A laser diode (LD) end pumped active- and passive- mode locked Nd:YAP laser at 1341 nm is reported. A Nd:YAP laser crystal is used as gain material. A saturable absorber V3+:YAG is used for passive mode locking and an acousto-optical modulator (AOM) is used for active mode locking. The output pulse train with a total energy of 0.82 mJ is obtained under the conditions of pump energy of 50 mJ and frequency of 10 Hz. The full-width at half-maximum (FWHM) is measured as 570 ns. The pulse repetition period is 7.7 ns. There are around 75 pulses in the pulse train,and each pulse has an average energy of about 11 μJ. An opto-electronic RbTiOPO4 (RTP) crystal works as a cavity dumper. A single pulse of 160 μJ with pulse duration of 680 ps is obtained. The laser beam diameter is measured as 1.2 mm and the beam propagation factor M2 is around 1.5 by using an InGaAs infrared detector.

The influences of amplified spontaneous emission (ASE) on the formation and evolution of pulses in actively Q-switched ytterbium-doped fiber laser (YDFL) are investigated experimentally. The experimental results show that the combined effect between the short switching time and the gain transient property of ytterbium-doped fiber (YDF) causes the initial ASE power fluctuation,which then forms the multi-peak structure in the output pulse after having been circulated and amplified in the cavity. Meanwhile,the high-level broadband ASE may give rise to the gain self-saturation effect in the YDF,making it difficult to form Q-switched laser pulses for the fiber laser. The output pulses may be eventually Q-switched ASE pulses,giving lower peak-power and larger pulse duration. By using fiber Bragg grating (FBG) to suppress the gain self-saturation effect,the gain supplied by the YDF can be greatly enhanced,making it easy for the laser to achieve the Q-switched laser pulse with low threshold,small duration,and high peak-power. When the YDFL with FBG is pumped with 160 mW,the Q-switched laser pulses with the peak power of 40.7 W and the duration of 30 ns are achieved.

The experimental study on transmission characteristics of high-peak power laser pulses with width of 5 ns and wavelength of 1064 nm via all-silica fibers with core diameter of 600 μm are demonstrated. According to N-ON-1 test mode,the laser induced fiber damage threshold and transmission efficiency curve are obtained. The 50% probability damage threshold is 24 mJ,the average output energy is 14 mJ,and the peak power approaches to 3 MW. The three processes of fiber delivery high-peak power laser pulsed are presented,which are undamaged stage (steady state),laser-induced plasma stage (unsteady state) and laser-induced fiber core damage stage (transmission cut-off). The damaged morphologies and damage mechanism are investigated. The synchronous increases of laser induced plasma threshold and entry damage threshold can improve optical fiber capability for high power laser delivery.

The intense few-cycle pulse compression technique based on 250-μm-inner-diameter single fused-silica hollow-core fiber (HCF) and subsequent negative dispersive compression stage by chirped mirrors is researched systemicly. Using the system,we study the influence of parameters like input pulse energy and gas pressure to the final duration and output energy of the compressed pulse. On this basis,7 fs compressed pulses with energy of more than 1 mJ and centre wavelength of 750 nm are obtained through this Ne-filled HCF system,and the driving source is from a 1-kHz Ti:sapphire laser generating 2.7 mJ driving pulses centered at 800 nm with 40 fs duration.

A picosecond ytterbium-doped fiber laser with average power of 30 W is constructed with a tri-stage master oscillator power amplifier (MOPA) configuration. The laser exhibits a pulse width of 20 ps,repetition rate of 59.8 MHz,and a beam quality M2 of less than 1.5. The diameter of the output fiber core is 30 μm. By using the laser as a pump source,near 3 W supercontinuum is generated from a section of homemade photonic crystal fiber (PCF) with 7 μm core diameter. An extra section of fiber with 15 μm core diameteris arranged between the picosecond laser source and the PCF so as to increase the coupling efficiency and avoid fiber facet damage. The supercontinuum covers the whole spectral range from 600 to 1700 nm of the optical spectrum analyzer. The unflatness of the spectrum is less than 10 dB (except for the residual pump laser peak at 1064 nm). The output beam spot is a white fundamental mode with a chromatic hexagonal surrounding.

Stimulated Raman scattering in Ba(NO3)2 crystal at ultraviolet band was studied by building the flashlamp-pumped E-O Q-switched all-solid-state Raman laser experiment system,and the fundamental wave is 1064 nm with the single pulse energy of 1 J and the pulse width of 9 ns,then the single pulse energy of 140.76 mJ at 355 nm with the pulse width of 8 ns was obtained through second harmonic generation of KTP crystal and third harmonic generation in BBO crystal. And 355 nm is used to be the pumping source to cause stimulated Raman scattering in Ba(NO3)2 crysal to acquire the Raman scattering light. It′s proved to be 368.15 nm by a spectrometer,with the pulse width of 7.1 ns,frequency shift of 1006 cm-1 and the gain coefficient of 78.51 cm/GW.

The time-resolved emission spectrum of laser induced Ni plasma is measured at atmospheric pressure using a femtosecond laser with pulse width of 30 fs and wavelength of 800 nm. The electron temperature of Ni plasmas and its temporal evolution are obtained through the relative intensity of Ni emission spectrum lines. In addition,the temporal evolution of Stark broadening and Stark shift of the spectrum lines are also obtained. It is shown that the electron temperature varies from 7500 to 4500 K when the time delay is in the range from 110 to 610 ns,which is different with the dynamic characteristics of nanosecond laser induced plasmas.

System size is of great concern when the laser ranging system is put into practical usage. A multi-pulse gain-modulated three-dimensional imaging system is presented,which uses low pulse energy laser as illumination source. By utilizing multi pulse accumulation method,a 5-μJ pulse laser source was used to achieve a detection range of 100 m with light fog and range accuracy greater than 3 m during indoor experiment . With the using of low pulse laser source the system size is greatly reduced.

Gas film cooling,for protecting the gain generators,and two-step combustion method,for improving combustion efficiency,were applied together to continuous wave DF/HF chemical laser. Portion of the main diluent-helium was transferred to inject at the converging section of the primary nozzle. The flowfield in cavity was numerically simulated and the results showed that spectra′s small signal gain had a small amplitude increase. The results did not exhibit high combustion efficiency as that in traditional two-step combustion method,and the high temperature gas flow demanded the combustion chamber to reach a much higher level. The total temperature could be lowered through increasing oxidizing gas flow and the gain coefficient was increased.

A design method of diffractive optical elements (DOE) based on dual-lens system is proposed. In the dual-lens system,the transmission and focusing of the beam need to be expressed by twice Fresnel diffraction,in order to accelerate the computing speed,we converted the Fresnel formula to the form of which contains fast Fourier transform so that the traditional iterative algorithm can meet the different design environments. By using this design method,we get the diffraction efficiency more than 90% in theory,and processes the element and make the experimental test,the effect of beam shaping that we expected is achieved. It is worthwhile,for more complex system of DOE design there,and there may be potential function for the high-power laser systems.

Lidar has been used for ocean remote sensing widely. The upward laser beam is distorted due to the rough sea surface. It limits dramatically laser transmission through sea surface and the application of Lidar under water. The beam distribution of upward laser beam through sea surface is studied based on the geometric optical theory,three dimension wave simulation and Monte Carlo simulation respectively. Results show similar beam distribution by the three methods. The beam profile is limited in ±10° for collimated vertical upward beam. Demonstration of beam distribution through man-made rough water surface is conducted in a water tank. Results show that the exit angle is actually limited within ±10°. The study will be useful to the design of Lidar application under sea water.

The distributed fiber Raman amplifier (DFRA) is more and more attractive for its particular virtues such as in-line,wideband and low noise etc. Because of the virtues of in-line and low noise,DFRA is used as the in-line amplifier in long-distance fiber optic hydrophone (FOH) and to measure the change of noise. The experimental results show that the increases of intensity noise and phase noise are below 2 dB. Meanwhile,compared with erbium doped fiber amplifier (EDFA),DFRA has better performances when it is used as the in-line amplifier in the remote FOH system. So DFRA can be used as the in-line amplifier in long-distance FOH.

It is found that the torsion characteristics of the long-period fiber grating (LPFG) are novel,which is written symmetrically by three-beam focused high-frequency CO2 laser pulses. Firstly,when the length of the twisted fiber is close to the length of the LPFG,the torsion characteristics have obvious relevance with the twisting direction. If the LPFG is twisted clockwise,the resonant wavelength and the peak loss will decrease linearly with the twist rate increasing. If the LPFG is twisted anticlockwise,the resonant wavelength and the peak loss will increase linearly with the twist rate increasing. The average sensitivities of resonant wavelength and peak loss are 0.133 nm/(rad·m-1) and 0.061 dBm/(rad·m-1) respectively. Secondly,when the twisted fiber is much longer than the LPFG,the torsion characteristics oscillate periodically;and the number of the oscillation (10 periods) overcomes the number of turns (6 turns) that the fiber has been twisted. The overall characteristics are basically unchanged if the volatilities are ignored. The torsion characteristics are analyzed theoretically by taking into the consideration of the twist-induced elliptic birefringence. Moreover it is found that the linear birefringence in the LPFG also plays a decisive role in the torsion characteristics.

Based on the unified theory of coherence and polarization of random electromagnetic beams and the propagation law of cross-spectral density matrix,the closed-form expression for the 2×2 cross-spectral density matrix of random cosh-Gaussian(ChG) electromagnetic beams propagating through a lens is derived,and used to formulate the degrees of cross-polarization,i.e.,the longitudinal degree of cross-polarization (LDCP) and the transverse degrees of the cross-polarization (TDCP) between two arbitrary points upon propagation. It is shown that the degrees ofcross-polarization depend on the focal length of the lens and beam parameters,such as the coefficient ratio,decentered parameter and self-correlation length. The degrees of cross-polarization of radom Gaussion Schell-model (GSM) electromagnetic beams propagating through a lens can be treated as a special case that the decentered parameter of random ChG electromagnetic beams approaches to zero. The main results are illustrated numerically and interpreted physically.

The objective of this study is to test whether hydrogen peroxide (H2O2) is involved in laser pretreatment induced drought tolerance in wheat seedlings due to its nature as a second messenger in stress responses. Plant is treated with 3 min CO2 laser pretreatment, laser pretreatment in combination with catalase (CAT), ascorbate (AsA) or diphenylene iodonium (DPI) and their effects on the lipid peroxidation, the activities of antioxidant enzymes and the concentration of photosynthesis pigment and seedlings growth and development were compared. The results show that 3 min laser pretreatment can enhance drought tolerance in wheat seedlings by decreasing the concentration of malondialdehyde (MDA) and increasing the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and the concentration of chlorophyll a, chlorophyll b, carotenoid and plant height, root length and root dry weight. But the promotive effect of laser pretreatment induced drought tolerance in wheat seedling is effectively reversed by the addition of CAT, AsA or DPI. The results suggest that H2O2 is involved in laser pretreatment induced drought tolerance in wheat seedlings and laser induced protective effect is likely related to NADPH oxidase-dependent H2O2 production.

The compressive residual stresses are generated by laser shock processing (LSP) on the metallic surface,and laser shock processing is a new surface strengthening technology which can modify material surface. With the finite element simulation software ABAQUS,the effect of the laser power densities and the spot configurations on the distribution of residual stress field of the material surface is simulated. The results indicate that the compressive residual stress field can be enhanced by increasing the laser power densities,but the “residual stress hole” may appear with the increase of the power densities. From the analysis of material displacement and the dynamic response of the surface stresses after the laser shock,it is found that the shocking on material surface and the elastic force of material together form the oscillation process,and the reflection waves (rarefaction waves) load reversely on the shocking spot edges,inducing the reverse plastic deformation,which is the so-called “residual stress hole”. The focalizing of the rarefaction waves to the center is influenced by the spot configurations,and the residual stress deletion at the shocking center is different. The results can be used to reduce the residual stress deletion at the shocking center and optimize the process parameters,which provide a basis for obtaining the better strengthened effect of the laser shock processing.

Laser welding with filler wire is a widely used welding technology. In view of the disadvantages of the welding technology with side wire feeding,a new method of coaxial wire-feeding is put forward based on an annular laser beam. The welding experiments have been done with the self-design internal coaxial wire feeding welding equipment. The results show that the coaxial wire feeding welding technology has prominent advantages on many aspects,such as stability of coupling between beam and wire,symmetry of heat resource,and optimization of energy distribution. The welding seam surfaces are smooth and flat and their cross sections are symmetrical. The property of isotropic quality is suitable for one-dimensional and multi-dimensional welding. Through altering of laser power,scanning speed,and wire feeding speed,a set of optimal process parameters have been obtained. The results of scanning electron microscope (SEM) analysis and tensile test show that the welding seam produced by this new method has excellent microstructure which is very dense without pores and impurities. Moreover,the metallurgical bonding between welding seam and substrate is very strong and has no obvious flaws.

In order to study the effect of Ti on microstructure and properties of Co-based alloy coating,Co-based alloy and Ti/Co-based alloy composite coatings are obtained on low carbon steel surface by 5 kW CO2 laser. Microstructure,microhardness,and sliding wear resistance of the coatings are studied. The results show that Co-based alloy coating consists of γ-Co,ε-Co,Cr23C6 and Ti/Co-based alloy composite coating consists of γ-Co,ε-Co,Cr23C6,TiC and so on. The Co-based alloy coating is made up of flourishing γ-Co dendrite and eutectic structure. Equiaxed solid solution and fine eutectic structure are observed in the Ti/Co-based alloy composite coating. The influence of in-situ synthesis TiC particles on microstructure of coating is prominent. And the microstructure is refined by changing it from dendrited to equiaxed grain by TiC.

Experimental study on high power fiber laser deep-penetration welding of automobile 5052 aluminum alloy in an overlap configuration is carried out,and the main influencing factors on fiber laser welding are analyzed,and the micro-structure and the mechanical properties of the welded joints are measured. Through analyzing fiber laser welding performance of automobile aluminum alloy,the influencing factors such as fiber core diameter,gap thickness between two plates,kinds of shielding gas,and the protection way on the morphology and properties of overlap-welded joint are prominent. High welding speed and narrow weld pool and heat affected zone (HAZ) can be obtained when welding by fiber laser. Under the proper welding condition,the weld topography of top surface and bottom surface is even and continuous. Micro-hardness in fusion zone is higher than that of base material. The tensile-strength of welding joints is higher than its shear strength. The fracture is happened in HAZ and its topography is a mixture of ductile fracture as main mode and brittle fracture as subsidiary mode.

Using particle image velocimetry (PIV),smoke flow visualization technology and Fluent software,shielding gas flow fields of coaxial powder feeder nozzle are researched in order to improve the shielding effect of gas flow on laser on-line rapid repair of aircraft structure damage. Influences of gas velocity from nozzle,crosswind velocity are systematically analyzed on gas impacting jet flow field. The results show that when the velocities of three-section gas flow are nearly consistent,the turbulent diffusion area disappears and a stable flow field can be obtained. When the gas velocity from center nozzle is smaller than that from outer ring,a vortex is generated and disturbs the stability of gas flow field. The crosswind produces prominent interfere to the gas protective range. With the increase of velocity of crosswind,the axis of shielding gas fields and nozzle get apart. When the velocity of crosswind surpasses 50% of the velocity of gas from nozzle,the shielding gas fails to protect molten pool totally because ambient air is mixed.

The microstructure evolution of bulk metallic glass Zr55Al10Ni5Cu30 during pulsed laser remelting is investigated. It is found that the remelted zone always keeps amorphous structure and the crystallization tendency in heat-affected zone (HAZ) increases with the laser energy density increasing or the scanning velocity decreasing. The crystallization in the HAZ can be avoided but the structural relaxation occurres when the scanning velocity is equal to or greater than 15 mm/s. When the crystallization occurres in the HAZ,the micron-scale spherical grain is formed in the pattern of the multi-layer with the inner coupled lamellar structure,and crystalline phases are composed of tetragonal Zr2Cu and face-centered cubic Zr2Ni. Crystallization in the HAZ near the bottom of molten pool is more severe than that in the region near edge of surface. The grain size in the HAZ near bottom of molten pool decreases away from the remelted zone,and the layer numbers of the spherical grain in the HAZ near the remelted zone are more than that near the substrate side.

The 00Cr12 alloy heat-resistant steel was strengthened by laser shock processing (LSP) with appropriate parameters,and its fatigue limitation was measured rapidly. The effects of residual stress and microstructure change of the surface layer of 00Cr12 alloy on its fatigue life were discussed and analyzed before and after LSP. The results showed that elastic-plastic deformation was induced by laser impulse on the material surface,which resulted in residual compressive stress and dislocations of high density in the material surface,so the fatigue life of 00Cr12 alloy was effectively improved by LSP. After LSP,the fatigue life of 00Cr12 alloy was 1.6 times as much as the sample without LSP. Compared with the traditional rising and falling methods,the relative error of the results obtained by Locati multistep method was small. This method could provide reliable data for fatigue design of machines.

Ni60 alloy coatings are prepared on the soft steel (Q235) surface by using a CO2 laser. Cross-section microstructure characteristics of the coating are studied by using scanning electronic microscope,energy spectrum,and micro-hardness analysis. The results show that the microstructure of Ni60 coating by laser cladding is typical rapid solidification structure. The morphology at the bottom of the cladding layer is a cell structure,whose growth is perpendicular to the interface of cladding and substrate. The morphology at the central and top zones of the layer is dendritic structure. The crystal grain of central zone grows with a single direction,but that of the surface layer grows with random direction. There are a large number of eutectic compounds at the middle of the dendrite. The black area contains a large number of inter-metallic compounds,such as alloy cementite. With the effects of solid solution strengthening,dispersion strengthening,hard phase strengthening,and fine grain strengthening,the hardness of the cladding layer is obviously greater than that of the substrate,which achieves the goal of hardening surface.

The 7050 aluminum alloy is processed by laser shock processing (LSP) with high energy high repetition rate Nd:glass laser. After LSP with the unchanged pump power and different amplified spontaneous emissions (ASE),the surface residual stress of 7050 aluminum alloy is measured by using X-ray diffraction (XRD) technology. Results show that there is a certain relationship between ASE and the surface residual stress of aluminum alloy after LSP with unchanged pump power. With the increase of ASE,the compressive residual stress of the sample surface gradually decreases. When ASE increases to 16.20 J,the absorbing layer (aluminum foil) has been completely molten,and the effective pulse directly impactes aluminum surface and generates 21 MPa tensile residual stress which directly affects the effect of LSP on 7050 aluminum alloy.

Laser-induced breakdown spectroscopy (LIBS) method was used to analyze steel samples. The impact of metallurgical structure on laser ablation properties of steel was analyzed. Heat-treating process was used on 45# steel to obtain three different metallurgical structures (pearlite+ferrite,bainite,and martensite). The changes of plasma temperature,electron density,and line intensity with laser energy for different metallurgical structures were analyzed. The results showed that plasma temperature,electron density,and line intensity of three different metallurgical structures had almost same tendency with the increase of laser energy. Under the same experimental conditions,the plasma temperature,electron density,and line intensity of pearlite+ferrite were the highest,those of bainite were the second and those of martensite were the lowest.

The mechanism and method of laser-guided discharge (LGD) to discrete surface processing are studied. In the study of LGD mechanism,it is found that laser guiding controlles the randomicity of processing by common arc discharge in two sides,including a big scale (spacing of discharge areas) and a small scale (inside of discharge area). The position of discharge areas are controlled by the laser focus according to the design. The deepness of discharge areas are increased. The consistency of discharge areas is improved. In the study of surface texturing by LGD,the highness of rim of textured crater and the SRa of textured surface are increased with the augment of peak current. The hardness of rim of textured craters is about 1000 HV. In the study of surface strengthening by LGD,the cross-section shapes of strengthened areas are controlled with the peak current and pulse width. In long pulse-width of discharge,the ratios of diameter to deepness of strengthened areas are similar. The diameters of strengthened areas with high peak current are bigger than those with low peak current. The deepness of strengthened areas with high peak current are deeper than those with low peak current. In short pulse-width of discharge,the deepness of strengthened areas are similar. The ratios of diameter to deepness of strengthened areas with high current are bigger than those with low peak current.

Slots with a width of about 25 μm is fabricated on Si (100) using a homebuilt micromachining system based on a 355 nm nanosecond pulse laser. Strong photoluminescence (PL) emission from the fabricated area is characterized by fluorescence microscopy and local fluorescence spectroscopy. Fluorescence emission in the wavelength range of 400-700 nm is detected with excitation wavelength range of 400-440 nm. Furthermore,a strong decay of the PL intensity is observed as a function of irradiation time. It can be confirmed that the optical property of silicon is changed after nanosecond pulsed laser fabrication. And a potential method to produce optoelectronic device based on silicon is tried with pulsed laser fabrication.

Laser forming of sheet metal is a new sheet metal forming process with the features of non-contact,dieless,spring-back free,and high degrees of flexibility. The bending process is affected by many factors. A thin aluminum-lithium alloy sheet metal used in aircraft is chosen as the object of the research and systematic experimental study is conducted with a semiconductor laser to investigate the effect of principal factors that influence laser forming. The experimental results reveal that,under the condition that other technological parameters are invariable,the bending angle increases with the increase of the laser power,number of scan,and sheet width. With the increase of laser scan speed,the bending angle increases at first,and then decreases. As the scan line from the free edge increases,the bending angle decreases at first,and then increases. With the increase of laser beam diameter,the bending angle decreases at first,then increases and finally decreases. The bending angle decreases with the increase of the sheet thickness.

SnO2 gas-sensing film is prepared on alumina substrate by laser micro-cladding SnO2 paste,which is obtained by mixing SnO2 nanoparticles with organic solvent. The effect of laser power on microstructure and gas-sensing properties of gas-sensing film are researched by X-ray diffraction (XRD) and field scanning electron microscope (FE-SEM). The results show that the grain sizes of SnO2 film gradually increase with raising laser power,while gas sensitivity to ethanol vapor decreases steadily. The gas sensitivity to 2×10-3 ethanol vapor of gas-sensing film fabricated by laser micro-cladding reaches a maximum value of 8.6,whose performance is equivalent to traditional screen-printed gas-sensing film.

The laser solid forming (LSF) titanium alloys from blended elemental powders are investigated. By combining the computation of the melting time of powder particles with the motion analysis of the solid-liquid interface of the melt pool,the formation mechanism of the unmelted powder particles during LSF from blended elemental powders is disclosed. That the powder particles inject into the "unmelted zone" is the main reason leading to the formation of the unmelted particles. The morphologies of the unmelted particles are presented as "crescent" or sphere when the spherical elemental powder particles are used as the deposited materials. The theoretical analysis agrees well with the experimental results. The morphology and formation condition of the composition segregation band during LSF Ti-xAl-yV from blended elemental powders are investigated. It is found that the composition segregation band is prone to occur when the V content in the Ti-xAl-yV alloys is near or higher than the critical concentration of element V,and this is caused by the low melt flow velocity near the solid-liquid interface in the melt pool. The uniform composition in the alloying clad layers can be obtained by controlling the powder delivery parameters,powder characteristics,and the processing parameters.

A new detecting method of pulse laser discrete scratching is presented to estimate the bond strength of film-substrate interface and a device is designed to achieve the automation of discrete scratch. Through detecting typical coatings failure the database is established. The optimal algorithm method is applied to the laser system in which it immediately approaches the power density range of laser with coating failed. Through the power meter detecting infrared beam reflective surface of the coating surface morphology of coatings,detection system obtains characteristic parameters;which will be compared with the failure database to arrive next point laser output power. Asymptotic approximation is used to determine the fact coating failure threshold and the design achieve intelligent discrete scratches.

As the demand of ergonomics and bionics,more and more free-form surfaces appear in product design. In order to mark on these relatively large undulating surface with laser,the dynamic focusing and three-axis beam control technology must be adopted. The principle of beam focusing by dynamic expansion was analyzed,and the best range was determined from the relationship between the misfocus and the location,sizeofthe beam waist. A dynamic beam focusing mirror was designed,and a three-dimensional laser marking system was constituted together with X,Y directions galvanometer. Marking experiment of free-form surface verified the effectiveness of the system. This form of marking can be also used for the other two-dimensional surface.

In order to improve heat shock resistance of phosphate laser glass,a surface strengthening treatment method with base and acid buffer solutions is studied. Evaluated from surface morphology and mechanical property of phosphate laser glass,it is demonstrated that this method is better than fine ground with 303 abrasive,surface treatment in strong mixed acid,and chemical-mechanical polishing. The results indicate that this method is more efficient to remove the surface drawbacks .Phosphate laser glass which is treated by this method presents higher surface micro-hardness and higher flexural strength as well. Experimental resultshows that the thermal damage threshold and laser efficiency of surface strengthened phosphate laser glass is improved when it is pumped with flashlamp in repetition frequency.

Applying the condition of electromagnetic wave restricted in horizontal direction,the conditions that each mode should satisfy are concluded from the one-dimensional rectangle doping photonic crystal. The dependences of defect modes on the mode quantum number and doping thickness are obtained for TE wave and TM wave. These results can be used to design multi-channel filter with frequency tuning.

The anisotropically absorbing bacteriorhodopsin (BR) molecules can be approximated by linear oscillators. BR film is isotropic in its initial state because of the random distribution of the BR molecules. Upon excitation by a linearly polarized light,those molecules with the dipole moment aligned closed to the polarization direction of the excitation light are dominantly pumped to the intermediate state and produce photoisomerization. However,those with the dipole vector in the perpendicular direction of the pumping beam have a little probability occurring the above change. Due to the change of molecular structure,the refractive index and absorption coefficient of the BR molecules change,then the macroscopic anisotropy was induced as a result. The photoinduced birefringence of the BR film is measured by the orthogonal polarization detection,the experimental results are basically consistent with the simulated results,which are obtained by utilizing the two-state model of BR molecule photocycle.

Uniformity of thin-film thickness is one of the main standards of judging optical thin film. The bad uniformity of thin film can damage the characteristics of costing system. As a main material of low refractive index to preparation of optic thin film,SiO2 is poor thermal conductivity and sublimes. The particularity of evaporation characteristic of SiO2 leads to obvious change of thin film thickness when SiO2 is evaporated by e-beam method,which affects the quality of thin film heavily. For the purpose of analyzing the impacts of evaporation characteristics of SiO2 on uniformity of thin film thickness,the heat distribution of e-beam spot is calculated and simulated,and the mass distribution is calculated. According to the mass distribution and the change of evaporation angle of point on evaporation surface,the thin film thickness distribution on spherical surface and flat surface is calculated. The reason of making the impact of evaporation characteristics of SiO2 on uniformity of thin film thickness,and the particularity of thin film thickness distribution are concluded,which offer references of adjusting and improving the technological parameters for thin film coating of SiO2 material.

To study the thermalization dynamics process of ferromagnetic thin films excited by femtosecond laser,numerical computation based on three-temperature (3T) equations with finite difference method was carried out,and the analysis of this process combining with the results of the femtosecond laser pump-probe experiment was given. A coefficient was introduced to characterize temperature dependence of the specific heat of spin system,and the rationality was analyzed in details. First,analytical research of reflectivity change of NiFe films was carried out and the modified model matched ultimately the experiment results of NiFe films. The laser power dependence of peak value of reflectivity change was studied. Also,the ultrafast thermalization dynamics of nickel (Ni) films with different thicknesses were investigated associated with the experimental results. When the thickness of thin film is less than the depth of penetration,electron,spin system and the balance value of the 3T system grow up obviously,and when the thin film is thicker,the thickness of ferromagnetic thin film hardly affects the thermalization dynamics.

The influence of the substrate temperature on the topography and microstructure of the diamond-like carbon (DLC) film in the pulsed laser deposition (PLD) is studied. When the diamond-like carbon films were deposited,the substrate temperature kept at 30,200,400 and 600 ℃ respectively. The microstructure and composition of the diamond-like carbon films deposited at different substrate temperatures were detected by the visible Raman spectroscopy and the X-ray photoelectron spectroscopy (XPS) respectively. The topography of the diamond-like carbon films was detected by the atomic force microscopy (AFM). The experimental result demonstrates that the substrate temperature influences microstructure,composition,ratio of sp3/sp2 and topography of the diamond-like carbon films in the pulsed laser deposition remarkably. When the substrate temperature increases,the ratio of sp3/sp2 in the film would decrease,the size and number of graphitic crystallites in the film would increase,the roughness of the film would reduce and the number of granules on the film would decrease. The reason to cause the experimental phenomenon is that transfer ability of the carbon ions and granules on the substrate would increase when the substrate temperature increases.

In order to develop low loss,high-performance 193 nm fluoride high reflection (HR) mirrors,the properties of 193 nm HR mirrors are researched in depth in this paper. The thickness of 193 nm reflective film is controlled by a 1/3 baffle with pre-coating technology. Different fluoride HR mirrors are deposited by a molybdenum boat evaporation process on fused silica substrates. Their optical properties (including reflectance,transmittance,and optical loss),microstructures (including cross section morphology and surface roughness) and mechanical properties (stress) are investigated and compared. Based on these studies,the NdF3/AlF3 193 nm HR mirror is designed and made. Under the present experimental conditions,its reflectance is up to 96%.

A novel refractometric sensor used to measure the refractive indices of glucose solutions of different concentrations using microfiber is presented. In addition,by solving Maxwell equations and numerical calculations,phase shift of microfiber caused by index change of ambient medium is obtained. Experimental results show that the measured values are in close agreement with the theoretical values. The sensor demonstrated here is featured with high sensitivity,compact size,and easy integration with the optoelectronic devices.

The response functions of direct-detection Doppler wind lidar at different atmospheric temperatures are simulated based on the principle of the Rayleigh Scattering Doppler wind lidar with the double-edge-technique. The wind speed errors induced by temperature profile changes are analyzed. It is shown that atmospheric temperatures have great impacts on the response functions,and at larger wind speed the temperature will produce greater wind speed error. In order to obtain a reasonable wind speed accuracy,the accurate temperature distribution of atmosphere is required. In this simulation,a formulation to estimate the wind speed errors at different temperatures and wind speeds caused by temperature errors is obtained.

In order to achieve three-dimension high-speed and large-scale measurement to underwater objects,an underwater line structured-light self-scan three-dimension measuring technology is presented. A galvanometer is adopted to reflect laser plane onto object′s surface. The laser plane intersects the surface of object and a light stripe which is photographed by a camera is formed. According to the position of each point of light stripe on image,the offset caused by refraction is calculated and compensated. Then utilizing the equation of laser plane in water,accurate 3D coordinates of detected points are accurately calculated out. Experimental results show that the model of underwater self-scan system and underwater three-dimension measurement method are feasible. The measurement precision in the space of depth of 0.5-1 m,measuring height of 0.5 m and measuring width of 0.6 m achieves 0.7 mm.

The navigation and positioning accuracy is mainly dependent on measurement accuracy of atmospheric polarization imaging. A four-channel time division multiplexing (TDM) atmospheric polarization measurement technique based on bionic principle is proposed and investigated. The technique measures atmospheric polarization signals with four detecting channels based on TDM. Compared with developed techniques,the technique simplifies measurement system and decreases effects from channel signal gain difference and atmosphere signal intensity change. Experimental results show that the technique significantly reduces measurement error and improves measurement accuracy of atmospheric polarization. A measurement system based on the technique can obtain reliable position information of the star for navigation and positioning.

This paper proposes a method of faults location for transmission lines by using broadband chaotic signals,which is experimentally demonstrated with a chaotic semiconductor laser. Chaotic signal is obtained by converting the chaotic light from the chaotic laser diode,and divided into two signals,one serving as probe signal and the other serving as reference signal. Faults are located by correlating the echo of probe signal with the reference one. The spatial resolution is determined by the time resolution of correlation curve. Experimental results show that 7.5 cm resolution can be readily achieved by common laser diode.

A miniaturized non-destructive optical system for measuring the 3D flaws of inner surface of a pipe is proposed,which is based on Fourier transform profilometry (FTP) using two microscopes and an amplitude grating. It is possible to get a magnified and clear image of a small object by using a microscope. The images of the inner surface of pipe can be non-contact captured in real time when the sensor is moving along the pipe driven by a micro-robot. Experimental results show that the reconstruction of 3D surface of the inner surface is obtained with high precision. This method can be used to measure the 3D shape of pipe inner surface,so it should be interesting for practical applications.

The surface accuracy of lithography projection objectives is on nanometer scale,so the accuracy of the testing interferometer is also needed on nanometer to sub-nanometer scale. A method to test the optical surfaces of lithography projection objectives using Fizeau interferometer is proposed. Through theory analysis and computer simulation,the system errors caused by phase shifting,reference surface,and detector nonlinear are investigated. Other factors affecting measuring accuracy including light source instability and environmental control are also analyzed. The relationship between measurement errors and interferometer structure parameters is presented. Some methods and measures for improving accuracy and decreasing measurement errors are put forward. The results of the computation show that the accuracy of the interferometer is mainly limited by the accuracy of the reference surface and the stability of the environments. The results also have an important reference value for the design and manufacture of Fizeau interferometers.