thin films and double-layer metal thin films etched by movable pulse laser is analyzed. The results show that, with a certain movement speed, the etching depth increases at the beginning, then the increase rate slows down, and the etching depth approaches to one constant maximum value. The temperature change at the interface between the metal and the substrate material lags behind that of the metal thin film close to laser source, and the substrate temperature rises continually after turning off the laser. As for double-layer metal films, the choice of thicker bottom layer with a high thermal conductivity is helpful to protect the polyimide substrate.

To improve the numerical simulation accuracy of carbon fiber reinforced thermal plastic (CFRTP)/stainless steel laser direct joining (LDJ), a fitting formula of thermal contact conductance is established based on the experiments. Taking the thermal contact resistance into account, we establish a three-dimensional finite element thermal contact model of LDJ. The theoretical simulation and experimental results are compared and analyzed. The results show that the thermal contact model is more consistent with the reality compared with the traditional model. Therefore, the thermal contact model can be used to characterize the influence of clamping pressure on the laser joining quality. When the laser power is 339 W and the clamping pressure is 0.1 MPa, the relative error is 12.3% for the traditional model and it is reduced to 2.8% for the thermal contact model. The numerical model can help to improve the accuracy of numerical simulation in the process of LDJ and choose optimal technological parameters.

An experimental study on the process of backside wet etching sapphire induced by pulse fiber laser is carried out by acoustic emission detector. In the backside wet etching sapphire process induced by laser, the detected acoustic emission signal contains a lot of characteristic information. The backside wet etching sapphire process can be characterized by parameters such as amplitude, marse and hit-counting of acoustic emission signal. Before the sapphire is cut through, the acoustic emission signal shows few acoustic emission events, large amplitude of 90-100 dB, large marse and small hit-counting. After the sapphire is cut through, the acoustic emission signal shows many acoustic emission events, small amplitude of 40-80 dB. Meanwhile, the marse becomes nearly zero, and the hit-counting is large.

The influence of different shielding gases on microstructure and property of laser welded joint is studied by the weld test of microalloyed C-Mn steel. The results show that, under the same condition of laser weld heat input, full-penetration weld seams can be obtained by three different shielding gases of N2, Ar and air, but the sags in the weld zone shielded by N2 are the most obvious. The microstructures of the weld zone are mainly lath martensite. In the weld seam formed in the air, there are a few acicular ferrites, the number of inclusions is more than that shielded by N2 and Ar, and the ratio of large scale inclusion is relatively high. In all three cases, the mean microhardness and tensile strength of the welded joint are higher than that of the base metal, while the mean microhardness of the weld seam in the air is smaller than that when shielded by N2 or Ar.

The influence of laser shock peening (LSP) treatment on the microhardness, residual stress and microstructure of the cladding layer surface of 316L stainless steel is studied. The results show that, the microhardness and residual stress of the cladding layer after LSP are improved obviously; the change of microstructure occurs obviously, and the grains are refined where columnar structures transform to equiaxial structures; the current density of self-corrosion of the cladding layer is reduced, and the corrosion resistance of the material is improved.

Pulsed laser ablation in liquid (PLAL) has attracted significant interest in the academic community for its remarkable characteristics of environment protection, wide application range and capable for composite material preparation. But the relative lower preparation rate of PLAL prevents it from further development. Silicon nanostructures with lattice (400~800 nm) and spherical (100~300 nm) patterns on microfluidic chip with promoted production rate is achieved by combining microfluidic technology and PLAL. The morphology structure and distribution are characterized by scanning electron microscope and spectrometer. The relationships between preparation rate of nanoparticles and microfluidic flow velocity as well as laser ablation power are obtained. The maximum preparation rate of PLAL enhances by 30%, up to 87.5 mg/min by the proposed method. Which provides a new technique route of PLAL industrial production.

In order to repair the sprocket of scraper conveyor, the 3D metal printing technology is used to test on 34CrNiMo6 steel plate samples. These samples are carefully examined to acquire metallographic structure, microhardness, indentation and wear resistance. Results show that the hardness is 2~3 times of that of the substrate material, and the wear resistance is also improved dramatically. Subsequently, the employment of this technology to repair a sprocket is carried out. A 3D laser scanner is used to scan a brand new and a worn sprocket to obtain the corresponding point clouds. The data are used to calculate the worn volumes of the sprocket. Software package CATIA is used for modeling and slicing with some newly developed add-on functions. Based on these data, the numerical control programs are established to define and control the repairing paths and parameters of the worn sprocket accurately. 3D printing, milling and test results show that the sprocket is properly repaired, which validates the secondary development, the numerical control programs as well as the developed add-on functions.

The dynamic behavior, metal transfer mode, as well as the characteristics of electrical signals during the fiber laser with high power and the pulsed gas metal arc welding (GMAW-P) hybrid welding process are studied. The results show that the pure Ar gas can be used as the shielding gas in the fiber laser welding. The mixing of the GMAW-P arc with the fiber laser leads to the expansion of laser plasma and the shortening of arc length. The comparison results of the voltage probability density show that the dynamic load fluctuation of the laser-leading mode is much more violent than that of the arc-leading mode.

Aimed at the problem that the seam tracking system with low adaptability is sensitive to noise in the actual welding environment, and combined with the strong feature expression ability and self-learning function of the depth convolution neural network, a welding seam detection and tracking system based on depth hierarchical feature is studied. The location of seam from noise-contaminated serial images is accurately determined by this system. A fuzzy immune self-adaptive intelligent tracking control algorithm is designed to completely solve the chattering problem of welding torch following the calculated trajectory. The experimental results show that, under the interference of strong arc and splash, the metrical frequency of sensor can be up to 20 Hz, the tracking accuracy of the welding seam is about 0.2060 mm, and the end of the welding torch runs smoothly during the process of welding. The system can realize real-time tracking of the welding seam, has strong anti-interference ability, and can accurately track the trajectory of the welding seam, which can meet the requirements of welding application.

In order to improve the water erosion resistance property of the 17-4PH stainless steel, Stellite6 alloy coating is prepared on the surface of 17-4PH stainless steel by laser cladding. The coating microstructure, phase composition and element diffusion are studied and the hardness distribution and water erosion resistance property of the coating are analyzed. The results show that the microstructure of the Stellite6 coating is composed of plane crystal, cellular and columnar crystal, dendrite, and equiaxed crystal. The phase consists of γ-Co solid solution with face centered cubic (FCC) structure, M23C6, Cr7C3, and CoCx. Fe and Co elements diffuse between the substrate and the coating layer obviously. The highest hardness of the Stellite6 coating is 561 HV, and its average hardness is about 1.4 times of that of the substrate. In the multi-channel and multi-layer cladding, softening phenomenon occurs in the overlapped regions and the transverse hardness of Stellite6 coating fluctuates periodically. Under the conditions of pressure being 80 Mpa, temperature being 80 ℃ and water erosion time being 30 h, the substrate surface is destroyed seriously. However, the Stellite6 coating surface basically retains the original appearance. It indicates that the water erosion resistance property of the coating has been significantly improved than that of the substrate.

The microstructure features of welded joints after laser tailor-welding and hot stamping of Usibor 1500 steels are investigated. The mechanical properties of welded joints after hot stamping are tested by the room temperature tensile test. The results show that the microstructure of the weld seam is composed of coarse lath martensite and the unevenly distributed second phase with white color under the optical microscope. The white phase number decreases with the increase of coating removal parts. The tensile fracture pattern of the welded joint is related to the distribution of white phase in the weld seam. The removal state of coating has a significant effect on the performance of laser tailor-welded blanks. The removal of upper coating can significantly improve the performance of welded joints. The tensile property of welded joints is significantly improved with the number of the lower coating removal parts increases. The tensile strength of welded joint reaches the maximum value when all of the coatings are removed.

By using femtosecond laser filamentation, the drilling of micro-holes in 2 mm thick polymethyl methacrylate materials in the air environment is carried out. During the experiments, the variations of the femtosecond laser filament length with average femtosecond laser power are summarized. The surface morphology and the diameter of the micro-holes are measured by scanning electron microscopy. The hole dimensions, the aspect ratio (depth to diameter) and the taper as a function of laser average power and processing time are analyzed. The results show that with the increase of the average laser power, the diameter and the taper of the holes increase obviously, while the aspect ratio decreases. With the increase of the processing time, the diameter of the holes increases, the aspect ratio decreases, and the taper of the holes increases first and then decreases and then increases, however it keeps an increasing trend in overall.

In order to reveal the influence of the pulsed laser shock effect on grain and its surface morphology of locally electrodeposited copper, one pulsed laser electrochemical composite deposition system is constructed, and the corresponding theoretical analysis and experimental verification are also performed. The shock effect in the deposition process is tested and the surface morphology of deposited samples is observed by scanning electron microscope. The results show that the interaction of the pulsed laser with the electrodeposition solution can refine the grain in local electrodeposition. In addition, as the laser energy increases, the deposited samples have more refined grains, broader width, smoother surface morphology and fewer air holes.

A fiber phase noise suppression system is built. By out-of-loop self-beat frequency, the noise floor of 6.8×10-18 is obtained in the average time of 1 s, and it falls down to 2.3×10-19 after the average time of 2000 s. The laser frequency with narrow linewidth is transferred in a 1.6 km fiber link when we use the proposed system, and the frequency stability of out-of-loop self-beat frequency signal is 1.2×10-17 in the average time of 1 s. Based on the 808 m fiber link which connects the two laboratories, the laser linewidth of (0.54±0.15) Hz and the frequency stability of 1.2×10-15 in average time of 1 s can be obtained in beat frequency measurement when we apply the proposed system to the comparison of 1.5 μm ultra-stable laser systems.

Due to the complex system, high calibration standard and long measuring time in the current multi-sensor three-dimensional (3D) measurement systems, we present a simple high speed single-sensor 360° 3D measurement system and a convenient high-precision calibration method. The system consists of a projector apparatus, a CCD and two front surface mirrors. The point cloud data of the object is obtained from three parts. The front surface is acquired directly from CCD, corresponding to the middle area in the picture. The rest two parts are collected from the two mirrors respectively, corresponding to the left and right areas in the picture. Firstly the system without mirrors is calibrated. Then the right and left systems containing the front surface mirrors can separately be calibrated with a double-sided projector screen. The continuous surface point cloud data under the global coordinates is obtained eventually. The experimental result shows that the proposed system has low cost, high precision and high reconstruction speed, and it is applicable to field calibration.

In the integer pixel correction searching for three-dimensional digital speckle, the epipolar constraint and the projective rectification principle are used to constrain the correlation searching range from the whole image to the same horizontal line after projection rectification, and then the disparity constraint is used to reduce the searching scope. The correlation searching process is time-consuming. A novel integer pixel correlation searching method for three-dimensional digital speckle based on gray constraint is proposed, which is based on projective rectification and disparity constraint. The proposed method can remove most of the candidate matching points in parallax scope. When the number of valid points is 85783, the size of the correlation window is 9 pixel×9 pixel, and the correlation searching time is reduced from 7.24 s to 2.15 s. Experimental results show that the efficiency of integer pixel correction searching for three-dimensional digital speckle can be improved greatly.

Accurate determination of satellite orbit is the foundation of providing the navigational service for navigation satellite system. Beidou navigation system is the new generation of navigation satellite system which has been developed independently in China. The Beidou satellites are equipped with laser retro-reflectors and the satellite laser ranging with the precision of centimeter or millimeter-level is regarded as the independent external calibration for the accurate measurement of Beidou satellite orbit and the microwave measurement system. In order to increase the laser observation performance of Beidou satellites, the improvements of daylight laser beam monitor, telescope fine tracking, noise filtering and so on are made, which make Shanghai laser station the first one to observe the synchronous orbit satellites in the daytime among the global laser ranging stations. Based on the international laser ranging observation mechanism, the global laser ranging campaign for Beidou satellites observation experiments is being implemented. Laser observation data of about 28 laser stations are obtained, which compensate the limitation of domestic stations. This provides a way for the domestic satellites to obtain the observation data of foreign stations. Using laser observation data from the global stations, the studies of the independent orbit determination and checking the accuracy of broadcast ephemeris for Beidou satellites are carried out. The results are applied in the performance evaluation of Beidou navigation satellite system.

In the ideal situation, a single photon is produced by the emission of quantum dot single photon source. A quantum dot single photon emission device is achieved when we combine the self-organized growth method with optical microcavity structure on patterned substrate. When we adopt a pyramid-shaped substrate to prepare quantum dots, quantum dot growth with a high degree site-controlled is achieved, and single photon source quantum dots are easy to prepare and isolate. The problem of multiple quantum dots occupying the same position can be solved when we use the pyramid-shaped substrate, and the quantum dot preparation in the pyramid-shaped substrate is beneficial to the photon emission and collection.

An intelligent steel stand is designed, which is set a groove on the steel stand center wire and embedded with fiber Bragg grating (FBG) sensor under the state of the center wire holding a certain load. FBG sensor can generate a certain strain before serving. Thus, the problems of low survival rate and limited monitoring range of FBG sensor can be solved. Based on the theoretical analysis of the strain transfer rate between embedded FBG sensor and substrate, the cross-sectional size of the groove, the bond length of the sensor and the elastic modulus of the packaging material are proposed to meet the designed requirements. Tensile experiments for the FBG intelligent steel strand are carried out in different monitoring ranges according to different holding values. The results show that the experimental data has good linearity and repeatability. When the holding value reaches 30% of the ultimate bearing capacity of the center wire, the monitoring range of FBG sensor is close to the limit tension of the steel strand. The monitoring for whole life cycle of steel strand can be achieved.

The high precision calibration of laser sensors in high-precision composite measuring machines is done. The calibration method of the optical axis perpendicular error angle by using the calibration block with double slopes with known base angles and the sine theorem is proposed. This method can avoid the errors from various directions caused by the non-perpendicular orientation between the optical axis of sensors and the worktable, which can effectively improve the measurement accuracy of this sensor and provide a basis for multisensor duplex measurement with higher accuracy.

At present, optical remote sensors are developing in the direction of large aperture and wide field of view. With the increase of the remote sensor′s diameter and field of view, corresponding calibration devices need to be developed to meet the radiometric calibration requirements of full aperture and full field of view. Therefore, a ultra-large aperture (3.2 m) uniform light source system is developed. Firstly, the spectral radiance of exit aperture is designed based on the integrating sphere theory and Plank theory, and the LightTools software is used for the simulation design of the exit uniformity and Lambert properties of the built-in light source distribution. Then, a set of radiometric performance measuring devices based on multi-detectors is developed to solve the problem of ultra-large aperture uniform light source measurement. The calibration algorithm is applied to make multi-detectors consistent. Finally, the new device is applied in the testing experiment of ultra-large aperture uniform light source, and its test uncertainty is analyzed. The results show that the integrated spectral radiance of 0.8 m exit aperture is more than 600 W·m-2·sr-1, the spatial uniformity of 3.2 m exit aperture is more than 98.362%, and the Lambert uniformity in central point of ±45° is more than 98.810%. The newly developed ultra-large aperture uniform light source meets the design requirements.

We experimentally investigate the iodine sublimation process using nonlinear spectroscopy induced by high-intensity femtosecond laser filamentation in air. It is demonstrated that femtosecond laser filament can induce clean characteristic fluorescence emission of sublimated iodine molecules in air. By monitoring the fluorescence of the molecular iodine at 341.6 nm (the D→X1Σ+g transition), we observe by time-resolved measurements that the fluorescence signal varies as functions of the heating temperature and the distance from the measurement position to the solid iodine sample, showing the possibility of exploring the matter phase transform with femtosecond filament induced fluorescence spectroscopy.

The transfer of output spectrum of traditional hydrogen fluoride (HF) laser to long wave and high efficient output of spectral lines, whose wavelength is more than 2.87 μm, is realized by optimizing structure parameters and adjusting reaction system formula. The results of experiment and theory show that the proportion of 2P8 spectral line decreases ceaselessly, and the ratio of spectral lines, such as 1P10, 2P10, increases gradually as the optical axis moving from 11 mm to 15 mm. Moreover, the output spectra of HF laser compete intensely in self and different bands, and cascade effect appears among them. All results extend the utility output spectrum range of HF laser, and make some long wave spectral lines output efficiently, which has an important guiding significance to research and application of the line selected techniques in HF laser.

In order to realize high spatial resolution elemental microanalysis, a gated signal amplifier is designed based on OPA 695 operational amplifier and is applied in weak signal detection in orthogonal dual-pulse laser-ablation laser-induced breakdown spectroscopy. This gated amplifier rejected the influence of strong electronic Bremsstrahlung emission successfully, and the weak atomic emission could be selectively amplified, thus the spectral analysis sensitivity and spatial resolution could be improved. Major aluminum and minor copper elements in an aluminum standard sample are analyzed experimentally. Under current experimental condition, the spatial resolution has been reached 0.9 and 1.2 μm while analyzing aluminum and copper, respectively. These spatial resolutions are significantly improved in comparison with 2.9 μm for aluminum and 6.2 μm for copper obtained experimentally without using this gated signal amplifier. This gated amplifier is low cost and is helpful for high sensitive detection of weak signal accompanied with strong and time-resolvable background.