Laser beam focused on stimulated Brillouin scattering (SBS) medium can produce phonon grating, whose density contrast direct ratio to superposition fringe intensity contrast of light field. Then the reason of broad-band laser SBS having higher energy threshold than narrow-band SBS is analyzed, and the qualitative analysis of broad-band SBS phase-conjugation laser resonator having higher startup energy threshold is given. A broad-band SBS phase-conjugation laser resonator of CrLiSAF is designed and operated, its free-running output laser pulse waveform, self-Q-switching output laser pulse waveform, pulse energy and beam divergence angle are measured. The results indicate that this resonator can produce 50 ns self-Q-switching narrow pulsewidth laser beam efficiently, its beam divergence angle is compressed by a factor of two.

Based on the theory of thermal analysis, heat conduction equation of Nd∶LuVO4 crystal slab side-pumped by diode laser arrays is built. By solving the heat conduction equation, the analytic expression of temperature field and thermal deformation distribution is obtained. When geometry of pumping diodes corresponds to 1 mm×4 mm, and the power is about 40 W, temperature and heat deformation field of numerical simulation results show that the maximum temperature rise of 11.63 K along x, and 11.00 K along y and z direction, respectively, and total thermal deformations are 0.050 μm, 0.034 μm and 0.48 μm along x, y and z direction, respectively. This work will supply the theory for design of Nd∶LuVO4 laser.

Laser diode pumped solid state laser (DPSSL) has many applications. The thermal effect of laser crystal produced by pumping light is one of the main factors affecting the characteristics of DPSSL. Usually, the temperature field distribution in laser crystal is found first, then the thermal distortion of laser crystal is calculated by integrating thermal strain along crystal. This process is complex and difficult. Under the condition that the side surface of laser crystal has constant temperature and its ends are adiabatic, the heat conduction equation and integrating thermal strain are combined, the differential equation and boundary conditions of laser crystal thermal distortion are set. The ordinarily used two-step method is simplified to one step and the new differential equation can be solved much more easily than the old one. The analytical solution of thermal distortion differential equation of laser crystal with circular cross-section has been got. A computation example is also given. By numerical calculating, the relations between thermal distortion and curvature radius of distorted pumped-end of crystal with pumping beam radius are analyzed. The proposed simplified method for thermal distortion of end-pumped laser crystal has some generalization.

A practical pulsed fiber laser based on master-oscillator power amplifier (MOPA) architecture is reported. A laser diode (LD) driver based on high-speed MOFSET is used as seed laser. The single mode double-cladding fiber is used in the two stages as preamplifier, and the double-cladding fiber is used in the booster. The laser can generate narrow pulse width output at repetition frequency of up to 600 kHz. At repetition frequency of 125 kHz, amplified laser with average power of 2.4 W and pulse width of 10 ns is generated. This robust pulsed laser is a good candidate for space-based 3D imaging lidar.

The mechanism which suppresses Q-switched tendency by self-frequency-doubled (SFD) effect in a SFD mode-locked laser with a semiconductor saturable absorbed mirror (SESAM) was theoretically studied and numerically simulated. The expression of nonlinear losses, including the saturable loss of SESAM and the nonlinear loss caused by SFD effect, was deduced. The partial differential equations for intracavity pulse energy were developed. The stable conditions of the mode-locked laser were theoretically studied by the perturbation method. It was proved that suitable SFD effect can suppress Q-switching instabilities and reduce the threshold of stable mode-locking. Numerical simulations of mode-locked laser with and without SFD effect were carried out, which certificated the theoretical analysis.

Vertical cavity surface emitting laser (VCSEL) array with a novel arrangement is reported. By the modulation of the arrangement of operture size and the center spacing of the units, we obtain high power density up to 1 kW/cm2 and good beam property of Gaussian far-field distribution. The divergence angle is below 20° in the range of operating current from 0 A to 6 A. This array is composed of 5 symmetrically-arranged elements of 200 μm,150 μm and 100 μm-diameter, with the center spacing of 250 μm and 200 μm respectively. The maximum power is 880 mW at a current of 4 A with the wall-plug efficiency of 0.3 W/A. The differential resistance is 0.09 Ω with a threshold of 0.56 A. By the comparison between the novel array and the 4×4 two-dimensional array with the same total lasing area, we can conclude that the novel array is better in the property of output power, threshold current, lasing spectra, far-field distribution etc. The theoretical simulation of the near-field and far-field distribution is in good agreement with the experimental results.

Using radiate bridge channels in place of ring channels for current injection, a new radiate bridge structure vertical cavity surface emitting laser (VCSEL) was fabricated in order to improve the thermal characteristic and its photo-electricity. The study on the new structure shows that the radiate bridge structure can reduce the electric and thermal resistance of VCSEL, and improve the device modes. The radiate bridge structure and the traditional structure VCSEL are made using the same process on the same wafer, and their performance are tested contrastively. The results show that the differential resistance of new structure VCSEL is 25% lower and the out power is 1.6 times higher than the traditional structure VCSEL. The characteristic of temperatures and modes is good, it can still operate at 80 ℃,the maximum output power can reach 17 mW at 60 ℃, and its thermal resistance is 1.95 ℃/mW. It operates with single mode all along, its performance is much better than traditional structure VCSEL.

Because of the different divergences is in slow and fast axes of laser diodes (LD) and the compress of the coupling structure, the pumped beam output from the coupling structure will be deteriorated. and its efficiency will be reduced. Whereas this problem can be well solved by adjusting the position and direction of laser diode arrays (LDA) in the stack. After ray tracing and analyzing of the output beam, the affection of laser diode stack (LDS) structure on the output beam distribution can be gotten. The project experiment test gets a good output spot and a coupling efficiency of up to 90%.

High power semiconductor lasers have found increasing applications in many areas. The junction temperature rise may not only affect output power, slope efficiency, threshold current and lifetime, but also cause spectral broadening and wavelength shift, which makes thermal management one of the major obstacles of pump laser development. It is more and more crucial to carry out thermal design and optimization. This paper studied the steady and transient thermal behavior of a single-bar CS-packaged 60W 808nm laser in continuous-wave state using numerical analysis method and experiments. Time constants, as well as thermal resistance and its compositions were quantificationally analyzed. Moreover, high power semiconductor lasers were produced based on the thermal design and optimization.

In order to improve the characteristics of the transverse mode of high-power vertical cavity surface emitting lasers (VCSELs), microlens are used to realize high power and single transverse mode by forming a compound cavity with P-DBR and N-DBR of the VCSEL chip. Convex microlens is fabricated by one-step diffusion-limited wet-etching techniques on GaAs substrate. A novel material structure with nine In0.2Ga0.8As (6 nm)/Ga0.18As0.82P(8 nm) quantum wells is employed to emit the wavelength of 980 nm. The diameter of the active layer is about 100 μm, and the nominal diameter of the microlens is 300 μm. The curvature radius of 959.81 μm and the RMS of the whole microlens surface of 13 nm are obtained. The maximum output power is 180 mW in continuous-wave (CW) operation at room temperature. The far-field FWHM divergence angle θ∥and θ⊥of the single device at a current of 1500 mA is 7.8°, 8.4°, respectively. The operation performance between microlens-integrated VCSEL and ordinary VCSEL is also discussed.

A method of time-delayed opto-electronic feedback control is applied to chaotic control in semiconductor laser. It can determine the parameter range of ［0.51, 0.60］ for the laser being chaos state by plotting the system’s maximal Lyapunov exponent varying with the current-modulated intensity by numerical calculation of laser’s dynamic equations. And it is realized for chaotic control of the laser by the scheme of time-delayed opto-electronic feedback. Numerical stimulation shows that the scheme can achieve two kinds of different chaotic control. It can change the system from chaos into intrinsic periodic state. The controlling signal can approach zero after control achieving, and the laser’s periodic outputs donot need the existence of the controlling signal. It can as well change the system from chaos into new periodic state. The controlling signal cannot approach zero after control achieving, and the laser’s periodic outputs need the existence of the controlling signal.

Using water as coolant, Steinen 1.5, 2.0 full-cone nozzles with spray cone angle 60° were applied to study heat transfer performance of spray cooling for high-power laser in non-boiling regime when mass flow rates ranged from 3.26 L/h to 5.0 L/h. The results indicate that heat transfer can not be judged by mass flow rates only. For the same nozzle, the increasing of pressure and mass flow rates resulte in the increasing of heat trarsfer performance. For different nozzles, the heat transfer performance doesn′t increase obvirously, if droplet velocity is not varied significantly, increased mass flow rates can change other spray parameters such as droplet flux, droplet size and film thickness, and all the parameters determine spray heat transfer performance together. Mass flow rates and droplet velocity are the key parameters to influence cooling efficiency. For the same nozzle, enhanced pressure could result in cooling efficiency drop. Compared with smooth wall, the rough wall has better heat transfer performance and cooling efficiency in non-boiling region.

A high energy laser beam sensor is developed using photoelectric and calorimetric compound method by temperature field calculation and structure design in order to measure long pulse mid-infrared laser. The sensor can measure the total energy and power density distribution. It is consisted of calorimetric pile, photoelectric and calorimetric compound detector array, temperature field sensors, analog to digital converter and signal processor. The sensor has the effective sensitive area of 12 cm×12 cm, the spatial resolution of 2.4 cm, and the temporal resolution of 25 Hz, with the total energy measurement uncertainty of less than 10% and the power density distribution measurement uncertainty of less than 7%. The experimental datas prove that the method can be used in high energy, large area and high spatial resolution laser beam measurement.

Based on the fundamental theory of improving structure stability, an initial structure of target chamber system was designed. With finite-element method (FEM), modal analysis was proceeded for the target chamber system, thus the weak links were found. Based on the weak links of initial structure, the initial structure of target chamber system was optimized. At last, the stability analysis was proceeded for the target chamber system. The results of analysis indicates that the target chamber system can obtain good stability, when the thickness of target chamber (T) is 50 mm, the angle of support leg to vertical direction (θ) is 27.2°, the rib with thickness B of 20 mm is added between the support legs, and the space distance of the rib is 120 mm. The translational displacement root-mean square (RMS) is 1.425 μm which satisfies the stability requirement of target chamber system in SGⅡ upgrade facility.

Principle and technique advantages of multiple streak tube imaging lidar are introduced. A multiple streak tube imaging lidar system is designed, the performance effect from each component is analysed, and some important parameters are discussed. Experiment to demonstrate the feasibility is carried out, the results show that the system can get range image and intensity image, some characters of the system are also demonstrated.

Based on theoretical equation of laser gyro beat output, scale factor forward-reversal rotation asymmetry of rate biased laser gyro is analyzed by theory, simulation, and experiment. Since the scale factor forward-reversal rotation asymmetry highly affects the precision of rate biased laser gyro, the relation between scale factor and rotation direction is analyzed by theory and numerical simulation, respectively, and a new kind way to measure the scale factor forward-reversal asymmetry is provided without knowing the laser gyro zero drift and earth rotation component. The experiments show that the scale factor forward-reversal rotation asymmetry of a laser gyro is approximately 0.02×10-6 with rotation rate of 72°/s.

Bi12SiO20(BSO) is a kind of photosensitive material. Its resistance would drop sharply when exposed to the short-wave-length light, such as UV, so it would be used as the sensitizing layer in the liquid crystal spatial light modulator (LC-SLM). In this paper, we have theoretically studied the principle of LC-SLM and the photoconductivity of BSO. The relationship between photocurrent and the power of the illumination is introduced. In the experiment, the photoconductive effect of a slice of BSO with different wave-lengths illumination is measured. The optical path difference caused by the LC-SLM exposed to the UV is calculated by computing the distribution of the liquid crystal director. The change of the optical path difference caused by UV is similar to the change of optical path difference when the LC cell is applied different voltages in the experiment;

By dimensionless analysis and comparison between coupled and uncoupled nonFourier thermoelastic equations and their solutions, the general non-dimensional number λ characterizing effect of thermal-mechanical coupling is given, and the effects of nonFourier thermal-mechanical coupling in materials irradiated by short laser pulse are investigated. It is shown that the thermal-mechanical coupling makes the laser-induced stress wave have higher speed, longer length and dampes swing compared with the uncoupling wave, it also excite a synchronous second temperature wave. The stress wave has saturation characteristic with increasing of parameter ε, and the stress wave can bear an exceptional dual-peak waveform under special conditions, whether it is coupling or uncoupling. The intensity of thermal-mechanical coupling depends mainly on λ, and also on the ratio of elapsed time from the pulse triggering to pulse duration, the larger the ratio value is, the stronger the coupling effect is. Therefore, large error can also be caused by ignoring thermal-mechanical coupling in analysis of a medium heated by ultra-short laser pulse, even under usual conditions with smaller absolute value of λ(10－3and lesser order of magnitude).

Cross sections for 5D→7S transfer in Rb, induced by collisions with He, Ar atoms, and H2 molecules, respectively, are determined by using methods of atomic fluorescence in a glass fluorescence cell. The resulting fluorescence includes a direct component arising from the optically excited state and a sensitized component due to the collisionally populated state. Measurement of relative intensities of the two components in relation with different quenching gas pressures yieldes the cross sections of σ(5D-7S) of (1.2±0.3)×10-17 cm2, (1.3±0.3)×10-18 cm2, and(8.3±2.1)×10-17cm2 for He, Ar, and H2, respectively. Cross sections for the effective quenching of the 7S state are also determined. The total quenching rate coefficient out of the 7S state is much larger for H2(1.7×10-10cm3·s-1) than for He and Ar. And the coefficient corresponds to the reaction and nonreactive energy transfer. We detenmine the cross section of (1.0±0.4)×10-16cm2 for reaction of Rb (7S) with H2 by experiment. And the cross section of (7.1±2.9)×10-17cm2 for reaction of Rb (5D) with H2 is obtained. The relative reactivity with H2 is in an order of Rb (7S)＞Rb (5D)

An ultra-long-period fiber grating (ULPFG) with asymmetric refractive index modulation is fabricated in common communication optical fiber by using high-frequency CO2 laser pulses. A highly sensitive humidity sensor based on this grating can be realized due to its high refractive index sensitivity. The ULPFG is coated with a new nano-composite hydrogel, which has strong water capacity. This kind of hydrogel can absorb water vapor in the air substantially to make its own refractive index change, which will induce the resonant peak shift of transmission spectrum of the ULPFG. And such a shift can be used in humidity measurement. The experimental results show that the maximum shift of the resonant peak can reach 30 nm when the surrounding humidity varies in the range of 38%～96%, and such sensitivity is three times higher than that of the humidity sensors reported before. Such novel humidity sensor can be found important applications in humidity measurement of the field of optical fiber sensing.

In order to improve the precision of simulated supercontinuum (SC) generation, the split-step Fourier algorithm is modified without increasing the computation amount. Traditional algorithm only refers to the dispersion coefficient of the central frequency. Due to the wide range of the supercontinuum, the error of the result would be big by using the traditional algorithm if the slope of the dispersion coefficient is large. According to the modified algorithm, the pulse could be regarded as the combination of many elements each with only one frequency. The elements with different frequencies could be processed seperately by using the modified algorithm, so the dispersion coefficients of all the frequencies could be refered to. The modified algorithm is applied in simulating the supercontinuum generation in the photonic crystal fibers with one and two zero dispersion wavelengths. And the results are compared with those of traditional algorithm. The simulation results show that the superiority of the modified split-step Fourier algorithm is not obvious in the photonic crystal fibers (PCF) with only one zero dispersion wavelength, but having certain superiorities in simulating the supercontinuum generation of the photonic crystal fibers with two zero dispersion wavelengths.

Considering phase compensation and small signal condition, we derive the four-wave-mixing coupling equations of the cascaded fiber optical parametric amplifier (CFOPA), from which the expressions of the output gain and phase are obtained. Utilizing the obtained expressions, the gain and bandwidth characteristics of CFOPA are analyzed and further compared with the single-segment fiber optical parametric amplifier(SFOPA). The 3 dB bandwidth of the CFOPA can reach 67.2 nm when the dispersion-shifted fiber (DSF) is dividing into ten segments, but the SFOPA is just 12.6 nm. So the bandwidth is increased 54.6 nm through cascading compensation. And then, the 3 dB bandwidth of the CFOPA will remain the same, but the gain decreases when considering the fiber loss and splice loss. Results show that the bandwidth can be broadened significantly by introducing multi-segments cascading compensation to DSF, and the obtained bandwidth is observed much broader and flatter when compared with that of SFOPA for a given DSF length, pumping power, or idle power.

Photonic crystal fibers (PCF) sensors have broad application in the pressure environmental monitoring.The birefringence of the dual-hole core photonic crystal fibers is analysed by the full-vect finite element methods, the photonic crystal fibers sensors response to pressure is simulated by the second-order differential equation theoretical model and the influence to the effective refractive index and the birefringence of the sensing element are discussed by the model, the high-pressure photonic crystal fibers sensors scheme is presented. Calculation results show that the birefringence of the dual-hole core photonic crystal fibers is very large. The system of the pressure photonic crystal fibers sensors is brevity and compaction.

Experimental investigations on anti-aliasing properties of acoustic low-pass filtering fiber-optic hydrophones are reported. Acoustic low-pass filtering fiber-optic hydrophones is a novel kind of fiber-optic sensors, which is proposed to eliminate the aliasing in fiber-optic hydrophone arrays. Theoretical and experimental results show that it has good acoustic low-pass filtering properties, and can restrain the high frequency interference strongly. Effects of high freqeuncy interference on demodulation results of fiber-optic hydrophones without acoustic filter and anti-aliasing properties of fiber-optic hydrophones with acoustic filter are studied experimentally. Results show that fiber-optic hydrophones without filter cannot work normally when the high frequency interference is strong, while the acoustic low-pass filtering fiber-optic hydrophones still work well. The demodulation results of acoustic low-pass filtering fiber-optic hydrophone are in good agreement with the results without interference, and the correlation coefficient of the demodulation acoustic signals is higher than 0.99. Acoustic low-pass filtering fiber-optic hydrophones provide an effective solution to the aliasing existing in modern photoelectric sonar systems.

Based on the transfer matrix method,the reflective spectrum characteristics of the phase-shifted fiber grating are analyzed by detailed theoretic. The corresponding mathematical model is established and validated. It is shown that the phase shift leads to the split of the reflective spectrum of the fiber grating. The wavelength of the split point is linearly and periodical to the phase shift. The reflectivity of the split point is symmetrical to the phase-shifted position and the central wavelength of the fiber grating. And the reflectivity of split point is approximately hyperbolically tangential versus the phase-shifted position.

Increasing the grating length is the best way to realize super-narrow bandwidth filter with low insertion loss and high sidelobes suppression, but the phase error induced in the fabrication process of long grating deteriorates the performance of grating filter to a large extend. Sampled fiber Bragg grating (FBG) have the advantages of flexible wavelength design, low manufacture precision and easily realizable apodization. The scheme of super-narrow bandwidth filter based on sampled FBG is taken emphasis on, and the influence of three kinds phase error on the filter performance of -1st ghost grating is analyzed, which provides reliable guide for future long grating fabrication. The phase error of a fabricated sampled FBG with length of 6.6 cm is compensated using reconstruction equivalent chirp (REC), and a super-narrow filter with symmetric reflection and transmission spectrum, insertion loss of 1.25 dB, sidelobes suppression of 21.55 dB, 3 dB bandwidth of 26 pm and 20 dB bandwidth of 70 pm is obtained.

In the resonator fiber-optic gyro (R-FOG), the detection precision of the system is influenced by the polarization-fluctuation deeply. Using the Jones matrix, the relationship between the drift caused by the polarization-fluctuation and the difference in the coupling ratios of the two eigenstates of polarization (ESOPs) is derived. To make the drift margin, the optimized coupling ratios of the two ESOPs are gotten. These optimized coupling ratios are only related to the loss parameters of the resonator in R-FOG. By the numerical simulation in Matlab, the curves between the drift and the coupling ratios of the two ESOPs are attained, respectively. The polarization-fluctuation error model about the correlation between the coupling ratios of the two ESOPs is set up. Based on the theoretical model above, the drift induced by the polarization-fluctuation is estimated in the reported open-loop experiment of R-FOG. It’s the theoretical base to overcome the polarization-fluctuation and do the experiments in R-FOG system.

It is inconvenience for the practical application of beam quality assessment because of the uncertainty when test beam quality factor about non-circular symmetry beam is done. The value of M2 will change if the reference frame or other experimental conditions are different because the test for M2 is based on reference frame. To have a unity of different laboratory coordinate systems of the M2, two cross-terms were introduced into present the relationship of beam spot spindle and laboratory coordinates under test. For describing the beam quality convenient, the M2 factor matrix is defined. The principle and method for test is studied, and a system to test the M2 factor matrix has been built. The law of beam width and quality factor M2 vary with the rotation of the coordinates has been studied by using two laser diodes who have the non-circular symmetry beam on the test system. Their M2 factor matrix have been tested and calculated at last.

The ray transmission characteristics of off-axis prism-pair are analyzed using geometrical optics method at different offset. The numerical model of off-axis prism-pair is built by ray tracing. The numerical relationship between the offset d and hypotenuse L of the off-axis prism-pair is obtained. The transmission direction, the number of ray transmission and the distribution of ray in the off-axis prism-pair are discussed at three different cases.The results show that the rays transmitting in the off-axis prism-pair have equal distance space distribution pattern when d=L/2n (n=1,2,3…)so it is much more benefit to obtain unform gain for each pass of rays and to realize multi-pass and amplification of slab-shaped gain medium.

The composite optical vortices (OVs) formed by two parallel, off-axis Hermite-Gaussian (H-G) vortex beams at the waist plane and their evolution behavior are studied. It is shown that the number, position and net topological charge of composite OVs depend not only on the control parameter, including the relative phase, amplitude ratio, waist width ratio and off-axis distance, but also on the mode structure of H-G vortex beams. By appropriately varying the control parameter and mode of H-G vortex beams and in the free-space evolution, the motion, creation and annihilation of composite vortices may appear, and the topological charge does not always remain unchanged. In particular, for the composite OVs formed by TEM00 and TEM01 vortex beams, the topological charge is not conserved by changing relative phase. The results are useful for the composite OV control and applications.

Using a 3D photo-thermal model for selective photothermolysis (SP), the effects of blood vessel parameters, such as blood vessel diameters, locations and numbers, on the photo-thermal interactions during SP were numerically studied. The numerical results show that the thermal damage rate of the targeted blood vessel would be decreased if there are other blood vessels existed in the neighboring region, the dimensions of which are determined by the diameter of laser beam and laser wavelength. Generally, if the other blood vessels are outside the laser beam, or deeper than 1 mm for 585 nm laser, their effects are neglectable. The study can be used for scheming and optimizing the clinical laser treatments.

For quantitative analysis in the particle field, a standard wire is generally used as the scaler for measuring the particle size. In order to understand the effect of the reconstructed wire with a certain depth of field on the experimental results, detail analysis of the intensity distribution and variation of the reconstructed wire at different positions are performed by theory and experiments. The influences of the normal scaling method on the particle image data are pointed out and a new scaling method, the non-in -time scaling manner, is given. Experiment results show that, the uncertainty of the particles size measurement is about 4% by keeping the precision of particle location. This new method can effectively solve the problem, which affects the precision of the particle size measurement. It can be used in practical measurements.

This paper studies the method of surface strengthening to 45 steel by laser-guided micro discharge, and compared the method by laser-guided discharge (LGD) with the method by high voltage-guided discharge(HVGD). It was found that the break voltage of electrode gap was decreased a grade, and the discharge pit was completely lapped over the laser focus by laser-guiding. The expanding speed of discharge pit was almost same in two kinds of discharge processing. Because of the effect of the diameter of initial discharge pit, the diameter of laser-guided discharge pit was always bigger than the diameter of high voltage-guided discharge pit. The most thickness of layer-strengthened in two kinds of discharge processing were almost same about 180 μm. The strengthened layer of discharge pit included the melted layer and hardening layer. The most hardness of strengthened layer was about 800 HV.

To obtain excellent welding joint, ultra-high strength steel 30CrMnSiNi2A was welded by laser. Microstructure, properties, tensile strength, tensile fracture and residual stress were investigated by means of optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness testing machine,electronic universal testing machine and X-ray stress analyzer. The experimental results indicate that microstructure of central welding zone, near central zone and edge zone is equiaxed crystal, dendrite crystal and rough cylindrical crystal, respectively. Microstructure of fusion zone is fine cylindrical and equiaxed crystal. Microstructure of heat-affect zone (HAZ) is mainly lath martensite, bainite and residual austenite. The phases of welding zone is mainly comprised of α-Fe, NiCrFe, Fe-Ni and MnSi2.The highest hardness value of welding zone is 518 HV, the highest value hardness of HAZ is 560 HV. The hardness decreases significantly from HAZ to substrate. The average tensile strength of welding joints is approximately 802 MPa. The fracture appears in substrate near welding zone. The impact toughness of weld joints is 75.7 J/cm2. The residual stress of welded joints is the compressive stress. The average residual stress of weld zone is -17 MPa, and average residual stress of HAZ is -59 MPa.

Based on optimum design of Ni-Zr-Al alloy composition using the cluster line criterion, the Ni60.2Zr33.8Al6 alloy coating is prepared by laser cladding on the magnesium surface. The result shows that the excellent metallurgical bonding between the coating and substrate is formed due to low melting point and good wettability of the Ni-based alloy. The coating mainly consists of amorphous, Ni21Zr8 and Ni10Zr7 phases. The composite strengthening and high chemical stability make the coating exhibit high hardness, good wear and corrosion resistances.

40Cr steel is a common quenched axis steel with high, tough, and plastic cooperation. However, quenched steel for high speed spindle rigidity and resistance is not satisfactory. It is easy wear at axle journals and affacts the precision. 40Cr steel with normalized one has been hardened by laser. To find a good technics for high-speed spindle by laser surface hardening, to improve 40Cr steels hardness and wear resistance.Analyse kinds of samples which are harden by different technics. Diameter of facula 7 mm, laser power 1600 W, speed of scan 15 mm/s is the best parameters. Then microstructures analysis, rigidity measurement are carried out. The result: the sample with the technics is the best for high-speed spind machining and milling. The hardness of hypo-surface layers hardness is 2.04 times of the conventional heat treatment, and it is wearable.

In order to study the effects of laser shock processing (LSP) on the vibration fatigue strength of nickel-based superalloy, water and aluminum foil were used for confining medium and ablation medium. K417 specimens were processed with YAG laser.With the wavelength of 532 nm, pulse duration of 10 ns, and output energy of 1.5 J. The laser was focused on a spot of 1.6 mm. The effects of laser shock processing on the vibration fatigue strength of K417 are investigated using up-down method. The experimental results show that laser shock processing can increase K417s vibration fatigue strength from 106.5 MPa to 285.5 MPa. Fracture analysis results show that laser shock processing strengthens the metal surface and suppresses the cracks initiation and expansion. So the K417's fatigue performance is improved.

In order to know the stress development in the film during growth and to study the origin and mechanism of the stress much deeply, an instrument based on light beam deflection for in-situ stress measurement in optical films by using two light beams is presented. An improved system is used to get the variation of the distance between the two beams. It is proved that the precision of the instrument is 2.2% after several times of measurement. This precision can satisfy the stress measurement of the thin film. The stress curve of SiO2 during growth is presented. As a result, the instrument represents an easy, stable, and high precision technique. It supplies an effective method for measuring the intrinsic stress.

With the help of abinitio full-potential linearized augmented plane wave (FPLAPW) method, the calculations of the electronic structure and linear optical properties are carried out for NaPd3O4 for the first time. The results show that the conductive of this material is mainly due to the contribution of Pd atom d orbital. The p orbits of the oxygen atom have also important influence for the conductivity. In essence, sodium atoms on the conductivity of the materials have played almost no role. There exists the ionic bond between O atom and Pd atom. Meanwhile, the spectral peaks at the transitions are analyzed from the imaginary part of the dielectric function. Furthermore, the origin of the different optical properties has been discussed.

High efficiency stimulated Raman scattering (SRS) of BaWO4 crystal was realized by an ultra-cavity single-pass configuration. When the pump source is 532 nm picosecond laser, five Stokes lines (559.64 nm, 590.26 nm, 624.42 nm, 662.76 nm, 706.18 nm) and three anti-Stokes lines (463.42 nm, 484.24 nm, 507.04 nm) are observed. The SRS thresholds and Raman gain coefficients for different scattering lines are measured, and the total conversion efficiency reaches 78%. When the pump source is 355 nm picosecond laser, three Stokes lines (366.52 nm, 379.40 nm, 393.22 nm) are observed, and according to the pump threshold of the first Stokes line the Raman gain is obtained as 51.8±2.7 cm/GW. Experiments have shown that BaWO4 crystal possesses advantages of easy growth, wide transmittance spectrum, high optical damage threshold, and large gain coefficient, which indicates this material will have important applications in generation of whole wave-band visible lasers.

In order to determine the optical constants of fluoride films in deep ultraviolet (DUV) to ultraviolet (UV), high-refractive-index materials such as LaF3, NdF3, and GdF3, and low-refractive-index materials such as MgF2, AlF3, and Na3AlF6 single thin films are deposited by a resistive-heating boat at different deposition rates and specific substrate temperatures on JGS1 and single crystal MgF2 substrates. Transmittances in 190～500 nm of all fluoride thin films are measured through business spectrometer in the ambient atmosphere. The optical constants of these films are determined from iterative algorithm combined with the envelope method. These dispersive optical constant values are fitted by Cauchy formula and index formula, respectively. The results are consistent with other relevant articles, which testifies the reliability of the results.

Four kinds of guest-host adulterate thin films were prepared by using spin-coating method, and then their thickness, refractive index, UV-Vis spectra and the signal of second harmonic generation (SHG) after all-optical poling were measured. The experimental result was shows that the value of SHG depends on the dipole property of azobenzene molecule for the same thickness, and the stronger the dipole property of azobenzene molecule is, the bigger the value of SHG is. Calculation result shows that the nitryl (-NO2) connected with benzene has the biggest second-order nonlinear optical coefficient d33 that equals to 4.97×10-1 pm/V, and the weakest equals to 2.55×10-2 pm/V. It can be explained in theory that different dipoling induces the different excitation extent for these azobenzene molecules. This work can offer a powerful experimental help to the design of molecular materials.

Rugate filter is a special inhomogeneous optical coating. The graded refractive-index profile makes it have better optical and mechanical properties than conventional homogeneous optical coating. The graded refractive index SiOx (0≤x≤2) coating materials with precisely controlled refractive index ranging from 2.74 to 1.59 (λ=1550 nm) are deposited by tuning its oxidation degree in reactive magnetron sputtering. Then high quality SiOx infrared rugate filters are successfully designed and fabricated by choosing proper refractive index amplitude apodization function and introducing refractive index matching layer on the interface, which provides a practical and economical technique for industrial fabrication of rugate filters.

Bi2Sr2Co2Oδ (BSCO) thin films were grown on Al2O3 (0001) substrates by pulsed laser deposition (PLD) technique. Laser induced thermoelectric voltage (LITV) effect was observed in those films on vicinal-cut substrate. The result of X-ray diffraction (XRD) showed that films on untilted Al2O3 (0001) substrates were c oriented. The temperature dependence of the electrical resistivity of films was measured by a standard four probes method, the result showed that films were semiconductor from 80 K to 360 K. The optimal film thickness was found in two tilted substrates with 10° and 15° angles, at which the peak voltage of LITV signals reach 0.4442 V and 0.7768 V respectively. The anisotropy of Seebeck coefficient lead to laser induced thermoelectric voltage signals.

Fourier transform is used to analyze the grazing incidence X-ray reflectivity curve of nanometer multilayer structures. The influences of preparing and measuring conditions on measuring results of multilayer structure parameters are simulated and the applicability and accuracy of Fourier transform is verified. The results show that the Fourier transform is more intelligible and quicker than traditional curve fitting method. The Fourier transform can exactly determine complex multilayer structure parameters without any subjective layer-structure model, which is a powerful analysis method for characterization of multilayer structures.

TiO2 sculptured thin films are prepared by oblique angle electron beam deposition. After heat treatment at different annealing temperature and time, the properties of birefringence and phase retardance are optimized. The results illustrate that the optimum annealing condition is for 4 h at 500 ℃ and the maximum birefringence is up to 0.115, which is far higher than the as-deposited films. According to the measurement of ellipsmetry, the phase retardance is about 90°at 550 nm, which means that it is suitable as a wave plate. Therefore, thermal annealing is a useful and feasible method to improve birefringence of sculptured thin films.

Based on different characteristics analysis of the systematic and random errors found in the spectral measurement data, two methods are put forward to diminish their impacts on the reverse determination accuracy of thin films’ respectively optical parameters. The first method uses spectral coefficient’s first order partial derivatives of thin films with respect to layer optical parameters to select measurement data. The spectral region or incident angle region characterized with opposite operation symbol of partial derivatives is chosen as the optimal measurement data region to minimize the deviations from the real optical parameters of thin films caused by systematic measurement errors. The second method injects independent random noise of same distribution to the actual measurement data. The data with noise are utilized as the real spectral coefficients of the thin film being measured in the reverse determination for many times. The reverse determination algorithm used is a mixed optimization method based on the discrepancy function minimization technique. The statistics mean values of all fit optical parameters obtained each time by the mixed optimization method are chosen as estimates of the real optical parameters of the measured thin film to diminish or eliminate the uncertainty of optical parameters caused by random measurement errors. These two methods are of obviously practical value to improve the determination accuracy of thins films’ optical parameters. And they also characterize with concise and definite physical meaning, expedient manipulation ability and good universality, not restricted to specific spectral regions or specific materials. They are of promising importance in the accurate reverse determination techniques of thins films’ optical parameters.

An universal calculation formula and system calibration method are proposed, and the height-phase mapping relation in Fourier transform profilometry is derived. Because the request on the geometry structure of new universal calculation formula is not strict, the experimental setup is simple and the projector and the imaging device can be located arbitrarily to obtain better information of fringes. And this makes the operation flexible. The system parameters under universal condition can be obtained by the system calibration method. It can avoid measuring the system parameters directly, which makes the system easy to manipulate and improves the velocity of measurement. The new calculation formula and calibration method have been applied to measure the object with 28.00 mm height, and the relative error is only 0.97%. The experimental result proves that the new calculation formula and calibration method can exactly rebuild 3D shape of objects and the system has better universality.

Based on digital interference technology and second-harmonic generation (SHG) technology, a experimental method in diagnosing the phase aberration and phase coincidence on fundamental frequency and SHG laser wavefront is designed in coherent control. According to such technology, an effective auto-controlling system is designed and applied successfully in the coherent control photocurrent experiments. The method using retrieval algorithm, bases on the relationship between the beam intensity and phase difference to calculate spatial morphology in order to achieve the voltage of adjusting the piezoceramics, so that the mobile-mirror gets a movement with less aberration. The experimental results show that system can adjust the phase difference between the fundamental laser and its SHG automatically in real time, and realize the both wavefront being parallel in light aperture.

Using single-shot chirped pulse electric-optic detector technique, the absolute electric field intensity can be obtained by tuning the angle to 45°, which is between crystal axis of quarter wave-plate (QWP) and linear polarization direction of detection laser. With charge coupled device (CCD), the size of terahertz spot can be gotten by probe-pump measurement. The energy of terahertz pulse is calculated with the experimental results. An effective method of measuring the terahertz pulse energy is provided.

Laser-induced breakdown spectroscopy (LIBS) was used to yield quantitative elemental information of ore samples. A Nd∶YAG laser beam with wavelength of 1064 nm was focused on the sample surface to generate laser plasma. The plasma atomic emission spectra were recorded by a micro-spectrometer. In order to optimize experimental condition, dependence of the spectral line intensity upon laser pulse energy and time delay of signal collection with respect to the initiating laser pulse were investigated. Strong influence of the laser pulse energy on the spectral signal was found in the experiments. However, time-delay had less effect on the spectra within the range of the selected time delays. Spectral lines of silicon (Si I line at 251.6 nm) and magnesium (Mg I line at 285.2 nm) were separately used to determine, the silicon and magnesium contents in the samples based on the external standard method. The relative standard deviations (RSDs) of the measured elemental contents relative to those standard values were 7% and 3% respectively for the silicon and magnesium elements. It provides a basis for the feasibility of rapid detection and elementary analysis with the laser-induced breakdown spectroscopic technique.

In a Fizeau interferometer using sinusoidal phase modulation technique, the variation of interference intensity with optical path difference (OPD) does not follow a rigorous cosine behaviour any more. This is because the presence of multi-reflection between the reference plate and the surface under test leads to multi-beam interferences. If the interference signal is processed according to double-beam interference theory, non-ignorable measurement error can be produced. In this paper, a sinusoidal phase modulation Fizeau interferometer used to measure micro-displacement with nanometer precision is established. The measurement error caused by multi-beam interference is analyzed in detail. Some parameters of the Fizeau interferometer are optimized and the measurement results are corrected using error compensation algorithm, so that the influence of multi-beam interference is reduced effectively.

A new measurement method for dynamic phase changes in fiber interferometers is demonstrated. The amplitude of the dynamic phase is obtained directly from the zero and fundamental frequency components of the fiber interferometer output by method of constructing match-functions without modulating the laser. It has the advantages of no active element in the interferometer, simple signal demodulation and large operating bandwidth. To test this new method, an all polarization-maintaining Mach-Zehnder fiber interferometer is constructed, and the simulation dynamic phase change induced by PZT is measured. Experimental results show that the calculated amplitude of the dynamic phase shift is a good linear function of the voltage applied to the PZT, which accords well with PZT’s properties of low-frequency and small amplitude. This method is applied to the measurement for the acoustic sensitivity of interferometric fiber-optic hydrophones, and the test results are in agreement with the results obtained by phase generated carrier method.

Four-quadrant detector (QD) is used for detector of extract track in free space optical communication, and influences tracking precision. The method of the variable step-size is given, and the influences of the facular size to the dynamic range and the detection sensitivity are analyzed. As the simulation precision is satisfied, simulation time is shortened. On the condition that the facular energy obeys the Gauss distribution, the influences of the background light, responsibility and dead-area to the dynamic range and the detection sensitivity are analyzed, especially the influence of the non-uniformity background light is analyzed. The result indicates that the dynamic range of facular position detection is increased, and detection sensitivity is reduced with the increase of the facular size. On the condition of the same facular size, the detection sensitivity as to obey Airy distribution is higher than Gauss distribution, the influence of non-uniformity to the detector is larger than uniformity.

A method called coherent hybrid is proposed to monitor the bias offset drift of Mach-Zehnder modulator (MZM) by mixing the unmodulated local oscillation lightwave with the modulated signal from the same light source and measuring the hybrid power ratio of the maximum to the minimum. The sensitivity at ±5% bias offset is improved from 0.02 dB to 0.3 dB compared with the traditional method by measuring the signal average power. Experiments are carried out with the developed feedback and control system based on this scheme to find the impairment factors and explore the proper solutions. The results reveal the feasibility and effectiveness of the method.

Phthalocyanines are such materials that optically limit nanosecond light pulses in a fairly wide range of the UV/Vis spectrum via excited state absorption processes, which can be used to protect human eyes, optical elements and sensors from intense laser pulses. Optical limiting response can be tailored over a broad range due to the high architectural flexibility of the phthalocyanine structure. A series of new highly soluble axially and peripherally substituted or bridged phthalocyanine-based organic functional materials with excellent optical limiting potential have been reported in recent years. The usual tendency of phthalocyanines to form aggregates can be effectively suppressed by axial substitution. The nanosecond nonlinear absorption and the optical limiting of axially modified phthalocyanines are dominated by a strong triplet state absorption in the optical region comprised between Q-bands and B-bands in their UV/Vis absorption spectra. This review lays special stress on introducing the recent progress in this area.