The cloud-channel transmission characteristics of given wavelength signal are analyzed by setting up a new ground-to-ground cloud-scattering model. By simulation, the predicted path loss of three typical clouds under given transmission configurations are expatiated theoretically and quantitatively. Furthermore, the effects of the path loss caused by elevation angles and transmitting beam width divergence are analyzed independently. The results show that the best communication range decreases when the elevation angles increase on the condition that field of view is fixed. When small transmitting beam width divergence is considered(less than 1°), the transmitting elevation angle must be adjusted so as to the facula on the bottom of cloud produced by the transmitting source light locating on the top of the receiver, but when transmitting beam width divergence is large relatively, elevation angles should be adjusted in order to make the first effective scattering volume maximal. The field cloud-scattering path losses on the communication range of 11.7 km under different receiving elevation angles were obtained by experiments carried in Nanjing, and the above analysis was validated by data. The conclusions obtained in this paper are wavelength-relevant, laser diode with 808 nm and 620 nm are chosen as the transmitting source light.

Thermal blooming has great influence on high power laser propagation in the atmosphere. It is very important to find a sacling law to evaluate the performance of adaptive optics compensation for the high power laser propagation in the atmosphere. Adaptive optics system with different spatial bandwidths has been simulated and phase compensation for focused beam under thermal blooming with different transmitter apertures and propagation lengths has been numerically calculated by four-dimensional propagation codes. The results show that the spatial resolution of adaptive optics system has little influence on the target beam quality. The target beam quality can be scaled by the thermal distortion parameter N.

The path independent algorithm is one of the important phase unwrapping algorithms, and diverse types of least-squares phase unwrapping algorithms are used widely. Since least-squares phase unwrapping algorithm does not hold back the error diffusing in space, an accurate unwrapped phase cannot be obtained by this algorithm directly, which limits the applications of the algorithms. A novel accurate phase unwrapping algorithm and the corresponding theoretical analysis are presented by analyzing the error characteristics of least-squares phase unwrapping algorithm. The validity of this new algorithm is shown by simulation and experimental examples of unwrapping, and the obtained phase proves that this new algorithm is accurate.

Quantitative three-dimensional imaging of cells of Chinese medical decoction pieces can provide a new method for microscopic identification of decoction pieces. To improve the digital holographic image quality, the recording and reconstruction processes of image-plane digital micro-hologram recorded with spherical reference light are studied theoretically and experimentally. A method for measuring the recording parameters of the holographic imaging system such as the magnification, object distance by using a standard test target is proposed. The two popular phase-unwrapping methods are compared experimentally. The results show that the image-plane digital micro-holography recorded with spherical reference light is characterized by more information recorded, very easy reconstruction and the real-time observation of the investigated specimen for determining the region correctly. The parameters of the holographic system can be determined accurately by using the reconstructed intensity image of a US Air Force test target. The unwrapped phase with big depth sample can be obtained accurately by using the lateral-shearing-based least square (LSBLS) algorithm. Using the edge reorganization technique the cell image can be better displayed.

Ladar has became a hot research topic in target recognition community for its ability to capture the object′s explicit 3D shape. To avoid the heavy computation burden faced by the traditional recognition methods, a fast ladar target recognition method is proposed. Adopting the coarse-to-fine strategy, the models are quickly pre-screened by using the proposed orthogonal projection contour features (PCF). Then the target is registered with the hypothesis models precisely by using the iterative closest point (ICP) method. Finally, the similarities between the target and models are calculated by integrating the features matching and points matching results. Therefore, the target is recognized to the model who owes the highest similarity. The experiments are performed using the point-clouds of 25 ground targets under 96 different viewing angles. The results show that the proposed method outperforms the existing methods greatly in the term of computation efficiency, and it is very robust to orientation error and occlusion. Thus, this method is the state-of-the-art and have a high application potential.

Different ideas exist on arc stability mechanism of laser-arc hybrid welding process. With high-speed camera and spectrometer, contrast analysis and research are made between method active gas (MAG) arc welding and hybrid arc welding in this paper. The results show that hybrid arc takes on a new shape and has two electric conduction paths independently. This phenomenon is called "double electric conduction mechanism" of the laser-pulse MAG hybrid welding process. This mechanism plays a very important role in maintaining arc stability and getting good appearance of weld during high speed welding process. It is also shown that the establishment of double electric conduction channel exists time sequence. The additional electric conduction channel ignites originally from the laser keyhole and then extends gradually to the whole space of the arc. Welding parameters, including distance between laser and wire, arc voltage and welding speed, have obvious influence on the double electric conduction mechanism.

A wear resistant hard particles reinforced intermetallic composite coating is fabricated on TA15 titanium alloy by the laser cladding process using 54.51Ti-37.68Ni-7.81B4C powder blends as the precursor materials. Microstructure and worn surface morphologies of the coating are characterized by optical microscopy (OM), scan electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). Wear resistance of the coating is evaluated under abrasive wear condition. Results indicate the hard particles including additional B4C and in situ synthesized titanium boride and titanium carbide are uniformly distributed in the TiNi/Ti2Ni dual-phase intermetallic matrix. The coating has high hardness and exhibits excellent wear resistance. The mainly wear mechanism of laser clad coating is slight micro-cutting and plastic deformation.

The thick nanostructured Al2O3-13%TiO2(mass fraction) ceramic coating is prepared by squash presetting type laser multi-layer cladding. The microstructure and bonding strength of coating are investigated, and the effect of coating thickness on bonding strength is analyzed. The results show that the laser-clad ceramic coating has no obvious interface between the layers but dense, continuous structure, and there is almost no pore and large penetrating crack. The coating is composed of fully melted regions (fine equiaxed grains) and partially melted regions (remained nanoparticles). In addition, most cracks in the coating are concentrated on the partially melted region. Due to multiple heating by laser beam, the grain size of lower layer is bigger than that of upper layer. The bonding strength of coating decreases with the increase of coating thickness, and the trend is fast at first and then slow. The bonding strength of coating with a thickness of 175 μm is beyond 78.6 MPa, while those of 350, 525, 700 μm thickness coatings are 66.3, 47.4, 36.2 MPa, respectively.

Directionally rapid solidified Ni-base superalloy DZ408 with ultra-fine columnar grain structure is produced by the laser melting deposition (LMD) manufacturing process. Microstructure and mechanical properties of the laser melting deposited DZ408 before and after heat treatment are analyzed and tested. Results show that as-deposited microstructure is directionally solidified dendrites with the primary dendrite arm spacing of approximately 26 μm and the secondary dendrite arm spacing of approximately 8 μm . The size of γ′ in the interdendritic zones is larger than that in the dendritic cores. The undirectional columnar layer and interdendritic shrinkage should be sufficient remelted to ensure the densification and epitaxy between the depositing layer and the previous one. After proper heat treatment, the room temperature tensile strength of the DZ408 superalloy is 1507 MPa, while the elongation along the deposition direction is 14.5%.

To repair the titanium alloy impeller for airplane starter, laser melting deposited Ti-6Al-3.5Mo-1.8Zr-0.23Si(TC11) titanium alloys, as well as the microstructure and properties of the interface, are investigated. The results indicate that the deposited TC11 titanium alloys and the interfacial re-melted layer present a typical Widmansttten structure and the heat affected zone (HAZ) within the substrate changes gradually from Widmansttten to duplex microstructure. Compared to the interface transition zone and the substrate, the as-deposited TC11 alloy possesses higher tensile strength and lower ductility. The damaged impeller blades are repaired by laser melting deposition in a point-by-point way. After machining and checking, the repaired impeller passes the over speed test and comes into real use.

NiCoCrAl-Y2O3 and Al2O3-13% TiO2 (mass fraction) coatings, formed with means of laser cladding on nickel-based alloy, are heated using high frequency induction sources. The coating and the cross-section are analysed by SEM, XRD, and EDS respectively. The results show that, MCrAlY/Al2O3-13% TiO2 ceramic coating has an excellent chemical combination due to elements obvious diffused in the interface. It is found that Al2O3-rich submicron particles embedded in the TiO2-rich matrix, three-dimensional net structure formed in ceramic coating, which could decrease inner stress between different materials. Meanwhile, thermal shock experiment of samples is tested which shows that Al2O3-13% TiO2 ceramic coating have excellent high temperature property.

Fiber of optical lens and color industrial video camera are used to capture image of cutting point in laser cutting process. Blue channel, green channel and red channel images are adopted to analyze cutting point geometry shape from color image. The position of laser beam focal point is used as origin of coordinates and the coordinate system is set up. The x axis is original direction and interval is 45 degree, the edge points of laser cutting region are searched from eight directions. According to distances from origin of coordinates to edge points, the laser cutting direction and cutting peak are fixed. Parabola model is set up, and the objective function is designed according to gray feature, gradient feature and direction feature, and the objective function is used to identify edge at bilateral cutting peak, and then cutting point geometry shape is identified. Test shows that the method has preferable adaptability, accuracy and real-time quality.

For the conduction cooled end-pumped zig-zag slab module, a novel 10 kW high power laser amplifier setup of the all-solid slab laser has been designed. The laser extractive efficiency of the amplifier with various laser power densities and various incidence angles is simulated with a laser amplifier model. The optical-optical conversion efficiency of the laser amplifier is measured in the experiment. The experimental result agrees well with the simulation. A seed laser is amplified in a pre-amplifier stage and two amplifier stages all-solid-state amplifier system with high power and high beam quality to a output power of 11.3 kW, with the beam quality 7.56 times diffraction limit and the runtime over 110 seconds. The optics-optics conversion efficiency is 30%.

The dynamic response characteristics of super-Gaussian pulse to reverse saturable absorption (RSA) effect are studied theoretically based on a couple model of nonlinear propagation and rate equations. The spatiotemporal evolution of laser intensity in RSA material and the dynamics of the interplay between the pulse and the carrier are investigated. Effects of the variation of excited-state lifetime are discussed and material parameters are optimized to avoid spatiotemporal distortion. The calculation supports guidelines for design of new RSA materials in spatiotemporal shape sensitive applications.

The effect of cost function on phase-locked based on dithering technique is studied. The cost function is often obtained by collecting the energy in a pinhole, and the diameter of the pinhole has a strong effect on the sign and value of the cost function. The effects of the fill factor of laser array, the number of laser beam, the radius of the light spot and wavelength on the best cost function are analysed in detail. It is found that the fill factor of laser array and the number of laser beams have a little effect on the best diameter of the pinhole for positive cost function which is located on 0.7~0.8 of the width of the main lobe of far field pattern. The radius of the light spot and wavelength have no effect on the best diameter of the pinhole. The best diameter of the pinhole for negative cost function will increase along with the number of laser beams increasing, but the fill factor of laser array has no effect on it.

In the investigation of gas laser pumped by electric discharge, the stability of laser output energy in repetition rate mode is the foundation of increasing its output average power and its application in practice. By adjusting the velocity of gas flow and optimizing the operating condition of laser, the output energy stability of laser in repetition rate mode is studied experimentally with joule level discharged-pumped pulsed HF laser, and the optimal operating condition of laser is obtained. The experimental results show that laser output energy decreases quickly with the repetition rate increasing; and increasing gas circulating velocity is beneficial to improve the discharge stability and the stability of laser output energy in repetition rate mode. When the gas mixture circulates at 3.5 m/s flowing velocity, laser can operate at repetition rate from 1 Hz to 50 Hz and operating stability keeps well. Under these conditions, each laser pulse of 130 mJ is obtained stably, and the fluctuation of output energy is about 5%.

A phosphosilicate Raman fiber laser (RFL) with Fabry-Perot cavity consisting of a pair of wide-band fiber loop mirrors (FLM) is proposed. A narrow-band fiber Bragg gratings (FBG) is used as a highly-reflective mirror in the same experimental configuration. The results show that the adoption of phosphosilicate RFL with FLM as a highly-reflective mirror instead of FBG can obtain laser output with narrow bandwidth and decrease the optical leakage from the highly-reflective mirror effectively. With the same output mirror, the laser using FLM as its highly-reflective mirror demonstrates a lower threshold and higher conversion efficiency than the one using FBG as the highly-reflective mirror. The output power of the laser at 1.24 μm is up to 4.31 W while the incident pump power is 9.45 W, the slope efficiency is 57.9% and optical-optical conversion efficiency is 45.6%.

Laser gyro is an angle sensitive device. In order to overcome the lock-in phenomenon, a sine wave mechanical dither bias is introduced. In order to eliminate the error accumulation in the lock-in traverse moment, random noise is often injected into the dither driving signal. Until now, there is no good rule to select a suitable noise form, and long performance measurement must be carried out to evaluate the effect of noise injection. A new method is proposed, which can evaluate the effectiveness of noise injection in very short time. Results of experiments show that this method is very effective and can be used to select a good noise type.

A stretched-pulse mode-locked fiber laser which can generate giant-chirp is reported. The nonlinear polarization (NPR) is applied to start the mode-locking. The laser consists of long single mode fiber (SMF) providing large normal dispersion, and grating pairs are utilized for compensation. The mode-locking laser operates at the normal-dispersion region, generates giant-chirp pulses of 2.17 ps and pulse energy of 1.81 nJ at a repetition rate of 36.96 MHz. The giant-chirp pulses are dechirped to a pulse duration of 70 fs. A more than 80 dB signal-to-noise ratio (SNR) for fundamental harmonic of the pulse train is observed in radio frequency analyzer. This kind of giant-linear chirp mode-locking laser is very suitable for chirp pulse amplification (CPA) system.

The SiNx/Si/SiNx multi-layer film is prepared by radio-frequency magnetron sputtering and thermal annealing. The average grain size of nanocrystalline silicon, the optical band-gap and the nonlinear absorption coefficient at 1064 nm laser are characterized and estimated. The rate-equation theoretical model of the dual-wavelength laser passively Q-switched by SiNx/Si/SiNx multi-layer film is established and the dynamics of the dual-wavelength pulse formation is numerically calculated. Simultaneous dual-wavelength passive Q-switching is realized in a laser diode (LD) end-pumped three-mirror compound resonator Nd:YVO4 laser using SiNx/Si/SiNx film as the saturable absorber. Both 1064 nm pulse with 20 ns duration and 1342 nm pulse with 19 ns duration are obtained. The results show that dual-wavelength passive Q-switching mainly results from two-photon saturable absorptions for 1064 nm and 1342 nm lasers, and that the difference of output losses between the two overlapping collinear cavities and the relative nonlinear absorption coefficients for dual-wavelength lasers influence the pulse durations and time separation of dual-wavelength pulses.

A design passively Q-switched Nd:YAG microchip laser based on graphene saturable absorber is presented. A thin layer of graphene is sandwiched between the Nd:YAG crystal and YAG crystal closely, and dichroic coatings on crystals is used as reflective mirrors for the plane parallel resonator. The Nd:YAG crystal is end pumped by a fiber-coupled laser diode via a lens imaging system. Employing graphene as saturable absorber, Q-switched Nd:YAG microchip laser is realized at the pump power threshold of 1.17 W with laser central wavelength of 1064.6 nm. The minimum pulse duration is 75 ns at 488 kHz and the repetition rate is tunable from 300 to 807 kHz with the increase of the pump power. The maximum output power and highest pulse energy of the laser measured are 38.4 mW and 54.7 nJ respectively.

The application of high power diode lasers is severely limited by their poor beam quality. In order to meet the increasing demands for industrial and defense applications, it is important to develop diode laser sources with both high power and high beam quality. The technology of linear array coupling is applied to multiplex twenty passively cooled diode lasers. 45°tilted cylindrical lens arrays and collimators are recommended to make the beam sizes and divergences of fast and slow axes equal, respectively. Wavelength coupling and polarization coupling finally are followed. A dual-wavelength 808 nm and 870 nm diode laser coupling source is successfully developed, with continuous output power of 1030 W, beam parameter products of fast and slow axes of 18.3 mm·mrad and 17.7 mm·mrad, respectively, and maximum electro-optical conversion efficiency up to 44%. High efficiency, high power and high beam quality laser output is achieved. It can be used as direct source in industrial and defense areas.

Organic dyes such as vanadium (IV) oxo(phthalocyaninato) (VOPc) nanoparticles have been fabricated by pulse laser ablation in aqueous solution. Under the condition of the same total incident light energy, the average diameter of VOPc nanoparticles, observed by an atomic force microscopy (AFM), increases with the pulse laser energy density. The ultraviolet-visible light (UV-Vis) absorption spectrum of VOPc nanoparticles colloid solution indicates that there is no more contribution for producing nanoparticles by so longer laser irradiation time. The nanoparticles reaggregation directly influences the preparation efficiency and the size of the produced nanoparticles, and finally it will achieve dynamic equilibrium with the process of producing nanoparticles. In aqueous solution the hydrophobic force is the main reason for the nanoparticles reaggregation.

Using the oxyfluoride silicate glass ceramics co-doped Er3+/Yb3+ ions, this paper tested fluorescence spectroscopy, absorption spectroscopy. The up-conversion luminescence properties of the Er3+ ion in the oxyfluoride glass-ceramics were studied, with analysis on the spectra of samples with Judd-Ofelt theory, and the intensity parameters are obtained, Ω2=4.4756, Ω4=1.0059, Ω6=1.2098. Radiative lifetimes of samples, transition probabilities, and fluorescence branching ratio spectral parameters are concluded. The results show that the samples formed fluoride microcrystal by heat treatment, which lower phonon energy and greatly improve the up-conversion efficiency. The infrared to green or to red up conversion luminescence intensities for the glass-ceramics are evaluated to be nearly 2 to 3 times as high as that of aluminosilicate glasses. Judd-Ofelt theory show that theoxyfluoride glass-ceramics co-doped Er3+/Yb3+ ions have high up-conversion efficiency, and it is one of fine materials for the production of micro-laser and three-dimensional display.

A new method of the reconstruction of focal spot and far-field focal spot measurement based on the diffraction grating is proposed, the validity of new method in expanding the measurement dynamic range and extracting the focal spot side lobe data is analyzed and the application condition is given in theory. According to the far-field spot measurement system available in laboratory and 1-D linear diffraction grating designed, power in the bucket (PIB) curve is taken as the measure of the validity of new method, the applicability of this new method is investigated by numerical simulation and experiment, in which the influence of the choice of the threshold on the results is discussed from the view of accurately calculating focal spot quality. The results are discussed and analyzed.

As the main transportation facilities, such as petroleum, natural gas, city water, and among others, the pipeline has been concerned extensively for its safety in operation. Meanwhile, to find and locate the positions of the persistent small-scale leakage of the pipeline is one of the major issues and difficulties faced by the safe operation of the pipeline. When Sagnac fiber interferometer is in the use of monitoring and positioning of a small leak on pipeline, the interference result of the two coherent laser beams in Sagnac ring will be affected by the random change of light polarization, thereby affecting the interferometer performance of linear Sagnac fiber optic interferometer. A new method is proposed to suppress the influence of random change of polarization on Sagnac interferometer. By modifying the structure of interferometer, an optical depolarizer is introduced into the Sagnac ring to improve the operational stability. Experimental results show that this method is a good solution to solve the deterioration of sensitivity caused by polarization fading.

A novel method is proposed from the perspective of restructuring the image patterns to be modulated to restrain the spectrum overlap. Three sinusoidal gratings with equal phase shift in traditional orthogonal composite grating based phase measurement profilometry (OCGPMP) are replaced by two sinusoidal gratings having π/2 phase shift and a uniform flat image. Moreover, set the spectrum modulated by the flat image between the spectra modulated by two of the sinusoidal gratings. For the flat image, carrier is only modulated by the direct current component. Therefore the spectrum overlap between the adjacent carrier channels is smaller than the traditional OCGPMP. Simulation and experiment results prove the new method can effectively restrain the effect of spectrum overlap, and improve the measurement accuracy more than 1.74 times.

Traditional laser range finder based on two-step frequency mixing has a poor phase measuring accuracy and it is difficult to eliminate systematic errors. A novel quadrature modulation method to achieve amplitude modulation of laser intensity is proposed. This method improves the accuracy of phase measuring and greatly simplifies the hardware design of laser range finder based on two-step frequency mixing. Design features of the prototype have been expounded in detail. A highly integrated quadrature modulator chip is used in prototype design, making the whole system compact and with no redundant components. The measured accuracy approaches ±1.52 mm when the modulation frequency is 62.5 MHz and the dynamic range can be improved by multimodulated frequency method as revealed by a detailed analysis.

It is difficult to calculate the content of a large storage yard by volume and density, which causes low precision and long period of data acquisition and disunity among measurement and calculation. A integration technology to achieve the 3D coordinate data by applying high-speed laser scanner, distance sensor, angle sensor and pitch sensor is proposed. Then a unified algorithm of 3D coordinates is deduced and 3D coordinate system of yard space is established to calculate the volume of material storage accurately. The system architecture, components, data processing methods and issues to be considered are also proposed, which can solve the measurement problem in a large material storage and improve the efficiency, accuracy and safety. In the experimental conditions, the absolute accuracy is less than 0.4%. Several projects show the simplicity, efficiency and accuracy of the proposed method. Measuring time less than 20 min for normal yard about 200 m once and the repeated error is less than 0.7%, which has good prospects and application worthy.

The quality of laser spot is studied in order to improve the precision of distance and thickness measurement system based on laser diode-position sensitive device (LD-PSD) laser triangulation. Static distance measuring experiments with different powers of laser diodes are conducted. The experimental results show that drift of the center of spot intensity increases measurement errors of the system in long-term continual work. The drift is mainly caused by high-frequency noise and spot displacement. For these two factors, an optical system based on the pinhole filter and beam splitter with prisms to improve the quality of laser spot is proposed, which is optimized and simulated by CODEV. Static distance measuring experiments are conducted again after adding the designed optical system to the rangefinder. The new experimental results prove that the precision of the system is improved from 25 μm to 8 μm. The design improves the practicability of laser triangulation measurement system for distance and thickness measuring in long-term continual work based on PSD.

A measurement system has been developed for organic and elemental carbonaceous based on the thermal-optical method. The factors are analyzed which interfered the split of the organic carbon from the elemental carbon. The laser intensity correction is used to compensate the laser intensity′s fluctuation induced by the temperature′s severe changes during the thermal analysis. The radiative transfer model of transmittance and reflectance through the filter is developed, and the measurement theories of the thermal-optical transmittance and reflectance are described. The influence of different optical correction methods to the organic carbon and elemental carbon measurement results are discussed.

For the requirements of cantilever vibration characteristics, a vibration system extra points measurement method based on self-mixing interference is purposed. This method is relatively simple, effective, and low cost compared to traditional measurement methods. Starting from the Lang-Kobayashi rate equation, vibration system extra points model is deduced and Monte Carlo random simulation method is used to simplify and correct the half-cycle extreme points formulcs. The order of the cantilever vibration natural frequency is 10 and amplitudes of the characteristic parameters are A10=B10=5.4601×10-13 in the case of free vibration.

The refractive index sensor with single mode-multimode-single (SMS) mode structure based on multimode interference effect usually needs cladding corrosion to improve the sensitivity, and it is vulnerable to the influence of temperature. To solve these problems, a novel fiber refractometer based on fiber core diameter mismatch multimode interference is proposed. The refractometer structured of single-mode fiber/dispersion compensation fiber/single-mode fiber (SMF-DCF-SMF) and a fiber Bragg grating (FBG) has a total length less than 100 mm. The experiment results show that the sensitivity of the sensor in measuring liquid with a refractive index of 1.33~1.39 is 232.8 nm, and the FBG has a good function of temperature calibration.

A high symmetry of the mode field distribution and high birefringent photonic crystal fiber (PCF) is presented, with uniform size of ellipse air holes arranging like diamond. A full-vector finite element method is used to simulate the fundamental mode field distribution, effective mode area, birefringence and dispersion. Circle air-holes PCF with the same parameters are also computed to compare with it. Both of the fibers have high symmetry mode field and nearly circular, which makes it couple with other fibers in optical devices easily. It achieves high birefringence of elliptical air-holes PCF up to 10-3.

A novel scheme of optical frequency up-conversion is proposed by using the high order sideband of the directly modulated low-speed baseband signal for injection locking of a distributed feedback semiconductor laser (DFB-LD). The operational principle of the proposed optical frequency up-conversion scheme is theoretically analyzed. Based on this scheme, optical frequency up-conversion of a 2.5 Gb/s is directly modulated baseband signal to 30, 35 and 40 GHz subcarrier modulation signal respectively. Higher carrier frequency (up to 60 GHz) can also be achieved in potential. The proposed scheme does not need expensive components like high-speed external modulator or high frequency radio frequency (RF) local oscillator, and it has the benefit of simple structure. It provides a viable solution for the optical-wireless hybrid access.

The grapefruit photonic crystal fiber is simulated using finite element method (FEM). The effective refractive index and field distribution of each mode are calculated. Based on the coupled mode theory and correlation function mode-solver, the transmission spectrum of fiber Bragg gratings in grapefruit photonic crystal fibers is studied and the result explains the reason of multiple peaks. The influence of the structure change of the fiber core diameter and air hole size on the transmission spectrum is simulated. The results show that the resonance wavelength would shift to the longer wavelength with the increase of the diameter of the fiber core. The resonance wavelength would shift to the shorter wavelength with the increase of the size of the air holes, and the change is different for each resonant pattern. The fabrication of Bragg grating in a photonic crystal fiber is investigated experimentally by phase mask method. Experimental data are consistent with simulation numerical results.

Optical fiber current sensors based on Faraday effect have a lot of advantages over conventional current sensors and have been studied extensively. The structure of Sagnac optical current sensors are developed on the structure of interferometric fiber-optic gyroscope. The external vibration is one of the most important limitations of Sagnac optical current sensors. To eliminate the effect of vibration, a new scheme is given out. The basic principle of the scheme is that there is an extra closed loop to compensate the vibration effect received by the sensing head. Then the polarization states of the lights spreading in the new scheme are analyzed with Jones matrix. The theoretical analysis and the result of the experiment both show that the novel structure of the optical current sensor could completely eliminate the vibration effect in the environment. It is useful to the high accuracy of Sagnac optical current sensor.

Tiled grating is one of effective the ways to solve the problem of grating aperture limit and the difficulties of tiled grating are the adjustment of sub-aperture grating and stability. Two classes of macro and micro drive modes are adopted to achieve the precision adjustment of sub-aperture gratings. A new tiled grating frame is designed to increase the stability of tiled grating frame. In the tiled grating frame, an integrated support structure is adopted to increase the natural frequency of the tiled grating, and flexible hinges are adopted instead of springs to increase the joint stiffness between the sub-aperture grating and the support frame. The experiment indicates that the tiled grating can keep in stability for more than one hour and the relative displacement standard deviation is 35.7 nm between sub-aperture gratings, which can satisfy the design requirement.

In order to overcome the shortcoming of small and untunable shear difference in the existing parallel splitting prisms, and expand the application scope of the parallel splitting prisms, a composite parallel splitting prism is made by one iceland crystal prism and two triangle glass prisms with adjustable distance. The composite prism has the following advantages: low cost, shear difference tunable in a large scale, excellent splitting ratio and total transmission ratio. The changes of tuning scale, the e light and o light splitting ratio and the total transmission ratio without antireflection film coating of the composite prism with the the change of structure parameters including the distance between the two glass prisms and the glass prism angles are analyzed theoretically. Computer simulation results are given too. Based on the results, an experimental sample is designed and fabricated. When the distance between two glass prisms changes from 15 mm to 180 mm, for the transmitted light via Iceland crystal prism with 3 mm shearing distance, the shearing distance can be tuned between 1.4~50.2 mm. And the splitting ratio of e light and o light is less than 1.1, the total transmission ratio is higher than 80%.

The effects of the experimental conditions (integration delay, laser energy and so on) on the strength of metal LIBS (laser-induced breakdown spectroscopy) spectra are investigated using a self-developed new liquid jet by LIBS. The plasma emission spectra of K2Cr2O7, Pb(NO3) and CdBr2 aqueous solutions at 532 nm laser excitation is obtained. And the characteristic spectral lines of toxic metals Cr, Pb and Cd are identified. It is found that the detection limits of Cr, Pb and Cd are respectively about 0.32, 15.6 and 57.6 mg/L. The results unfold the rapid detection capability of the liquid jet by LIBS on toixc metal in water.

The technology of the directly laser absorption spectroscopy for CO2 concentration measurement is described. A tunable diode laser near 2 μm is used as optical source. The multi-pass absorption technology combined with optical fiber transmission technique is improved for this method. Seventeen absorption lines of CO2 are observed and the corresponding spectral parameters (i.e. positions, the transition of absorption band) are presented. The absorption line of CO2 molecule near 2008 nm is recorded in different pressures, from which calibration factor of experimental system at low pressures is retrieved. A CO2 molecule concentration of (2.754±0.145)×1016 cm-3 in the sample gas is also achieved. The resulting accuracy in the retrieved values of gas concentration could be strongly limited by an accuracy of a vacuum gauge using in our measurements. It is proved that this spectral measurement method is an attractive tool for gas concentration monitoring application and isotope abundance analysis.

A new type monochromatic X-ray crystal spectrograph which can be used to catch the K-shell line images of the imploding aluminum wire arrays was developed. The core component of the spectrograph is the crystal analyzer which was designed to the shape of logarithmic spiral in meridian plane. By taking advantages of the logarithmic spiral, monochromatic X-ray image of Z-pinch plasma can be obtained with the imager system in large field of view. Experiments have been carried on the "Yang" accelerator. In experiment, the hydrogenlike line (1727.7 eV) and heliumlike line (1588.3 eV) images of the imploding Al wire arrays were obtained. The results showed that the spectrograph can reflect the exploding modality of Z-pinch Al plasma, and multi-hot spots due to magnetic Rayleigh-Taylor instability also appeared on the images.