The design, simulation and measurement of the microwave cavity for the cold atom clock are presented. Single-ended loop coupling is used to stimulate the microwave field. Based on the result of simulation, the loop coupled from the side surface of the cylindrical cavity will induce a more symmetric microwave field than that coupled from the end face. The mode selection is realized by finely tuning the coupling loop. This method is not only simple, but it can also effectively reduce the volume of microwave cavity. Finally, the microwave cavity developed is tested and the results indicate that the performance of the microwave cavity meets the requirements of stable integrating sphere atom clock with small volume. Moreover, no reflective coating, which will affect the microwave field pattern, is needed for cooling atoms. This is beneficial to enhance the clock signal, and finally will improve the signal to noise ratio and the contrast.

According to the Bayes and Parseval theorem, myopic deconvolution algorithm for multiframe turbulence degraded images in frequency domain is presented. Atmosphere turbulence long exposure optical transfer function is used as the estimated optical transfer function. According to characteristics of the cost function in frequency domain, partial Newton algorithm is introduced. This algorithm can handle unregistration of multiframe images and obtain ideal recovered image. The restored result of the computer simulation multiframe turbulence degraded images shows that it has good restoration effect at different turbulence intensities and signal noises, even though the images are unregistration.

In order to illustrate the change of turbulence distance for partially coherent flat-topped (PCFT) beams propagating through non-Kolmogorov (non-K) turbulence, based on the extended Huygens-Fresnel principle and the definition of turbulence distance using relative M2-factor, the analytical expression for turbulence distance of PCFT beams through non-Kolmogorov turbulence is derived. The turbulence distance of PCFT beams through non-Kolmogorov turbulence depends on the generalized exponent parameter, inner scale and outer scale of turbulence and the initial second order moments at the plane of z=0 (namely, beam parameters including beam order, wavelength, coherence degree and beam waist width). The results show that the turbulence distance of PCFT beams through non-Kolmogorov turbulence firstly decreases towards a minimum and then increases with the increasing of generalized exponent parameter, increases with the increasing of beam order and wavelength and decreasing of coherence property, and does not monotonously vary that the turbulence distance firstly decreases and then increases with the increasing of beam waist width.

A design method of field-widened Michelson interferometer (FWMI) applied as the spectroscopic filter for high spectral resolution lidars (HSRLs) is proposed. The theoretical principles and design criteria are described in detail. Making use of the field-widen and thermal compensation conditions, the FWMI can achieve large incident field within a certain temperature range. The design result of the near-infrared FWMI is provided. The performance analysis of designed FWMI indicates that its available incident divergence is larger than 2°, and its working performance remains constant within (20±0.5) ℃. What′s more, according to the tolerance analysis, the design result meets the current glass processing technic. The design procedure and method introduced have guiding significance for the FWMI design and production.

Considering the design feature and requirement in high precision of geometric calibration of the earth annular ultraviolet (UV) limb imager, a new method based on UV collimator, high precision theodolite and six-dimension rotator is proposed. Geometric calibration is done as soon as the new device is built-up. The result shows an agreement of 2 pixel or less with the theoretical design in limb altitude and a biggest deviation of 25 pixel in limb azimuth orientation. The combined standard uncertainty analysis indicates a 0.488 pixel and a 0.612 pixel uncertainty in limb altitude and azimuth orientation respectively, both reaching sub-pixel precision. With the successful accomplishment of the geometric calibration, the method and the device offer an important reference and a realized platform for the pre-optic-mechanical installing and measuring of the similar type of instrument.

A contrast enhanced image fusion algorithm is proposed to improve the visual effect of fused image from infrared and visible images at low lightness. Estimating background luminance by bilateral filter, the subband-decomposed multiscale Retinex with bilateral filtering is proposed, and original images are decomposed using proposed transformation. Coefficient matrixes in the same subband are fused by using detail enhancement strategy based on local space frequency, and fused coefficient matrixes in different subbands are fused by global variance weighted sum. The fusion result is needed for the transition from the logarithmic domain to the display domain by improved nonlinear stretching. The results of experiments demonstrate that the proposed algorithm can effectively overcome the halo phenomenon, improving definition of fused image, and the detail information is more salient.

For the near-field in-line digital holography, the multi-plane reconstruction method used to eliminate the twin image works well when the reconstructing distance is exactly equal to the actual recording distance. However, it does not consider and analyze the influence when there is a deviation between the two distances. In practice, it is difficult to accurately measure the actual recording distance, and the deviation between the reconstructing distance and the actual recording distance always exist in the digital reproduction. A thoughtful analysis for this method is presented and it is found that this method is very sensitive to the distance deviation, and as the deviation increases its efficiency and effectiveness will be greatly decreased. The distance deviation sensitivity of this method can be used to improve the auto-focus accuracy and sensibility in the reconstruction of Gabor in-line digital holography. Principle analysis and experimental verification confirm the above conclusions.

Laser shock processing (LSP) is carried out on K403 nickel-based alloy turbine blades and the high temperature high and low cycle complexed fatigue tests are conducted to verify the reinforcement effect. The results of the fatigue experiments show that a greater flatness area near the fatigue crack initiation (FCI) is induced by LSP, the fatigue striation spacing on the fatigue crack growth (FCG) area decreases and lots of second cracks are generated after LSP. Grain refinement and high residual compressive stress on the surface layer are induced by LSP. But when the K403 nickel-based alloy after LSP is subjected to heat treatment at 550 ℃ for 150 min, a part of residual compressive stress has got relaxation while the refined structure has still remained good thermal stability. Compared with the untreated samples, the fatigue life of turbine blades is increased by 140% after LSP. The grain refined structure and residual compressive stress after relaxation are the main causes of improvement of nickel-based alloy fatigue life.

In order to study the effect of laser shock processing (LSP) on the electrochemical corrosion resistance of magnesium alloys, the electrochemical corrosion behaviors in 3.5% (mass fraction) NaCl solution of AZ31, AZ61 and AZ91 magnesium alloys are investigated by electrochemical method and Ndglass laser with the wavelength of 1064 nm and pulse width of 20 ns. Its surface morphologies, microstructures, microhardness, self-corrosion potential and electrochemical impedance spectroscopy (EIS) are also examined and analyzed. The experimental results show that electrochemical corrosion resistance of magnesium alloys are improved after LSP. With the increasing of laser power density, the self-corrosion potential of magnesium alloy begins to move towards a positive direction, the corrosion current density decreases and the impedance arc becomes larger. When power density reaches to 0.7 GW/cm2, the current density increases and impedance arc becomes smaller. The effect of the Al content, solution and aging treatment on the corrosion potential and EIS of magnesium alloys by LSP are discussed and analyzed.

Studies on the microstructure and properties of butt joints by laser welding 1.5 mm thickness DP1000 dual phase advanced high strength steel used tensile test, microhardness test, scanning electron microscope (SEM) and optical microscope(OM) are presented. The reason of the decrease of joint′s strength and ductility is discussed. The results show that a serious softening has occurred in heat-affected zone (HAZ) of the welding joints, and the most serious locates in the tempered zone and the incomplete crystalline zone of HAZ. The strength of welding joints decrease by 10%~15%, and the ductility of welding joints exceed 60%. The main reason of the joint′s strength descent is the existence of tempered martensite which is obtained in the welding process, and the tempered martensite′s strength is lower than the quenching martensite. The main reason of the joint′s ductility descent is the uncoordinated tensile deformation of different joint subareas, and the deformation mainly takes place on the softened zone of HAZ. The welding fusion zone, the base metal and other zones of HAZ hardly occur deformation.

In order to study the dynamic strain on 2024 aluminum alloy surface induced by a pulsed laser shock wave, the pulsed laser is used to impact on a 2024 aluminum alloy sample, and the dynamic strain on the 2024 aluminum alloy surface which is under the effect of the pulsed laser shock is measured by a polyoing lidene fluoride (PVDF) piezoelectric sensor. A dynamic strain model of 2024 aluminum alloy surface loaded by the pulsed laser shock wave is established and verified by experimental data. The results show that the laser shock wave and surface wave can′t couple by adjusting the parameters of laser pulse. The relationship curve of the dynamic stress-strain of 2024 aluminum alloy under high strain rate of pulsed laser shock wave is similar to the static stress-strain relationship curve of 2024 aluminum alloy under static tensile condition. The experimental results are consistent with the dynamic strain model of 2024 aluminum alloy surface loaded by the pulsed laser shock wave.

A lot of information reflecting laser welding process are involved in laser-induced plasma. The electrical signal and spectral signal from laser-induced plasma are detected by a synchronous electrical and spectral information acquisition system and the signals are compared. And then the relationship between electrical signal and plasma temperature is illustrated. The electrical signals of the induced-plasma for stainless steel A304、stainless steel 430 and carbon steel Q235 in laser surface auto genous welding are detected in real-time and analyzed by the probability density distribution. The analysis of the standard deviation of probability density distribution of the electrical signal from the strainless steel A304 laser welding with the most obvious deep penetration characteristics is presented. The results indicate that the temperature variation of laser induced-plasma can be real-timely detected by the electrical signal, and laser welding mode can be identifed by the probability density analysis of the electrical signal of the laser induced-plasma and the laser welding mode of stainless steel A304 can be determined by the standard deviation analysis.

Application of aluminum alloy heavy section is limited for its worse weldability, low welding efficiency and large welding deformation. 5083 aluminum alloy plates of 25 mm thick are welded using IPG YLS-6000 fiber laser and ultra-narrow gap fiber laser beam welding method. The microstructure and mechanical properties of joint are tested by optical microscope, scanning electron microscope and tensile testing machine for low temperature. The results shows that defect free butt joints with 7 layers are obtained with ultra-narrow gap laser welding. The width of weld is uniform and less than 4.5 mm. Microstructure of weld consists of columnar grain and some discontinuous dot-like precipitated phases. There are no obvious coarse grains but some precipitation in heat affected zone (HAZ). The microhardness of the HAZ is slightly lower than that of weld metal and base metal, and the microhardness of base metal is the same to that of the joint. The tensile strength of joint increases a bit when temperature decreases (such as at 273 K、243 K、213 K and 183 K), which performs as well as the base metal. Samples are bended by 180° without large defects observed, which shows the joint has excellent plasticity.

The self-cleaning lotus-leaf-like superhydrophobic surfaces are of great importance for various potential applications. Micro craters in hexagonal matrix with nano substructures are effectively fabricated on mold steel (H13) with an area of 25 mm×25 mm by means of a high-power picosecond laser in cooperated with a high-speed galvo scanner. This kind of micro-nano structured H13 surface is used as a micro-nano imprinting master for replicating superhydrophobic silicone rubber surfaces under 165 ℃, 6 MPa in ambient air. Micro protuberances decorated by nano substructures, similar to those of lotus leaf, are formed onto the printed surfaces of silicone rubber, transforming the rubber surfaces to be superhydrophobic with a contact angle of 153.3° and a contact angle hysteresis of 3.2°. The picosecond laser fabricated micro-nano template is capable for repeated imprinting with good durability.

A groove-shaped array with average 25 μm interval, 25 μm wall thickness, 75 μm depth and a columnar array with average 30 μm side length, 25 μm interval, 43 μm depth are processed by 1064 nm picosecond laser on polytetrafluoroethylene (PTFE) surface at room temperature. The water contact angle of the modified PTFE surface is 167° so that super hydrophobic surface of PTFE is prepared. It is observed that the super-hydrophobic surface reflects metal luster underwater through the glassware when the super-hydrophobic PTFE is entirely immersed in pure water. The experiment conducts that the super-hydrophobic surface can enhance reflection intensity of visible light due to total internal reflection of super-hydrophobic surface underwater.

A femtosecond pulse shaper is set up based on a liquid crystal spatial light modulator. The pulse shaper is driven by home-developed LabVIEW programs. The second harmonic generation (SHG) spectrum is recorded when the femtosecond laser pulse is modulated by a sinusoidal phase function. The multi-photon intra-pulse interference phase scan (MIIPS) trace is obtained with the parameter δ, witch is the initial phase of sinusoidal phase scanning, scanning from 0 to 4π. The effects of the sinusoidal phase′s amplitude and frequency (α and γ) are studied in detail for the optimization of MIIPS. The results not only provide a guidance for the phase measurement and compensation in MIIPS, but also supply a method for narrowing and shaping SHG spectrum, which will be useful in many fields, such as two-photon absorption spectroscopy, femtosecond chemistry and femtosecond biology.

Although the traditional iodine-stabilized 532 nm optical frequency standard is high frequency stability and uncertainty, it is complex and not portable. Lower frequency stability is acceptable in some cases such as absolute gravimeters, on which smaller size and portable are focused. A compact iodine-stabilized solid-state laser at 532 nm is established, which is portable for its small size. By the way of measuring the frequency beat with the original iodine-stabilized 532 nm optical frequency standard, the Allan deviation is 2.4×10-12 for 1 s averaging time, and the absolute frequency of the laser is 563260223436 kHz, whose uncertainty is 52 kHz (coverage factor k=2). The system has been applied to absolute gravimeters at National Institute of Metrology.

A high-power all-fiber mid-infrared supercontinuum laser source that consists of a 1.55 μm nanosecond-pulsed erbium-doped fiber laser, a cladding-pumped thulium-doped fiber amplifier and a segment of single-mode ZBLAN fiber is reported. Firstly, the pulse breaks up through modulation instability and the laser shifts to a longer wavelength through Raman processes in the single-mode fiber. Secondly, the nanosecond pulses are amplified through a thulium-doped fiber amplifier. Finally, the output spectrum from the thulium-doped fiber amplifier is extended to the mid-infrared wavelength by using a segment of single-mode ZBLAN fiber. The output power from the ZBLAN fiber is 2.2 W with the launched pump power of 3.95 W at 2.0 μm wavelength region, the emission spans the wavelength range from 1.9 μm to 3.75 μm with a 10 dB bandwidth of greater than 1600 nm. In addition, a higher output power mid-infrared supercontinuum laser source is achieved by increasing the average output power of the thulium-doped fiber amplifier. The ZBLAN fiber produces an average output power of 16.2 W with the coupling pump power of 21 W at 2.0 μm wavelength region, the emission spans the wavelength range from 1.9 μm to 3.5 μm.

Simulations of free electron laser (FEL) experiments based on the laser-wakefield accelerator, which will be conducted at Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Acadomy of Sciences, are performed. Direct-seeding with high harmonic generation (HHG) is proposed as the scheme for free-electron laser experiments at SIOM (SIOM-FEL). The theoretical and simulation results show that the FEL signal will be amplified about 200 times compared with the initial high harmonic generation when the electron beam energy spread is 1%, the emittance is 0.3 mm·mrad and the peak current is about 10 kA. What′s more, the application of the transverse gradient undulator (TGU) can furtuer improve the FEL performance even with a relatively low peak current.

For traditional conic refractive laser beam expanders being difficult of fabrication, hard of equipment, bulky and heavy weight, especially difficult to achieve lens array with high fill factor, an approach of laser beam expander by using stepped diffractive surface to approximate conic aspherical surface is proposed. It is shown that the incoming Gaussian beam with typical waist radius of 2 mm is enlarged to the designed expanding ratio of 2.8 times by the diffractive laser beam expander. By making the different sections of the surface with different steps to get two types of improved structure, which aims at keeping the stability of laser mode, the problem of fidelity and typical fabrication line-width of binary diffractive elements being not fulfilled at the same time is solved. The fidelity is raised to 95.82% with the minimum lithography line-width above 2 μm of each section, which meets the fabrication requirement of existing lithography technology. Analysis of the main errors affecting the system fidelity shows that the value is still above 95% when defocused error is -1~1 mm and decenter error is below 0.1 mm of eyepiece and 1.68 mm of objective lens, which make the system easy to install.

As the basic material of light emitting diode (LED) substrate, the quality of sapphire directly affects the production yield of high-brightness LED substrate chips. The detection and positioning of internal defects in sapphire crystal bar can greatly reduce the production cost and improve the yield. Based on machine vision technique, an internal defect detection and positioning system are bulit for sapphire on the basis of laser light scattering tomography taking the processing requirements on sapphire substrate into consideration. LabVIEW and image acquisition card and data acquisition card from NI Company are adopted in this system. The detection and positioning of internal defects in sapphire crystal is realized by scanning the sapphire crystal layer by layer through the light scattering effect generated by the irradiation of high-intensity linear laser on defects. A lot of image processing methods such as image enhancement, image segmentation and image extraction are adopted to extract and analyze the defects, enhancing the real-time performance and visuality of this system. The experimental results show that this system can identify the scattering particle defects in sapphire crystal effectively, and position them in depth direction accurately.

A type of pump reflector for large aperture active mirror slab amplifier is designed. The amplifier is different from the conventional multi-segment-amplifier (MSA). The reflector should be specially designed to improve the efficiency of the pump Xe-lights. For the unique structure, the theoretical optimized curve function is calculated by Matlab. TracePro is used to simulate the designed reflector based on the optimized function, and get the theoretical efficiency of the reflector. Compared to the flat reflector, the efficiency is 17.58% higher. A 11 experiment is designed and used to test the performance of the reflector, whose efficiency is 15.19% higher than the flat one.

Lithium triborate (LBO) possesses desirable nonlinear optical characters, as well as stable chemical and mechanical properties. Its dispersion is sensitive to the change of the crystal temperature, which allows this nonlinear optical crystal to be used to achieve noncritical phase matching. This paper demonstrates a femtosecond synchronous green-pumped singly resonant optical parametric oscillator (OPO) based on lithium triborate. As the pump source, a frequency-doubled mode-locked Yb-fiber laser-amplifier system is used, which can produce femtosecond laser with high average power and large mode field area. By adjusting crystal temperature, tunable high power femtosecond laser can be obtained from red to near infrared using noncritical phase matching method. The signal pulses of the optical parametric oscillator have a wide spectral tuning range of 670~880 nm and idler pulses are tunable in the range of 2320~1270 nm. At a pump power of 3.4 W, the output highest average power of 660 mW at 694 nm central wavelength is achieved with the pulse duration of 132 fs and the slope efficiency of 19.4%.

Frequency stability of Q-switched Nd:YAG laser significantly affects the wind measurement accuracy of direct detection Doppler Lidar. The typical free frequency drift of diode-pumped Nd:YAG laser working at doubling frequency 532 nm based on seed injection can reach 15 MHz/min, correspondingly to a weed speed measurement error of 4 m/s. By using virtual instrument control technology of Labview, the frequency of pulsed laser is successfully scanned, and iodine absorption line 1109 is matched automatically, which get the frequency on one of the two slopes of the line. Standard deviation of frequency stability is about 0.8 MHz for a long time (more than 2 h), while the equivalent wind speed error is 0.2 m/s. The requirement of frequency stability is achieved during long-term lidar measurements.

For the dead zones phenomenon of longitudinal modes modulating signal in the total reflection prism laser gyros (TRPLG) during in single longitudinal mode frequency stabilization, a novel technique for the double longitudinal mode frequency stabilization of the TRPLG is studied. By analysing the theory of power tuning curve, amplitude and phase characteristics of the small jitter modulation signal in double longitudinal mode are derived. The double longitudinal mode frequency stabilization scheme is proposed, and the control system for the double longitudinal mode frequency stabilization of the TRPLG is built by software and hardware circuit design. In the fixed and varied temperature environments, the experimental tests for the single longitudinal mode and double longitudinal mode frequency stabilization are conducted. The results show that, comparing with the control method for single longitudinal mode frequency stabilization, the frequency stabilization accuracy of the double longitudinal mode can be improved by over 60%, and the accuracy of gyros is also increased accordingly.

A coherence length tunable solid-state laser based on the spectral dispersion principle is reported. A grating and several right-angle prisms are taken as the coherence length tunable module, which is then put in the laser resonant cavity to replace a mirror. The beam expanding characteristics of prisms and the dispersion characteristics of the grating are used to continually tune the coherence length of the laser. A resonant cavity based on NdYAG is established. An output laser of 1064 nm with power stability less than 0.5% and tunable coherence lengthes from 10 cm to 50 cm are achieved. Both the experimental results and the theoretical analysis show that there is a good linear relationship between the coherence length and the magnification of prism expander.

For N31 and N41 Nd-doped phosphate glasses with strong multiband absorption and emission, Rhodamine 6G (R6G) is chosen as the fluorescence label to realize high resolution two dimensional observation of subsurface defects (SSD) in these glasses under wide field microscopy, as the excitation and emission bands of R6G are different from the emission and excitation bands of Nd-doped phosphate laser glass respectively. It is demonstrated that the detected defects are classified as SSD by comparing the R6G fluorescence microscopy images and related optical microscopy images. The transformation of SSD during polishing process is analyzed according to related R6G fluorescence microscopy detection results. The results show that the crescent cracks which are near the tail end of deep Median type cracks are comparatively hard to be removed in the Nd-doped phosphate glass. These crescent cracks may induce strong modification to the incident optical field, and relatively increase the probability of laser induced surface damage.

The pumping damage resistance and thermal properties of the new Nd-doped phosphate laser glass are investigated under high energy flash lamp pumping. The laser output results show that the laser output ability of the new Nd glass specially designed for repetition-rate application is similar to that of the high-peak-power application type Nd glass, and higher than that of the early designed high-energy application type Nd glass. The thermal expansion property of the new Nd glasses is analyzed, as well as their laser output properties before and after acid-etching and ion exchanging. Especially, the pumping thresholds of the new Nd glass are measured under high energy and repetition rate conditions. The impact and correlation among the lasing, pumping, surface strengthening, and thermal properties are analyzed and discussed.

In order to validate the possibility of using the optical coherence tomography (OCT) imaging technology to non-invasively exam the ancient porcelain and using the section characteristics of the glaze reflected by OCT images to ancient porcelain classification, an OCT imaging system is used to test 8 different type and color ancient porcelain chips selected from 5 different kilns. The section structure images of these samples are obtained. The characteristics of OCT images about the size and distribution of bubbles and strong scattering particles, the uniformity, stratification and transmittance of the glaze layer are analyzed. The experimental results show that the imaging characteristics of 8 different ancient porcelain samples obtained by OCT imaging technology have significant difference, illustrating that species and kilns of glaze can be distinguished based on the section characteristics by OCT imaging technology.

Based on the mechanism of the surface plasmon amplification by stimulated emissions of radiation (spaser), a bowtie nanoantenna structure is proposed for single molecule detection by surface enhanced Raman scattering (SERS). The localized surface plasmon resonance (LSPR) properties and the SERS characteristics of the bowtie nanoantenna are numerically analyzed by the finite element method (FEM). The results show that the LSPR strength and the local electric field intensity of the bowtie nanoantenna can be greatly amplified, and its scattering cross-section and electric field strength are up to 1.1×104 and 1×102 times of the non-spaser bowtie nanoantenna, respectively. Meantime, the maximum SERS enhancement factor is 1016 generated by the bowtie nanoantenna, which is enough to accurately detect a single molecule. Moreover, there is a higher SERS enhancement factor of 1012 on the entire surface of the nanoantenna, which is also sufficient for single bio-molecular detection.

According to the high precision testing requirements on aiming at the baseline variation of infrared sight, a measuring method of infrared sight zero momentum based on camera pose adaptive mathematical model is proposed. A new adaptive algorithm of camera pose is designed. A camera pose correction model is established, which is applied to zero momentum measuring system, solving a problem of zero momentum measuring error caused by camera tilting. The pinhole targets and sighting divide image are located by gravity method, and sub-pixel subdivision of edge points is achieved by Zernike orthogonal moments. An experimental system is constructed. The measurement accuracy is superior to 0.02 mil (1 mil=0.254 cm) which is verified by experiment. The result meets the high precision testing requirement of infrared sight baseline variation.

Synchronization measurement of multi-beams for high power laser facility is achieved at the same time. The time correlation and duplicate measurement method, temporal profile diagnostic module of tripled frequency, and the high-speed digital oscillograph and transient photodiode are used. The synchronization adjustment is obtained by arbitrary wave generator and optical delay cell of front end. Results show that the errors of the synchronization measurement are less than 30 ps. The measurement technology and methods are important for synchronization measurement of multi-beam laser facility.

A new micro-pulse lidar (MPL) system used for atmospheric horizontal visibility measurement is developed, especially the optical unit. The system uses a Y-fiber bundle instead of mirrors in the traditional lidar system, not only improving the compact of the structure, but also solving the problem that is always very difficult to adjust the transmitting and receiving optical paths to parallel in the traditional system, so that it can avoid the influence of the geometrical overlap factor and reduce the complexity of the data processing. This paper analyzes the experimental results of the new MPL in Hefei, and uses the sub-slope method invert aerosol extinction coefficients to obtain atmospheric visibility and its variation. According to the results, the atmospheric visibility has a clear diurnal variation. The correlation coefficient between the results and the other measured by HW-H1 gype forward scatter visibility instrument is 0.81. In addition, the theoretical error analysis results also show that MPL measurement error is less than 20% when the visibility is less than 10 km, indicating that MPL system can achieve the measurement of the atmospheric horizontal visibility effectively.

A practical method based on virtual instrument technique in order to realize operating points automatic control for Mach-Zehnder (MZ) electro-optic intensity modulators (EOIM) is propsed. Operating point at the minimum of the transmission curve can be automatically controlled steadily by means of “sweep—phase discrimination and compensation” in a closed loop feedback system. When the output power of the laser is 6 mW, EOIM is controlled steadily at minimum point for an hour. The average optical output power of the EOIM is 1.198 μW, standard deviation is 0.123 μW and fluctuation is less than 0.43 μW at minimum point with control. When the additional electronic pulse signal is modulated at minimum point of EOIM, light pulse with mean extinction ratio (ER) of 25.71 dB is produced. Under pulse modulation, the output pulse ER is 9.94 dB higher than that in the condition without control, and fluctuation is less than 0.5 dB/h. Which improves working stability of MZ electro-optic modulator greatly.

A high speed optical communication system based on field-programmable-gates-array (FPGA) is designed, which can be used in ground to satellite communication. FPGA is used as central process, and pulse position modulation (PPM) is selected. A new frame structure is designed to solve frame synchronizing problem, and four separating phase clocks are used to synchronize PPM slots. FPGA′s working clock is decreased and structure of the system is simplified in the new design, and Gray code is used to decrease bit error. The data rates can reach up to 20 Mbit/s, and bit-error-ratio (BER) is 8.9×10-9. The system provides experimental supports for follow-up image data transforming between ground and satellite.

Micro/nano optical fibers have the optical property of large evanescent fields, which makes their coupling phenomenon more obvious compared with the normal optical fibers. The simulation of three parallel micro/nano optical fibers is performed by using the software of COMSOL Multiphysics which is on the basis of the finite element method. The results show that the coupling power distributions are approximation as the transmission distance changing when the distance between parallel micro/nano optical fibers is changed. The distributions are periodical and coupling periods increase when the distances increase. The polarization of incident light has an influence on coupling period and coupling efficiency. By utilizing the coupling characteristics among three parallel micro/nano optical fibers, a 3×1 micro/nano optical fiber coupler is designed and its coupling efficiency is approximately 93.3% when the appropriate coupling length and distances between the optical fibers are chosen.

The fiber Sagnac loop filter for wavelength demodulation of fiber Bragg grating (FBG) sensor is greatly influenced by environmental temperature. A new stable demodulation method is proposed to eliminate the influence of temperature. The principle of wavelength demodulation is introduced, and the optical configurations are presented. Using a polarization maintaining fiber Sagnac loop as the edge filter and a distributed feedback (DFB) single wavelength laser as a reference light, FBG signal and reference lights are demodulated. Optical intensities of the transmission and reflection outputs from Sagnac loop filter are detected simultaneously, which are normalized and analyzed by the differential detection method. Theoretical analysis and experimental results show that using this technology, the temperature influence on the Sagnac loop filter is sufficiently eliminated, and the stability of the demodulator is improved. When the Bragg wavelengths range from 1302 nm to 1318 nm, the wavelength shift of the demodulator due to temperature is small as 2.4×10-4 nm/℃, which is as 1.8×10-4 times as that of an uncompensated Sagnac loop filter without the DFB reference light.

A new type displacement sensor based on few-mode multi-core fiber is presented. The sensor consists of two segments of single mode fiber and a segment of few-mode multi-core fiber. The sensing principle of the sensor is investigated and the experiments are performed to verify its feasibility. The experimental results show that the sensitivity of this sensor is -61.17 pm/μm with the elongation from 0 to 60 μm, error between the experimental results and the theoretical calculation is less than 3.9%. So the minimum change of displacement detected is 17 nm by using an optical spectrum analyzer (OSA) with high resolution.

According to the dynamic variations in the application of the data relay satellite system with microwave and laser hybrid links, the dynamic disturbance conditions are analyzed and the dynamic resource scheduling method is discussed based on the dynamic adjustment principles of resource scheduling. To maximize the sum of scheduling tasks priorities, as well as to minimize the variations in scheduling scheme, a hybrid system dynamic scheduling model with two levels optimization target is established. A dynamic inserting fast heuristic algorithm under multi-class disturbance is proposed, which includes the directly inserting tasks operation, shifting and inserting tasks operation, deleting and inserting tasks operation. The results show that the optimization results of dynamic insert algorithm are superior to the rescheduling algorithm in rate of scheme change, which is reduced by 60.10%. The computing speed of the dynamic insert algorithm is superior to the rescheduling algorithm obviously, which could effectively solve the dynamic scheduling problem in data relay satellite system with hybrid links.

The polarization dependent gain (PDG) of fiber Raman amplifiers (FRAs) with backward multiple pumps is investigated systematically, by numerical method based on the nonlinear coupled equations describing the properties of fiber Raman amplifiers. The PDGs induced by all waves Raman interaction, by pump-signal Raman interaction, by pump-pump Raman interaction and by signal-signal Raman interaction are studied respectively. The results show that compared to the FRAs with single pump, the FRAs with multiple pumps can obtain not only flat gains but also uniform PDGs. This study can be used to estimate the PDGs of a FRA with backward pumps induced by pump-signal Raman interaction, pump-pump Raman interaction and signal-signal Raman interaction. These results are useful and important for reducing the PDG of a FRA.

A kind of three-tier hybrid plasmonic photonic crystal which is respectively constituted by a metal layer of silver (Ag), a low refractive index dielectric layer of SiO2 and a two-dimensional photonic crystal layer, is proposed. A clear plasmonic transverse-magnetic (TM) bandgap can be formed in this hybrid plasmonic photonic crystal. The defect cavity is constituted by introducing a unit cell defect in the center of the two-dimensional photonic crystal layer. The volume of the hybrid plasmonic photonic crystal micro-cavity is based on nano-scale, which is much less than the conventional optical micro-cavity, and the photon energy is well confined in the low index layer, so light can be limited at deep sub-wavelength scale. With some different structure parameters, the numerical analysis method of three-dimensional finite difference time domain (3D-FDTD) is used to analyze the characteristics of this hybrid plasmonic photonic crystal. The analysis indicated that this kind of nano micro-cavity has an ultra-small mode volume of 0.0141 (λ/n)3 and an ultra-high Q/V.

Baffle design is an important part of geostationary earth orbit (GEO) imaging system design engineering. According to characteristic of space stray radiation environment, the influence of the varied sun shading angle to the baffle′s structure is analyzed, and height-diameter ratio is discussed. Then, the difference of stray light suppression between bladed and honeycombed structure is studied in different off-axis angles, and the Tracepro simulation results show that the bladed one has a better performance of suppression than honeycombed one with improvement from 5% to 28%. Moreover, referred to the works of blackbody, an improved two-stage baffle is obtained, and an example of baffle design of GEO imaging system is cited. It is indicated that the point source transmittance (PST) curve is less than 10-8 at sun shading angle, and the problem of diffraction effects in inner edge of single-stage structure is removed. The new structure is better in stray light suppression and satisfies the engineering application requirements.

As one of the critical target of lithographic lens, pupil non-balance is modulated by many factors. It is necessary to distinguish the respective contribution of those factors. In this paper, a method is introduced to calibrate pupil balance by removing telecentriciy, and a comparison is made with another approach based on finding centroid. A user defined program, which is written in Matlab with the function of manipulating Code V and LightTools data, is consequently made up to implement the above technique and calculate the real position of pupil intensity in angular plane without telecentircity. Beside, a series of simulation on an optimally designed lithographic lens under off-axis illumination is given to show the verification. It is revealed that this method is functional in calibrating pupil non-balance with a high level of implement efficiency.

Spectral absorption method is an effective means to detect methane concentration. Through the prism chamber combined with the application of photonic crystal fiber, the on-line detection of methane concentration with a high precision by the spectral absorption is realized. Due to the environment temperature, pressure and the influence of the system itself, the received signal contains a lot of noises. According to the characteristics of strongly ability to generalize and seek the global optimal point, support vector machine (SVM) is used to process the signal of methane detection. Through Matlab simulation based on the SVM principle, it can effectively filter out noise, separate the effective signal and assess the effect of denoising with signal to noise ratio (SNR). Using this method to filter can make the SNR reach above 130 dB, which is greatly improved compared with the traditional wavelet denoising, to achieve the ideal denoising purpose.