Distributed reconfigurable satellite system is a new type of "modular" spacecraft architecture. Each module of the spacecraft can be manufactured and launched independently, and they form a whole by space laser energy transmission and data exchange. In order to study the key technologies of space laser energy transmission and improve the transmission efficiency, a ground verification experiment of the laser energy transmission system is designed. The key parameters like the output characteristics and conversion efficiency of GaAs cells to different wavelengths of laser are measured. The relationship between the laser intensity and transmission efficiency is analyzed. The experimental results show that with 793 nm laser for the transmission medium, GaAs cells′ laser to electric conversion efficiency is up to 48%, and that the whole electric-laser-electric transmission efficiency of system is 18%. The experiment verifies the feasibility of efficient laser energy transmission.

Based on the Gamma-Gamma distribution of the intensity fluctuation for light propagating in random media, the statistical properties of received photons of a lunar laser ranging (LLR) system are studied, in which an adaptive optics system is equipped to correct the effect of atmospheric turbulence. A completely statistical description, i.e., the probability density functions of the fluctuation of the received photons, is presented which takes into account most of optical processes. On this basis, a series of characteristic quantities of the received photons, including average value, fluctuation variance, cumulative probability function, and so on, are calculated in the general conditions of the atmospheric turbulence. With these characteristic quantities, a performance evaluation of the LLR adaptive-optics system is obtained quantitatively.

The enlargement of reconstructed image of computer generated hologram (CGH) display system based on phase-only special light modulator (SLM) can be realized by theoretical algorithm and experiment. Based on analysis of the theory of CGH, the method to enlarge the size of reconstructed picture by similarity principle of Fourier transform is proposed, and the adjustable reconstructed image size of CGH from frequency domain to space domain is achieved. It′s confirmed that the reconstructed image which is two to three times bigger than before can be displayed clearly by the experimental platform based on SLM. The suppression of zero-order bright spot is realized in some degree base on phase shift theory. The experimental results show that this theory can realize to enlarge the reconstructed image effectively, and get clear reconstructed image without the effect of zero-order bright spot under the help of phase shift theory.

There are significant differences between biological alumina ceramic and polymer in mechanical properties, chemical properties and thermal properties, so the performance differences set a challenge to achieve the high strength joint between them. A thin titanium film is deposited on the biological alumina ceramic, laser transimission joining experiments between Ti coated bio-ceramic and polyethylene terephthalate (PET) are conducted by using a near infrared continuous wave (CW) diode laser, which solves the connection problems of bio-ceramics and polymers. The joined samples are tested by lap-shear test to determine the joint strength, and examined by optical microscopy to obtain the joint morphology and joint width. The effects of the laser power and the scanning speed on joint strength and joint width in laser transmission joining process are also investigated. The parameters window for laser transmission joining process is obtained via the single factor process analysis, and a reasonable range of processing parameters is provided for laser transmission joining.

In order to investigate the effect of laser shock processing (LSP) on impact toughness of AZ31B magnesium alloy, AZ31B magnesium alloy samples are treated by using NdYAG laser with a wavelength of 1064 nm, a pulse width of 15 ns, a pulse energy of 10 J and a spot diameter of 3 mm. The surface layer structures of laser treated samples are analyzed by using transmission electron microscopy (TEM). Surface residual stress is assessed by using X-ray diffraction technology, the value of impact energy of samples are examined by an impact tester (Model JB-300B), and the fracture surface morphologies of charpy impacting samples are characterized by scanning electron microscopy (SEM). Test results show that a nanostructured surface layer can be fabricated on AZ31B magnesium alloy by using optimized laser parameters, and surface grain size is about 20 nm. The surface residual stress is converted from tensile stress (17 MPa) to compressive stress (-125 MPa) by LSP. The mean impact energy of samples is changed from 5.3833 J to 9.2333 J and increases by 71.5% after LSP. The impact toughness improvement of samples by LSP is attributed to a combination of surface nanocrystallization and residual compressive stress.

Continuous wave (CW) Nd:YAG laser beam bead-on-plate welding of Fe-Ni (36%, mass fraction) alloy is carried out. The morphology of the cross section is analyzed by optical microscope. The influence of welding parameters (laser power, scanning speed, defocusing amount, welding angle and heat input) on the morphology of the cross section is studied. The results indicate that large negative focusing position will weaken the weldments, consequently, is of disadvantage to self-fusible welding. And the increase of laser power is more helpful to improve welding penetration than slowing down welding speed when the focusing position is fixed. The influence of the relationship between laser power and welding speed should be considered when heat input (laser power/welding speed) is used to characterize the morphology of the weld.

A study on transmission laser bonding of silicon with glass by NdYAG pulse laser is conducted. The mechanism of transmission laser bonding of silicon with glass is expounded. Combined with a central composite rotatable experimental design, response surface methodology (RSM) is employed to establish mathematical models of relationships among various welding process parameters and lap-shear strength as well as bond width. Then the analysis of variance is checked and these mathematical models are validated. Effects of different bonding parameters on lap-shear strength and bond width are discussed. Based on this, desirability function is introduced to optimize the parameters of the bonding process and the result of optimal experiments is verified. The results obtained indicate that the developed mathematical models can be used to show the relationship between responses and parameters. Predicted results of parameters optimization developed by desirability function are consistent with experimental results. Therefore, this study provides an effective direction to enhance the bond quality and minimize the bond cost.

Single layer and multilayer Zr55Al10Ni5Cu30 bulk metallic glasses are deposited on the commercial pure zirconium substrates by laser solid forming (LSF). The composition and microstructure of the deposits are researched. The results show that the deposits are mainly constituted by amorphous materials. The crystallization degree does not increase remarkably with the increase of deposited layers. The crystallization mainly occurs in the overlapping zone between the adjacent traces and layers of the heat affected zone (HAZ), especially the adjacent layers. The bonding type between deposit and substrate is metallurgy bonding. There is epitaxial growth of dendrites emerging at the thin transition zone which is only 35 μm, the composition dilution mainly occurs in this transition zone.

Laser surface melting is carried out using a pulsed NdYAG laser on specimens made of CL60 steel, after that the rolling wear properties of specimens are studied using a MM-P2 rolling friction and wear test machine. The surface topography of the specimens before and after the rolling wear test is measured by a micro XAM 3D surface topography instrument. Metallographic examinations of the specimens are taken out after the rolling wear test using metallographic microscope and scanning electron microscope. It turns out that the laser melted spots stand out during the experiments due to its higher hardness. The laser melted spots are not only reducing the plastic deformation themselves, but also hindering the plastic deformation of vicinity base material on the same circle. The laser melted spots can reduce the scraps peeling off from specimens and the rolling wear resistance is improved. Different distributions of laser melted spots can form different surface topographies after wear.

At present laser thermo-repairing for the defects on gray cast iron surface is becoming an important way of casting equipment cycle remanufacturing. A reliable numerical model for the repair process is established, where the heat source expression and boundary conditions are refined. Then the model is verified by experimental results to achieve higher precision. The calculation results show that the secondary repair is processed in a warm-up state. Compared to single repair, multilayer repair can provide more methods to control temperature cycle curve. In the material fused circulation on matrix surface, the materials are compressed at first and stretched then in length and width direction. Compression stress is given priority in the repair stage, and when materials in thickness direction are under alternating tensile-pressure stress cycle, tension is given priority. Stress becomes more focused in the U trough bottom than its sides.

The polished P-type single crystalline silicon wafer deposited with tellurium film is scanned by femtosecond laser. Tellurium is doped in silicon as N-type dopant. The doped layer is irradiated by 248 nm, 30 ns excimer laser for annealing. Single crystalline silicon doped with tellurium is prepared. Silicon photodiode detectors with high response at room temperature are fabricated using the doped single crystalline silicon. At -4 V reverse bias voltage, the response is 0.86 A/W near 1000 nm, and the external quantum efficiency is larger than 106.6%. By increasing the reverse bias voltage, the response increases, the cutoff wavelength extends to infrared direction. At -8 V reverse bias voltage, the cutoff wavelength extends to 1235 nm. The maximum response is 3.27 A/W at 1080 nm with -16 V reverse bias.

At present, Nd∶YAG laser feedback interferometer has been achieved. However, in the actual application some deficiencies still exist in this system. Basic parameters of Nd∶YAG microchip laser are measured and the instruction of the invisible light with the wavelength of 1064 nm is realized, with the improvement of the measurement range and the compensation of air refractive index, by combining red indicating device, collimating and beam expanding device and the refractive index of air compensating system with the original Nd∶YAG laser feedback interferometer. So Nd∶YAG laser feedback interferometer is more convenient to use with a broader application and higher accuracy.

A novel system of chaotic oscillation frequency enhancement and control of chaos in two spatial coupled semiconductor lasers due to optical feedback is presented. Characteristic of chaotic frequency enhancement and control of chaos in the lasers are studied and a static frequency detuning formula is given. For the case of single-laser feedback, chaotic enhancements are effectively achieved when the feedback is at high levels, in which, the strong feedback can result obviously in frequency enhancement in the dual-lasers while the frequency can be enlarged to 3.57 times of the intrinsic frequency of one laser and 2.86 times for the other. Chaos-control region is found in low feedback levels. In this region, dual-lasers can be conduced to single-cycle, dual-cycle and triple-cycle. The frequency can be enlarged to 3 times of the intrinsic frequency of one laser and 2.58 times for the other when the dual-lasers are with the feedback. Chaos-control region is also found in low feedback levels, and dual-lasers can be controlled to single-cycle, dual-cycle and triple-cycle. The developing path from single-cycle locking to quasi-cycle and then to chaotic frequency enhancement is put forward in detail when the single-feedback or the dual-feedback is present.

Er3+-doped silica microspheres with smooth surface are fabricated through surface tension induced by heating and fusing a single tapered silica fiber between two discharge electrodes. The tapered fiber is dipped with quantitative erbium nitrate solution. Single mode laser of 976 nm is coupled into microsphere through near-field coupling by evanescent wave from biconical tapered fiber, exciting high power density whispering gallery modes (WGM) in the microsphere. And downconversion emission spectrum of C+L band of optical communication is obtained, which is emitted from stimulated Er3+ distributing all over the surface of microsphere. Single-longitudinal-mode and multi-longitudinal-mode lasers are also measured at around 1555 nm and 1600 nm. The diameters of the microspheres tested in our experiment are between 70~150 μm, and the concentration of the erbium nitrate solution is about 10-5～10-4 mol/mL. The methods of microsphere fabrication and rare earth doping are simple and practicable for fast measurement of the luminescence of rare earth doped materials.

The line shape of power spectrum of frequency-modulated laser with delayed self-heterodyne method is presented. Theoretical analysis is carried out and a mathematical expression is used to describe the line shape. According to the theoretical results, the line shape of frequency-modulated laser measured by delayed self-heterodyne method is the convolution of the natural line shape and the transfer function related with the modulation signal and the testing system. The dependence of line shape on the modulation frequency and the length of optical delay is analyzed based on the obtained expression. Experiments are carried out and the testing results verify the theoretical analysis results.

The heat transfer characteristics of the spray cooling with ammonia are experimentally investigated on a smooth surface and two porous surfaces with different sintered grain sizes. It is found that porous surfaces significantly enhance the heat transfer as a result of wicking action of porous structure and potential active nucleation sites. In nucleate boiling region, with the decrease of sintered grain size, heat transfer of porous surfaces performs better; the maximum heat transfer coefficients of 100612 W/(m2·K) and 96464 W/(m2·K) are achieved with the heat flux of 367 W/cm2 at the flow rate of 0.0133 m3 /(m2·s) for the porous surfaces with sintered grain sizes of 28 μm and 49 μm. When the flow rate increases from 0.0133 m3/(m2·s) to 0.0181 m3/(m2·s), the appearance of critical heat flux (CHF) density is delayed and the heat transfer coefficient is increased by 47% to reach 147503 W/(m2·K) at the heat flux of 367 W/cm2.

Random distributed feedback fiber laser (RDF-FL) is a novel kind of light source based on distributed Rayleigh scattering and Raman amplification, which has characteristics such as simple structure, good directionality as well as long-distance transmission and shows a broad prospect in the application of optical fiber sensing and communications. However, the pump threshold is relative high just because of the weak Rayleigh scattering feedback. In this paper, two methods, half-opened cavity and ultra-long ring cavity structures, are used to reduce the threshold of the RDF-FL. On this basis, the input-output characteristics and frequency spectra of the RDF-FL are analyzed theoretically and experimentally. The results show that the first-order threshold of the RDF-FL can be reduced to 0.8 W and 1.0 W respectively. This research is helpful to further understanding the mechanism of RDF-FLs as well as the design of novel random fiber lasers.

A hybrid cascaded phosphosilicate fiber Raman laser (RFL) with output wavelength of 1270 nm is proposed. By using 1330 cm-1 and 197 cm-1 Raman shift of phosphosilicate fiber, the laser of 1064 nm is shifted to 1270 nm. Symmetric and asymmetric cavity structure are designed for the second-order Stokes Raman light. The comparative experimental results show that the asymmetric structure can reduce oscillation threshold, improve conversion efficiency and avoid the optical leakage from the cavity in the high reflection end effectively. The oscillation threshold of asymmetric phosphosilicate RFL is 3.70 W, the maximum total output power is 2.38 W with the pump power of 8.66 W, the conversion efficiency from 1064 nm to 1270 nm is 22%.

An intracavity continuous-wave singly resonant optical parametric oscillator (OPO) with wavelengths of 1.9 μm and 2.4 μm is demonstrated. The 1.9 μm and 2.4 μm dual-wavelength continuous lasers are obtained through intracavity pumping the MgO-doped periodically poled LiNbO3 (PPMgLN) and yttrium vanadate (NdYVO4) crystal with a single semiconductor laser diode (LD). 750 mW signal wave at 1.9 μm and 370 mW idler wave at 2.4 μm, are simultaneously obtained when the LD power is 5.5 W at room temperature. The corresponding conversion efficiencies are 13.6% and 6.7% respectively, so the whole efficiency is more than 20%. The output power instability is no more than 1.8% over a measurement period of 5 h. Additionally, the threshold characteristics and conversion efficiency of PPMgLN crystal with different lengths are analyzed. By output wavelength stability test, it is found that better control of the temperature of crystal can improve the phenomenon of wavelength drift.

Three power amplifier system is reported in which the Nd∶YVO4 crystal is pumped by laser diode (LD), in which 1064 nm picosecond laser output average power is more than 21 W. When the repetition frequency of 56 MHz, the average power of 3 W picosecond seed pulse is injected, a maximum power of 26 W is got by a three-stage power amplifier system with the optical conversion efficiency of 25%. The picosecond pulse duration is less than 17 ps, power instability in 1 h is less than 2%, and the light beam quality M2 is less than 1.5. A RbTiOPO4 (RTP) electro-optical switch is as a marking switch and the main-minor pulse ratio is up to 2101, which is suitable for the use of the marking machine.

To improve the signal-to-noise ratio and filter the useless signal, Ta2O5 and SiO2 are chosen as the film materials. Electron gun and ion-assisted deposition system are used for film preparation. The interference cut-off filter films which have specific transmittance at 589, 1064, 1178, 1342 nm are deposited. In the actual coating process, the refractive indexes of materials are not stable in different conditions. In addition, the monitoring method lead to the errors. Optimizing the parameters and designing the film system can effectively control film thickness monitoring accuracy. Therefore, the optical properties corresponding to the wavelengths are enhanced. The experimental results show that the filter film can withstand high temperature, wet and other environments, completely meeting the demands of yellow laser.

As a method of micro fabrication, laser induced forward transfer (LIFT) technology can be used to make microstructures. Presently, the fabrication process has become a popular issue in the field of micro-machining. A Cu thin film is transferred from one quartz substrate to another quartz substrate by regulating the pulse power density of Gaussian distributed laser beam. The transferred Cu thin film is characterized by optical microscopy, scanning electron microscopy (SEM), and X-ray photoelectron microscopy (XPS) analysis. The relationship between pulse power density of laser beam and size, special morphology and uniformity of transferred Cu film is discussed, and the oxidation condition of the transferred Cu film is also studied. Moreover, the mechanism of the transferred process is analyzed based on the results. It is found that the Cu film transfer process can be realized when the average pulse power density of laser beam reaches 1×105 W/cm2. With the increase of pulse power density of laser beam, the size of transferred Cu film is also enlarged, and reaches a certain value at last with the morphology transforming from plane to crater-shape. Almost no oxidation phenomenon is observed on the Cu when transferred Cu film is sputtered off 10 nm in thickness. The transferred film adheres well to the target substrate, and no obvious diffusion phenomenon is observed between Cu film and the target quartz substrate.

Fourier transform is used to analyze grazing incidence X-ray reflectivity curve of thin film. It is a powerful analysis method for the characterization of layer thickness, interface roughness, etc. In the Fourier transform analysis, the window function has a very important effect on the transform result. By analyzing the Fourier transform of rectangular window (FFT) and wavelet window Fourier transform (WFFT), it is found that WFFT can effectively suppress the appearance of interferential peak in the FFT auto-correlation function, which is very important for identifying true and false peaks and the adjacent peaks. In addition, the film thickness error varies in aperiodic oscillation with the increasing signal length, and this change is associated with the oscillation of reflectivity curve. The ability to distinguish layer thickness is better when intercepting the reflectivity curve near the valley of Bragg diffraction peak. Ni film and Si/Ti/Ni/Ti multilayer are characterized by FFT and WFFT, which verifies the above conclusions and provides a powerful analysis method for the characterization of unconventional multilayer structures.

ZnO nano-crystal film with uniform and dense distribution is prepared by radio frequency (RF) sputtering and hydrothermal method, and its luminescence under field-emission electron excitation is obtained with the help of carbon nanotube arrays cathode. The results show that under the excitation of electron beam, the spectrum of ZnO nano-crystal film has two emission peaks, in which the yellow or green peak is based on defect luminescence while the ultraviolet peak originates from intrinsic excitons of ZnO. With the increase of electron beam density, the luminescence intensity of ultraviolet peak increases rapidly. In addition, different from usual ZnO films, the ultraviolet peak of ZnO nano-crystal film spectrum exists red-shift, which reaches violet band.

Corneal contour measurement has significant meaning in ophthalmology, but it is difficult because of high transmittance of cornea. According to the characteristics of cornea and by taking advantage of non-diffracting grating structure light projection system, the contour of corneal surface coated with fluorescein is measured. A model of non-diffracting grating structure light projection system is proposed and experiment of corneal surface contour measurement is designed. A measurement platform is set to realize rabbit corneal contour measurement, and corneal deforming phenomenon caused by increasing intraocular pressure is observed. Experimental result shows that the corneal contour can be measured precisely by non-diffracting grating projection system. Feasibility of intraocular pressure measurement according to variation of corneal contour curvature is validated.

Based on the actual interferogram grabbed by a ZYGO interferometer, the phase is retrieved by two-dimensional fast Fourier transform (FFT) method and the factors which impact phase retrieval accuracy of FFT method including edge errors, window function, filter design, interferogram extrapolation and the number of carrier fringes are comprehensively analyzed, by comparing with the phase-shift measurement results. It is found that for the direct 2D FFT method, the edge 0.05R circular area of the interferogram has the biggest phase retrieval errors and decides the value of global errors. Window functions almost have no improvement for edge errors. Optimization of filter design can improve edge errors in some degree. Interferogram extrapolation can reduce edge errors effectively and it is the best way to enhance phase retrieval accuracy for continuous optical surface test. Accurate measurement results can be achieved when the frequency is 1/13~1/3 of the space resolution of the interferogram with peak-to-walley (PV) value of phase retrieval errors less than λ/20. The higher the carrier frequency is, the better the detail resolution is.

The laser displacement sensor which uses position sensitive detector (PSD) as position detector can realize the displacement measurement in small space, but the PSD is vulnerable to external environment. Therefore, there are lots of noises in the output signal which severely affect the accuracy of PSD position detection. For the purpose of effectively extracting the useful PSD position signal, this paper presents a wavelet threshold denoising technology to improve the accuracy of position detection of laser displacement sensor based on PSD. Based on the discrete wavelet transform, the original signal of the PSD can be decomposed into multiple scales and then be reconstructed with quantified wavelet coefficients which contain the noise by soft thresholding function. The result of wavelet denoising is evaluated by the experiments such as using different kinds of base wavelet, changing the decomposition scale and considering different amounts of signal samples. The experimental results indicate that, by selecting the appropriate combination algorithm of wavelet denoising, the denoised signal can maintain the mean value of the original signal and the standard deviation can be minimized to 2 μm or below, which significantly improves the position detection accuracy of the sensor and shorten the measurement period.

Instead of using the traditional detectors made of a series of concentric annular rings with a small aperture in the center, a high sensitivity, low noise, high resolution and cooled CCD is employed to detect the scattering pattern. An optical fiber is placed in the focal point of the receiver lens to make the transmitted light away from the optical axis. The image of scattering pattern recorded by CCD can be processed to get the curves of light intensity distribution with the scattering angle. Further, the particle size distribution can be calculated by Mie scattering code with inversion technique. It is possible to measure very diluted dispersions or fogs with CCD based low angle elastic light scattering measurement system due to its high sensitivity, high angular resolution. Although low angle elastic light scattering seems a more accurate method for its measurement principle, it is not an intuitive method. Normally the accuracy of laser particle sizing is verified by standard particles which are measured by other optical methods. A non-optical method is suggested. A mono-disperse droplet generator is used to produce a chain of droplets with same size, same droplet spacing to verify the laser scattering droplet sizing results.

Laser ranging is a kind of high precise measuring technology for spacecraft orbit determination. The traditional laser ranging is to measure the roundtrip flight time of laser pulse to collect precise measurement of range that allows the spacecraft to achieve its requirement for precise orbit determination. For the long distance spacecrafts farther than the moon, the above measuring way is not suitable and the one-way range measurement via laser pulse time-of-flight from ground stations to spacecrafts should be utilized. For this measuring mode, the laser signal energy falls off only as square of distance and the laser signal can reach the place beyond the moon to the planets. The one way laser measurement will become a significant way for interplanetary laser ranging. By using the ground satellite laser ranging system, laser measuring experiments to geosynchronous satellite equipping laser detector and timing counter are successfully implemented. The comparison and analysis for laser data obtained from both the one way and the roundtrip flight measurements are carried out. The measuring results validate the feasibility of one way laser ranging. The measuring experiments provides reference for further study on the one-way laser ranging and design of laser measuring terminal system for interplanetary spacecraft in future.

In stimulated scattering energy signal detection of inertial confinement fusion (ICF), background noise has a serious impact on the extraction of useful information. Aiming at this issue, a new variable parameters amplification and filtering circuit (VPAFC) is designed, and a denoising method based on denoising source separation (DSS) is proposed. By using variable gain amplifier, bandwidth-adjustable filter and signal noise reduction software, the whole system can not only adapt to the amplitude change of signal in weak signal detection, but also restrain the noise both outside useful signal band and structural interference inside. In order to test the new circuit and the efficiency of the algorithm, a system with weak scattering light energy signal detection device and data acquisition is constructed. Experimental result shows that the system can fit the amplitude change quickly by adjusting parameters online, and its output can keep a signal-to-noise ratio above 40 dB when the input voltage drops to 2 μV.

A method for fiber fault location with distance measurement and visual fault search is presented. Broadband red chaotic signal, generated by utilizing the optical feedback of a red diode laser, is used as the signal light. Distance measurement between initial point and fiber fault is obtained by correlation between reference and back reflected signal waveform. Further visible search is realized by the dazzling spot at fault position owing to the leakage of signal light exactly. Experimental results demonstrate that the proposed method can realize the locations of single and multiple fiber faults, and the fiber fault at about 500 m is measured with a resolution of 3.9 cm, which is independent of the range of the fault position.

Machine-ruling method is one of the important methods for making plane grating. In order to improve the grating′s performance and application level, it is particularly important to analysis the influence of ruling line′s equal-distance curve and location error on plane grating performance, such as resolution, scattered light, etc. According to Fermat principle, a light-tracing mathematical model that simulates collimated monochromatic light incident on a plane grating which contains line′s curved error, and location error and corresponding diffraction light imaged on the focal plane is established. The influence of above-mentioned grating line errors on grating performance is studied. Results show that grating line′s curve and location error mainly influence grating sagittal and meridional spectral performance, separately, line′s curved error has little effect on grating resolving power and scattered light. According to the analysis above, the ruling system of grating ruling machine is improved. Statistical average value of grating line′s location error caused by modified ruling system is reduced to less than half of the original amplitude. Thereby grating scattered light is effectively suppressed.

From the angle of the transmission spectrum of long period fiber grating (LPFG) and the wavelength interrogation technology for fiber Bragg gratings (FBGs), the edged filter characteristic of LPFGs is studied. A double-edged filter wavelength interrogation technology for FBGs is proposed. The theoretical model is deduced and the experiments of temperature and vibration signal monitoring are verified. The demodulation system, which is repeatedly tested under the excitation frequency of 580, 1000 Hz and 2500 Hz, respectively, shows broad dynamic frequency band of 3 kHz, fast response time and high accuracy, with the extensive application prospects.

A large-angle polarization-independent broadband guided-mode-resonant filter is proposed based on two-dimensional honey-comb silicon photonic crystal slab with ultralow refractive-index substrate material like polymethy lmethacry late (PMMA). The broadband operating range is determined firstly based on the dispersion relationship and rigorous coupled wave analysis (RCWA). Then the impact of silicon membrane thickness and air hole size on the performance of proposed device under surface normal incidence is investigated and an optimal set of physical parameters for 1.55 μm communication window is obtained correspondingly. Its performance affected by oblique incidence and polarization is also analyzed. It shows that broad bandwidth over 110 nm can be obtained with greater than 98% normalized transmittance under surface normal incidence. The common bandwidth of two polarizations will reduce with the increase of incident angle. But it can still cover the whole C-band window (from 1525 nm to 1560 nm) with over 98% normalized transmittance when the angle reaches 18°.

A high speed and high reliable underwater optical communication transceiver system based on digital signal processor (DSP) is proposed, and the modulation timing sequence and signal processing procedure is analyzed. In the transmitter, the DSP accomplishes Reed-Solomon codes encoding of the information need to be sent and filtering, threshold decision, the decoding and demodulation of the received information. The field-programmable gate array (FPGA) accomplishes the modulation of the information encoded in the DSP. Under the condition that the pulse width after underwater propagation is less than 100 ns and the frequency deviation from the mean is less than 15%, the dependence of the pulse position modulation (PPM) modulation rate on the chosen Galois field is discussed and the signal processing speed as well as the interfaces communication speed are analyzed. The analytical results show that the designed transmitter system can accomplish full-duplex and real time communication with a speed as high as 73 kbit/s, which can be used for real-time communication of multi-media information, such as voice and images. The pulse shape of laser after a propagation of 100 m in case Ⅱ water is simulated through Matlab as well as the timing sequence of a frame of data transmitted through FPGA and sampled sequence of a frame of data obtained through analog-to-digital converter (ADC). The structure of the designed transceiver provides a certain reference to the design and accomplishment of underwater optical communication system in the future.

A method of spontaneous synchronization based on a continuous variable quantum key distribution (CV-QKD) system is proposed. This method can effectively overcome the disturbance effects which are generated by the environment in the transmission process of continuous variable quantum. The scheme realizes the synchronization between the sending terminal and the receiving tevminal. The mechanism of this synchronization scheme is introduced theoretically, and then the feasibility of this synchronization scheme is verified based on a continuous variable quantum key distribution system. Based on the experimental data, the key performance indicators for this synchronization scheme such as required time and successful probability are analyzed.

A high sensitivity of surface-plasmon-resonance(SPR) fiber optic sensor based on the wavelength modulation with tapered probe is studied theoretically and fabricated. The influence of different taper ratios (TRs) on the sensitivity and accuracy of the sensor is analyzed. It shows that with the increase of the TR, the sensitivity increases and the accuracy reduces. Considering the two indicators, the sensor has a good performance when TR is between 1.2~1.8. Based on the theoretical simulation result, the tapered probe is fabricated and the experimental system is set up. The experimental results show that the sensitivity of the sensor is 3.94 μm/RIU, which is well consistent with the result of theoretical simulation (3.90 μm/RIU).

For further investigating the fiber laser mode control, the bending properties of large mode area fibers need to be studied. Begining with the Helmholtz equation, by comparing the field distributions of straight fiber and bent fiber modes, the mode evolution ways between straight and curved large mode area fibers transition are determined. Based on mode superposition and excitation theory, the mode coupling efficiency formula about straight and bent fiber transition is derived. With the help of coupling formula and finite element method, the mode coupling efficiencies of a step-index large mode area fiber in straight and curved state transition are calculated. The results show that self-coupling and cross-coupling processes exist when fiber transits between straight and curved states, and the coupling degree varies with the degree of bending and mode order, in which the coupling efficiency of the fundamental mode is always higher than that of other modes and the coupling loss of higher order mode is larger than that of lower order mode. The fiber transition between straight and curved states costs the total power to exchange for the effective inhibition of higher order mode.

The coupling characteristics of dual-core photonic crystal fiber with rectangular holes array are researched based on horizontal coupling theory of parallel waveguide. The affections of fiber′s structural parameters for coupling characteristics are numerically calculated. The simulation results demonstrate that enlarging hole pitch in vertical or reducing hole pitch in horizontal and decreasing hole diameter can shorten the coupling length of fiber and the difference of coupling length in X- and Y- polarization. A kind of polarization splitters based on rectangular lattice structure with minimal coupling length (125 μm) and higher extinction ratio (38 dB) is designed.