Deeper researches on the impacts of a cliff layer on uni-traveling-carrier photodetector (UTC-PD) are presented, especially the influence on 3 dB bandwidth. The results show that a cliff layer enhances the intensity of the electric field which extends to the absorption region in the heterojunction, makes the electron transit time and electron accumulation level reduce in the absorber, and eventually leads to the increase in 3 dB bandwidth and saturation current. The results also reveal that, both the doping concentration and thickness of cliff layer have a significant impact on 3 dB bandwidth. For a thicker cliff layer, as the product of the thickness and doping concentration is unchanged and the collection region remains depleted, the 3 dB bandwidth drops with the increase of cliff layer thickness. However, for a thinner cliff layer, typically ten to several tens of nanometers, whether the cliff layer thickness or the doping concentration is alternated, the decreases of 3 dB bandwidth can be ignored, that is, the 3 dB bandwidth is almost invariant.

532 nm and 1064 nm laser outputs of Nd:YVO4-KTP solid laser, as pump beam and seed light, respectively, are injected into a degenerate optical parametric amplifier with a periodically poled KTP crystal. The bright high order transverse mode TEM01 quadrature amplitude squeezed field, which is generated by the nonlinear optical parametric process, is measured to be 2.2 dB squeezing degree with a homodyne detection system. A group of transformed signal data is saved by a digital storage oscilloscope. The Wigner quasiprobability distribution function of the squeezed field in the phase space is reconstructed using quantum tomography technique with the self-made software, and it′s found that there is a good agreement between theoretical and experimental results.

Recently, laser therapy has been widely used for treating portwine stain (PWS) and other vascular lesions. However, the mechanism of the vascular injury during the treatment process is still not clear. In this paper, a hamster dorsal window chamber model is constructed to investigate the dynamic change of the vessel during pulsed laser treatment. A CCD camera and microscope are used to capture the dynamic variation of microvessels after 1064 nm laser pulse exposures. Experimental results show that the vessel continues expansion with the increasing of the radiant exposure, and vasoconstriction appears when the energy accumulates to a certain value with a single laser pulse. After multiple laser pulse irradiation, vessel expansion, blood coagulation and vasoconstriction are observed. These results may provide useful feedback for the treatment of PWS by near-infrared long wave laser.

We study the impact of laser acupuncture with different methods and parameters on type-II collagen-induced arthritis (CIA) model rat serum interleukin-1β (IL-1β), interleukin-15 (IL-15), interleukin-17 (IL-17), tumor necrosis factor α (TNF-α), vascular endothelial growth factor (VEGF) and cortisol (COR). The rats are randomly divided into model group, medication group, acupuncture group, deep laser acupuncture 1 mW group, 5 mW group, 10 mW group, the surface laser acupuncture 50 mW group, 100 mW group, 150 mW group, and normal control group is set, selecting Zusanli and Shenshu as acupuncture points. Samples are selected after 10 days of treatment. We use double-antibody enzyme-linked immunosorbent sandwich assay (ELISA) to measure serum cytokine level. Serum IL-1β, IL-15, IL-17, TNF-α and VEGF in the model group are significantly higher than those in the normal group (all P0.05); serum IL-17 level is the highest in the deep laser acupuncture 1 mW group and the lowest in the surface laser acupuncture 100 mW group, and the difference is statistical (P<0.001); serum TNF-α level is the highest in deep laser acupuncture 1 mW group and the lowest in drug group, and the difference is statistical (P<0.001); serum VEGF level is the highest in deep laser acupuncture 50 mW group and the lowest in the deep laser acupuncture 5 mW group, and the difference is statistical (P<0.05); serum COR level is the lowest in the acupuncture group, and the highest in surface laser acupuncture 150 mW group, the difference is statistical (P<0.001). Laser acupuncture can effectively reduce CIA rat serum proinflammatory cytokines levels such as IL-1β, IL-15, IL-17, TNF-α and VEGF, increase serum anti-inflammatory cytokines levels such as COR, and its effect is related with action mode of laser acupuncture and parameter settings.

In order to keep the detail information of edges while suppressing noise in laser active imaging, hybrid filter based on pixel classification is proposed. Based on contour curvature, the pixels are divided into different classes. Lee filter is used to suppress speckle noise and fuzzy weighted averaging filter is used to suppress other mixed noise. A contour point screening method is proposed to select candidate contour points from noisy image. Then the contours are thinned into single pixel. After eliminating the bogus contours brought by the noise and those that are comparatively week, the contour curvatures are calculated. According to the contour curvature, the pixels of the image are divided into different classes. For the pixels belonging to different classes, fuzzy weighted averaging filter and Lee filter with different filter parameters are used, which makes the proposed method own pixel-level adaptability. Experimental results indicate that the proposed method outperform the classical Lee, Kuan and wavelet soft-thresholding filter in denoising and keeping detail edge information.

Infrared images typically have the problems of target fuzzy edges and details. The variable infrared image enhancement algorithm of bimodal Gaussian function specification is introduced. Firstly, by converting the image to the gradient domain, image gradient histogram can be obtained. Then, by constructing a bimodal Gaussian function, the distribution of the gradient histogram can be restricted. Finally, by using the variational method to reconstruct the image from the gradient field, the contrast and target edges and details of the image are improved. The cutting of the amplitude of noise in the transform of gradient field prevents the amplification of noise. Based on actual experimental results, both in visual effects and quantitative indicators of the assessed value of the image information entropy, the algorithm is significantly better than the histogram equalization and specification. Therefore, it gives a good visual effect for the infrared image.

A method for the generation of 2×2 optical ring lattice array by coaxial superposition of Laguerre-Gaussian beams is proposed. The formation and distribution characteristics of optical ring lattice array are discussed in theory, then optical ring lattice array is produced by numerical calculation. The hologram of optical ring lattice array is generated by conjugate-symmetric extension based Fourier computer-generated holography, and the optical ring lattice array is experimentally produced based on a reflected-type spatial light modulator. Excellent agreements between theoretical and experimental results are observed. Optical ring lattice array provides more controllable parameters and more complicated light distributions, so the research results provide some theoretical and experimental foundations for atom trapping of light beams.

A novel target recognition method for laser active imaging based on a kind of local invariant feature named fast retina key point (FREAK) is proposed, which could be used when moment, geometry and contour features of target are difficult to extract. A feature point detection method called difference of features from accelerated segment test (FAST-Difference) is proposed. It combines features from accelerated segment test (FAST) with difference of Gaussian (DoG), which can rapidly extract feature points that are robust for a variety of transformation. FREAK descriptor is used to generate the feature vectors and cascading matching method is used to complete the fast matching for feature vectors. The proposed method has characteristics similar to those of human vision. In the feature point detection stage, the FAST-Difference method uses DoG for multi-scale detection. In the feature vector description stage, FREAK descriptor has similar topology structure with human retina. In the feature vector matching stage, cascading matching method imitates saccade search of human retina. Experimental result indicates that the proposed method can quickly and effectively recognize the partly-illuminated tower-like target in laser active imaging and satisfy the real-time requirement of the recognition system.

The welding property of Mg-9.8Li-2.9Al-Zn alloy with the thickness of 2 mm using the CO2 laser is investigated. The joint forming, weld defects and structural evolution are studied with optical microscope (OM) and scanning electron microscope (SEM). The mechanical property of the weldment is tested using the microhardness and longitudinal tensile test at room temperature. The result indicates that the rapid cooling during the laser welding results in the fine microstructures with more α-Mg phase in the weld, compared with that in the base metal. The metastable phase MgLi2Al transforms into the stable phase AlLi. The weld microhardness (about 105 HV) is bigger than that of the base metal (about 85 HV). The longitudinal tensile test of the weldment shows the fractured location along the base metal with the reference yield strength of 172 MPa and the percentage elongation after fracture of about 24%.

The FeCrNiCoMn high-entropy alloy coating with nice surface topography is prepared on 45# steel by laser cladding. In order to study the property of resistance to high temperature softening of the coating, the annealing experiments of coating are performed at 550 ℃, 700 ℃, 900 ℃, 1000 ℃, 1160 ℃ for 2 h, respectively. The microstructure, phase structure and microhardness of the coatings annealed at different temperatures are investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and microhardness tester, respectively. The results show that the coating after laser cladding is mainly composed of typical dendrites and exhibits simple face-centered cubic (FCC) and minor body-centered cubic (BCC) structure phases with average microhardness of 540HV0.2. The microstructure of the coating grows up slightly after being annealed at 550 ℃, 700 ℃ and 900 ℃. However, the coating forms relatively more BCC phase when anneals at 900 ℃. While at 1000 ℃ and 1160 ℃, the microstructure grows up gradually, and the phase structure transforms into single FCC structure. As the annealing temperature increases, the microhardness of the FeCrNiCoMn cladded coating increases firstly, and then decreases, the highest microhardness is 665HV0.2 after being annealed at 900 ℃. It indicates that the FeCrNiCoMn high-entropy coating after laser cladding exhibits nice tempering resistance below 900 ℃.

The dynamic processes of NdYAG pulse laser ablation fused silica on the rear surface and inside are investigated by ultrafast time-resolved optical diagnosis. The evolution processes of time-resolved optical images of plasmas expansion and shock wave propagations are obtained. The results show that the multi-shock waves are emerged when the focused laser irradiates the rear surface of sample. Moreover, the reflection waves will be yielded when the generated shock wave arrives at the front surface of sample. Plasma channel is gained and the intense micro-explored damage sites will come into being when the laser focuses inside the sample. Meanwhile, it is found that the intensity of reflection and reflection shear waves at interface are determined by the incident angle of shock wave. The propagation velocities are different for different shock waves.

To study the effects of magnetic field stirring on the laser metal deposition (LMD) parts, a device of rotating magnetic field is designed and introduced to the LMD processes of titanium alloy. The microstructure of the laser deposition layers is characterized and the deposition layers′ microhardness is tested. The results show that the convection in the laser melting pool caused by magnetic field makes the top cross-section of single pass concave-shaped. With the higher rotating speed of magnetic field, the α lamellar is finer, and the micro-hardness of deposition layers is much harder which can be 440 HV0.1. It indicates that rotating magnetic field intensifies the convection in the pool and increases its cooling speed, which leads to finer microstructures and better mechanical property.

To enhance the tribological behaviors of Ti-6Al-4V alloy, high-temperature self-lubricating wear resistant composite coatings reinforced with hard TiC and TiWC2 carbides, self-lubricating Ti2CS and CrS sulfides are fabricated by laser cladding. The phase compositions and microstructures are investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), respectively. Sliding wear tests of the composite coating and substrate are conducted at ambient temperature, 300 ℃ and 600 ℃, with the Si3N4 ceramic ball as the counter-body, and the corresponding wear mechanisms are discussed. Results indicate that the mean microhardness of the composite coating (1005 HV0.2) is about 2 times higher than that of substrate (360 HV0.2). From ambient temperature to 600 ℃, due to the combined effects of hard TiC and TiWC2 carbides and self-lubricating Ti2CS and CrS sulfides, both the friction coefficient and wear rate of the composite coating decrease in comparison with the substrate. The composite coating has excellent high temperature self-lubricating and wear resistant properties.

With the polarization-selective property of the resonance leaky-mode grating mirror, a 35-layer grating mirror with 1000 nm period and 70 nm groove depth is designed and manufactured. The corresponding sample is prepared through the micro-nanofrabrication process. The bi-reflectivity of the sample is measured by contrast method, and its reflectivity is about 87% for TE wave and 98% for TM wave, which proves its polarization selection at the central wavelength of 1064 nm, and that is agree with theoretical result. Then the grating mirror is placed in a NdYAG laser cavity as the end mirror, with which a linearly polarized TEM00 laser beam at 1064 nm is got, its degree of polarization is about 95.7% and power is 14.4 W with pump current of 20.1 A.

The power-ratio-tunable dual-wavelength fiber laser with linearly-polarized output and its polarization maintaining fiber power amplifier are demonstrated. Two pairs of fiber Bragg gratings with polarization-matching techniques are employed as the mirrors of the resonator to insure the linearly-polarized output with central wavelengths of 1035 nm and 1030 nm, respectively. By introducing the cavity loss at 1035 nm, the power ratio of the two wavelengths can be continuously changed. With the dual-wavelength fiber laser as the seed, two-stage polarization maintaining fiber amplifier is established to scale up the output power. By changing the power-ratio of the two wavelengths of the seed, the affection of seed characteristics on the dual-wavelength power amplification is studied to realize the adjustable power-ratio of the amplified output. When the output amplitude of dual-wavelength on the spectrum is tuned to be equal, the maximum output power of 7.77 W is achieved. Future power scaling operation can be achieved by increasing the pump power or adding the amplification stages, which provides the possibility in application to generate terahertz wave by optical nonlinear difference frequency.

Numerical study on focal spot overlapping can provide important supports for the construction of an excimer laser angular multiplexing system. The simulation methods of focal spots overlapping are introduced first. And then simulations of 18 laser beams overlapping are performed based on single laser beam focal spot profiles and laser pointing stability. Profiles and parameters of overlapped laser focal spot on target surface are given. Finally, the relations between imaging quality and laser pointing stability are studied under the requirements of isentropic compression experiments. Many conclusions are drawn from the study. The uniformity of focal spot can be raised by overlapping. What′s more, better beam pointing stability is needed to keep the uniformity when the imaging quality is excellent. Otherwise, the outstanding imaging quality is wasteful. The beam pointing stability can just be within a certain range when imaging quality is common, for the uniformity cannot be improved much by better laser pointing stability.

Spatial optical solitons in nonlinear optics occupy a very important position, while most of the theories are obtained under paraxial constraints, and can not meet the application under the condition of the large incident angle of the initial beam. One-dimensional nonparaxial spatial optical solitons in nonlocal nonlinear media using Helmholtz theory are investigated. An exact analytical solution to the nonlocal nonlinear nonparaxial propagation equation in the cases of high and weak nonlocalities is deduced. It′s numerically found that the degree of nonlocality can affect the widths of nonlocal soliton beams, but has no effect on their stabilities. Contrarily, nonparaxiality can affect their stabilities, but has no effect on their widths.

A noise-like pulsed Raman fiber laser using graphene oxide saturable absorber is reported, which adopts the all-fiber double-ring configuration, comprised by an Er-doped fiber resonator and a Raman fiber resonator. The Raman gain fiber is a 700 m commercial silicon-based high nonlinear fiber. When the pump power of the diode laser is 4.16 W, the Raman fiber laser generates stable 500 ns pulse trains at 250 kHz repetition rate. The central wavelength is 1690.2 nm and the radio of signal to noise is 53 dB.

In order to produce the single frequency tunable laser output at 1064 nm, a diode-pumped electro-optically tunable single frequency Nd:YAG laser is designed, which includes an electro-optically birefringent filter (PBS-LN) consisting of both a polarizing beam splitter (PBS) and a lithium niobate (LN) crystal, used as both a single longitudinal mode selector and a frequency tuning element. The principles of mode selection and frequency tuning of the PBS-LN are theoretically analyzed, and the characteristics of single longitudinal mode oscillation and frequency tuning of the Nd:YAG laser at 1064 nm are investigated experimentally. The experimental results have shown that the Nd:YAG laser can steadily oscillate in linearly polarized single longitudinal mode, and by changing the transverse voltages applied to the LN element, the wavelength of single longitudinal mode laser at 1064 nm can be tuned by 0.474 nm, corresponding to the frequency tuning of 142.2 GHz. Such an electro-optically tunable single frequency Nd:YAG laser will find wide applications in the fields of laser interferometry, laser radar detection and laser spectroscopy, etc.

The characteristics of an extracavity pumped Sr:WO4 anti-Stokes Raman lasers at 969 nm are studied. The Sr:WO4 Raman resonator is pumped by an actively Q-switched Nd:YAG laser at 1064 nm with its axis tilted from the pumping laser direction. The non-collinear phase matching between the pumping radiation, the generated first Stokes and the first anti-Stokes radiations are achieved. Besides the first anti-Stokes laser radiation, three orders of Stokes laser radiations are generated simultaneously. The output energy, temporal and spectral information of the output laser radiations are investigated. At the highest pumping laser energy of 120 mJ, the highest energy of the anti-Stokes radiation is 0.74 mJ with the pulse width of 3.9 ns. Meanwhile, the total output energy of the Stokes radiations is 23.9 mJ with 19.6 mJ of 1323 nm second Stokes component. The conversion efficiency from the pumping radiation to the Stokes and anti-Stokes radiations is 20.5%.

Auto alignment system, which is used for beam adjustment in high power laser driver system, is not only the key subsystem ensuring the routine operation effectually and safely, but also the main method to ensure the beam quality. An Ethernet local area network (LAN) is built and digital CCD is used for beam image acquisition and transmission, so that image data can be directly converted into digital signals and output via Ethernet to computer. Gaussian smoothing filter algorithm is used to improve the accuracy of image processing, while fuzzy algorithm is applied to the motor control process which can shorten the alignment time. The experiment is completed on No.9 system of SG-II laser facility. Experimental results show that all adjustments of alignment are finished within 5 min and the accuracy of image acquisition and processing can be up to 1 pixel.

The concept of hybrid-pumped Tm-Ho co-doped pulse fiber laser by pumping the laser with a 1570 nm continuous-wave laser and a 1565 nm pulse laser is demostrated. The experimental setup is built up and stable pulse train of 2 μm is obtained. Directly gain-switched pulse train of Tm-Ho co-doped fiber laser is generated to compare the two methods of generating pulse laser. The results show that the hybrid-pumped pulse train is more stable than the gain-switched pulse train at the same laser output power level, and the energy fluctuation of the hybrid-pumped pulse train is less than 5%. Hence, the hybrid-pumped method is a more effective approach to generate stable pulse train. It should be noted that the pulse width of gain-switched pulse is narrower than that of the hybrid-pumped pulse.

Modulation of activated impurity on filter property of double barrier photonic crystal quantum well is studied by computational simulation method. The results show that no matter which layer the activated impurity is doped in, there appears light gain amplification (with different maximum values) and bandwidth narrowing (with constant minimum values) in filter channels of quantum well. With different sensitive responses in different channels, response of magnification and bandwidth to impurity in inner-barrier layer is more sensitive than the one in outer-barrier layer; similarly, the response to single-layer medium is more sensitive than the one to multilayer. When there is activated impurity in well layer, sensitivities of channel in center well responding to impurity in single-layer and in multilayer medium are the same, but the response sensitivity of shortwave channel to impurity in multilayer is more sensitive than that in single-layer medium. Inversely in long wave channel, no matter which layer activated impurity is doped in, the response sensitivities remain an equivalent extreme value. These properties provide positive guidance for design of photonic crystals with narrow bandwidths, high-quality optical filtering and high-multiples optical amplifiers.

The absorption property of one-dimensional photonic crystals with defect layer by the approach of transmission matrix is studied. In the photonic crystals, the medium layers are nonmetal, and the defect layer is metal. The relationship between absorption of real material and wavelength is given out, and then the absorption property of the photonic crystals is studied systematically, which is made up of arbitrary material. The effects of the incident angle, the refractive index of defect layer, the refractive index of medium layer, the thickness of medium layer and the periodic structure on the absorption property in the one-dimensional photonic crystals are given. Some valuable results are obtained. By adjusting the parameters of the photonic crystal, the affect of these parameters on the absorption property of the photonic crystals is found, which provides important theoretical basis for the design and preparation of photonic crystals.

The method based on frequency-wavenumber domain filtering has great potential in suppressing the incident wave. However, the inspection error can′t be avoided, the noise in reflection wave fileld got by this method is so much. High-resolution laser ultrasonic testing is used to realize the wavefield visualization in the aluminum plate. Adjacent waves subtraction after arrival time matching and the frequency-wavenumber domain filtering are both used in this paper to weaken the incident wave. The results show that the proposed filtering method has a good performance in improving the visibility of the damage-reflected wave, and the included noise is less.

Revised Edlen′s equations by Boensch and Potulski in 1998 are mostly used to calculate air refractive index at present. Since the correction coefficient of water vapour influence on refractive index is performed with four wavelengths (644.0 nm, 508.7 nm, 480.1 nm, and 467.9 nm) and the temperature between 19.6 ℃ and 20.1 ℃, the accuracy will be influenced when the laser wavelength is 633 nm, which is mostly applied in optical precision measurement, and the environmental temperature is far away from 20 ℃. To solve this problem, a refractive index measurement system based on phase step interferometry is presented. The correction coefficient of water vapour influence on refractive index is measured and the revised equations are acquired with the wavelength of 633 nm and the larger temperature range (14.6 ℃~24.0 ℃). The comparison results show that the accuracy by presented equations is better than that by Boensch′s equations.

In order to study on the spatial measurement accuracy of standard laser source near-field parameters, the theoretical model of near-field intensity distribution of standard laser source is established. The surface response non-uniformity correction program of the scientific grade CCD and calculation algorithm of laser near field is proposed. Using corrected scientific grade CCD and two-dimensional scanning device, the 50 mm×50 mm soft-stop images of 1053 nm standard laser source are obtained by S-shaped scanning and capturing. The near-field image of standard laser source is got by the sub-aperture image mosaic. The test results of near-field intensity distribution are accordance with the theoretical results. The main difference between them is the high frequency components mainly caused by the roughness of off-axis parabolic mirror and random noise of the scientific grade CCD .The analysis of near-field parameters test results is that the uncertainty of modulation is 0.08 (k=2), and the uncertainty of contrast is 0.01 (k=2). The near-field measurement confidence of laser measurement system of National Science and Engineering is improved by the study results.

The mode number of optoelectronic oscillators is the key parameter to establish the relationship between the oscillation frequency and loop group delay in the distance measurement method based on optoelectronic oscillators (OEO), and the mode number error can affect the accuracy directly. Due to the low frequency stability of OEO, the accuracy of mode number by measuring the oscillation frequency and inter-mode frequency spacing is not high. The influence of frequency stability on the mode number error and the change law of frequency drifts are analyzed. Then a new method to determine the mode number without changing the structure of OEO is proposed. In this method, the frequency spacing between oscillation mode and x-order-higher mode and the frequency spacing between oscillation mode and x-order-lower mode are measured separately to get the inter-mode frequency spacing, in order to compensate and reduce error induced by frequency drifts. The mode number measurement error model of this method is established. Experiments are conducted by using different methods, and the experimental results are consistent with error analysis.

The fabrications for the tapered fiber probes with the laser-induced chemical deposition method (LICDM) and the surface enhanced Raman scattering (SERS) detection performance of the prepared probes are experimentally investigated in this paper. Our results show that, it is difficult to deposit nanoparticles on the surface of the small cone angle tapered fiber probes with LICDM. The main reason is that the taper surfaces are mainly covered by a relatively low-intensity evanescent field. By lengthening the reaction time, however, it is still possible to deposit nanoparticles on small-angle tapers with the light-scattering effect, which is caused by the silver nanoparticles. With the inducing laser power of 100 mW and the reaction solution of 0.005 mol/L, tapered fiber probes with different cone angles are successfully prepared after depositing for 60 min. The testing results show that for this specific preparation condition, the tapered fiber probe with the cone angle of 8.2° exhibits the highest SERS spectral intensity, which is almost unchanged for different excitation laser powers.

We present a method for fabrication of concave polydimethylsiloxane (PDMS ) microlens array. A digital maskless grayscale lithography system based on digital micromirror device (DMD) is established. Microlens array with a square base is fabricated in photoresist by the system, which is used as replication model. By replica molding technique, a concave PDMS microlens array with a square base is fabricated. Experimental and test results show that the edges of PDMS microlenses are clear, the surfaces are smooth, and the spotlight performances are favorable. The light intensities which transit the microlens array are uniform. The approach described in the paper is a new method for fabrication of concave PDMS microlens, which has advantages of facile, effective, low cost, and arrays can be replicated by larger scale.

For polarization-division-multiplexing coherent optical orthogonal frequency-division-multiplexing (PDM-CO-OFDM) systems, two blind phase estimation algorithms, including the decision-directed (DD) scheme and the DD plus decision-feedback (DF) scheme, are proposed. The proposed algorithms are verified in a 112 Gb/s PDM-CO-OFDM system, and compared with the traditional pilot-aided (PA) algorithm. The simulation results show that the DD algorithm can achieve better performance, but is less tolerant to laser linewidth, the DD+DF algorithm can greatly improve the performance and the laser-linewidth tolerance of the DD algorithm ,and the phase recovery result is much better than PA algorithm using five pilots.

In order to realize an accelerometer sensor with high performance, miniaturization anti-electromagnetic interference, long-work hours and long-distance transmission, a novel micro-electro mechanical system (MEMS) fiber-optic accelerometer based on asymmetric torsional mirror is proposed. A dual fiber collimator is used to measure the change of tiny angle of torsional mirror. The MEMS fiber-optic accelerometer consists of asymmetric torsional mirror, drive electrode and dual fiber collimator. The operation principle of the accelerometer and optical detection of the device are analyzed. Basic design and analytical optimization of the device are discussed. The MEMS fiber-optic accelerometer is fabricated successfully by MEMS processes. Measured results of the accelerometer are consistent with the theoretical values. Experimental results indicate that the dynamic range of the accelerometer is ±2g, the bandwidth is 600 Hz and the resolution is smaller than 10-4g. Besides, the accelerometer has good linearity and repeatability. The MEMS fiber-optic accelerometer takes the advantages of fiber-optic measurement, including compact MEMS structure and simple fabrication processes.

Mathematic models of the fiber-optic distributed disturbance sensor (FDDS) based on the phase-senstive optical time-domain reflectometry (OTDR) are established and the influences of the frequency drift of the laser on the sensor are simulated and experimented based on multiple-wave theory. The simulation results demonstrate that the frequency drift of the laser is a critical factor that results in the reduction of the positional accuracy of sensor and the signal-to-noise ratio (SNR). The SNR is less than 2 dB by moving averaging and subtraction of the traces with disturbances from traces without disturbances and by moving averaging and moving differential method when the frequency drifts of the laser are larger than 25 MHz/min and 30 MHz/min, respectively. It means that the two location methods fail to locate the disturbance. Experiments are made with lasers with frequency drifts of 3 MHz/min and 19 MHz/min, respectively. The experimental results show that the location errors with the two location techniques are both 100 m when the laser with a frequency drift of 3 MHz/min is utilized. In contrast, it fails to locate the disturbance when the frequency drift of the laser is 190 MHz/min. The investigation results are helpful to select the laser source and improve the location precision of the sensor.

Vibration active control is one kind of main methods to eliminate interference and improve machining accuracy. The premise of vibration active control is the precise measurement of micro-vibration signal whose frequency is upper 5 kHz. A full-fiber micro-vibration distributed sensor is designed using frequency modulated consecutive wave (FMCW) and light intensity modulation technology, aiming at the shortage of existing grating sensor used for micro-vibration signal measurement, such as low frequency, complex structure and individual measurement etc. Through piezoelectric transducer (PZT) micro-vibration measuring experiment and simulation, it can prove that top frequency of 60 kHz for distributed measurement is achieved.

Acquisition, pointing and tracking (APT) system is an important part in space laser communication, which is the premise and guarantee for normal work. The composition principle of system, operational principle, key technology, system design and engineering implementation are researched in detail. The simulation experiment indoor and dynamic experiment outdoor are carried out, respectively. The tracking precision in simulation experiment is 2~3 μrad, which proves this system can be used in inter-satellite laser communication. Dynamic demonstration experiment is achieved between airship and ship. The results prove that the acquisition probability is higher than 95%, and acquisition time is less than 60 s. Because of turbulence effect, tracking precision will decrease observably. The tracking precision in turbulence is 5~25 μrad, Development of APT system establishs the foundation for space laser communication execution successfully.

The identification system of impact location is constructed by a fiber Bragg grating (FBG) sensor network, and the wavelet transform, the frequency spectral analysis and support vector classifiers algorithm are used to identify the impact location. According to the impact test on the division area, the relationship between the impact area and signal characteristics is explored. On the basis of using wavelet transform to remove the low velocity impact signal baseline interference, the identification method of low velocity impact area location based on signal amplitude frequency characteristics is proposed. Support vector classifiers machine whose input is signal amplitude frequency characteristics and output is impact area to realize the identification of low velocity impact area location is built. The result shows that for 36 impact area on the 500 mm×500 mm×2 mm carbon fiber reinforced plastics plate under test, 33 impact area is accurate identification, regional location accuracy is above 90%, regional location accuracy is 40 mm×40 mm and each area identification time is less than 1011 ms. The research results provide a scientific and reliable method for the identification of the carbon fiber composite material plate location.

A novel staring laser warning system based on microcantilever focal plane array is presented. The direction of incident laser can be measured by CCD and microcantilever focal plane array. The microcantilever bends owing to laser radiation captured by infrared lens, meanwhile CCD records the change by means of optical readout system. The experimental results indicate that the field of view is ±15° and the resolution is 0.5°, when the focal length of infrared lens is 60 mm and the microcantilever size is 80 μm×100 μm. The warning system, with large filed of view and high resolution, avoids the interference and damage of CCD caused by laser radiation.

In order to improve spots centroid detection accuracy of Hartmann-Shack wavefront sensor (HS-WFS) to achieve high-precision of wavefront test of optical system, a centroid detecting method is proposed. The nonlinear filtering and the windowing spot image in global processing are used, combining with median filtering, cubic spline interpolation and adaptive Otsu thresholding for a single spot in local processing. The regulation of centriod error and calculation time with different interpolation points is discussed. For a spot image with noise, the centroid detection error is only 0.0442 pixel. Compared with the traditional methods of nonlinear filtering, the Otsu thresholding method and the detection windowing, the accuracies are increased by 91.86%, 87.97% and 31.79%. The known wavefront aberration of an optical system is simulation tested. The wavefront testing accuracy is 0.0098 λ in peak-valley (PV) value, and is 0.0027 λ in root-mean-square (RMS) value. The results show that this method enhances the accuracy of centroid detection, and is suitable for high-precision optical systems.

Spaceborne ocean colour remote sensing urgently requires large relative-aperture and wide field of view imaging spectrometer. Based on the research objective of large relative-aperture and wide field of view, a spaceborne imaging spectrometer optical system is designed using a folded Schmidt telescope and a modified Dyson spectral imaging system. The relative-aperture of which is 1/1.2, the field of view of hyperspectral image is 3.9°, and the working waveband is from 0.35 μm to 1.05 μm. Based on the aberration theory, the principle of spherical aberration correcting is analyzed in modified Dyson spectral imaging system. Ray tracing, optimization and the analysis of the design results are performed by ZEMAX software. The analyzed results demonstrate that the MTFs for different wavelengths are all about 0.77, both the line bending and the band bending of the spectrum are less than 6% of the pixel, which is easy for spectral and radiometric calibration. The design results satisfy the requirements of specifications with a small volume and suitable for spaceborne remote sensing.

Scanning lidar can produce a profile image about atmosphere and play an important role in studying boundary layer, structure of cloud, distribution and transport of air pollution. However, traditional Fernald and Klett methods cannot be applied to the situation of large zenith angles. Usually, by using two-angle method, the lidar constant is corrected, and then atmospheric extinction coefficient is obtained. But this is a multiple-solution problem. It is difficult to optimize the solutions just by setting some relevant conditions. The atmospheric region between adjacent slant paths is basically horizontally uniform. The lidar constant is estimated by using linear regression in that region. Then the best lidar constant is optimized with relevant constraints. The atmospheric extinction coefficient is inverted. By theoretical simulated and measured data analysis, the inversion result is still very good even when the zenith angle is large and lidar signal quality is not very good. Results show that this method can display atmospheric structure very well.

In order to reduce the influence of the joint error of three-dimensional (3D) laser scanner′s multi-sensor point cloud, a simple method to correct the joint error layer by layer is presented, which is based on a columnar standard detected object. The standard detected object is scanned, and the scanning data are fitted to get each section′s coordinate of the circle center. The section′s true value circular function is got by using the actual radius of the cylinder. Translational rigid transformation between each layer′s measured data and true value circular function is done to get this layer′s joint error and corrected value. In order to reduce the influence of random error, repeated measurements are done, and the average corrected value is calculated. Then, some verification experiments are conducted on the measured data of cylinder, cuboid and plaster mannequin, which are placed in different locations. The comparison of stitching result between before and after the correction is made from two aspects of ocular observation and quantified data analysis of sampling sections. The results show that the corrected point cloud can joint together more smoothly, and the relative errors of measured data become lower prominently.

To study the characteristics of X-ray backlighter generated by laser irradiating a foil, a backlit elliptically bent crystal spectrometer is developed based on the ellipse focusing theory. The elliptical mica (002) crystal is employed with 1350 mm focal length, 0.9586 eccentricity and 50°~67° Bragg angle. The laser is of 30° incident angle and perpendicular to long axis of elliptical mica. Diffraction detecting angle is 100°~120° and the wavelength is 0.14~0.16 nm. X-ray CCD is taken as the signal detector. The experiment is carried out on SGⅡ where the 7# and 8# lasers irradiate 10 μm Cu foil simultaneously. CCD obtains the X-ray spectral information of the similar helium and Kα spectra of Cu plasma X-ray. It is demonstrated by spectrum unfolding that spectral lines have obvious basement, and the spectral resolution is over 700 after difference denoising with the least square method.

Multimode Brownian osicillater model of material molecules is set, and the method to calculate the three-pulse photon echo signal is discussed. The model of the Multimode Brownian oscillator is used to analyze the vibration of the Nile blue molecules and the vibration of the Nile blue molecules is regarded as the weighted coupling result of the Gaussian, overdamping, inhomogeneous and underdamping models. Changing the weight of these four models to alter the correlation function of the Nile blue molecules, we numerically simulate the three-pulse photon echo signal. Experiment about the three-pulse photon echo of the Nile blue ethanol solution is conducted. The concentration of Nile blue ethanol solution is 8×10-5 mol/L, the wavelength and the pulse width of the femtosecond laser light source are 623 nm and 40 fs, respectively. The three-pulse photon echo signal is measured to discuss the vibration model of the Nile blue molecules.

In order to further improve the performance of quick measurement of unburned carbon in fly ash by laser-induced breakdown spectroscopy (LIBS), Na2SiO3 and KNO3 are employed as binders to improve the compressibility of the fly ash powder. The fitting coefficient of calibration curve, sensitivity, measuremental accuracy, precision and limit of detection are compared between the two binders, and the performances of Si 251.61 nm and Si 288.16 nm used as the internal standards for C 247.86 nm individually are also investigated. The experimental results show that the fitting coefficient of calibration curve, measuremental accuracy, precision and limit of detection of fly ash mixed with Na2SiO3 are better than that of fly ash mixed with KNO3, and Si 251.61 nm as the internal standard for C 247.86 nm can improve the measuremental sensitivity of unburned carbon in fly ash.