A xenon flashlamp-pumped Cr∶Tm∶Ho∶YAG laser operating at 2.1 μm is demonstrated. Since the Cr∶Tm∶Ho∶YAG has a high threshold owing to its quasi-three-level nature and the complex energy transfer process between the doped ions, optimum ions concentration proportion and long pulse pumping are employed to achieve the 2.1-μm laser operating at room temperature. The ceramic pumping cavity with high diffuse reflectivity of 95% for effective pump band is used. With the cooling water temperature of 15 ℃, the maximum laser average power is 23.5 W at 10-Hz repetition frequency, and the maximum laser pulse energy is 2.58 J with a maximum slope efficiency of 4.3% at 5 Hz.

Propagation of coherent and incoherent combined laser beams in atmospheric turbulence is numerically calculated by using extended Huygens-Fresnel principle. With beam propagation factor (BPF), the influence of atmospheric turbulence on far-field beam quality of coherent and incoherent combined laser beams is evaluated quantitatively. The investigation reveals that the far-field coherent combining irradiance distribution have the multiple side-lobes pattern of non-Gaussian character while propagating in free space with weak turbulence, and it have the advantage of high peak intensity over the incoherent combining counterpart. With the coherence length decreasing, the far-field coherent combining irradiance distribution gradually evolves into the pattern of its incoherent combining counterpart. The quantitatively calculation shows that for laser arrays with different laser number or different laser wavelength, the coherent combined beam quality is no better than its incoherent combining counterpart when propagating in stronger turbulent atmosphere. The mathematical model and calculation result can offer a reference for choosing and evaluating different combining schemes.

A simple and effective tunable fiber laser is presented. The linear-cavity laser consists of a three-port optical circulator (OC), a tunable fiber Bragg grating (TFBG), a segment of high-concentration erbium doped fiber (EDF), and a wavelength division multiplexing (WDM) coupler. By using an OC as the total-reflection mirror and a strain-induced uniform FBG as a partial-reflection mirror and a wavelength selector, a tunable wavelength is obtained. With single TFBG, a single wavelength lasing with a maximum wavelength tuning range of 6.00 nm, from 1543.50 to 1549.50 nm, is achieved experimentally. Within this tuning range, the full-width at half maximum (FWHM) of the laser output is smaller than 0.01 nm and the side mode suppression ratio (SMSR) is better than 50 dB.

The packaging induced stress is the main factor impacting the threshold current, the characteristics of laser, and the life time of laser diode arrays (LDA). A method is imperative to measure the packaging induced stress in the LDA. The basic theory of stress affecting the electro-fluorescence degree of polarization (DOP) of LDA is stated. Electro-fluorescence DOP of high power LDA is measured. Results show that the DOP of LDA change obviously when the driving current grows. LD arrays in different packaging ways are tested. The DOP of the LDA under test is sensitive to stress. When pressure is applied to the center of the array, the distribution of DOP along the array undulates acutely. According to the DOP test of a lot of components, some characteristics within big package-induced-stress are obtained. The result shows that the distribution of stress induced by different materials and different packaging ways is distinctive from each other.

A rate equation model of multi-quantum wells vertical-cavity surface-emitting laser (VCSEL) is presented after theoretical analysis. The effects of photon density and the carrier capture-escape-tunnel time on the frequency response of VCSEL are simulated by the small signal analysis. The results both of simulation and experiment show that the modulation bandwidth of VCSEL is broadened with the power increasing. In addition, we simulate the small signal frequency response of the parasitic circuit of internal-contact oxide-confined VCSEL after analyzing its parasitic parameters.

Performance of a high repetition-rate long-pulse UV-preionized TE CO2 laser with an active volume of 1.17 L utilizing pulser/sustainer discharge technique is investigated in detail. The laser operates with a high repetition-rate of 100 Hz and output laser pulse full width at half maximum (FWHM) of 23.0 μs. The voltage/current waveforms under stable glow discharge and arc discharge are given respectively. The laser output pulse energy varies from about 0.40 J to 4.0 J as the charging voltage on the sustainer circuits rises from 12 kV to 30 kV. Under the same sustainer charging voltage, the laser output power increases linearly with the pulse repetition rate. With sustainer charging voltage of 22 kV and repetition rate of 100 Hz, the laser output power only decreases from the highest 257 W at the beginning to 247 W at the end of 10-min continuous operation. All the experimental data show that, compared with the conventional TE CO2 laser with low inductance quick discharge, it generates a long laser pulse profile containing greatly suppressed initial gain-switch spike, tolerates arcing discharge in repetition rate operation, and decreases more slowly under high repetition-rate long-time operation.

A noise reduction signal processing method of lidar atmospheric backscattering signal with the empirical mode decomposition (EMD)is propased, and the simulation in the system is confirmed by experiment. The noise reduction algorithm based on EMD is suitable for processing of pulse signal (e.g., Block, Bump, and pulse echoing, etc.). The algorithm is used for analyzing and processing Mie lidar atmospheric backscattering signal. It shows that the noise reduction method can reduce the noise in the atmospheric backscattering signal and provide primary data of high signal-to-noise ratio (SNR) for the extinction coefficient retrieval at the next level.

If the frequency of a laser is modulated sinusoidally, the first harmonic component of saturated absorption signal can be used as error signal to stabilize the frequency of the laser. We introduce the principle of using sampling integration technique to obtain the first harmonic signal and the realization of sampling integration and digital proportional-integral differential (PID) controller by means of a microprocessor. Compared to traditional lock-in amplifiers and analog PID controllers, the new technique is more reliable in performance, simpler in construction and easier to be realized. An external-cavity diode laser (ECDL) frequency stabilization system is built with this sampling integration based on Cs atom saturated absorption. Relative frequency fluctuation better than 1.2×10-9(p-p) can be achieved and the average locking duration is about 7 days. The system can also automatically scan the saturated absorption peaks, lock to the desired peak and resume locking when lock is broken by accident.

Scanning accuracy of phased-array laser radar is one of the significant features of liquid crystal phased-array component. One method is proposed to obtain the quantitative calculation of the scanning error. Rayleigh-Sommerfeld formula is utilized to figure out the far-field laser beam accurately and the angle errors is gained. Then the scanning error can be measured based on the ratio of angle error to 3 dB main-lobe width. Finally three typical factors which are voltage discreted, manufactural accuracy, and Gaussian pre-processing, are simulated using this method, and it can be concluded that the magnitudes of the scanning errors are on the orders of 10-3,10-2,10-5, respectively. Thereby, the impact of the manufactural accuracy on the scanning accuracy must be emphasized for laser radar liquid crystal phased-array component.

Beam automatic alignment system is an important sub-system used in high power laser inertial confinement facility for beam adjustment. Far-field alignment is a key technique of the automatic alignment system. Based on the character of diffraction grating, the new far-field alignment system can sample far-field flexibly. The main factors that affect the precision of the far-field detection system are analyzed. The result shows that the systemic error which includes projection error and aslant imaging error is 7.49% of the spatial filter pinhole, and stochastic error which includes object-image error and diffraction light suited error is less than 1% of the pinhole.

A multilevel wavefront correction technique is proposed to improve the effective correction bandwidth of a high-resolution adaptive optics system based on stochastic parallel gradient descent (SPGD) algorithm. At every level of wavefront correction based on SPGD, the control elements of the high-resolution wavefront corrector are subdivided into many clusters according to their locations. The control elements in each cluster are driven by the same control voltage which is treated as a control variable in SPGD algorithm. The higher the correction level is, the bigger the number of independent control variables is. The multilevel SPGD adaptive optics system corrects the distorted wavefront in the sequence from low level to high level. The numerical model of a 3-level SPGD adaptive optics system with a pixelated piston-type wavefront corrector having 16×16 control elements was built, and the simulation correction experiments for a certain stochastic phase screen introduced by atmospheric turbulence were performed on the system. The numerical simulation results demonstrate that the convergence rate of multilevel SPGD wavefront correction is increased by 23% than that of conventional SPGD wavefront correction. It indicates that the multilevel wavefront correction technique can indeed improve the effective correction bandwidth of adaptive optics system based on SPGD algorithm.

Principle and characteristic of super-structured fiber Bragg grating (SSFBG) en/decoder based on equivalent phase shift (EPS) are analyzed, and double band en/decoder is proposed. The +1st and +3rd spectra are successfully linked by designing grating structure with unchanging grating length. The new en/decoder well inherits the advantage of traditional equivalent phase shift, such as flexible design, low manufacture precision and strong wavelength-division-multiplex (WDM) compatible ability. The theoretical and experimental data indicate that double band en/decoder meliorates the en/decoder performance of coherent optical code division multiplex access (OCDMA) system by 3 dB. The essence is the improvement of phase information in unit grating length.

A new method to realize simultaneous measurement of strain and temperature by using a long-period fiber grating with rotary refractive index modulation (R-LPFG) which fabricated in twisted common communication optical fiber by using high-frequency CO2 laser pulses, is reported. The fundamental core mode of R-LPFG simultaneously couples to the odd and the even modes of the asymmetric cladding modes (L1k) due to especial refractive index distribution, which leads to two separated resonant peaks of R-LPFG. The strain and temperature characteristics of R-LPFG are studied experimentally. The results show that the two split resonant peaks continue separating when the strain was applied to it, but shift to the same direction and almost have the same temperature sensitivity when the environmental temperature changes. The temperature sensitivities are about ～0.07 nm/℃.

A novel optical fiber refractive sensor is proposed and demonstrated experimentally. It is based on side polished fiber Bragg grating (SPFBG) manufactured by wheel side polishing method. When about half of SPFBG is overlaid by refractive index liquids, the reflective Bragg wavelength is split into two. The difference between the two reflective Bragg wavelengths has related with the refractive index of overlaid material, but their strain responses are the same, which have no-reference to the ambient temperature. Hence the difference between two reflective wavelengths can be used to measure the changes of the outer refractive index accurately, and to reduce the effect of strain during the measurement. The experiments show that the resolution of the sensor is 0.0001 with outer refractive index in the range of 1.4298 to 1.4479.

A novel temperature sensor of photonic crystal fibers (PCF) based on liquid ethanol filling with refractive index sensitive to temperature is proposed. The temperature properties of the sensor were investigated by the full-vector finite element method with a perfectly matched layer. Theoretical calculations show that filling the air-holes of a PCF with ethanol will enhance the temperature influence on the mode field. Both the effective refractive index and the confinement loss decrease with increase of temperature. After filling the liquid ethanol, the mode field infiltrates more through the cladding of fiber as the wavelength increases, and becomes more sensitive to temperature. Under the condition of the same hole spacing, the larger the duty ratio and the longer the input wavelength are, the stronger are the dependence of the effective refractive index and the confinement loss on temperature. The effective refractive index basically reduces linearly when temperature increases. When the wavelength λ=1550 nm, hole to hole spacing Λ=2.3 μm and duty ratio d/Λ=0.7 (d represents the hole radius), the confinement loss reduces from 3.5×102 dB/m to 22 dB/m as the temperature changes from -20 ℃ to 70 ℃.

Radial basis function network method is presented for demodulation of Fabry-Pérot pressure sensors, and its principle and error are analyzed theoretically. At first eigenvalue is extracted from interference spectrum, and with the eigenvalue of the spectrum and the length of the cavity the radial basis function network is trained. The trained network can forecast cavity length. In the experiment of demodulating MEMS Fabry-Pérot pressure sensor with metrical range from 0 to 2 MPa, its resolution reaches 0.1 MPa, and the linearity between the length of the cavity and pressure achieves 0.98858. In the simulation, the relative error of this new method is just 0.02% and the maximum absolute error of the length of the sensor cavity is less than 0.1 μm. The experiments show that this new method meets the practical demand with its high resolution.

In order to achieve high brightness fiber-coupled output of diode laser array, a simple but efficient system was designed. Firstly, the output beam from a laser diode arrays (LDA) was collimated by fast and slow axis collimation module. Secondly, the collimated beam in the slow axis was divided into 4 parts (any other amount of the divided parts if needed) by the beam-shaping set of two parallel plane mirrors, and then reordered in the fast axis. Finally, the shaped beams were focused into a fiber (600 μm, NA=0.37) by a focusing lens. The beam-shaping efficiency was 98.87％, and the total system efficiency was 77.2％. This beam-shaping system is simple but effective and useful.

Utilizing the image of spatial filter’s pinhole of high power laser systems and diffraction of sample grating, with an insertable negative lens for the pinhole’s on-axial illumination, a new system for far-field detection of laser beam is presented. This far-field detection system, which is fully demonstrated on the experimental system, can fully use space through off-axial grating sampling. The experimental results indicate, that the average far-field alignment error is less than 1.42% of spatial filter pinhole diameter, which meets the alignment system requirements (5% of spatial filter pinhole diameter).

To evaluate the efficacy and safety of CO2 laser sclerectomy with iridectomy (CLSI)as an main initial treatment for diagnosed primary glaucoma, after intraocular hypertension rabbit model is created, right eyes are treated with an improved CO2 laser glaucoma treatment system with self-feedback and left eyes are treated with traditional trabeculectomy. Postoperative anterior chamber reaction, filtering bleb, mean intraocular pressure (IOP), and pathology examination are observed. Anterior chamber reaction of laser group is lower than that of traditional surgery group. On the 14th and 21th days postoperatively, obvious decrease of functional filtering bleb number and increase of mean IOP are found in traditional surgery group . There is statistical significance between these two groups (P<0.05). Compared with laser group, more serious hemorrhage and fiber proliferation, and much shorter lifespan of filtering route are observed in traditional surgery group. CLSI is a safer and simpler operation procedure that effectively reduces IOP with less complications.

In order to find a novel red-sensitive photopolymer, a photopolymer material sensitized by azure I as a dye is fabricated by dry processing, and its holographic storage characteristics are investigated. It is illuminated under the incident wavelength of 632.8 nm of He-Ne laser. Through the measurement of experiment and the computation of corresponding formulas, the holographic parameters of material, such as transmittance, diffraction efficiency, exposure sensitivity, and refractive index modulation, are gained. It is discovered that the maximum diffraction efficiency reaches 66%, the best thickness is 140 μm, the maximum transmittance approaches 80%, the maximum exposure sensitivity is 1.5×10-3cm2/mJ, and the maximum refractive index modulation is 9.7×10-4. The analog image is stored in the material and the transmittance and reconstructed holograms have good fidelity. All of the results demonstrate that the material is appropriate for high-density holographic storage.

The newly developed Co-based alloy powders is taken to prepare a ceramic particles, with reinforcing Co-based alloy gradient coating on surface of Cu-Cr alloy for crystallizer through pulse laser induced reaction in-situ. The microstructure and property of the gradient coating is studied experimentally by means of analysis techniques. The result shows that large-area Co-based gradient coating has synthesized with the laser processing parameters: average power of 50 W, frequency of 15 Hz, pulse width of 3 ms, scanning speed of 4.0 mm/min, and overlapping rate of 20%-25%. There are three different elements and structure layers consisting a gradient coating on the surface of Cu-Cr alloy. The main structure of the coating is α-CoCr2(Ni, O)4 alloy phase, with Fe-Ni, Cu-Ni as the solid solution phase enwrapped in it. The number and density of carbide ceramic particles synthesized in-situ increases gradually from inside layer to outside layer in the gradient coating. Hardness of the Co alloy gradient coating increases obviously, from 94 HV (substrate) to 432 HV (the out layer of coating), and the least wear lost is 0.008 g. It can prove that the wear resistant of the Co alloy gradient coating prepared by laser induced reaction in-situ is excellent.

For studying the actual action area of shock wave in laser shock processing(LSP), the Al2O3 ceramic materials have been impacted at new absorbing layer. The effect of horizontal inflation on actual shock processing is analyzed with the variety of ablation characteristic. The change of transforming area and depth is analyzed through the shock processing of 0Cr18Ni9 austenitic stainless steel and 3A21 antirust aluminum alloy, and the universality of the inflation effect is validated for different materials. It can be found that the inflation of plasma have direct contact with the material of confinement layer.The active function diameter of the shock wave is about 12 mm if the flexible coating is used with the light beam diameter of 8 mm.

Influence of CO2 laser bending on glass microstructure are studied by means of infrared (IR) spectra, X-ray powder diffraction (XRD) and scanning electron microscope (SEM). Test results show that slight phase separating tendency occurrs during the laser bending process, and the original triquetrous elements of ［BO3］ change into the tetrahedral elements of ［BO4］ by combining Na2O. Meanwhile, aggregation extent of Si increases and leads an enhancement of the Si—O bond intension. There is SiO2 crystal phase in the un-irradiated specimen with no obvious crystal phase in the irradiated one. And irregular globular grains of different dimension could be observed in the original specimen. On the contrast, the processed one presentes a character of uniform glass-phase.

In order to obtain excellent gas jet from laser’s nozzle, a combinatorial supersonic laser jet cutting nozzle is designed. The control equation for computational fluid dynamics (CFD) is also derived, where standard k-ε model is used for onflow. Using triangle unstructured grid for computing, applying finite volume algorithm to discretizing the control equation, the equation is solved by coupling solver. Velocity and pressure coupling problem is solved by applying SIMPLEC algorithm, and further more the jet field analysis is fulfilled. The analysis indicate that the optimum pressure-inlet is its designed pressure (7×105 Pa), under which the jet field performs best and so it can be sufficiently applied to cut thick workpiece with high velocity. Comparing the results of CFD analysis with that of image lab obtained, it is found that the two results have a quite good consistency. Thus, the CFD analyzing method is proved practical.

CO2 laser direct-writing ablation micromachining technique is used to fabricate the microchannel on the polymethyl methacrylate (PMMA) substrate. The correlation between the process parameters (the laser power and the beam translational velocity) and the micromachining quality (the depth and the width of the microchannel) is investigated. A laser power of 4.5 W and beam translational velocity of 76.2 mm/s is used to make ablation of the microchannel with a hydraulic diameter of 100 μm on the PMMA substrate. The time for the ablation process is 30 s. This technique is steady and efficient in the batch production. The microchannel has the same Raman spectra as that of the PMMA substrate. The spectra shows that they have the same chemical effect on the polymerase chain reaction (PCR) mixture. The presence of the bumps of resolidified material on the edges of the microchannel has no influence on the hot-press bonding result and the PCR microfluidic chip could satisfy the pressure and the sealing requirement in PCR process. An amplification of a DNA template with 180 bp fragment of arabidopsis thaliana is successfully performed with this chip, in less than 30 min. This result exhibits the availability of CO2 laser direct-writing ablation technique on the micromachining of the PMMA continuous-flow PCR microfluidic chip.

Copper-based powder metallurgy friction matearial is treated by broad-beam laser to improve its combination property. And its microstructure, hardness, density and the friction and wear characteristics are systematically studied by means of SEM, TEM, XRD, microhardness tester, Brinell hardness tester as well as friction and wear tester.The test results show that after laser surface modification, the α-Cu aggregate occurs edge dissolved and the large aggregates of α-Cu dismember to small mass, and the α-Cu aggregate nanocrystals are generated. The density of friction material increases by 6%, the hardness increases by 12.7%, the wear resistant performance increases by 45%, and the friction coefficient enlarges by 1％.

Characteristics of laser multilayer welding of 16-mm thick high strength steel 11CrNi3MnMoV with filler metal in different energy input modes are studied. A narrow gap groove is designed, and dual beam single pass multilayer laser welding with filler metal is carried out. By comparing the weld forming characteristics of single with dual beam laser welding with filler metal, porosity and incomplete fusion is regarded as the main defect of the joint. Moreover, the welding stability and alignment state of wire is obviously improved when the duel beam is used. At the same time, the welding defect, i.e. porosity, is impressed sharply. In addition, problems of incomplete fusion and narrow girdling are solved in the case of combining interbedded heat preservation and hot wire technology. As an optimized welding technology, the tensile strength of the joint processed by dual beam laser welding with hot wire can come up to 97% of matrix metal. Dimple shear fracture is the main failure mode at the fracture surface.

Theory analysis shows that the copper molten amount has great influence on the joint of copper-steel welding for the large difference in physical and chemical properties between copper and steel. Considering the high laser reflectivity of copper, laser welding for copper-steel joining based on slope butt joint and laser beam offsetting to the steel side is researched. Copper-steel butt joints are welded under three different welding parameters. The observation of microstructure and the measured mechanical properties show that joint quality strongly depends on the molten amount of copper in weld. When the copper molten amount is small, the interface between the copper and the weld is clear, and the joint has no defect and shows good mechanical properties. When the copper molten amount is large, there is no clear interface between the copper and the weld, pores and cracks are observed in weld, and the mechnical performance of joint is poor. Experiment results indicate that with the laser beam offset of 0.8 mm. A low fusion ratio of copper and steel is achieved and a defect free joint is obtained.

According to the physical model of laser-assisted pre-stress forming, a set of dimensionless quantities was proposed and a similarity criterion was established with equation analysis and dimensional analysis, for the physical quantities such as temperature field, forming efficiency, and elastic energy conversion. Two models with a model ratio of 1∶3 under geometry and physical similarities were analyzed with finite element methods. The results show that with the models satisfying similarity criterion, the output quantities are of physical similarity in correspondence with the input quantities.

The delivery behavior of the elemental powder has important influence on the composition of as-deposited sample during laser solid forming (LSF) from blended elemental powders. In order to ensure the consistency of the elemental powders delivery processes, and further to realize the composition control, the delivery behavior of the elemental powder during LSF is investigated. Based on the analysis of gas-powder two-phase flow, a mathematical model is established to describe the motion of the powder particles inside and outside the nozzle, and the influence of the powder characteristics on the powder delivery behavior is investigated. It is found that both the powder particle exit velocity and the motion acceleration increase with the decrease of the powder particle size and density. The consistency condition for different elemental powders delivery process is obtained, which is the identity of the exit velocity of the elemental powders. Based on the consistency condition, the match relation among the elemental powder characteristics (including the particle size and density) can be obtained, which ensures the consistency in composition between the laser deposits and the premixed elemental powders during LSF from blended elemental powders.

The bond characteristics of titanium porcelain Noritake Ti-22 bonded to pure titanium fabricated by laser rapid forming (LRF) technigue is evaluated. Titanium specimens are fabricated using commercial titanium powder and laser raped forming system, based on the optimized processing parameters. And the coefficient of thermal expansion (CTE) of LRF titanium is evaluated. The bond strength is analyzed with three-point-bonding test according to ISO9693 Standard, and the titanium surface after debonding is analyzed by scanning electron microscope (SEM) and energy disperse spectroscopy (EDS). There is no significant difference in the CTE between cast titanium and LRF titanium. The CTE of LRF titanium matchs that of Ti-22 porcelain. All titanium-porcelain specimens prepared from LRF titanium exhibit a mixed failure mode of cohesive and adhesive failure. The bond strength of LRF titanium and Ti-22 is above the lower limit value in the ISO9693 Standard (25 MPa). Laser rapid forming of titanium alloy seems to be an alternative technique to conventional casting of dental alloys for porcelain fused to metal restorations.

Based on triangulation method, the closed loop of the control system was used to control the output of the laser pulse. Acousto-optic Q-switched Nd∶YAG pulsed laser was employed to dress bronze-bonded diamond wheels in orthogonal direction. Diffuse and imaging situation of the wheel surface has been studied. Through comparative analysis, the cylindrical lens was selected, A set of fairly complete receive optical system was improved, and the laser ablation system was calibrated. According to the results of calibration, the circuit was adjusted, reasonable laser and technological parameters was selected to carry on the laser truing and dressing experiment for the wheel. The results show that accuracy was significantly improved. Based on those above, the technique of laser-machinery truing and dressing of bronze-bonded grinding wheel has been studied. Namely, the grinding wheel was trued and dressed by mechanical method after trued and dressed by laser. The accuracy was further improved, and the surface topography was improved too.

Surface defect induced by machining in fused silica is the main causation weakening anti-laser-damage ability in actual application. The technology using local high temperature CO2 laser treatment repairing surface characteristic defect in fused silica is developed. It is presented that scale of surface defect is decreased and microcosmic interior structure quality of defect is improved after CO2 laser repairing. Through measuring the damage-threshold of repaired defect, is discovered that damage threshold of scrape-line with depth 200 nm is increases about 100 percent, and the damage growth threshold and anti laser radiation times of initial damage pit with diameter 10-100 μm is increased obviously too. It proves that the method using CO2 laser treatment repairing surface defect in fused silica can improve anti-damage ability and the life extending is doable.

The morphology of in-situ synthesized TiC and TiB2 in laser cladding NiCrBSiC coatings on TC4 alloy was observed by atom force microscope (AFM), scanning electron microscope (SEM) and transmission electron microscopy (TEM), and the growth mechanism of TiC and TiB2 phase was discussed. The results show that, TiC phase in the coatings is equiaxial dendrites with facet and non-facet growth interfaces (the growth interface presents non-facet for small dendrite and facet for large dendrite). TiB2 phase shows flat hexagonal prism which heterogeneously nucleates on TiC dendrite and grows with faceted mode. The special structure with TiC in the core and TiB2 in the exterior was obtained.

A new method for micro-forming——micro-forming technology of metal foil under laser driven flyer loading method is developed. The forming mechanism combined with flyer speed model and pressure loading model is discussed and preliminary forming experiments are completed. The surface of formed aluminum foils is smooth, and has high copying ability with good formed precision. The influence of laser energy on forming depth is examined by topography instrument when the laser spot diameter is 1 mm, and single pulse laser energy of 25-40 mJ, the forming depth of aluminum foils shows linear relationship with laser energy. With single pulse laser energy of 45-50 mJ, the forming depth increass largely due to the rupture.

Assemble nozzles are most widely used in the laser cutting presently, and their resulted jet structure influences laser cutting quality and efficiency remarkably. Based on the axial symmetric N-S equation of compressible liquid, we establish the onflow model to simulate convergent nozzles’ free jet with different internal parameters by using structural grid and finite volume of quadratic precision. The law of the influence of contractive angle of taper nozzles and curvature radius of convergence nozzles’ convergent section on jet structure parameters is revealed, and it can provide a basis for optimization selection and design about laser cutting nozzles.

The newly developed Co-based alloy containing a certain amount of Ni, Cr, Fe, C, Si, MgO, Y2O3 and nano-Al powders is taken to prepare a ceramic particles, to reinforc Co-based alloy coating on surface of Cu-Cr alloy for crystallizer through pulse laser induced reaction in-situ. The microstructure morphology and coating mechanism is studied experimentally by means of optical micrograph, SEM, and TEM analysis techniques. The results show that under conditions of optimized powder elements and process parameters of the laser-scan (power 50 W, frequency 15 Hz, pulse width 3 ms, scan rate 4.0 mm/s), the coating with a metallurgical interface forms between the Cu alloy substrate and coating is prepared on the surface of Cu-Cr alloy.The structure of Co-Cr-W-C alloy with fine grain and high hardness is formed in the coating, and the ceramic particles in the coating are produced by YAG pulse laser inducing in-situ synthesis, which strengthen the coating. Carbides of W,Cr are precipitated in the coating and that dispersion strengthens the coating. The Co rich area formed in the transition layer of coating leads to the formation of the Cu rich area.

Ho3+/Yb3+ codoped oxyfluoride silicate glass has been prepared. According to differetial thermal analysis (DTA) studies, the as-made glass was crystallized. X-ray diffraction (XRD) spectrum, transmission electron microscope (TEM) spectrum, absorption spectrum and up-conversion luminescence of glass ceramics were measured. The average crystallite size of CaF2 glass ceramics was calculated by Scherrer formula and compared with that of TEM. The crystal growth characteristics of nanometer CaF2 as well as effects on the diameter of CaF2 were studied by the kinetics theory of crystal growth. The dynamics equation of crystal growth of nanometer CaF2 was obtained. The upconversion fluorescence emission spectra of Ho3+/Yb3+ in oxyfluoride silicate glass ceramics were investigated and the upconversion luminescence mechanism of oxyfluoride silicate glass ceramics was analyzed . The results indicate that the oxyfluoride silicate glass ceramics is a potential luminescence material for upconversion green lasers.

The variation of temperature has an effect on maximal birefringent index of mica crystal, which accordingly influences the use precision of mica wave-plate. In order to reduce this negative effect and improve the precision of mica wave-plate under different temperature conditions, the thermal maximal birefringent index coefficients of mica crystal is measured by using the method of polarization interference spectrum. Firstly, with Daojing UV-3101PC spectrophotometer, the polarization interference spectrums of mica wave-plates with thickness of 80 μm, 300 μm and 813.5 μm are measured and the spectral drift is discovered at different temperatures. Then through accurate judgment of extreme points of the polarization interference spectrums, the maximal birefringent index of the mica wave-plate is calculated exactly. At last, expressions of the thermal maximal birefringent index coefficients for mica crystal are deduced at visible and ultraviolet bands. The experiment is performed under the condition of 0.05 nm wavelength resolution and the measurement accuracy of birefringent index can reach 10-5.

Yttria-stabilized zirconia (YSZ) films have been prepared by electron beam evaporation at different oxygen partial pressures and deposition rates, using the starting material made of 7% (mol fraction) Y2O3 (99.99%) mixed with ZrO2 (99.99%) powder. The residual stress of YSZ films was measured by viewing the substrate deflection using an optical interference method. The influences of oxygen partial pressures and deposition rates on residual stress were studied. The results show that residual stress of all the samples is tensile. The value of stress decreases with the increase of oxygen partial pressure, then increases with the further increase of oxygen pressure, and increases monotonously with deposition rate increase. The thermal stress plays an important role in the total stress. The value of residual stress is influenced by variations of intrinsic stress and extrinsic stress. In addition, the microstructure of the YSZ films was characterized by X-ray diffraction (XRD). The causes of residual stress were given with micro-structure changes.

HfO2/SiO2, Y2O3/SiO2 ultraviolet multilayer thin films were annealed in air at 400 ℃ through different models: temperature rising linearly or step by step. It was found that the peak reflectances of all samples raised at 190～300 nm if the temperature was rised step by step. Corresponding single-layer thin films were annealed through the two different ways, the physical thickness of HfO2 layer reduced. If the temperature rised linearly, the refractive index of Y2O3 film reduced, which also resulting in blues shifting. If the temperature rised step by step, the wavelength would shift to shorter way because of the reduce of physical thickness. Microstructures of the films before and after annealing were characterized by X-ray diffraction (XRD) , it showed that annealing could crystallized the materials.If the temperature rising linearly, bigger crystals would cause more scattering, then reduce the reflectance of the film.

In this work, Ge films have been deposited on Si (100) substrates with the Si1-xGex∶C buffer by chemical vapor deposition method. X-ray diffraction、scanning electron microscopy and Raman diffusion spectra were applied to characterize the Ge/Si1-xGex∶C/Si samples. The results show that the concentration of Ge atoms in Si1-xGex∶C buffer declines gradually from the surface to the substrate and the average Ge content in the Si1-xGex∶C buffer decreases while the growth temperature of the buffer increasing, this is related to the diffusing of Ge atoms due to the higher growth temperature (780～820℃). Ge films grown on the Si1-xGex∶C buffer have only one crystal orientation and the crystal quality of Ge films decreases while the growth temperature increases.

The 4H-SiC films heteroepitaxially deposited on AlN/Si(111) substrates by chemical vapor deposition (CVD) are investigated in this work. X-ray diffraction (XRD), scanning electron microscope (SEM) and cathode illumination (CL) are used to analyze the structure characters, surface morphology and optics properties of the samples. The XRD spectrum shows that the SiC films have single (0006) orientation. The CL spectra indicates that the type of the prepared SiC films is 4H, and the CL efficiency of SiC films enhances with the increase of the growth temperature. It is found that lower substrate temperature is not beneficial for Si and C atoms to select the proper sites, leading to poor crystalline quality. While higher substrate temperature enhances the etching effect of H2 and desorption of absorbed atoms, which goes against the film growth. In addition, the ratio of C/Si influences on the growth of SiC as well. Excess Si results droplets on the surface, while excess C causes Si vacancies in the material. From these experiments, we point out that the preferred substrate temperature for 4H-SiC heteroepitaxy is between 1230 ℃ and 1270 ℃, the proper ratio of C/Si equals to 1.3.

An analytical formula of temperature distrbution in La0.67Ca0.33MnO3 (LCMO) film irradiated by KrF excimer laser is presented using one-dimensional thermodiffusion model. The relation between surface temperature and irradiation duration of pulsed laser is obtained. Fitting the laser induced thermoelectric voltage (LITV) response waveform of LCMO film, it shows that the time constant is 1.39 μs. The thermal diffusion coefficient and conduction length of the film are calculated, and the results are 4.5×10-8 m2/s and 71 nm respectively. Based on the time constant and a simplified LITV formula, the anisotropy Seeback coefficient of thin films can be deduced, and it is 2.80 μV/K for LCMO.

Jamin lateral shearing interferometer is very useful in wavefront measurement, especially for the white light. To improve the performance, a phase shifting Jamin lateral shearing interferometer is proposed. The interferometer is formed by inserting polarizers, a quarter-wave plate and an analyzer in the Jamin lateral shearing interferometer. The shearing interference is combined with the phase shifting with a simple configuration. With phase shifting interferograms, the precision of the interferometer can be improved. The interferometer is kept as an equal optical path system. It still suits the wavefront measurement of the white light. In experiments, phase-shifting interferograms are obtained by rotating the analyzer. The usefulness of the interferometer is verified.

The time domain characteristics of femtosecond pulse propagation through a scattering surface are investigated theoretically and experimentally. The input femtosecond pulse and output pulse from scattering surface are measured and compared by frequency-resolved optical gating. Theoretical analysis and experimental results show that when femtosecond pulse propagates through scattering surface, it will be broadened and distorted. The full time width at half maximam peak of input pulse is 64 fs, and the average of that of transmitted pulse is 117 fs. The characteristics of the transmitted pulse are discussed. Probability functions of real and imaginary components of transmitted pulse show good agreement with Gaussian distribution. Probability distribution of the intensity follows exponential distribution. The experimental results of the intensity autocorrelation of input pulse and intensity correlation of femtosecond time domain scattered field shown, and the time correlation between them are also discussed.

A new method for detecting orthogonal signals of laser interference fringes based on four-quadrant detector is presented. Using the quadrant characteristic of four-quadrant detector and the vector superposition principle of the cosinusoidal interference fringe distribution within the detected region, the orthogonal signals for fringes has been detected successfully. The experimental results show that the orthogonal signals of fringes can be detected expediently by rotating the four-quadrant detector around its center. When the other interference fringes with different period is detected, the orthogonal signals of fringes can also be obtained easily only by rotating the four-quadrant detector to another orientation. In order to restrain noise effectively, a difference technique has been adopted in signal processing. Compared to the traditional detection method, this method is easy to operate and has strong anti-jamming ability.

High laser pulse contrast ratio is one of the most important terms during the interaction of ultrashort laser pulse and substance. In order to enlarge the range of the pulse contrast measurement, a third-order correlator based on the technique of cross-correlation between the fundamental and second harmonic waves of ultrashort lasers is built. Using this correlator, the contrast ratio of ultrashort laser pulses from a typical Ti:sapphire oscillator is measured. The results show that the conversion efficiency of second harmonic and third harmonic of ultrashort laser pulse can be enhanced, and the dynamic range in pulse contrast measurement can be made much wider by using convex lenses, and the correlator’s widest dynamic range in pulse contrast measurement is about 108.

We focus on a defect that often occurs in spectral phase interferometry for direct electric-field reconstruction(SPIDER) systems: the features of the measured pulse should be predicted properly so as to adjust suitable parameters for the phase retrieval. This defect actually makes some limitations to the applicability of these systems. Errors occur likely when chirped pulses are to be measured. To prove this, we set up a conventional SPIDER system to measure the femtosecond pulses from a Ti:sapphire laser and the chirped pulses resulted from the broadening of a BK7 glass block. The duration of the chirped pulse is 295 fs, while 322 fs is obtained after spectral shear correction. The latter is closer to theorectically predicted value of 313 fs.The experimental results show that errors do occur when the measured pulse has obvious chirp, yet not enough dispersion is offered by the broadening unit of the SPIDER system. However, this error can be decreased by calibrating the spectral shear by means of recording the spectra of the upconverted pulses.

A new compact microfluidic chip based on multimode interference (MMI) waveguide is designed and simulated, which can be used to measure the refractive index of liquid in micro-channel through the interference of multiple optical guide-mode waves. The change of concentrations or composition in liquid leads to different refractive index, the change of refractive index can be measured by the output power of MMI waveguide, and then the information of liquid can be determined in details, such as the composition and concentrations. The sensitivity of refractive index can reach 0.0001 according to simulation. Two pieces of chips are proposed for different flux fluids, which can be applied to the microfluidic chemical analysis chip.

A type of one-dimensional photonic crystal (PC) with traditional medium (refractive index n1>0) and active medium (refractive index n2=n0－ki) alternant multilayer is designed. Its transmission spectrum is studied by transfer-matrix method.Simulation results show that it has two narrow transmission bands amplified whose half-width values are both about 0.6 nm with n1=1.45 and n2=3.8－0.10i, and the corresponding central wavelengths are only up to the thickness of the medium. An M×N matrix filter with gain is designed using M×N PC units with different thickness. The affection of thickness and refractive index of the mediums on the channels of this filter is investigated.The results reveal that the spacing and transmittivity of the channels,which are located in region of visible and infrared light, could be adjusted by changing the parameters of mediums.This will help the needed filter design.

Accumulated intensity noises are investigated and the noises are induced by cross-phase modulation (XPM) effect and amplified spontaneous emission (ASE) in dynamic intensity-modulation direct-detection (IM-DD) optical fiber links with multiple fiber segments. A reasonable correction for Q parameter while computing the transmission penalty considering higher order XPM effect is added in the expression of XPM induced degradation. The effect on bit error rate of dynamic lightpath link caused by the two noises is elicited through simulation analysis. The relation between XPM effect and the links’ structure parameters in dynamic network, including the length of fiber segments, wavelength spacing, amplified spontaneous emission noise from amplifiers, etc., are proposed theoretically and numerically, and it is very useful for dynamical link establishment.

Optical gate based on electro-absorption modulator (EAM) now plays an important role in all-optical 3R regeneration, multiplexing, logic gates, and wavelength conversion for its polarization insensitivity and weak pattern effect. A novel numerical model on cross-absorption modulation (XAM) in bulk EAM is proposed. Using the finite-difference time-domain method, the optical gate in EAM is numerically calculated. And the influence of bias voltage, power and width of the pump pulse on the EAM gate is analyzed respectively. Related experiments concerning XAM is also conducted. Experimental results are in agreement with numerical calculation. Error-free 3R regeneration by an EAM as the reshaping optical gate is also performed for 40 Gb/s RZ signal that is degraded by residual dispersion or polarization mode dispersion.

Energy transport in femtosecond laser ablation can be divided into two stages: 1) laser energy absorption by electrons during the pulse irradiation, and 2) phase change stage that absorbed energy redistributes in bulk materials leading to material removals. We review challenges in understanding the phase change process mainly for the femtosecond ablation of wide bandgap materials at the intensities on the order of 1013～1014 W/cm2. Thermal vaporization and Coulomb explosion are two major mechanisms considered for material removals. Based on the discussions of energy transport, the estimation equations and unsolved problems for threshold fluence and ablation depth are presented.