To develop tunable trtansversely excited atmospheric (TEA) CO2 laser used in differential absorption lidar (DIAL) system, the kinetic characteristic of a TEA CO2 laser is investigated, base on the theory of six-temperature model rate equation. The output characteristic of the laser is calculated. A rapidly tuned TEA CO2 laser at high repetition frequency is manufactured by the result of calculation. With the method of a resonant reflecting mirror scanning a fixed grating, the rapidly tuned TEA CO2 laser output is realized. The pulse energy of spectral lines such as 10P(42)～10P(48) in fundamental-transverse mode is over 100 mJ at a repetition rate of 100 Hz, and the pulse width is no more than 100 ns. The far-field divergence angles of 10P(46) spectral line are 2.41 mrad (horizontal) and 2.27mrad (vertical), namely, 1.6 times of diffraction limitation. The laser can be tuned between two different rotational lines spanning the wavelength range within 10 ms.

Based on E. Sano′s metal-semiconductor-metal photodetector (MSM-PD) model, an improved numerical model is presented. The model is built with parallel current sources and capacitance. The sum of excess electron and photon in absorption layer is studied, and the rate equations are solved. The capacitance is calculated, the nonlinear relationship between the dark current and the terminal voltage is derived, and the linear calculation of the dark current in conventional model is improved. The mathematical expression of the photoelectric current is presented. The simulation analysis by Matlab indicates the calculation is simplified with a higher precision. This model represents the change of photoelectric current under some bias and illumination conditions, and shows the transfer of photoelectron in devices. This model can also be used in measuring and simulating weak signals.

Shifting of the optical mode from symmetric distribution to asymmetric distribution by separate confinement asymmetric waveguide structure reduces optical absorption loss by carriers, and permits higher doping of the p side to reduce resistance. Based on the theoretical analysis for the optical field distribution characteristics of GaAsP/GaInP tensile-strained single quantum well (SQW) lasers with asymmetric waveguide, the thickness of waveguide layers was optimized, and a high-power semiconductor laser with Al-free active region was fabricated and studied experimentally. For a 900 μm cavity length device, the typical threshold current density is 400 A/cm2, and a low internal loss around 1.0 cm-1 is achieved. Under continuous wave (CW) operation condition, 150 μm aperture devices achieve a CW output power of 6 W, the maximum slope efficiency of the prepared devices is 1.25 W/A, and the lasing wavelength is 807.5 nm. Horizontal and vertical far-field divergence angles are 3.0° and 34.8°, respectively. The characteristic temperature of the laser in the range of 20～70 ℃ is estimated to be about 133 K. Separate confinement asymmetric waveguide structure is proven to be an impactful method for reducing optical loss and improving the characteristics of high power diode lasers.

A compact continuous wave (CW) 589 nm laser is reported by intracavity sum-frequency mixing in a composite cavity. The laser has two sub-cavities. Nd:YAG crystal and Nd:YVO4 crystal were pumped by two laser diodes respectively in the two sub-cavities. In the two cavities wavelengths of 1319 nm from Nd:YAG (corresponding to the 4F3/2-4I13/2 transition) and 1064 nm from Nd:YVO4 (corresponding to the 4F3/2-4I11/2 transition) were chosen to be mixed into 589 nm laser. Through designing of the cavity, the optimum matching of modes and gains for the two wavelengths was obtained. In the overlapping of the cavities, sum-frequency mixing was generated with a type I critical phase matching BiB3O6 (BIBO) crystal. A stable laser output of 24 mW at 589 nm with low noise was obtained at the incident pump power of 750 mW for the Nd:YAG crystal and 600 mW for the Nd:YVO4 crystal.

A laser-diode pumped all-solid-state 355 nm continuous-wave ultraviolet laser with intra-cavity tripling and efficient output was achieved by cavity design optimization. Ultraviolet laser at 355 nm is obtained by using a doubly cavity, and type-Ⅰ critical phase matching BIBO crystal for intra-cavity sum frequency mixing. With incident pump power of 20 W in Nd:YAG and 8 W in Nd:YVO4, TEM00 mode ultraviolet laser at 355 nm of 114 mW is obtained at last, corresponding to an optical-to-optical efficiency of 0.4%, and the power stability in 4 h is better than ±3.2%.

A laser diode (LD) array side-pumped high-power continuous wave 1338 nm Nd:YAG laser was reported. By analyzing the characteristic of transition and corresponding stimulated-emission cross section in Nd:YAG crystal, according to the coupling condition of energy transition and material-determined wavelength, reasonable coupling parameters of laser rod and cavity mirrors were designed. Therefore, the 1064 nm and 1319 nm lasering was suppressed and 1338 nm laser was successfully gained. Using the high power LD side-pumped module, the output of laser with planar-planar cavity were studied under transitions of the output mirror of 5.3%, 7.4% and 11%. The output of the different cavity lengths were studied. The maximal 1338 nm wavelength output power of larger than 100 W was achieved under 555 W pumping power. The optical efficiency of the laser system is more than 18% , the slope efficiency is about 35% and the M2 of the output beam is 36.

Selective oxidation has evolved into a key technology in fabrication of high-performance vertical cavity surface emitting lasers (VCSELs). The oxide layers have been pursued to form current apertures and index guiding. However, there exists considerable controversy whether the selective oxidation follows a linear or parabolic growth rate. Oxidation experiments have been done at different temperatures for the two ring groove and perforated ring mesa structures employed in VCSEL. Results show the influences of geometry of mesa structures on the oxide growth rate depend on temperature. Reasonable theoretical analysis is given.

A novel collimator for collimating the fast and slow axis of laser diodes array (LDA) simultaneously is designed optimized by ZEMAX and also fabricated by using a precise three-dimensional control actuator to erode the side of a D-type fiber. This collimator consists of a D-type fiber with a series of longitudinal cylindrical lens array which has the same refractivity as fiber and acts as the slow axis collimator for LDA. Meanwhile, the D-type fiber is also able to collimate the fast axis of LDA with its transverse D-type structure. Experimental results show that the angles of divergence of fast and slow axis are 1.82 mrad and 10.4 mrad respectively after collimation. The power loss is less than 10%.

An area-directed interpolation algorithm for underwater laser image (AIU) was proposed. Firstly, wavelet transform was performed on the low-frequency components to remove speckle noise and enhance image quality. Then an image was segmented into object area and background area. And whether an interpolated pixel belonged to the object region or not was decided by an approach combining the method of nearest neighbor and statistical mode. The points in the same area are interpolated linearly. For transition pixels between different areas, nonlinear interpolation formulas were designed. Large weights were assigned to neighboring pixels belonging to the same area with the interpolated pixel in the nonlinear formulas, while the neighbering pixels in the different area with the interpolated pixel were assigned with little weights. By choice of different weights, the contrast between object and background can be adjusted to obtain clear object and facilitate object discover and observation. Experiments demonstrate that this method is efficient and feasible.

Based on evanescent wave theory, the all fiber thermooptical variable optical attenuator (VOA) made of side-polished fiber overlaid with thermooptical polymer material was studied. The relation between the refractive index of overlaid polymer material on the polished section of side-polished fiber and optical loss in the core was derived to help select thermooptical material with suitable refractive index for VOA. Proper side-polished section was designed, and advanced wheel side-polished technique was used to fabricate side-polished fibers and achieve an optimal variable loss effect of VOA. An excellent all-fiber thermooptical variable optical attenuator with helical electrode and optimized packing was fabricated. The test result of the all fiber thermooptical VOA showed that it had insertion loss less than 0.1 dB, loss range of 0～80 dB, polarization dependent loss less than 0.02 dB, and back reflection over 70 dB. The all-fiber thermooptical VOA fabricated by this means can be controlled electrically with high reliability.

Based on the theory of light propagation and diffraction characteristics of grating, the optical energy transfer of bi-grating imaging system is studied and the expression for the intensity of combined beams is given. Combined with bi-grating imaging formula, the influence of bi-grating properties and imaging place on intensity of combined beams is analyzed. The results show that intensity of combined beams is closely related with diffraction efficiency and location of two gratings. In three bi-grating imaging systems, the intensity of combined beams is measured. The experimental results are consistent with theoretical anticipation.

The optical effect of laser on protecting wheat from ultraviolet-B (UV-B) damage was tested. A patented instrument, coherent-to-incoherent optical converter, was employed to transform semiconductor laser into incoherent red light. The wavelength, power and spot diameter of incoherent red light are the same as that of semiconductor laser. A semiconductor laser and incoherent red light with wavelength of 650 nm and power density of 3.97 mW/mm2 directly irradiated the embryo of wheat seed for 3 min respectively, and when the seedlings were 12 days old they were irradiated by 10.08 kJ/m2 UV-B radiation for 12 h in darkness. Changes in the concentration of malondialdehyde (MDA), UV-B absorbance compounds, soluble protein, chla, chlb, the activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and the growth parameters of seedlings (root length, root dry weight) were measured to test the optical effect of laser. The results showed that semiconductor laser pretreatment could enhance the SOD, POD and CAT activity, UV-B absorbance compounds, soluble protein, chla and chlb concentration, and root length, while incoherent red light pretreatment could not. When the cells of plant were irradiated by UV-B, concentration of cyclobutane pyrimidine dimers (CPDs) in wheats leaves was detected by enzyme-linked immunosorbent assay (ELISA) method, incoherent red light treatment could not eliminate active oxygen and prevent lipid peroxidation in wheat. The results also demonstrate that the plant DNA was injured by UV-B radiation and the semiconductor laser irradiance has the capability to protect plant from UV-B-induced DNA damage, while the incoherent red light could not. It is suggested that the potential mechanism is not the optical effect of laser treatment.

Three metal membranes of stainless, Al and Cu with thickness of 10～50 μm are selected and processed by femtosecond (fs) laser to fabricate arrayed micro holes. The relationships between micro hole diameter and laser microprocessing parameter have been researched in detailes. The experimental results of laser drilling of stainless, Cu and Al have been examined. It is shown that the diameters of micro hole are increased with single pulse energy and pulse number. Stainless is available for fs laser micro drilling of metal filtration membrane. The straight arrayed structure micro holes with diameters of 2.5～10 μm and spaces of 10～50 μm have been achieved in stainless of depth of 25 μm. Comparing with traditional sintered metal porous membrane, the fs laser microprocessing metal filtration membrane has some excellences in uniform hole diameter, straight and arrayed hole, adjustable size and space of holes, and it is benefited to increase the hole area rates in the membrane and improve the permeated water flux.

Through controlling the related processing parameters of continuous wave CO2 laser, LY12CZ surface was remelted by laser and after remelting the fatigue test, fatigue fracture, microstructure and micro-hardness were analyzed. The result showed that there was no obvious difference between the fatigue life of specimen with and without laser remelting. The fatigue fracture indicated that the fatigue crack resource was at the surface of remelting region, and the crack extended along the grain boundary of the columnar crystal and broke suddenly in the substrate. After remelting, the grains at the surface were obviously fined, and the micro-hardness of the surface was improved by 40% in contrast to substrate.

The laser-induced photo-acoustic (PA) spectrum of NO molecule in the wavelength region of 420.0～470.0 nm is collected with an optical parametric generator and amplifier pumped by an Nd:YAG laser as excitation source. The spectrum is composed of regular progression that comes from the excitation of X2Π(v″=0)→A2Σ(v′=0,1) and X2Π(v″=0)→E2Σ(v′=2,3,4), F2Σ(v′=1,2,3), R2Σ(v′=0,1). The variation of PA signal versus laser intensity indicates that these transitions are realized via two- or three-photon process. The signal corresponding to the two-photon process is stronger than that of three-photon process. So the optimum excitation wavelengths are 452.4 nm or 429.6 nm to detect NO with the technique of PA and with visible light as excitation source. Based on experimental data, the vibration constants of NO A2Σ, E2Σ, F2Σ and R2Σ excited electronic states are calculated from the wavelength of the spectral peaks. They are 2346 cm-1, 2342 cm-1, 2397 cm-1 and 2381 cm-1 respectively, and agree well with results by other methods.

Relative parameters of nanosecond diffraction-free Bessel laser pulse were theoretically analyzed and measured in experiments. The expressions of the optical intensity distribution behind an axicon illuminated by a plane wave, maximum diffraction-free distance, minimum central spot radius were given based on the generalized Huygens-Fresnel diffraction integral theory. Relative parameters were also theoretically simulated and calculated. In the experiment, high stability nanosecond Bessel laser pulses were generated by using a Q-switched Nd:YAG laser with a plane-antiresonant ring (ARR) resonator and an axicon system. The pulse duration, maximum diffraction-free distance, optical intensity in the cross-section and minimum central spot radius were measured. Experimental results were consistent with the theoretical analysis. The fine structure of the optical intensity in the laser beam cross-section was presented by film-scanning, and the resolution of the beam pattern is much higher than that in a laser parameter analyzer.

The photonic band gap (PBG) of eight-fold photonic quasicrystal (PQC) with dielectric cylinder structure is studied using the finite difference time domain (FDTD) method, and the effect of disorder of cylinder size and displacement of cylinder sites on the width, site and anisotropy of photonic band gap is numerically investigated. When the disorder of cylinder size and displacement of cylinder sites increase, the central frequency of the photonic band gap has a redshift, and the relative band gap width decreases. The band gaps are much more sensitive to disorder of cylinder size than displacement of cylinder sites. When the disorder of cylinder size is half the cylinder radius, the band gap disappears completely, but the band gap only changes 1% for the same size of displacement of cylinder site. The isotropy of band gap is maintained in a large range of structure disorder.

Smith-Purcell radiation (SPR) from prebunched electron bunches moving in parallel with the surface of periodic ideal metal grating is analyzed. The influence on SPR by the energy, length, and current density distribution of electron bunches and grating structure is analyzed in detail. The radiation of multi-prebunched electron bunches is also studied. With the increase of electron bunches energy and decreases of prebunched electron bunches size and grating period, the corresponding frequency of the peak of the angular distribution of radiative energy becomes higher. For the same grating period and electron bunches parameters, triangle grating produces a higher corresponding frequency than sinusoidal grating. The less electron bunches size is, the larger the radiative energy is. The radiative energy and frequency are mainly dominated by the longitudinal length of electron bunches. Terahertz radiation will be obtained with reasonable parameters for bunches and grating.

Under the same conditions, such as the powers of signal and pump, compared with single pump, the dual-pump produces higher optical parametric gain and broader gain bandwidth. As the signal gain characteristics directly interact with the parametric gain parameter, an optical parametric amplification (OPA) model is established based on highly nonlinear fiber (HNLF) with dual-pump, and the characteristics of phase matching condition, parametric gain and signal saturation gain are discussed. The time-domain finite-difference method is adopted to simulate the characteristics of saturation gain. The results indicate that parametric gain is related to fiber parameters, launched pump and signal wavelength and power, while the signal saturation gain is related to pump power.

A simulation program is finished for applying the optical parametric chirped pulse amplification (OPCPA) technique to the high energy perawatt laser system. Taking periodically polarized LiNbO3 optical parametric amplifier as an example, the influence of noncollinearly angle, crystal length, gain bandwidth and high-order nonlinear effect on the front end OPCPA under quausi-phase matching conditions is analyzed. This work provides theoretical and experimental reference for the design and application of OPCPA.

Edge-cladding is a key factor in improving saturated small signal gain coefficient of large laser glass. Two kinds of compound, CuO and CuCl, are used as the original materials of Cu2+. The effects of Cu2+ doping content and different original material on glass forming-regions, crystallization stability, physical and chemical properties and absorption coefficient of P2O5-ZnO-Na2O glasses are studied. The results reveal that both CuCl and CuO can enlarge the glass forming-regions and improve the crystallization stability. The absorption coefficient is improved greatly with the content rise of Cu2+, it reaches 59.46 cm-1 at 1053 nm with CuCl mole percent of 6%, and is almost a maximal value.

Embarked from the component and structure of phosphate laser glass, its chemical-mechanical polishing (CMP) mechanism is analyzed. Through experiment, it is demonstrated that the phosphate laser glass has strong selectivity to polishing solution pH value and has high polishing efficiency under slight acidic or neutral condition. By adding pH value adjustment additive in the polishing slurry, the acidity of polishing environment is maintained, as well as the polishing efficiency and polishing quality. An ultra smooth surface of phosphate laser glass with root-mean-square (RMS) 0.6 nm is obtained, through controlling the pH value and density of polishing solution.

In vivo chlorophyll fluorescence excitation spectra at 675 nm emission wavelength of six phytoplankton species belonging to dinophyta and bacillariophyta were studied. The fourth-derivative analysis was performed on the spectra to set up the uniform initial central wavelengths for excitation spectra of dinophyta and bacillariophyta, respectively, according to the position and number of maxima on the derivative spectra. With these determined wavelengths as centre, Gaussian decomposition and multi-peak fitting were done to the spectra to establish Gaussian database on the level of divisions. The results suggested that at the excitation wavelength from 350 to 550 nm, significant differences of Gaussian database presented between dinophyta and bacillariophyta while similar characteristics were found in the same division. The fitting curve reconstructed from Gaussian parameters was in coincident with the in vivo excitation spectra. Gaussian decomposition could reproduce overlapping pigment fluorescence peaks. This method provides not only a useful tool to differentiate dinophyta and bacillariophyta, but also a new technique for determination of in vivo photosynthetic pigments.

For detecting wavefronts from the system with long optical path or multi-component lens with one by one aligning, the phase-shifting lateral shearing interferometry of convergent beam with the convergent beam as light source for interferometry is proposed, which is based on Michelson interferometer. The mathematical expression of the laterally shifted wavefront of convergent beam is established and compared with that of general lateral shearing interferometers. The shearing and wavefronts displacement are analyzed, and the phase-shifting interferometry is adopted to obtain the sheared wavefronts. The results show that the lateral shearing phase-shifting interfermetry of convergent beam can measure the real-time wavefronts of convergent beam with repetitions of peak-valley (PV) value and root-mean-square (RMS) of 0.022λ and 0.014λ respectively. The experimental results are compared with that by Zygo interferometer, which proves the validity of the proposed technique.

An improved method for measuring angular displacement is proposed based on an existent measurement technique. The choice of proper initial angle of incidence makes a lateral shearing interference easy to realize between the two beams reflected from the front and back surfaces of a plane-parallel plate. One-dimensional position sensitive detector is used to measure the offset of the light spot focused upon the photo sensitive surface of the detector by a lens. According to the interference signal′s phase and light spot′s offset, the angular displacement is measured. In this optical configuration, the use of a reflecting mirror increases the optical path difference in the plane-parallel plate, which improves the sensitivity of angular displacement measurement. Finally, the influence of the initial angle of incidence on the ratio of shear is analyzed and the measurement accuracy based on this method is discussed. The experimental results show the improved parallel plate interferometer can achieve a measurement repeatability of 10-8 rad order of magnitude.

A novel method for measuring the non-orthogonality of the interferometer system in a step and scan lithographic tool is presented. First a linear module among the non-orthogonal factor, scaling factor and process related system error has been developed. By real lithographic process the alignment marks are transferred to the wafer, and after development the positions of marks are read out by optic alignment system in the same lithographic tool. The measurement data are used to calculate the non-orthogonal factor and scaling factor of the interferometer by the linear model according to the least square principle. Experimental results show that by this method with the same wafer in different rotation, the measurement repeatability of the non-orthogonal factor is better than 0.01 μrad, and the measurement repeatability of the y to x scaling factor is better than 0.7×10-6. With different wafer in the same condition, the measurement reproducibility of the non-orthogonal factor is better than 0.012 μrad, and the measurement reproducibility of the y to x scaling factor is better than 0.6×10-6.

A 1×2 array Dammann grating beam splitter for implementation of frequency resolved optical gating (FROG) is proposed. Beam splitting with Dammann grating can avoid the material dispersion in traditional beam splitters. The measuring result by the newly established FROG is compared with that of a traditional multi-pulse FROG. Theoretical and experimental results show that when the input pulse width is larger than 50 fs, the pulse broadening introduced by Dammann grating and general beam splitter is almost identical; but when the input pulse is shorter than 50 fs, the broadening effect of Dammann grating is obviously less than that introduced by general beam splitter, especially for laser pulses shorter than 20 fs.

Research on optical coherence tomography (OCT) applied in pearl identification and nacre measurement is represented. Due to the difference of scattering properties for various components, OCT image characteristics can exact the two-dimensional information of subsurface structure of pearls, which could only be previously accomplished by the conventional section. An OCT system mainly composed of fiber Michelson interferometer with wideband source of 1310 nm central wavelength and Fourier-domain optical delay line has been implemented. The system can complete the nondestructive and real time detection, with scanning speed of 1 frame/s, depth resolution of 15 μm and penetration depth of 3 mm. Experimental results included determining the structural identity: nacreous layer or shell nucleus, quantifying the nacre thickness (measuring errors less than 20 μm), and showing abnormal information of shell-nucleous features.

The all optical clock recovery scheme has certain tolerance for degraded input signal. A novel scheme including semiconductor optical amplifier (SOA), chirped fiber Bragg grating (CFBG), and stimulated Brillouin scattering (SBS) is proposed and demonstrated to recover the clock from the input degraded non-return-to-zero (NRZ) data stream. SOA and CFBG enhance the clock component, and the clock information is extracted from the clock component enhanced signal based on SBS. For different degraded signals, the signal-to-noise ratio (SNR) of the input stream is the key factor to the clock recovery. When the input SNR is worse, the noise of recovered clock spectrum is higher, and the amplitude of extracted optical clock is lower. The clock of NRZ signal could not be recovered as the clock-to-data ratio of the enhanced signal is less than -10 dB.

Double-grating coupler based on two fiber-Bragg-gratings (FBGs) has the advantages of compact structure and enhanced filtering efficiency. The influences of gratings′ characteristics were investigated thoroughly, and the result showed that maximum drop efficiency and minimum backreflected return wave could be achieved by choosing proper gratings′ position in the coupler region. Furthermore, by adjusting the gratings′ length and ultraviolet (UV) refractive modulation depth, a novel balanced configuration with the two Bragg gratings inscribed into the coupler waist′s center was designed and fabricated, which showed simultaneously optimized add and drop filtering responses. The experimental measurement demonstrated that the uniformity of coupler waist should be responsible for the inequality in drop bandpass, and the filtering performance of double-gratings coupler can be enhanced by improving fused taper technique.