532 nm green laser with an average power of 63 W based on an intracavity-frequency-doubled lamp-pumped acousto-optic(A-O) Q-switched Nd∶YAG laser is reported. The structure of dual-lamp-pumped gold-plated metal cavity, pumping uniformity and the cooling uniformity and reliability of KTP frequency-doubled crystal are analyzed and a highly reliable set for cooling frequency-doubled crystal is developed. The optimum geometric cavity length of 549 mm is got through studying the influence of the frequency of A-O modulator and the temperature of frequency-doubled crystal on the output power of frequency-doubled laser with L-shaped cavity. When the pumping power is 4.9 kW and A-O modulating frequency is 4 kHz, the 532nm output power is 44 W with the pulse width of 80 ns; When the A-O modulating frequency is 10 kHz, the 532 nm output power is 63 W with the pulse width of 140 ns, frequency-doubled efficiency is 64%, total electrical-optics efficiency is 1.2% and beam quality is M2=11.1.

The characteristics of a laser diode (LD) end-pumped actively Q-switched Nd∶YAG/GdVO4 Raman laser are studied. The average output power and pulse width are measured at the different pump power and pulse repetition frequency. At a repetition rate of 20 kHz and an incident pump power of 7.4 W, an average output power of 1.3 W is obtained, and the corresponding optical-to-optical conversion efficiency is 17.4%. The maximum pulse energy of 74.4 μJ is obtained with a repetition rate of 15 kHz and an incident pump power of 6.8 W. Compared with Nd∶GdVO4 self-Raman laser, the actively Q-switched Nd∶YAG/GdVO4 Raman laser has a higher average output power and a higher conversion efficiency at the same experimental conditions.

In laser resonator, temperature gradient distribution exists in the edge cooling laser crystal, which makes laser crystal be equivalent to a thermal lens. The laser beam diameter changes with the pump power and the laser resonator structure due to the thermal lens effect, which influences the output power. Rate equations considering the variation of the laser beam diameter are presented and numerical methods are used to solve them. The theoretical results show that the relationship between the output power and the pump power depends on the laser cavity structure. Experiments are taken with 940 nm end pumped Yb∶YAG with emission of 1030 nm. Experimental results show that output power is influenced by the cavity structure. The experimental data agree well with the stimulation results.

A laser-diode (LD) side-pumped Nd∶YAP all-solid-state intracavity frequency-tripled 447 nm continuous-wave (CW) blue laser was reported. After analysis and comparison of several optical crystals, Nd∶YAP was chosen as the gain medium to generate 1341.4 nm fundamental laser. Inside the cavity, a type Ⅰ critical phase matching (CPM) LBO crystal was used for 670.7 nm second harmonic generation (SHG), and a type Ⅱ CPM KTP was used for sum frequency mixing (SFM) of the 1341.4 nm and 670.7 nm radiation to generate 447.1 nm blue light. By using a four-mirror folded-cavity resonator, the parameters of laser cavity were optimized and selected according to cavity stability analysis. Output characteristics of different cavity lengths were studied by experiment. The output power of 447.1 nm CW blue laser reached 114 mW at the incident pump power of 534 W, corresponding to an optical-to-optical conversion efficiency of 0.02%, and the causes of low efficiency were analyzed.

The experimental results of high-repetition-rate and high-efficiency 2 μm laser is demonstrated on intracavity optical parametric oscillator (OPO) in KTP pumped by 1064 nm laser. The pumping threshold of KTP doubly resonant OPO is calculated, and the design method of intracavity KTP OPO is proposed. Walk-off compensation is realized by a pair of identical KTP crystals. When cut at φ=0°,θ=53°, a KTP OPO could get output at near degeneration wavelength of 2.128 μm. The average output power of 46.5 W at 2.128 μm is obtained under the condition of 470 W laser diode pump power at 808 nm and the acoustic-optical Q-switching repetition rate of 7.5 kHz. The optical-optical efficiency is 9.89% , the slope efficiency is 14.5% and the M2 of the output beam is less than 2.8.

The theoretical and experimental studies on thermal effect of LD edge-pumped slab lasers were carried out. Based on a real edge-pumped slab crystal (2.5 mm×14 mm×40 mm), the three-dimensional (3D) thermal model was built up. Then the temperature distribution and stress pattern of the slab were calculated by finite element analysis. The thermal distortion of slab crystal under 120 W pumping power was obtained, and the thermal focal length for different pumping powers was estimated. The LD edge-pumped slab laser was designed and packaged. The thermal focal length was studied experimentally, and its relationship with pumping power was dicussed. Experimental results agree with theoretical analysis.

During lasing process, the active medium is not cooled actively in heat capacity laser, so the temperature of the active medium increases sharply. As a result of the decreasing stimulated emission cross section with increasing temperature, the laser gain declines obviously. Based on the relation between the temperature and the stimulated emission cross section of Nd∶phosphate and 1% doping Nd∶YAG, the changes of power output and pump threshold in heat capacity lasers are calculated. The results show that the power output declines obviously and the pump threshold rises sharply with increasing temperature in heat capacity lasers because of thermally induced change of stimulated emission cross section.

Coupling systems are the key elements in end-pumped solid-state lasers, the aberrations of which greatly affect the efficiency of the lasers. A laser diode (LD) end-pumped Nd∶YVO4/LBO blue laser at 457 nm was taken as an example, the effects of aberrations of different coupling systems on the beam quality and the output power of the end-pumped solid-state laser were analyzed. At the same incident pump power and the same cavity parameter, the beam quality and the output power were greatly improved using the improved coupling system, at incident pump power of 30 W, continuous-wave output power of 4.3 W at 457 nm was achieved, the optical-to-optical conversion efficiency was 13.7%.

In order to study the efficient coupling system and its stimulation method for the end-pumped structure of high power laser diode (LD) arrays, a hollow duct coupling system for 12 kW LD pumped Yb∶YAG laser was designed by ray tracing method. Based on the LD bar’s structure and beam parameters, the source models about LD bar and array were simulated by arranging emitters with Gaussian beam. In the coupling system, two lenses and silver-coated flat reflectors were used to concentrate pumping radiations. The experimental results have confirmed that the coupling system achieve a high efficiency and the energy distribution is agreed well with the theoretical analysis. The coupling efficiency of the system is 92.3% on the condition of 94% reflectivity of reflectors. The coupling beam shows excellent propagation characteristics and large uniform pump field on the surface of gain medium which meet the requirement of the Yb∶YAG laser very well.

The structure and thermal management of many-heat focus resonator is more flexible than that of single heat focus resonator. Whereas, the stability of many- thermal focus resonator is affected by more factors, such as the arranging of laser head, which need optimizing design. To get stability output, the single focus double rod resonator, the double focus 3 rod symmetrical resonator and the double focus 3 rod laser with unsymmetrical cavity are analyzed and compared. With the theoretic results, by mounting three laser heads with two thermal focus into a flat-flat symmetrical thermally-near-unstable resonator, a continuous-wave power stabilized output of 1125 W at 1064 nm is obtained with a optical-optical conversion efficiency of 32% and a beam quality of 15 mm·mrad under the pumping power of 3480 W.

A new method of heat dissipation in a laser diode end-pumped solid-state laser is proposed, and the heat is dissipated from the pumped end with a piece of diamond disk clinging to the pumped end and from the side surface of the crystal rod. The finite element method (FEM) is used to analyze the effect of heat dissipation, and a comparison is made of the cooling effect of the new method with that of traditional method dissipating heat through the side surface of crystal rod. The results indicate that the heat concentrated in the pumped end of the crystal rod can be efficiently removed by the new method, which greatly decreases the temperature difference in the pumped end, and that the highest temperature point appears inside the gain medium, which lowers probability of break in the pumped end, and obviously reduces the thermal effects of the crystal rod. With the same power injected into the crystal rod, experiments are done to compare the output power of a laser diode end-pumped solid-state laser with the two different heat dissipation methods. The results show that the method of direct heat dissipation from the pumped end can sufficiently weaken the influence of thermal effect on the power output and this method is particularly suitable for solving the problem of heat dissipation in a high-power end-pumped solid-state laser.

A new type of Nd∶glass laser resonator with high stability and high power output was designed and demonstrated. With the corner cube array as the cavity mirror and the flat glass as the output mirror, the Nd∶glass laser outputs 1.06 μm laser pulse with pulse energy more than 450 J, the beam divergent angle about 0.6 mrad, and the electro-optic efficiency of 2.1%. The beam spots collected in the experiments are not a series of small beam spots with equal amplitude but a high intensity spot in the middle with many small spots around it. The experimental results are explained and discussed. The idea of laser beam coherent combination using the corner cube array is brought forward.

Nd3+-doped phosphate glass amplifier with high gain and broad band is important in inertial confinement fusion (ICF) laser driver research. After analyzing all the factors which determine gain of a laser diode array (LDA) pumped Nd glass rod amplifier, the optimum parameters are presented. The ray-tracing model is set up to simulate the deposition process of LDA side-pumped Nd glass rod amplifier, and the relative program is developed. Based on the simulation, the structures of amplifiers without and with micro-lens are optimized. From the error analysis of LDA pointing, it is found out that the amplifier without micro-lens is more preferable. A rod amplifier with 2 mm Nd glass and 8.1 kW pumping power is manufactured. The fluorescence distribution of the amplifier is uniform. As pumping power is 7.7 kW, the amplifier gain is 40. When a polarizer is added behind the amplifier, gain of the amplifier is very stable.

A novel mutual-injection phase-locking fiber laser combination technology based on corner-cuber was proposed. The phase-locking principle was theoretically analyzed and two coherent combination schemes respectively utilizing spherical corner-cuber and planar corner-cuber were introduced. The mutual-injection phase-locking coherent combination experiment of two fiber lasers based on planar corner-cuber was demonstrated, and the locked wavelength centered at 1085.22 nm, the steady interference strips with visibility about 0.5 and the line-width of compression of 44% are experimentally observed. The combined output power is more than 2.4 W with a power combination efficiency of 120%. The relationship between the wavlength shift and the injecting power is found to be in the inverse proportion pattern for two fiber lasers with different injecting power ratio.

The experimental results observed in passively mode-locked Er-doped fiber laser with positive dispersion are analyzed theoretically. The static pulse characteristics are simulated numerically according to Master equation, and the conclusion is that stable passively mode-locked pulse with large chirp will be obtained in the cavity with positive dispersion. The evolvement process of pulse is simulated by coupled nonlinear Schrdinger equations, and the original small signal with large time-width evolves to stable mode-locked pulse after some cycles. The multiple-pulse operation observed in this laser is analyzed, and the results display that the multiple-pulse is caused by peak power limiting. The multiple-pulse operation evolvement is simulated, and the same results with experiments was obtained.

A novel adjustable pulse laser based on phase control of the coherent beam combination is proposed. Corresponding experiment setup with all fiber-based components is designed and manufactured. By controlling the phase difference of the two coherent beams which are coherently combined in a fiber coupler, pulse laser with adjustable repetition rate, pulse duration and duty cycle can be generated. In order to generate stable pulse, the close-loop control method is induced to compensate the phase difference noise. Different wave signals such as rectangular wave, sine wave, triangular wave have been used to modulate the phase difference in experiments, and corresponding pulse lasers are demonstrated. Rectangular wave signal with different parameters is used to modulate the phase difference in experiments, corresponding pulse laser with repetition rate from 1 kHz to 500 kHz and duty cycle from 20% to 80% can be generated. Pulse with 300 ns pulse duration can be demonstrated with repetition rate of 500 kHz. This pulse laser generate technique provides a new approach for the generation of high power, multi-parameter adjustable pulse laser.

Narrow pulse generation is one of the key technologies of ultra-wideband (UWB) radio wave communication. To simplify the photonic generation of UWB signal, a novel method for UWB microwave signal generation using a passively mode-locked fiber laser is proposed and demonstrated. Er3+-doped fiber as long as 3 m is used to get enough dispersion for achieving the wider pulse width, so that the frequency range of the pulse is between 3.1 and 10.6 GHz, as defined by FCC (US Federal Communications Commission). Based on the principle of harmonic mode-locking, the polarization is adjusted to get different periods of pulse so that the repetition rate is increased. In the experiments, the UWB signal is generated by beating the modes of passively mode-locked fiber ring laser at a wideband photo detector. A wideband numerical oscillograph is used to observe the wider pulse. The UWB photonic source with 8 different repetition rate outputs is gotten by adjusting the polarization controller.

A tunable Yb3+-doped double-clad fiber (YDCF) laser has been demonstrated experimentally using a high-power 975 nm laser diode (LD) as the pump source, a large-mode-area YDCF as the gain medium and a blaze grating-based Littrow configuration as the tunable mechanism. With the optimal fiber length of 14 m and the effective reflectivity 20% of the blaze grating, the threshold pump power of the laser is ～1.3 W. Through rotating the blaze grating, the output lasing wavelength can be broadly tuned from 1046 nm to 1121 nm. When the injected pump power is 48 W, a tunable output of 23.7 W at 1089 nm is achieved with a slope efficiency of 53%. Numerical simulation is performed to analyze the laser output characteristics, and the experimental results are in good agreement with those by numerical simulation.

An Yb-doped double clad large mode area(LMA) fiber laser with a novel simple cavity configuration is demonstrated. This fiber laser system applies one end face of the fiber directly as a cavity mirror, which is fine polished after collapsing. Laser is obtained with the 4% feedback of the end face which has been polished at an angle of 0°, and mode-locking is achieved by using a semiconductor saturable absorber as another cavity mirror. The average output powers are 144 mW and 120 mW with the repeatition frequency of 68 MHz (the corresponding single pulse energies are 2.1 nJ and 1.8 nJ ), and the pulse widths are 9.9 ps and 4.8 ps,respectively. By increasing the pump power, stable multi-pulse outputs of 150 mW and 220 mW are obtained, which demonstrates the power energy of two and four pulses accordingly. Furthermore, by adding grating pairs inside the cavity, the output wavelength is tunable in the 1020～1080nm range.

To fabricate nonabsorbing windows (NAWs) near the cavity facets can reduce the light absorption and prevent early catastrophic optical damage (COD) of the cavity facets, which is an important skill in improving the output characteristics of the high power laser diode (LD). High power 657 nm red LD wafer was epitaxied by a two-step metalorganic chemical vapor deposition (MOCVD) technique, and NAWs were fabricated by Zn impurity diffusion using a closed ampoule method. NAWs fabricated at a diffusion temperature of 550 ℃ and a diffusion time of 20 min are very effective in improving the LD’s performance. Stable fundamental mode continuous wave operation is achieved at up to 100 mW without any kinks, which is three times of the maximum output power of conventional LD without the NAWs. The slope efficiency of the LD is also improved about 23% than that of the conventional LD. At ambient temperature of 20～70 ℃, the maximum outputs of the LDs are all over 50 mW, and the calculated characteristic temperature and the lasing wavelength increment are about 89 K and 0.24 nm/℃, respectively.

In the latest 20 years, X-ray imaging technology has developed fast in order to meet the need of X-ray photo-etching, space exploration technology, high-energy physics, procedure diagnosis of inertial confinement fusion (ICF) etc. However, conventional imaging methods are hardly suitable to X-ray range, grazing reflective imaging and coding aperture imaging methods have been adopted more and more. KBA X-ray microscope is grazing non-coaxial incident X-ray microscope, and four mirrors distribute spatially. The front pair is not perpendicular to the back pair strictly, but tilts a small angle along the ray, and it brings very large difficulty to analysis of image quality. Thus general optical CAD program is not suitable to this kind of optical system. In this paper, programming for non-coaxial grazing incident microscope is discussed in detail, and it is used to analyze the synthesis errors. When the tolerance of object distance is between -0.4～+1 mm, the tolerance of grazing incident angle is between -8″～0, and the tolerance of angle between the bimirror is within -20″～0, the blur is permitted.

An elliptical crystal spectrometer has been developed based on elliptical focusing principle to diagnose spatial spectrum of X-ray of Z-pinch plasma. An elliptically bent Si(111) crystal was employed with 1348 mm focal length, 0.9480 eccentricity, 30°～54° Bragg angel, 54°～103° viewing angle and 0.31～0.51 nm spectral range. A semicircle film carrier with 50 mm radius was designed to receive spectral signals. The influence of elliptical disperson on spectral resolution was analyzed. The first experiment was carried out on the Yang accelerator. The transition spectrum of Ar jet plasma X-ray was recorded. The measured wavelength is accorded with the theoretical value with spectral resolution λ/Δλ of 300～500.

In this paper, propagation of quasi-continuous wave in photonic crystal fiber (PCF) is theoretically and experimentally investigated. With the nonlinear Schrdinger equation (NLSE) and split-step Fourier transform method, evolution of spectrum and pulse profile of quasi-continuous pump is numerically simulated, and the nonlinear mechanism for supercontinnum (SC) generation is analyzed. By comparing different simulative conditions, it′s shown that modulation instability (MI) in anomalous dispersion region dominates the spectrum broadening. Moreover, the effects of pump power, pulse width and fiber′s nonlinear coefficient on SC are also studied. Based on the theoretical results, quasi-continuous wave with pulse width of 80 ps was lunched into a 70m long nonlinear PCF and SC with the spectral range from 1300 nm to 1700 nm was generated, covering the whole communication window.

The fiber technology provides many advantages for the front end of a laser driver, such as convenience to divide, robustness and stability. A fiber front end scheme is proposed to meet the requirements of next generation high-power petawatt laser facility. Experimental investigation has been done to focus on the broadening and amplification of the chirped pulse. Phase-locked signal of the mode-locked fiber laser is set as the reference clock for the system to synchronize the optical switches. Waveguide amplitude modulator is used to choose the needed frequency of signal. Acoustic optical modulators (AOM) are used to restrain the amplified spontaneous emission (ASE) between fiber amplifiers. Experimental results show that after passing through the large-mode-area ytterbium amplifier, chirped pulse with 4.1-kW peak power, 760-ps is obtained. High degree of robustness, reliability and ease of use make this fiber front end an optional seed pulse for high-power short pulse laser facilities.

A method utilizing rotation effect of the quartz crystal to generate vectorial polarized beam is proposed. The quartz crystal is divided into twelve sectors with the same angle, and the thickness of the individual sector is designed with specific value. According the property of the crystal, the polarization direction of the incoming planar polarized beam is changed with different rotation angle in different sectors. So the beam with spatially different polarization is formed. Furthermore the irradiance distribution near the focus with a high-numerical aperture lens is also calculated with two-dimensional Simpson calculus(ZDSC) method. It is found that the focusing property of the vector beam is very similar to that of the cylindrically polarized beam. The method can be used to generate cylindrically polarized beam to meet the practical application needs.

This paper reports the mechanism of two-photon absorption photopolymerization and the femtosecond laser technology used for biocompatible materials ORMOCER three-dimensional micro-nano processing.Two-photon absorption photopolymerization was achieved in ORMOCER resin, the resolution reached 0.5 μm less than the diffraction limitation. The mathematical expression of two photon photopolymerization threshold is derived, the effect of the scanning speed V and the laser power P on the transverse size is studied. Using two-photon femtosecond laser micro-processing technology fabricates a typical microbial devices such as micro-well array,micro-pole-array, and photonic crystal micro-biological scaffold.

Based on the two-center model, the steady-state nonvolatile two-step, two-color holographic recording performance with low-intensity continuous-wave light for LiNbO3∶Fe∶Mn is studied theoretically. The contributions to the space charge fields from the different electron transfer processes between the deep-trap centers (Mn2+/Mn3+) and the shallow-trap centers (Fe2+/Fe3+) are compared numerically. It is found that the direct electron exchange between the Mn2+/Mn3+ and the Fe2+/Fe3+ levels through tunneling effect dominates the amplitude of the total space charge field. This direct electron transfer process plays a key role in the two-step, two-color holography performance also. In addition, the amplitude of the space charge field of deep-trap centers (Mn2+/Mn3+) dominates the amplitude of the total space charge field is proved theoretically.

In optics tracking and detection system, frequent autofocus always result in shake of axes, which will cause image to wobble. A new algorithm that can estimate current frame image of optic equipment be in focus or not is proposed in this paper. According to current image be in focus or not and corresponding threshold, optic control system can choose the time of auto focus automatism. The algorithm measures object edge and edge direction, then get several grads points along the normal line and calculate edge sharpness value. Based on the measure precision of optic-equipment, a threshold value will be set beforehand. If edge sharpness value is more than threshold value, it can conclude current frame digital image is in focus. If image is out of focus, optics system then takes autofocus program. This algorithm test several thousands of digital images be get from optics tracking and detection system, the result shows that correctness of this algorithm is more than 93%. It can finish processing one image during the time of 2 ms.

A new complex encrypted image hiding technology based on discrete cosine transform (DCT) is presented. The complex encrypted image acquired by encoding the image to be hidden with double random phase is embedded in the DCT domain of the enlarged host image by rule. With neighbor pixel value subtraction (NPVS) algorithm, the hidden complex encrypted image is extracted from the coefficients of the host image hiding information transformed by IDCT and the original hidden image is restored with the correct double random phases. The correlation value of the host image hiding information and the decoded hidden image are studied with different embedding factor ω. The effect on the decoded hidden image is analyzed as the host image hiding information is cut by different occlusion and the three-dimensional object information hiding based on digital holography are also numerically simulated with ω=0.2. The results indicate that this image hiding technology has large capacity hidden information, robust anti-cut capacity and good security characteristic.

Multi-heads laser texturing (LT) technology using polygon scanning beam modulation is proposed to increase the production efficiency to meet the industrial need and produce cold roll steel sheet with controllable surface topography. Optical design, system principle and the practice are introduced. The results indicate that single-head pulse repetition frequency of 30 kHz and crater density of 7×7 dots per square millimeter can be obtained, with pulse width ranging from 0.03 ms to 1 ms. For roll with length of 1800 mm and diameter of 600 mm, when textured in 6×6 dots per square millimeter, the texturing efficiency can reach 35 min per roll, enough to meet the industrial requirement. Meanwhile, round texturing craters are obtained, which improves the uniformity of the steel sheet and its mechanical properties effectively. Double-heads laser texturing equipment based on this technology is already in practice and the results are satisfying.

Mie theory and design of a probe of cloud droplet based on this theory are introduced in this paper. A 685 nm diode laser is used to illuminate the cloud droplets in the sensitive area in the probe. The forward-scattering part and backward-scattering part are included in the optical receiving system. The former collects energy between the solid angle of 4°～12°, and the latter collects energy between 126°～134°. The size of the cloud droplet can be obtained by the data from the energy of the forward-scattering. When the size of the cloud droplet is known, the phase state of the cloud droplet can be inferred from the ratio of forward-scattering to backward-scattering. In the end, the intensities of forward-scattering varied with sizes of cloud droplets and the ratios of forward-scattering to back-scattering varied with the refractive indexes are presented by using the Mie theory.

In order to study the influence of the pulse number on the topography of ablation craters. Craters were processed on the surface of the cast iron by nanosecond pulse laser. The relationship between the depth of the crater and the number of the pulses was analyzed. The crater depth almost linearly increases when the pulse number is under 10. Then the depth growth rate becomes slower and slower. When the pulse count is above 15, the quality of the crater is poor, because of the crater is deeper, and the molten metal cannot splash out of the crater. The increase of crater diameter will be slower with the pulse number. In order to get the temperature distribution and the topography of craters, the temperature field of the ablation was simulated. The simulation results are consistent with the measurement results, which demonstrate the rationality of the model.

In order to study the effects of laser remelting on microstructure of composite ceramic coating prepared by plasma spraying, in view of the characteristics of laser remelting, a finite element model for analyzing the transient temperature field of three-dimensional moving laser remelting Al2O3-13%TiO2 （mass fraction）composite ceramic coating prepared by plasma spraying was established by using the employment of ANSYS parametric design language. The temperature field in the coating and substrate was analyzed. The results show that the ceramic coating cannot be total remelted due to low conductivity of ceramic when the coating is thick enough. According to the distribution of temperature field, the coating can be divided into the remelted zone, the sintered zone and the remained plasma-sprayed zone. The thickness of the remelted zone and the sintered zone is larger using a lower laser power and scanning speed under optimum parameters. The experimental results show that the composite ceramic coating forms three different zones after laser remelting, i.e. the remelted zone (fine equiaxed grains structure), the sintered zone and remained plasma-sprayed zone (lamellar-like structure). The obtained experimental results show a good agreement with the simulation results, which indicates that the established numerical model is correct and reliable.

The Cr3C2-CrB reinforced Ni-based composite coating is successfully in situ synthesized by laser cladding on steel A3 substrate by prior pasting. The microstructural and metallographic analyses are performed by metallurgical microscope,scanning electron microscope(SEM), energy-dispersive spectrometer(EDS), and X-ray diffractometer(XRD). The microhardness and wear-resistance of the coatings are investigated. It is indicated that a smooth and in situ synthesized Cr3C2-CrB reinforced composite coating can be achieved employing a proper amount of (B2O3+Cr2O3 +C) doping under suitable processing parameters, and the excellent bonding between the coating and substrate is ensured by the strong metallurgical interface. The bottom of the coating is composed of γ(NiFe) dendrite containing Cr,Fe borides and carbides. In the middle and upper zones of the coating, lots of pre-eutectic Cr3C2 rods are abreast arranged and CrB particles dispread in the Fe2C/γ(NiFe) eutectic matrix. Because of the presence of Cr3C2–CrB reinforcements and their homogeneous distribution, the composite coating gives the high average hardness of HV0.31100 and better wear resistance. The wear mass loss of the composite coating is just one third of that of the pure Ni60 coating.

Effect of quasi-vacuum environment during pulsed laser ablation with high repetition rate is investigated . The comparison of ablation rates for pulsed laser drilling in steel with different repetition rates and different ambient pressures shows that the quasi-vacuum environment can be the main reason for the increase of ablation rate during high-repetition-rate pulsed laser ablation. The density distributions of ambient air are investigated in two different time scales. The experimental results show that the quasi-vacuum environment occurs in the pulse laser ablation and continues for several hundred microseconds after laser pulse. If the subsequent laser pulse interacts with the material during this time, the high ablation rate will be achieved as that obtained in vacuum.

In order to repair broken disc cam and improve the mechanical properties of its surface, such as wear resistance, corrosion resistance, anti-compression,laser cladding coating was made on the surface of disc cam.The laser cladding on complex disc cam was studied .For acquiring the uniform cladding on the surface of disc cam ,some basical conditions which must be followed during the laser cladding on the complex disc cam was put forward. As to meet these condtions, formulas which were used in the moving control of laser cladding on the surface of disc cam were deduced.At last, cladding of disc cam was analyzed by the microscope,scanning electron microscope(SEM) and other equipments,and the experimental results show that the process method provides cladding with uniform width and thickness and solid combination.The hardness of disc cam surface is increased by two-three times.

By means of the linear approximation method, we calculate the intensity correlation time T of the single-mode laser system with the cross-correlation intensity λ between noises modulated by time period. The results show that whether λ=0, λ>0 or λ0 and λ<0, the evolution of the intensity correlation time T with Ωλ presents high-frequency oscillation for smaller Ωλ. Increasing Ωλ, the oscillation frequency becomes small and amplitude decreases. Finally, the intensity correlation time T is consistent with that of λ=0.

Electric conductivity of laser plasma and its characteristic parameters were studied by parallel-plate electrode method for pulsed Nd∶YAG laser ignition of boron-potassium nitrate. The ignition threshold values of laser plasma of B-KNO3 (40/60 mass fraction) and B-KNO3-phenolic resin (40/60/0.5 mass fraction) are 34.07±8.06 J/cm2 and 28.56±2.62 J/cm2, and their ionic charge flux and average kinetic energy are 1.82×10-5 C/(mm2·s), 10.85×103 eV (at 62.05 J/cm2) and 2.29×10-5 C/(mm2·s), 13.61×103 eV (at 60.80 J/cm2) respectively. The ignition delay time of plasma depends on laser energy density in exponential decay, and the delay time of B-KNO3 doped phenolic resin is larger than that of B-KNO3 under a relatively low laser energy density, but same over 35 J/cm2. The results shown that phenolic resin accelerates the ablation of B-KNO3, and plays an important role to produce higher ionic concentration and kinetic energy of reactivity ablation products.

Propagation properties of the TE mode for three slabs waveguide with left-handed materials (LHM) as core layer were studied. The results indicate that guided and surface waves can both propagate in the waveguide system. There is no TE0 mode for guided waves. There are TE0 or TE1 mode for surface waves only. It is found that two guided wave modes with the same mode number can coexist in the waveguide with special structure parameters. The influence of structure parameter on the properties is analyzed.

Ta2O5 and SiO2 single-layer films and multilayer high reflectance films have been prepared by reactive magnetron sputtering. Influences of the process parameters on the quality of optical films and the underlying mechanisms were studied. A passive control method based on fitting the optical spectra can effectively improve the quality of the multilayer films prepared in the transition region. Results indicate that in addition to the high deposition rate, films deposited in the transition region also have higher refractive index and lower optical losses, compared with those deposited in the oxide region. The changes of the deposition rates during the deposition process of a multilayer film in the transition region depend on the changes of the sputtering voltage, which can be compensated with the fitting method by monitoring the sputtering voltages. 40-layer Ta2O5/SiO2 high reflectance films were prepared in the transition region on fused silica substrate, which has a surface roughness of 0.56 nm. The reflectance of these mirrors reaches 99.96% as measured by cavity ring-down spectroscopy.

Amorphous silicon thin films deposited on glass are successfully crystallized by frequency-doubled Nd∶YAG laser with a flat-top beam. Beam shaping optical system of fly′s eye lens array for achieving flat-top beam with uniform intensity distribution is introduced, and with this beam the amorphous silicon thin films is crystallized. The surface morphology of laser-crystallized samples are studied by atomic force microscopy. Raman spectra are measured to confirm the phase transition from amorphous silicon to polycrystalline silicon (poly-Si), and the surface roughness of the thin film after crystallization is enhanced. The grain size and crystallinity are calculated for different laser fluences with Raman spectral data. Both of the grain size and crystallinity evaluated from the data of Raman spectra are found to increase almost linearly with the laser fluence from 400 to 850 mJ/cm2. However, the Raman signal for poly-Si disappeares when the laser fluence exceeds 1000 mJ/cm2. In this experiment, it is about 850 mJ/cm2 to produce the best crystallization.

Several cameras are used in three-dimensional（3D） measurement system with linear-structure light, to measure whole profile and partial detail of complex object with high-precision and 360° measurement range. A measurement system , which is composed of four cameras, has been developed . A new calibration method is presented to calibrate the cameras simultaneously. It uses direct linear transformation model and a self-designed drone control field with many control points to calculate the model parameters, and adopts duality interpolation to rectify the 3D coordinates of measured object . The calibration process of the system is particularly described . Furthermore, a novel method, which is based on two-dimensional discrete Fourier transform, to extract multi-resolution control points on drone is introduced. The result shows the method can calibrate several cameras synchronously for multi-sensor measurement system.

Base on the heterodyne laser Doppler theory, a heterodyne laser Doppler vibrometer(LDV) with fiber structure was designed and implemented . The sensitivity and communication rate of the system, and the influence from water surface wave were tested in anechoic tank. The experimental results show the smallest detectable sound press of 105.6 dB/μPa. On hydrostatic water surface, the acousto-optic communication rate reaches 5 kbit/s without error; some signal is Dropped on hydrodynamic water surface, but using the spread-spectrum modulation, the acousto-optic communication rate reaches 30 bit/s without error.

In this paper, a micro-ring resonant filter(MRRF),consisting of two cascaded coupled racetrack rings and using MMI as input/output coupling structure, was designed and fabricated on the Si substrate by using a UV sensitive polymer material SU-8 as the core material of the waveguide and polymer material CYTOP as the bottom cladding layer. According to the scanning electron microscope (SEM) results, the cross sectional size of waveguide of the device is 2 μm×1 μm, which is in accordance with the designed value, the waveguide shows high sidewall quality. The propagation loss of straight optical waveguide is measured to be 2.0 dB/cm at 1550 nm wavelength. The near field optical pattern from the output port of MMI structure and the output spectrum of the MRRF were obtained. The measured results show that the power ratio of the MMI was close to 50∶50 in a relatively wide range of wavelengths, and the filtering was realized, the measured free spectral range FSR of device is about 0.94 nm, which is close to the designed value. The study results show that it is simple and feasible for fabricating MRRF with fine waveguide by using SU-8.

An improved method of distinguishing chaotic signal based on Wigner distribution (WD) is presented. The narrow band characteristic and the peak value fluctuation of the three-dimensional time-frequency spectrum are used to distinguish chaotic signal. The method is proved to be feasible by the calculation of Lorentz system. The WD of the chaotic signal is compared with that of the Gaussian noise, and the result indicated that their spectra can be distinguished. The WD is used to dispose the output light of the fiber ring laser base on semiconductor optical amplifier (SOA) too, and the result is similar to that of Lorentz system. So it could be verified that the experiment output is chaotic light. Three-dimensional WD accurately shows the spectral characteristic of the signal and can be used to differentiate whether the system is in nonstable state or chaotic state or noise. It is an intuitive and effective method for distinguishing the chaos either generated from dynamic equations or experiment output.

Laser pulse is the main signal of submarine optical wireless communication at present. To simulate the time-domain broadening of laser pulse propagating underwater, the small-angle approximation method, as a simple and inexpensive one, is presented in this paper. The classical electron scattering theory is applied to the photo scattering effects. Based on L. B. Stotts model and the appropriate water volume scattering function, an expression of laser pulse waveform is derived, and the widths of pulse propagating different distances are simulated under certain water quality conditions. The simulated results are in agreement with experimental measurement data and their precision, for longer-distance propagation, is higher than that of traditional methods, which can demonstrate the validity of this method, and provide an important basis for dealing with the problem of inter-symbol interference of longer-distance laser communication underwater.

A novel scheme of radio-over-fiber system to generate frequency-quadrupled optical millimeter-wave by using an external modulator and a fiber Bragg grating (FBG) filter is proposed and experimentally demonstrated. In the central station (CS), the data signal and radio frequency (RF) signal are mixed to drive the optical external modulator. We adjust the direct current (DC) bias to generate signals whose odd-order optical sidebands are suppressed. A FBG filter is employed to suppress the carrier signals, and the second-order sideband modes are transmitted to the base station (BS) in fiber. In BS, two second-order sidebands beat to generate optical millimeter-wave with quadruple frequency in the 60 GHz photodiode. The experimental results show that the 40 GHz optical millimeter-wave is generated by 10 GHz RF resource. The millimeter-wave eye diagram and the demodulated baseband eye diagram show good performance and the power penalty is less than 1 dB. The eye diagrams and power penalty result prove that 2.5 Gbit/s downstream signal can be transmitted over 40-km along fiber.

Solar energy is widely considered as the best choice to replace the traditional fossil energy in 21st century, as one of the renewable “green” energy sources. Recent progresses of photovoltaic (PV) electric power generation, including solar cells, related optics, and industrial trends in the world and China, are reviewed briefly. Viewing the technology progress of the world, it may be concluded that the coming ten and more years will be an important period for both PV technology and industry. It is expected that PV power will become main force of the power grid by 2020, superior to the traditional technologies. It is recognized that the technology of high efficiency multiple junction solar cells based on Ⅲ-Ⅴ compound semiconductors, coordinated with high concentration optics concentrating photovoltaics (CPV), is one of the major directions.