The law of wet oxidation rate is studied with experiments in vertical-cavity surface-emitting lasers (VCSEL) in order to accurately control the oxidation aperture. Wet oxidation experiments are carried out upon the samples of VCSELs at different temperatures, and micro-probe analyses are made at different oxidation depth by scanning electron microscope (SEM). It shows that the element content in oxidation products is different at different oxidation depth especially that of the oxygen element. The reaction style and the oxidation products are analyzed and discussed, and a mathematical model on oxidation rate vs time is built up. The oxidation rate is derived, which is in an exponential growth law during the wet oxidation. At constant temperature, the oxidation rate becomes more and more steady with increase the oxidation time. The oxidation process quality can be improved by lowering the oxidation temperature and prolonging the oxidation time appropriately.

The impact of output coupling ratio in passively mode-locked fiber ring laser was studied based on basic principle of passively mode-locked fiber ring laser. Theoretical simulation shows that there is a best ratio between gain and output ratio. And the ratio should be 30% when the small single gain is 7.5 dB. Ratio(R) of 5%, 10% to 40%, and 60% to 90% was experimentally carried out when the length of gain fiber was 3 m. The experiments show that, when R=5% to 10%, spectrum width is the widest (about 25.4 nm) and tunable range of spectrum width is wider (>12 nm). The fluctuation of pulse magnitude is the smallest when R=10% and 30%. The single pulse energy is the largest one (about 3.86 nJ) when R=70%. To get the highest pulse energy while keep the pulse stable theR should be 30%. To make the pulse spectrum wider, the pulse energy higher while keep the output stable, the R should be 10%. The fiber laser with R=10% and Er3+-doped fiber(EDF )length of 3 m was experimentally carried out, with the repitition rates of 15.87 MHz, spectrum width of 25.4nm and single pulse energy of 0.52nJ, which wouldn’t be impacted by librations of desk, movement of fiber laser or temperature variation. The fluctuation of pulse magnitude is 4%.

According to the packaging structure of uncooled 980 nm semiconductor laser module, the chip epitaxial layer, heat sink and solder layer in the epitaxy (epi)-down bonded lasers module were designed, and the heat distribution of mini-dual in line (DIL) uncooled 980 nm semiconductor laser under the continuous-wave (CW) drive conditions was simulated using the finite element method (FEM). The thermal properties of epi-down and epi-up bonded lasers were compared, and the photoelectric properties of actual laser module were tested. Epi-down bonded uncooled 980 nm semiconductor laser can work steadily over a wide temperature range of 0～70 ℃, with a small wavelength shift of 0.2 nm, full-width at half-maximum (FWHM) less than 1.6 nm, side-mode suppression ratio (SMSR) of more than 45 dB, and a high optical power of 200 mW. The results show that the optical and thermal characteristics of epi-down bonded uncooled 980 nm semiconductor laser have been greatly improved, and it can meet the need of high-performance miniature erbium-doped fiber amplifier.

A method which stabilizes the frequency of the slave laser in long time by confocal F-P cavity and stabilized He-Ne laser is reported. A frequency-stabilized He-Ne laser is employed as a reference, He-Ne laser and slave laser are injected to confocal F-P cavity which is scanned by a signal generator and a high-voltage amplifier at the same time. The transmission peak signals which are detected by photodetectors are delivered to data acquisition card. A program using LabVIEW software can determine all peak positions and calculate the relative position of transmission peak signals of He-Ne laser and the slave laser. Feedback voltage is generated to make the relative position of He-Ne laser and the slave laser equal to setting values, then the stability of He-Ne laser is translated to the slave laser. Using this method, a laser diode (DL 100) is stabilized at wavenumber of 11716.1706 cm-1and the frequency drift is less than ±2 MHz in one hour.

Based on the Gaussian pulse component analysis, a new deviation of laser pulse system in time-domain is defined, and its validity is further verified experimentally. The actual energy distribution of input and output optical pulses on microsecond level is gotten through high-speed photoelectric detector, and the envelops of energy distribution is fitted by Gaussian pulse components with a tolerance range of 3%. Comparing ideal values with actual values of the independent Gaussian components after getting though the system, the deviations can be calculated. According to the definition, by analyzing the changes of existed components and the causes of new components, both the physical mechanisms of optics-system interaction and the optimization of system can be studied.

Three methods for analyzing and processing the laser scattering signal of bubbles in water, the threshold detection, noise elimination processing and power spectral estimation, are put forward. Using the above three methods, the measured signals for different scattering angles are processed respectively and the angular distribution of light intensity scattered by bubbles in water is obtained. Compared with Mie result and water scattering intensity, advantages of three methods are analyzed. The average value and the absolute deviation respectively are centered in the threshold detection and noise elimination method to estimate the bubble scattering intensity, and the DC component could not be isolated by them. The angular scattering property of bubbles obtained using the power spectral estimation agrees with the result based on Mie theory. Bubble and water scattering could be distinguished based on this method, and the difference of them would be nearly one order of magnitude. Experimental results show that the power spectral estimation is the most reasonable method for processing the laser scattering signal of bubbles.

Since the first soft-X-ray was achieved, to realize the low excited threshold and table-top soft-X-ray laser is a significant research. Capillary discharge soft-X-ray laser is one of the crucial quomodo to realize table-top soft-X-ray laser. The capillary discharge 46.9nm soft-X-ray laser has been detected by X-ray diffraction diode(XRD). The experimental results indicate that the influence of the material of the electrode on capillary discharge soft-X-ray laser is not the critical factor. Considering the sputtering of the element, choosing the electrode made of molybdenum is advantageous. The shape of the electrode mainly influences on the conduction of the pre-current pulse but not on laser, and it is easier for the pre-current pulse to conduct in longer capillary by choosing the pyramidal electrode.

In order to transform 2D tri-state light signals to electronic signals, a new method applied to implement ternary optical decoder is presented, and the decoder consists of a semi-transparent mirror, orthogonal polarizers, micro-lens arrays, photodiode detector arrays, 2D SRAM arrays and an embedded system. A simulation device of the decoder was designed and fabricated based on a commercial CMOS image sensor and a 32-bit embedded CPU. Experimental results, decoding to the output of ternary logic optical operation unit, show that the accuracy is 100%; the data width is 128 bits and can easily be extended to kilobits and myriabits. Compared with other similar researches, it has the advantages of high data width, programmability, controllability and well scalability.

Photonic crystal fiber (PCF) has many special characteristics, which strongly depend on its structure. The location error or deformation of the cladding holes can be introduced readily during the complex fabrication process, which will change the characteristics of the PCF intensely. A commercial single-mode polarization-maintaining PCF was investigated when the size and location of one of the two larger side holes were changed. In order to give relationship between the location error or deformation of the cladding holes and the dispersion characteristics, the simulations of the PCF dispersion characteristic were given for the case that the location of one side larger hole was changed while the size and form kept invariable. Secondly the case, that the size of one side larger hole was changed without shifting, was simulated. The simulation results for the case of changing both location and size of this hole were demonstrated at last. All the simulation results show that the structure deformation affects the properties of the polarization-maintaining PCF strongly because the effective index of refraction, zero group velocity dispersion wavelength, polarization beating length, mode structure etc. are changed.

A novel scheme to generate optical millimeter-wave (mm-wave) signals by using single-sideband (SSB) modulation technique was proposed and experimentally demonstrated. Odd order sidebands were suppressed by proper adjusting the direct current (DC) bias of signal-arm intensity external modulator in central station. One of the second order sidebands was filtered out and SSB modulation was realized. The mm-wave generated by SSB modulation can be transmitted over 148 km in theory. In experiment, a 2.5 Gbit/s data and an 10 GHz RF clock were mixed. The mixed signals were applied to drive a single-arm intensity modulator to generate 40 GHz double sideband signals. Then a filter is used to get a 20 GHz SSB signal. The effect of optical carrier-to-sideband ratio (CSR) on downstream transmission in radio-over-fiber (ROF) system was analyzed and the performance of the ROF system can be significantly improved when CSR is 0 dB.

At present, the spectrum evolution of the beat signal can be used to measure the fiber nonlinear coefficient. By theoretical simulations, the effect of the stability of the output power, the frequency and the linewidth of the laser on the measurement of the nonlinear coefficient were analyzed. The simulations agree well with the experiments. The propagation properties of a kind of photonic crystal fiber (PCF) are analyzed with the compact supercell method. Taking self-phase modulation (SPM), fiber loss and dispersion into account, the transmission process and the evolution spectra of the beat signal propagating along the PCF are analyzed by using the split-step Fourier method. The results show that the stability of the laser output power has little effect on the measurement of the nonlinear coefficient, but the linewidth and the stability of the central wavelength have more effects on it. Proper parameters should be established to get a more accurate measurement result, in order of the nonlinear coefficient.

Distributed optical fiber sensing based on Brillouin scattering is one of the subjects of intensive investigation all over the world at present. For the distributed fiber sensing based on Brillouin optical time-domain reflectometry, the heterodyne detection achieves the highest sensing resolution, and the key problem is how to obtain the referenced light with Brillouin frequency shift. The principle of frequency shift based on LiNbO3 waveguide electro-optic intensity modulator (EOIM) is analyzed in detail. The 11 GHz frequency shift at 1550 nm is obtained experimentally with a 15 Gbit/s LiNbO3 waveguide. It is convenient to change the optical intensity of the sidebands by tuning the DC bias voltage while the microwave modulation frequency and power are fixed. Particularly, when the DC bias voltage is set to 6.5 V, the modulator achieves minimum total output optical intensity, and the first sideband with Brillouin frequency shift reachs the maximums relative intensity and signal-to-noise ratio (SNR). These results can be used for Brillouin heterodyne detection in the distributed optical fiber sensing.

The basic principles of multi-parameter tunable optical fiber grating wavelength tuner based on stress, displacement, space angle are analyzed and relative experimental researches are performed. According to the tunable formulas derived in detail, a series of numerical simulations about tuning relationships are presented. On the basis of numerical simulations, we design a multi-parameter tunable optical fiber grating wavelength tuner based on stress, displacement, space angle. Then we carry out relative experimental research. Experimental results indicate that the relation of center wavelength tuning with the force and displacement is linear. The linearity of three fiber Bragg grating (FBG) are above 0.9975. With space angle as a function of the wavelength of FBG, the fitting curves are approximately sine (cosine) relations. And the experimental results match the theoretical analysis perfectly.

By fused biconical tapering at the fusion point of single mode single-core fiber and single mode twin-core fiber, a power tapered fiber coupling technique is implemented. The difficulties in direct-coupling with light source and single made fiber and signal detection in the two cores due to its special structure are solved. The analysis about the coupling theory of single mode single-core fiber and single mode twin-core fiber is given. With the combination of direct-coupling and weakly coupled-mode theory, the coupling equations of single mode single-core fiber and single mode twin-core fiber are proposed. The factors which influence the coupling power are also discussed. This theory analysis can explain the coupling character effectively.

Using the fluorescence inspected system and optic fiber, the solid powder fluorescence of oil cuttings is inspected directly. Experimental results are similar with the results measured in solution, such as the emissive and excitation wavelength. The corresponding fluorescence spectroscopy parameters are obtained by inspecting the solid powder of oil cuttings directly, and analyzing the samples of multi-component by Gaussian fitting method. And the characteristics of the solid powder of oil cuttings are analyzed. It provids a new way to analyze the characteristics of the oil cuttings quickly and directly. At the same time, the impaction of the difficulty of energy transfering in the solid power on the excitation of fluorescent is also discussed.

In one-dimensional quadratic crystals with modulation of both the linear and nonlinear susceptibilities, the transmission properties of the beam, whose wave form is the square of hyperbolic secant, are investigated by split-step integral approach. Numerical calculations indicate that fundamental soliton is rapidly excited when only fundamental wave (FW) is launched, and it presents inherent oscillation. The second harmonic wave (SHW) excites soliton, but the corresponding dispersive wave is obvious. However, while both FW and SHW are launched, and their amplitudes and beam widths are appropriate, both excited solitons are stable. The periodicity of fundamental soliton oscillation is move evident, and the dispersive wave of SHW is extremely weak. Moreover, there is a critical value of the launched SHW amplitude for the excited soliton to reach the optimum state.

The experimental investigation of the fiber Bragg grating (FBG) sensor in monitoring action for the laser thrombolysis is introduced. In laser thrombolysis, the pulsed laser is absorbed by blood, leading to cavitating bubbles. The shock wave is generated during bubble expansion and collapse. With a tunable distributed feed back (DFB) LD laser as the light source and an edge filtering demodulation, the shock wave was measured by FBG based sensing system. In experiment, the peak power of the shock wave response increases with the laser power, and the FBG responsibility for the shock wave in the blood after ablation of clot is similar to that in blood without clot. According to this similarity, whether the clot is ablated or not can be distinguished. In the in vitro experiment, the measured ablation time is 23 s.

The image quality was degraded because of imaging in cloud and fog. The essence was atmosperic scattering for light between scene with observation point. The restoration method was projected for the images imaged under bad weather. First, the mechanism of atmosperic scattering was analyzed. Second, the attenuation model, airlight model and phase distribution function in directions of atmospheric scattering were introduced. Third, the formula of atmosperic light intensity was derived. Based on the models of attenuation and airlight and the pathlength was considered, the advanced multi-scale Retinex algorithm (AMSR) was applied for removing cloud in color remote sensing images. The AMSR method included three steps. The first one was to obtain the complementary image. The second one was that the complementary image was enhanced. The third one was to the complementary image from the enhanced image. Because of the sence information was lost following with removing cloud, the criterion of information entropy was applied to judge the quality of enhanced images. The results show that the AMSR was suitable for removing cloud in color remote sensing images. The best image was stretched in the range of k=1.5±0.1 times standard deviation near the mean brightness and the information entropy was largest.

A novel photopolymer sensitized by four photosensitizers is prepared in order to broaden the photosensitive spectrum and increase the recording density and capacity. The holographic recording properties such as diffraction efficiency, exposure sensitivity and the refractive index of the photopolymer are studied. The results show that the maximum diffraction efficiencies reach 61%, 47% and 44%, at three different exposure wavelengths of 632.8 nm,514.5 nm, and 488 nm. The sensitivities reach 1.92×10-3, 9.28×10-4 , and 5.63×10-4. The refractive indexes reach 4.7×10-4, 3.34×10-4 , and 2.93×10-4. Comparing the characteristics of the samples such as diffractive efficiency, exposure sensitivity, refractive index modulation ect., it is found that for performance of the system all the parameters decrease. But the effect on the reconstruction is little. At the same time, the properties of different thickness samples with the same exposure intensity are preliminarily studied. The results show that the broadening photopolymer is propitious to wavelengths multiplexing and sparse-wavelength angle-multiplexing, and all the results provide a reliable test basis.

Multiple-array configuration can achieve higher resolution by copying sub-aperture configuration to expand the size of the whole array. A modified signal noise ratio (SNR) is proposed to evaluate the imaging performance of optical sparse aperture systems. Based on the traditional array configuration, including the annulus, Golay-6 and the Tri-arm, two different ways for designing the multiple-array configuration are investigated. The imaging performances of six multiple-array configurations are analyzed according to their modulation transfer functions the evaluation criteria of the correlation coefficient and the modified SNR. The optical imaging experiments with the image of remotesensing as propagating object have been fulfilled. The results show that the main-array configuration plays the key role on the quality of the imaging, and the sub-array configuration can only improve the imaging performance to a certain degree. This means that the different design of the multiple-array configurations may lead to the different quality of the imaging. In order to optimize the array, the characteristics of the main-array should be considered to choose the way arranging its sub-array configuration.

A new method for particle-size measurement of digital holography by Hough transform is proposed. The numerically reconstructed images of a particle-field hologram are approached in a way that in-focus images of particle in the volume are integrated into a plane and the edge of particle image is extracted, then by using Hough transform, the particle information of the size and the location is obtained. Computer simulations of the 2D and 3D particle fields are performed. The experiment is conducted for the field of diameter 90 μm standard particle, and the measuring absolute error is 6 μm. The research results show that the method is feasible.

The scanning area limitation (SAL) and maximum flying velocity (MFV) in laser flying marking system are analyzed. Under the same SAL, the influence of grapics entering into the different direction of scanning area on the maximum marking offset (MMO) is studied. Under the condition of the uniform motion, the relationship between MFV and maximum markable time (MMT) as well as MMO is deduced. For the graphics entering scanning area horizontally and vertically, the experiment of laser flying marking using first entering first marking(FEFM) scanning algorithm is carried out. At different markable time, the experimental MFV value agress well with theoretical ones.

A TiC-ZrC particulate reinforced Ni-based composite coating has been synthesized in-situ by laser cladding with pre-pasting on steel 45# . The microstructural and metallographic analyses were performed by scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS) and X-ray diffractometer(XRD). The microhardness and wear resistance of the coatings were tested. The results indicate that the composite coating is bonded metallurgically to the substrate. The microstructure at the bottom of coating consists mainly of oriented dendrites of γ(NiFe). The microstructure locating at the middle and upper zones contains both TiC-ZrC particle and acicular Cr3C2 phase dispersed in the matrix of γ(NiFe) solid solution. The TiC-ZrC particulate reinforced composite coating has a high average hardness of HV0.31300 and better wear resistance. The wear mass loss of the composite is just one fourth that of the pure Ni60 coating. The improvement in wear resistance is due to the presence of numerous of in-situ synthesized TiC-ZrC particles and their well distribution in the composite coatings.

The characteristics of the pressure distribution and Mach disk position are analyzed for simple nozzle and complicated nozzle based on Hall design method, and the difference of dynamic characteristic of gas flow is compared particularly. The trend is revealed that the difference of dynamic characteristic between the two nozzles becomes smaller with the increase of working pressure. It is demonstrated that using the simple structure nozzle to replace the complicated flow line structure nozzle is feasible for decreasing the cost of laser cutting under the high pressure condition.

Thick-film positive temperature coefficient (PTC) thermistor on Al2O3 ceramic substrate was prepared by laser sintering of thick-film electronic paste. The effects of laser processing parameters and the temperature of post heat processing on thick-film PTC thermistor width, surface microstructure and performance were studied. The minimum linewidth of thick-film PTC thermistor by laser sintering is 40 μm. The temperature coefficients of resistivity (TCR) of PTC thermistor is around 2965×10-6/℃, and the performance is equivalent to traditional oven-fired electrical paste. The laser power density and the temperature of post heat processing have great effect on the sheet resistivity and TCR of PTC thermistor, and there exist optimum values for these parameters.

It is very important for temperature field testing in laser processing. Temperature field is an important parameter which affects the quality of laser processing. In order to control profile of laser molten pool and improve process design, precision and quality in laser processing, it is very necessary to study the temperature distribution. The image processing based on digital signal processor (DSP) was presented. It was used to measure the temperature field of laser molten pool. A new method of image processing was developed with DSP as personal computer, without PC. It makes the system become simple and efficient. It shows that some important informations included 2D morphology and size, numerical value distribution and dynamic characteristics of temperature field in laser molten pool can be obtained. In the future, it will be much more available on online measurement and feedback control in laser processing.

The impact of the moisture on character of laser induced pulverized coal plasma was conducted to determine the influence of moisture on quantitative measurement of coal by laser-induced breakdown spectroscopy. Two samples (Shenhua coal and Pingshuo coal) with close carbon and silicon contents but different water contents were chosen and prepared as received basis and dry basis individually. Calcium atomic spectra lines were used to calculate the plasma temperature at delay time of 83 ns, 500 ns, 917 ns and 1292 ns. C247.856 nm and Si390.5523 nm were chosen to estimate electron density. The results show that the plasma temperature declines as the delay time is prolonged， lower plasma temperature and poorer spectra lines intensity are presented in the samples with moisture，but electron density does not change significantly with different samples.

Based on the optical rotatory dispersion effect, an quartz optical filter is constructed with quartz crystal and polarizer for picking up the 590 nm spectral line in the intracavity frequency-doubled Nd∶YAG/BaWO4 Raman laser. The operating principle is analyzed by means of Müller matrix and Stokes parameters. The filtering performance is tested by AQ-6315A spectrometer with the intracavity Raman yellow laser as the light source. The experimental results show that the 1180 nm spectra line is extracted after filtering. The filter is compact, does not change the direction of optical beam, and can be applied to frequency-doubled laser.

A new soft optoelectronic function material, which can transmit optical and electrical signal simultaneously, was made by injecting ionic liquids (ILs) into a quartz capillary tube with the inner diameter of 0.32 mm. 10 types ILs were used to make transmission media and their characteristics were studied experimentally. It is found that optical and electrical signal can transmit respectively when the frequency of electric signal is higher than 10 Hz. The numerical aperture of the medium can achieves 0.554, which is bigger than that of the traditional optical fiber transmission medium. The attenuation is relative to both the types of ILs and wavelengths. The impedances are sensitive to temperature, and at the same temperature the impedance disparity of different transmission media can reach more than 10 times. The maximal AC voltage that the medium can transmit increases with the increase of frequency.

Six new organic conjugated azo compounds were synthesized and their structures were confirmed by Fourier transform infrared spectroscopy(FT-IR), 1H nuclear magnetic resonance apparatus ′H NMR and elemental analysis. By using femtosecond laser, the off-resonant third-order optical nonlinearities of the compounds were measured with degenerate four-wave mixing (DFWM) technique. The third-order nonlinear optical (NLO) susceptibilities χ(3) were (3.31～3.96)×10-13 esu. The nonlinear refractive indexes n2 were (6.08～7.27)×10-12 esu. The second-order hyperpolarizabilities γ of the molecules were (3.44～4.11)×10-31 esu. The response times τ were 102～111 fs. The influence of the molecular structure on the third-order optical nonlinearity was studied. The third-order optical nonlinearity is improved by many factors such as aromatic heterocycle with small delocalization energy, long conjugate chain, formation of acceptor-donor srtucture, strong electron-donating abilities of substituents, and good coplanarity.

Broadband terahertz (THz) technology has widespread applications in the fields of national defense, scientific research and so on, and photoconductive antenna is an essential approach to generate THz wave. The impact of growing and annealing temperatures on material carrier lifetime and resistivity was analyzed. Four small-aperture photoconductive antennas of BowTie and Dipole structures were fabricated on low-temperature-grown GaAs (LTG-GaAs) grown at 230 ℃ and 250 ℃ respectively, and annealed at 475 ℃. As a result, the 250 ℃ grown antennas have higher THz wave output power and broader spectrum up to 3.6 THz, in contrast to the 230 ℃ grown one. In addition, the output power generated by BowTie antenna is stronger than Dipole antenna. Moreover, it is verified that both of the small-aperture photoconductive antennas can generate THz wave under 10 V bias voltage.

By employing film-forming polymer with low molecular weights, supplementary monomers and different photosensitive reagents, a green sensitive polyvinyl alcohol/acrylamide based photopolymer with high diffraction efficiency and photosensitivity is reported, the absorption spectra, the effects of dye concentration and film thickness on diffraction efficiency and photosensitivity are studied systematically. Diffraction efficiency higher than 82% is obtained at the exposure level of 20 mJ/cm2, maximum diffraction efficiency can reach to 92%. Furthermore, the angular selectivity of the photopolymer is also tested and its corresponding Bragg selective angle width is 0.57°. The preliminary applications of angular and spatial multiplexing holographic storage are also demonstrated, bright and distinct holographic storage samples are obtained readily.

The nanocrystalline silicon films are prepared by pulsed laser ablation at the ambient Ar pressure of 10 Pa and the target-to-substrate distance from 1 cm to 6 cm. Both the X-ray diffraction (XRD) and Raman spectra indicate the films are nanocrystalline, which means that they are composed of Si nanoparticles. The surface morphology of the nanocrystalline silicon films is observed by using scanning electron microscopy (SEM). The result shows that with increasing target-substrate distance, the average size of Si nanoparticles first decreases and reaches its minimum at 3 cm, and then increases. The transport dynamic process of the ablated particles in different target-to-substrate distances is numerically simulated by Monte Carlo method. The numerical simulations accord with the experimental results.

In order to get a high dynamic range in pulse signal-to-noise ratio (SNR) measurement and ensure a high measurement accuracy, a research is taken on the calibration of pulse SNR measurement. As we know, a beam will generate multiple reflections with a fixed interval between every two neighboring reflections when it reaches a glass mirror. The light intensity will suffer the degression caused by these reflections. A calibration method for the pulse SNR is provided, and a formula for calculating the multiple reflections from glass mirror is established. Experimental results show that between two neighboring reflections from the back surface, the optical path delays are always close to 24 mm, and the attenuations of relative intensities are always about 10-2. From the analysis on pulse sequence, the dynamic range of the pulse SNR measurement is obtained to be about 2.6×10-8. Furthermore, the effects of material absorption and group velocity dispersion to pulse SNR measurement are also discussed, and it is found that these two factors are neglectable.

Displacement measurement based on laser speckle is an important method widely used in practice, which is commonly realized by digital image correlation (DIC). However, the traditional method in pixel search algorithm is not very efficient for its correlation calculation. A new method of multi-characteristic windows is presented. Three distinct speckle sub windows with different sizes and different areas are selected as the calculation windows, which can not only guarantee the computational veracity properly, but also reduce the computation effectly. Experiments show that it is feasible and efficient, for it satisfies the computational veracity and improves the computational speed.

In practical measurement, the positioning precision of position sensitive detector (PSD) is greatly affected by the size and asymmetry of the spot. A three-ray positioning model of PSD caused by laser spot is established systematically based on the Gauss energy distribution character of laser beam. The positioning error is derived under the character of the spot by its shape. The validity of the PSD positioning model is proved by experiments. The positioning errors caused by the asymmetry of the spot, the change of the spot size in transmission, and the speckle caused by the interaction between the laser and object can be compensated by using this positioning model in laser triangulation measurement. And the precision of positioning can be improved effectively. Experiments show that the compensated error can reach 0.07 mm.

The response characteristic of near infrared detector PDA400 was measured, then the theoretical analysis and experimental study,which focused on the relation between detector's response characteristic and metrical result of continuous-wave cavity ring down technique, were both carried on. With the linear response function, the output signal of PDA400 was deducted when ring down signal was used as input.In this case,analusis shows that the signal shape of PDA400 has turned from single to double exponential function. After the response times of PDA400 in different gains were measured, the fitting method of ring down signal in two typical detector's gain(20 dB and 40 dB) was studied, and two kinds of methods were proposed and tested with experiments. Furthermore, when considering detector's nonlinear response, the method of data processing is discussed too.

The technology of photoacoustic spectrum has features of high sensitivity, continuous and fast in situ measurement in detecting acetylene in low concentration. A new wavelength modulated photoacoustic spectrometer based on a near-infrared tunable erbium doped fiber laser (TEDFL) and a high power erbium doped fiber amplifier (EDFA) is developed. This system is demonstrated with low concentration acetylene measurement at the 1530.37 nm transition line, by incorporation of a first-longitudinal resonant photoacoustic cell with double absorption optical path and lock-in harmonic detection technique, yielding a detection limit of 1.3×10-9 at room temperature and atmospheric pressure and this can meet the demands of acetylene detection and analysis in industry, environment monitoring and power system.

This letter introduced the Mueller matrix method (MMM) with polar decomposition to precisely analyze the PR activities of semiconductor optical amplifiers (SOAs), where the SOA is described by a Mueller matrix M which is decomposed to a diattenuator MD, a retarder MR, and a depolarizer MΔ. The polarization rotation (PR) is determined by the retarder matrix MR, and the rotation angle θ can be calculated by θ=arccos[Tr(MR)/2-1]. It employed a computer-controlled measurement system to obtain Mueller matrix M of the SOA. Experimental results showed the amplified spontaneous emission noise in SOAs will decrease the degree of polarization of optical signal. And the PR angle was linear to input optical wavelength, while it was nonlinear to injected current and optical power. Moreover we apply a pump-probe scheme to investigate the photoinduced PR and cross-gain modulation effects in the SOA, and we found both PR angle and output power were nonlinear to the controlling optical power while obtain the orthogonal PR by controlling of a ～3.5 mW laser. Based on above results we realized a high-speed polarization switching with response time less than 300 ps, which is applicable to high-speed data communication at Gb/s.

Radio-over-fiber system has a broad prospect in broadband wireless communication networks. Due to the coexistence of multiple standards of broadband wireless communication networks, the frequency of local oscillation signal used in base station is different from each other. A novel scheme is presented to generate and deliver multi-channel local oscillation signals simultaneously and remotely by making use of an optical phase modulator and an optical periodic band-pass filter in central station. The single local oscillation system in central station can be shared by a number of base stations which belong to several standards. The frequency and the line width of local oscillation signal is analyzed theoretically. The simulation to generate and deliver multi-channel local oscillation signals such as 19.2 GHz, 25.6 GHz and 38.4 GHz simultaneously with an single electrical drive signal operating at frequency of 6.4 GHz is performed. The theoretical analysis and simulation results both show that local oscillation signals have very high purity, and the purity is not affected by the line width of the source. Then a bi-directional scheme is proposed. In such scheme, the compatibility of multiple standards can be solved very well. The chromatic dispersion and the cost can be reduced extremely. In addition, the capacity of system could be enlarged.

With the key technologies breakthrough of phase encoding, it is necessary to analyze the bit error rate (BER) performance of coherent optical code division multi-access (OCDMA). The impacts of beat noise, multi-access interference (MAI), shot noise and thermal noise in coherent OCDMA are studied in this paper. A Gaussian approximation method, based on the moment generation function (MGF) of the noises, is introduced to evaluate the bit error rate by taking the polarization into account. Numerical result between beat noise and MAI is compared. When all the interference signals are parallel or upright with the targeted user, we derive the upper and lower bound of BER respectively, the BER of random polarization between them. It is shown that, the beat noise is the dominant factor which influence BER performance of the coherent OCDMA system. The impact of polarization is increasing with the receiving power increasing; when the BER is below 10-10, it increases quickly with the increasing of user number; when the BER is larger than 10-10, it changes slowly with the increasing user number.

The characteristics of slow light in the 2D triangular rods photonic crystal line defected waveguide have been investigated with plane wave expansion (PWE) method. It is found that the filling factor of the photonic crystal and the radius of defect rods decide the propagating characteristic of the guided mode in the photonic crystal band gap. The group velocity of the guided mode decreases rapidly as increasing the filling factor. The effect of radius of the defect rods on the group velocity is stronger than the former. The waveguide structure with group velocity smaller than 0.01c is demonstrated through detuning the filling factor and defect rods size. Group velocity dispersion (GVD) of the slow light is analyzed, and it is found that the magnitude of GVD value in the area of ultra slow light is about 105～106 and propagation with high efficiency can be guaranteed.

Optical packet replication with accurate cycle and consistent pulse power is realized by using the semiconductor optical amplifier (SOA) optical fiber ring cavity. In order to suppress the amplitied spontaneous emission (ASE) noise and avoid the ring cavity resonance, the method of introducing non-circulation assistant light is proposed. Using the simplified model, the theoretical analysis and the simulation for the output noise and the signal-to-noise ratio (SNR) are carried out. The relation between output SNR and the duplication times is obtained. The impact of assistant light and attenuation coefficient upon SNR is analyzed in detail. The experiment results are consistent with theoretical results. In order to make the output pulse power of optical packet replication consistent, a SOA is used for the power equilibrium of the output packet. 15 times duplication with the SNR declining less than 3 dB and the pulse power keeping nearly consistent is implemented.

Multiple Optical Label that generated by combining multiple optical orthogonal codes (MOOC) in serial can increase the quantity of available labels. An optical packet switching (OPS) system adopting MOOC label is demonstrated, and the corresponding techniques including packets generator, label processing, switching control mechanism and switching matrix are discussed. The experiment results of this system realize the packet switching function under the condition of three edge nodes and one core node, and verify the feasibility of the proposed MOOC label scheme.

A 4-cm-long chirped fiber grating (CFG) with 35 nm bandwidth of reflected spectrum is studied with the exertion of local pressure on the fiber through the application of transverse force to a small grating section. One or several narrow transmission windows can be shaped in the reflected spectrum of the chirped fiber grating. Location and depth of the transmission window is changed with the induced pressure. A physical model is developed in order to estimate the phase shifts induced by pressure. Numerical simulation based on the piecewise-uniform approach is also used to calculate the consequent changes in reflected spectrum. Experimental and theoretical datas are in good agreement.

In the polarization division multiplexing system, the communication capacity can be doubled, depending on the transimission of two othogonal polarized beams as different channels in one optical fiber. These channels need to be seperated in the receiver end. Besides the polarization mode dispersion (PMD), polarization dependent loss (PDL) also affects the stability of system. On basis of the principles of PDL, the numerical relationship between the included angles of two orthogonal signal channels and PDL is derived for polarization division multiplexing system, and the effects of PDL to the system are also analyzed. According to the theorical model, the corresponding experimental structure is built to verify the theory through one axis attenuation in the optical fiber and the test curve description. The experiment shows that the crosstalk can be controlled below -10 dB when differential group delay (DGD) is less than 10 ps. Up to 140 ps, system cannot work any more with the same signal power of two channels. The research is useful to the stability of system.

Laser beam quality evaluating is a classical issue in laser optics field. Several beam quality factors have been proposed and utilized. Nevertheless, there have been no standard methods for characterizing and diagnosing laser beam quality. In addition, with the development of coherent beam combining technique, there is no uniform beam quality factor to evaluate the coherently combined beam. In the present paper, several beam quality factors that already exist are summarized and discussed briefly, then beam propagation factor (BPF) as a universal standard for evaluating high energy beam quality is introduced and studied in detail. The physical principle and the measuring technique in practical engineering are briefly introduced, and the universal characters for evaluating single laser beam and coherent combined beam are analyzed. Numerical calculation results show that BPF is fit for evaluating high energy beam quality due to its advantages in perspicuous principle, handy-for-measuring and all-purpose in application fields.

The new phenomena induced by femtosecond lasers lead to the new area of ultrafast science. It is a significant challenge to explain the phenomena associated with complex non-equilibrium and non-linear processes. Although there is a growing body of experimental observation, a comprehensive model remains undeveloped. We review the challenges in understanding the photon absorption stage mainly for the femtosecond ablation of wide bandgap materials at the intensities of 1013～1014 W/cm2. Major opinions and challenges in ionization mechanisms are presented by primarily considering multiphoton ionization and avalanche ionization.