All-optical 3R (reampifying, retiming, reshaping) technique is the trend of the all-optical communication network and all-optical clock recovery is one of the key techniques of all-optical 3R technique. With the application of new phase modulation format, the research of all-optical clock recovery of new phase modulation format is attracting more and more attention. A new scheme of clock recovery of variable bit-rate non-return-to-zero differential phase shift keying (NRZ-DPSK) signal based on tunable demodulator is proposed. The tunable demodulator composed by Fizeau interferometer based on free space light converts the NRZ-DPSK signal into return-to-zero (RZ) signal which includes clock component. The demodulator can demodulate 2.5 Gb/s to 40 Gb/s NRZ-DSPK signal. The demodulated RZ signal is injected into the fiber loop laser and all-optical clock recovery from the length of 27-1 pseudo-random bit sequence (PRBS) NRZ-DPSK signal is realized. The extinction rate of the recovered clock is higher than 10 dB.

A pattern recognition model for haze identification with atmospheric backscatter lidars is proposed. The process of building the characteristics sample database for haze pattern recognition is described in detail. The classification of haze particles by using Bayesian discriminant function, as the selection basis of haze optical characteristics vector, is presented. Computer simulation for the proposed pattern recognition model of haze identification is carried out. Two self-calibration approaches are employed to check the validity and stability of the model. By analyzing the applicability of this model for atmospheric lidars, the advantage of polarized high spectral resolution lidar (HSRL) is highlighted.

Mechanism of chemotherapeutics for tumor therapy is to restore infinite proliferous cancer cells to normal apoptosis, therefore, apoptosis monitoring has important guidance for clinical treatment. A novel and robust method for apoptosis monitoring of tumor cells is engineered based on dynamic laser tweezers, using SKOV3 cell line as typical sample. SKOV3 cells are cultured under four gradient concentrations of cisplatin, and trapping efficiency of four groups are measured by proposed system, which presents great advantages of celerity, low consumption, and label-free explorations for living cells without perturbing experimental conditions in combination with classical probes. The proposed technique has great potential in improving cancer treatment by monitoring the objective efficacy of tumor cell killing.

We present an experimental method to measure the curvature radius and focal length of liquid lens based on digital holographic microscopy. Considering the features of liquid lens such as non-contact, small size and non-transparent wall, a vertical optical path based on Mach-Zehnder interferometer with aberration correction capacity is used to record the hologram of sample. The phase distribution of the object wavefront carrying the liquid level information is numerically reconstructed from the recorded digital hologram and the surface contour curve is achieved by numerical computation and fitting. Then the curvature radius and focal length of the liquid lens can be obtained. In order to certify the validity of this method, a standard plano-concave lens is measured. The experimental results show that this method is an effective approach with high precision and non-contact for measuring the curvature radius and focal length of liquid lens.

Aiming at the non-adaptive problem and incomplete detection of single Gaussian background model (SGM), an improved single Gaussian background model method for moving object detecton is proposed. This method combines SGM and the mean shift algorithm to detect moving objects. The initial background model is decided by using N frames of images, and the moving objects are detected, the pixel which belong to background points are updated according to the single Gaussian model algorithm, and the pixel which do not belong to the background points in the updated background model are corrected using the mean shift algorithm, the background model corrected by the mean shift algorithm is used as the final background model. The moving objects are detected using the background difference method. The experiments show that the improved method can overcome the non-adaptive shortcoming and have high detectivity.

The method of combining computer with optical holography to manufacture circular-viewing plane hologram is proposed. An integrated Fresnel ring hologram is first obtained by computer generated holography. Then the reconstruction image of the ring hologram is chosen as the target for recording optical hologram, and finally the integrated circular-viewing plane color hologram is obtained. The principle of integrated circular-viewing plan color hologram is analyzed in detail, and verified by experiment. This technology enhances the display flexibility of stereo-holography; the computation speed of the circular-viewing plane color hologram is also improved.

Incoherent digital holographic adaptive optics is a new technology of wavefront sensing and correction. Combined with appropriate numerical algorithm, wavefront sensing and compensation can be achieved by the wavefront recording and reconstruction ability of the holography. Based on the basic principle of the Fresnel incoherent correlation holography (FINCH), the incoherent digital holographic adaptive optics is investigated through theoretical analysis and simulations. Holograms of the guide star and the distorted object are recorded respectively using a modified Michelson interferometer. Aberrations in the distorted hologram can be compensated digitally by using the complex conjugate of the guide star hologram. The effect of the size and position of the guide star on the wavefront compensation are investigated quantitatively through experiments. The aberrations can be well compensated by the guide star chosen from a suitable area which is measured by the parameters of system. Furthermore, the isoplanatic region of the system is demonstrated.

Behavior of stainless steel-carbon steel laminated sheet (SCLS) including interfaces during pulsed laser bending is investigated using a multi-layered finite element model (FEM) based on thermal-structure indirect couple method. Through the analysis on temperature field, stress-strain field and displacement of stainless steel layer, carbon steel layer and the bonding interface during laser bending process, the impact of interface on bending angles and bending quality are explored. The results show that during laser bending process, temperature transfers smooth across the bonding interface, while transverse stress and strain have obvious mutations. After deformation, tensile stress exists at both the top and bottom stainless steel layers and compressive stress exists at the middle carbon steel layer. When laser power is 140 W, scanning speed is 800 mm/min, the defocus amount is 10 mm, the maximum stress of Z-direction on the bonding interface is 87.5 MPa, which is smaller than the bonding strength of the laminate sheet (≥210 MPa). An effective curved laminate sheet is achieved using both experiment and simulation methods and the error is less than 5%. The simulation provides a good basis on both theory and experiment for better bending quality of SCLS.

The technique of pulsed fiber-laser tangential profiling and radial sharpening of bronze-bonded diamond grinding wheels is studied theoretically and experimentally. The mechanisms for laser tangential profiling and radial sharpening of bronze-bonded diamond wheels are theoretically analyzed, and the four key processing parameters that determine the results of laser truing and dressing, including laser power density, overlap ratio of laser spot, laser scanning track line overlap ratio, and number of laser scanning cycles, are summarized and proposed. Furthermore, the effects of these four key parameters on graphitization-damaged layer of grains, sharpness of cutting edge graims, surface smoothness of bond, and mean protrusion height of the diamond grains after laser processing are experimentally studied. The ideal values of the laser power density, overlap ratio of laser spot overlap ratio, laser scanning track line, and number of laser scanning cycles are found under current experimental conditions.

Numerical method is adopted to analysis the tendency of cracking layer during the laser cladding on tooth surface of helical gear. The results show that a high temperature gradient generates in the cladding layer and mostly concentrates in the tooth root. It turns to be a tensile stress, so the cracks will be easily in tooth root. Cracks will generate in tooth root and extend to the outside surface along the direction of perpendicular to scanning direction. Double scanning technology is put forward to solve this problem. Calculation results show that the tensile stress in cladding layer is significantly decreased using this technology and the area that stress concentrated inside clad coating can also be reduced. Therefore, the distribution of stress field inside clad coating can be improved radically, and it is quite beneficial for cracking controlling. Teeth surfaces are clad by different scanning methods and laser parameters in experiment. The results show that double scanning technology is benefit for controlling the cracking of cladding layer on tooth surface, and reliable parameters fit for laser cladding on tooth surface of helical gear are verified according to the results.

Fiber laser cladding repairing is performed on the surface of stainless steel with wire feeding. The effects of laser process parameters on the cladding track geometry are studied. In order to apply on multi-track and multi-layer cladding repairing practice, the best range of overlapping rate is also investigated. The results show that the laser cladding track geometry is mainly attributed to laser power, scanning speed and wire feeding speed, while defocusing distance has relatively small effect on the formation and geometry of cladding track. When the laser energy density is 100 J/mm2 and the wire fusion rate is 39.44×10-6 g/J, the stable and smooth cladding track is obtained. When the overlapping rate varies from 45 % to 53 %, the values of multi-track single-layer cladding surface smoothness are 100 μm or less.

The manufacturing of clearance features is the crucial issue for direct manufacturing non-assembly mechanisms. To improve the processibility of clearance feature, tilted display is adopted to reduce the support within the clearance. A dimension error model for overhanging structure is established and a verification experiment is conducted, firstly. Then clearance feature of 0.2 mm with a series of tilt angles is manufactured by selective laser melting (SLM) to investigate the effects of process parameters, such as layer thickness, tilt angle and energy input on clearance size. Finally, a collapsible abacus is manufactured. Results show that the clearance size increases with increasing tilt angle, decreasing layer thickness or energy input when the tilt angle is lager than 40°. It shows that the theoretical dimension error fits the experimental results well. With laser power of 150 W, scan speed of 800 mm/s and layer thickness of 25 μm and 35 μm, the clearance sizes are 140 μm and 120 μm,respectively. A collapsible abacus manufactured under the above process parameters can achieve designed performances well. It provides a feasible method for direct manufacturing of mechanisms.

Transformation toughening and dispersion toughening are the main toughening mechanisms on zirconia. Zirconia is used as the toughening phase of laser cladding layer, and the TA15 titanium alloy is selected as substrate on which the cobalt-based composite powder (Stellite-6) with 5% (mass friction) of ZrO2 is cladded. The results indicate that zirconia can refine and purify the microstructure of the coating and improve compactness of the coating to some extent. Moreover, the cracks which appear in the coating have been repaired, the microstructure of the coating has been improved. The X-ray diffraction spectrum has proved phase structure of zirconia ceramic in the coating is monoclinic, which has indicated the appearance of transformation toughening. The microhardness and wear resistance of the coating have been improved with the addition of zirconia. This study offers some references for improving the quality of laser cladding layer.

In order to study the spectral radiation characteristics of laser molten pool in laser cladding, grating spectrum detection technology is used to detect the spectrum of molten pool in nickel silicon boron alloy powder laser cladding, spectral distributions in different powers, speed and time are obtained. It is shown that at the wavelength of 550 nm spectrum relative strength is 500 when power is 900 W, and it increases to 600 when power becomes 1000 W, keeping power constant, spectral radiation intensity decreases when scanning speed increases but increases with time and achieves the stable state after 15 s. There is a certain relationship between the quality of laser cladding layers and spectrum fluctuation of molten pool. The results show that when power is 900 W and scanning speed is 2 mm/s, the quality of laser cladding layers is better, the body has small deformation, and the fluctuations spectrum relative strength of the molten pool is relatively little.

Laser active imaging systems are usually used in important region surveillance and dangerous target identification. However, the imaging system is easy to be disturbed and this leads to the distortion of the images. The positions of the target, imaging system, interference and the laser power change momentarily, so the dazzling effect is different in every frame. Therefore, how to evaluate the influence of the laser on imaging systems must be better understood. A new no-reference image quality assessment algorithm based on the dynamic features of consistent multi-frame images is proposed, which is called feature-point dynamic (FPD). The feature-point matching correlation and area diversification of one frame are calculated in the target region. The difference of correlation, area distribution, structure, frequency and salience of multi-frame images are also compared in the target region. The normalized results are obtained via product of these factors above. The luminance imaging experiment is performed for the targets by utilizing the laser active imaging system. The disturbed images of different disturbing powers and different spot positions are obtained. The proposed FPD algorithm is used to evaluate the laser-dazzling images, and the results show that the FPD gives a more reasonable evaluation for multi-frame laser-dazzling images in the period of time. The evaluation results reflect the invalidation of the target identification algorithm objectively.

As noninvasive biomedical imaging techniques, optical coherence tomography (OCT) and optical coherence microscopy have good application prospects in future. A swept-source imaging system based on a polarization-dependent semiconductor optical amplifier (SOA) enabled Fourier domain mode locked laser (FDML) is demonstrated, which can be used for the two imaging techniques mentioned above. The FDML with a polarization-dependent SOA generates ~32 mW output power at 45 kHz sweep rates, with a tuning range of 115 nm centered at 1326 nm. Because of the broad bandwidth and high saturation power of the polarization-dependent SOA, the laser has the advantage of simple structure. It uses only one SOA for operating with enough bandwidth and output power. Using the SOA-enabled FDML laser, an OCT system with axial resolution of ~12.9 μm, transverse spot size of 9 μm and sensitivity of 105 dB is achieved. The structure of the epidermal cells of onion can be observed by this imaging system.

According to the mode field distribution characteristics of semiconductor lasers and single mode fiber, the coupling of the single mode fiber and semiconductor laser is studied by the mode coupling theory, the results show that the fiber end face into a wedge micro lens can make the coupling of fiber and semiconductor laser meet the requirement of the mode field matching and phase matching. Micro lens parameters of wedge type fiber are optimized using the genetic algorithm, the result is that the coupling efficiency achieves the optimum value with wedge-angle of 88°, cylinder lens radius of 3.44 μm and coupling distance of 6.13 μm, the coupling efficiency reaches 88.9% when using the Zemax optical simulation software to simulate the coupling model, the maximum coupling efficiency is 81.36% after laser spot welding and the high and low temperature environment test. The experimental results are similar to the simulation results, the output coupling power can satisfy the demands of seed source power for fiber laser.

The impact of center waveguide layers, mode expansion layers and confinement layers on semiconductor laser performance with mode expansion layers has been investigated using the crosslight software. A structure with stripe width of 50 μm and far field divergence angle of 23° is obtained, whose threshold current is 117.8 mA and confinement factor is 2.37%. The far field divergence angle can be as low as 18° when the threshold current is 200.9 mA. After optimization the far field vertical divergence angle is reduced by about 20° without obvious threshold current increas. The results show that the mode expansion layers do not reduce the electrical properties and the temperature stability characteristics of lasers.

The short pulse laser characteristics of Nd3+:YAG/Cr4+:YAG diffuse-bonded single piece and the semi-external cavity passively Q-switched lasers are investigated respectively. It is found that the semi-external cavity structured passively Q-switched laser can emit laser pulses with pulse duration less than 1 ns, single pulse energy greater than 1 mJ and peak power higher than 1 MW, much better than the performance of the single piece laser. Using the developed laser and a home-made high resolution fiber spectrometer, a compact LIBS system is set up. The performance of the LIBS system is evaluated in the cases of standard iron alloy samples and the Pb contained liquid samples. Qualitative analysis result and quantitative relationship curve are obtained.

By scanning each mesh point of the wave-front, a kind of wave-front reconstruction method is proposed. Based on Hudgin model, the known P reference points are chosen at the diagonal of aperture array. For each reference point, one wave-front is obtained by scanning row data of the array, and another wave-front is obtained by scanning column data of the array. So, 2P wave-fronts are obtained for the P reference points. The average of the 2P wave-fronts is the required. How to choose reference point is introduced. It leads to that the high-low coordinates symmetrical arrange reference points are optimum selection. An error estimation model of wave-front is made. It is concluded that wave-front error is improved as the number of reference point increases. Experiments are performed for the new method and the traditional matrix inversion method. The result of experiments shows that the two methods have equivalent effect, and the new method has less amount of calculation and better practicability.

InGaAs/GaAs single quantum well is grown on different misoriented substrates by the metal-organic chemical vapor deposition (MOCVD) technology. The samples are characterized by photoluminescence (PL) spectroscopy at room temperature. The effect of offset substrates, growth temperature and V/III ratio of quantum well layer on PL wavelength, intensity and full width at half-maximum (FWHM) has been studied. The samples with smaller offset from GaAs substrates (100) towards show the higher PL intensity with narrower FWHM. The PL intensity increases with lower growth temperature of quantum well. The samples with high V/III ratio show high PL intensity while the PL wavelength exhibits red shift.

Combinating of mechanical vibration theory equations, preliminarily the theoretical vibration response curve of structure of the quarter of 3° freedom car body with different parameters is analyzed. Using laser heterodyne techniques, an experimental measurement program for vehicle vibration information is designed and built. Against the case that two vehicles of similar appearance, engine output consistent, the vibration information and time domain vibration spectral analysis are experimentally measured. By analyzing the vibration signal time domain, and frequency spectral curves measured, the frequency feature points of the two vehicles are found successfully. The two cars are marked and distincted well, and the blind of video imaging vehicle models identification method is made up.The relevant work provides a preliminary theoretical and experimental basis for the vehicle identification technology based on laser detecting the vibration signals.

The calibration accuracy of laser stripe vision sensor is directly related to accuracy in measurement. The commonly adopted calibration method is model-based calibration method. The model will become significantly complicated and the calculation will become complex when a high measurement accuracy is required. In order to calibrate the laser stripe vision sensor with high accuracy, high efficiency and low cost, a direct calibration method for laser stripe sensor based on gauge block which does not require model is proposed. Firstly, a calibration target is designed. Secondly, a lookup table of the direct mapping relationship between image coordinates and three-dimensional coordinates of feature points is built. Finally, three-dimensional coordinates of an arbitrary point can be obtained from the lookup table directly or with least-square fitting algorithm. Experimental results demonstrate that this direct calibration method has high accuracy. Its average absolute measuring accuracy is 0.0279 mm in y direction and 0.0237 mm in z direction. It concludes that this method can meet the requirements of high accuracy measurement, and the calculation is simple and easy to implement.

Gap fiber Bragg grating (g-FBG) exhibits both Fizeau interference and phase-shifted fiber Bragg grating (PSFBG) spectrum. Their different sensitivities to micro-gap and temperature are demonstrated respectively, based on which a micro-gap and temperature simultaneous measurement method is proposed. The reflective spectra with different micro-gaps are tested by g-FBG experiments, which fits the simulation results. Data analysis shows that the micro-gap measurement error is less than ±5 nm. A g-FBG based sensor is made and simultaneous micro-gap and temperature measurement is obtained. Temperature measurement is achieved with a sensitivity of 8.3 pm/℃ and a low error of 0.1 ℃. This proposed g-FBG based simultaneous micro-gap and temperature measurement exhibits the advantages of high-accuracy, compact size, and flexible designing. With the related equation between temperature and micro-gap, temperature-induced gap change can be compensated and the temperature-independent micro-gap measurement is able to implement.

Microwave frequency measurement is an important part of electronic warfare systems. The electric field frequency measurement method has disadvantages of bulky system volume, high power consumption and weak immunity to electromagnetic interference, and the light auxiliary frequency measurement method has defects of either wide frequency range with low-resolution or high-resolution in narrow measurement range. We propose and experimentally demonstrate an instantaneous microwave frequency measurement method with wide range and high resolution based on dual polarization modulation. This method measures in a large range of microwave frequency with a relatively low resolution, and then in a small range with high resolution. The experimental results show that this method can achieve instantaneous frequency measurement resolution better than ±0.14 GHz in 2.7~19.4 GHz range.

The traditional visual attention mechanism is complex and rough-detection for visual saliency detection indoor red-green-blue (RGB) image. In order to overcome these defects, a new fast visual saliency object detection method based on fusion depth information on indoor RGB image is proposed. A certain scale image is obtained by sub-sampling and pyramid-quantization to reduce the spatial resolution of the images so as to decrease the computational complexity. The intensity, red-green and yellow-blue three-channel features visual attention mechanism significant detection model is proposed to acquire saliency map. The saliency growing strategy is proposed to acquire the precise saliency region in the saliency analysis. The fusion depth information is utilized to detect the objects in salient region. The feasibility and effectiveness of the algorithm is verified in indoor detection experiments.

For the situation where the current signal extraction algorithms for the photon Doppler velocimetry (PDV) data are weak in the performance of anti-noise, a method based on trajectory search with the short time Fourier transformation (STFT) spectrum of the PDV data is proposed to extract the valid target signal. The Algorithm uses the iterative MeanShift progress weighting the search direction to get the maximum value points of the density function and these points can be regarded as the trajectory points of valid signal. Experimental results show that, when the proper initial point is given, the algorithm can accurately extract the valid signal from the short-time Fourier transform spectrum which contains a large amount of noise and interference signal, this signal extraction algorithm for PDV has strong robustness in strong noise condition.

To solve the problem of human localization and tracking in the service space of human-robot coexistence, a novel method based on collaborative perception using distributed laser radars for human tracking is proposed. First, laser data obtained from each of radars is evaluated statistically, separately. All data are divided into static data and dynamic data. Static data are employed to calibrate the laser radars for background subtraction. Dynamic data are then sent to server computer by wireless network. Data from different radars at the same moment are formed into one frame to realize data synchronization and integration. Finally, contour model matching based interative closest point algorithm is implemented on each frame of laser data to distinguish the targets. To realize human tracking, targets between two frames are associated using association gate based on their positions and speeds. Experimental results demonstrate the effectiveness of the proposed method in solving the problem of human localization and tracking. Compared to vision-based tracking methods, the system performs better in terms of localization accuracy and tracking success rate.

Bore-sight error estimation for the mobile mapping system (MMS) plays an extremely important role in the quality of the point cloud, especially when the MMS scans the same area from different routes and angles, unideal bore-sight error estimation seriously reduce the point cloud registration accuracy. For fine calibration of the bore-sight error, a bore-sight error self-calibration method based on plane fetures of MMS is propsed, the computing model of point cloud of MMS is given, the Gauss-Helmert adjustment model is established based on plane features of MMS, and the solution is derived based on the least square method. The experiment results show that the bore-sight error is easily computed by the proposed method, and the computation result is reliable and effective

Compared with fiber amplifier, fiber laser oscillator has the advantages of compact structure, good stability, high threshold of mode instability and good beam quality. Single-end pumped 1 kW all fiber laser oscillator is studied in detail theoretically and experimentally. Rate equation model which considers the fiber bending loss, mode coupling, changing pumping wave and cladding lights stripping is presented. Using a China made combiner, a single-end pumped all fiber laser oscillator is built. Laser power of 1.04 kW and optical to optical efficiency of 69% are obtained when the pump power reaches to 1.5 kW. The beam quality is measured and the results show that the M2 factors are all less than 1.25 in different powers. With one hour steady laser operation, the power fluctuation is less then 1%.

The basic optical properties of the optical microfiber coupler are discussed. Optical microfiber couplers with well optical property are achieved by using the optical microfiber drawing system with online optical monitoring system. The vibration characteristics of the optical microfiber coupler are analyzed and studied experimentally. Person stepping signals are caught successfully by the optical microfiber coupler sensing system, which proves that the optical microfiber coupler sensing system has high sensitivity to the vibration signal and it may have potential value in the local area monitoring fields.

An improved time division multiplexing network method is proposed to solve such problems as the long queuing delay time, the low link utilization ratio and the non-ideal network throughput which are caused by the increased nodes when time division multiplexing(TDM) technology is used in the ultraviolet communication network at present. Based on the model of ultraviolet communication vertical transceiver, this method selectes the central node to radio into the adjacent cell by taking weighted algorithm of power factor into consideration, and distributes the adjacent cell different slot sections by using piecewise slot method to achieve the goal that the nodes in the far area can use time slot repeatedly and the contradiction between the increased nodes and the limited time slot can be solved. The simulation analysis indicates that, compared with TDM, when the network node number is 40, this method can decline 4 ms in the queuing delay time, raise 2.7% in the link utilization ratio, and increase 1800 bit/s in the channel throughput.

As the investigation deepened, it is necessary to measure the velocities of multiple targets, such as several flyers and a large number of granules, using just one probe, in the field of explosion and shock waves physics, intense laser, weapon, et al.. The operational principle and topology of photonic Doppler velocimetry are introduced. The signal characteristics and signal processing are analyzed, when the velocities of multiple targets are measured with just one probe, and the velocity resolution and spatial resolution are two key factors for measuring multiple velocities. According to the analysis, a photonic Doppler velocimetry is assembled on the basis of the optical Doppler effects,using the components well developed in the telecommunication industry, and the velocity of the explosively driven metal plate are tested by the proposed photonic Doppler velocimetry. The experimental results show that the velocities of one large aluminum flyer,several small aluminum flyers and a large number of lead granules are measured with just one probe, the velocity is up to 2.5 km/s,and the work distance is up to 20 mm.The research results will provide a valuable reference for the practical application of photonic Doppler velocimetry to measure multiple targets′ velocities.

A new multi-area perimeter security system based on optical fiber Michelson interferometer and pattern recognition technique is proposed and demonstrated. The polarization-insensitive optical fiber Michelson interferometer is used as the vibration sensor for perimeter intrusion detection system (PIDS) which reduces the polarization-induced fading. Strain measurement of fiber bonding on host material is analyzed. Noise suppression, behavior analysis and alarm judgement are realized by using level crossing (LC) method and pattern recognition (PR) technique. The experiment results show that the system is able to analyze the original signal with LC method and extract the feature values with response time less than 0.5 s. Behavior pattern is generated through neural network training. Rain-induced noise and other environmental noise are eliminated by dynamic means algorithm (DMA). So the all-fiber perimeter security system with low lost, high reliability and high praclicability is realized.

Based on evanescent wave absorbed theory, a segmented structure optic fiber sensor is proposed. The waveguide models of the segmented structure and straight are simulated and analyzed by using beam propagation method (BPM), which shows the high-order modes are excited repeatedly at the first transition of the each segmented region in the segmented structure. The effects of the different structures, core diameters and concentrations of solution on the sensitivity of the sensors are investigated, and the sensitivity is tested by using the different concentrations of the methylene blue solutions. The experimental results show that, with the fixed core diameters, the sensing region length of segmented structure sensors is 5 cm, which is shorter than that of the conventional single straight sensor 6 cm. However, the sensitivity of segmented structure sensors is 0.0135 L/mmol, which is higher than that of conventional single straight sensor 0.0102 L/mmol. The segmented structure evanescent wave sensor can effectively stimulate the fiber low-order modes to the high-order modes, and than the sensitivity is enhanced. The results are consistent with theoretical models and simulation analysis. The proposed sensor not only has a high sensitivity, but it is robust due to the larger core diameters and shorter length of the segmented region, which is suitable for materials spectrum measurements.

In a visible light communication (VLC) system, the light-emitting diode (LED) is the major source of nonlinearity and exhibits memory effects due to the in-band non-flat frequency response. The LED nonlinearity with memory effects degrades the error vector magnitude (EVM) and bit error rate (BER) in the VLC system. In general, the predistortion technique is mostly utilized to compensate for the LED nonlinearity and thus enhances the performance of the VLC system. However, the existing predistortion techniques cannot work adaptively and neglect the LED memory effects. A new predistortion architecture is proposed by adding a feedback path to obtain the LED output signal and estimating the LED nonlinearity with memory effects by memory polynomial model adaptively. The simulation results show that the proposed technique outperforms the existing methods in terms of BER.

According to the polarization coupling model of the polarization-maintaining delay optical fiber coil, considering the reciprocal parasitic waves with large amplitude, the interference intensity of the optical system in the fiber-optic current sensor (FOCS) is calculated, and the theoretical relationship between the scale factor and the polarization crosstalk of the delay fiber coil is obtained. The effect mechanism of the temperature dependence of the polarization crosstalk on the scale factor is revealed, and the corresponding suppression methods are proposed. To ensure the scale factor error to be within 0.2% under the varied temperature condition, it is essential for the polarization crosstalk of the delay fiber coil to be less than -30 dB. The experimental results show that the temperature performance of the FOCS can be improved greatly when lowering the tension of winding fiber, reducing the quantity of the glue, and utilizing the frame with low temperature coefficient. The variation of the scale factor is decreased from 0.63% to 0.07% over the temperature range from -40 ℃ to 70 ℃. The research work offers a theoretical guide for the design and manufacture of the optical fiber delayed coil in the FOCS.

The operational principle and heterodyne technology of photonic Doppler velocimetry are introduced, time division multiplexing (TDM), wavelength division multiplexing (WDM), time and wavelength division multiplexing, are analyzed in detail. According to the analysis, a multiplexed photonic Doppler velocimetry (two TDM, two WDM) device is designed, and the velocities of explosively driven aluminum plates are tested by the proposed MPDV. The experimental results show that the MPDV is achieved well, four frequency curves and velocity curves are measured with just one interference signal, the velocity is up to 2.5 km/s, and the flight time is 16 μs, the interference signal, frequency curve and velocity curve are distinct from those of photonic Doppler velocimetry and heterodyne multiplexed photonic Doppler velocimetry. The solution will provide a valuable reference for the multiplexed photonic Doppler velocimetry.

With the development of microelectronics technology, it is necessary to study the fabrication process for high aspect ratio and a vertical sidewalls micro-nanostructures on the substrate. High quality nano master grating can be fabricated by X-rays lithography. By using sophisticated nano electroforming technology, high-quality nano metal grating can be replicated from the mother mold grating. A technique for preparing high aspect ratio diffraction grating metal molds is introduced. Based on synchrotron radiation lithography technique, polymethyl methacrylate (PMMA) nano gratings with line width of 0.25, 0.5, 1 μm, and the height of 2.0 μm are prepared on a silicon substrate. Using precision electroforming technique, nickel nano-grating mold with the line width of 0.25, 0.5, 1 μm, and the 1 μm gratings aspect ratio of 1.5 is fabricated from the PMMA grating master mold. In order to obtain high-quality PMMA nano-grating, the adhesive is used to overcome the deficiencies of structures collapsed, by optimizing exposure parameters, small triangular structures at the bottom of the gratings are eliminated.

In order to reduce the influence of random errors and outliers on the accuracy of vehicle laser Doppler velocimeter, an adaptive Kalman filter algorithm is proposed. Based on the "current" statistical model (CSM) and combined with the actual characteristics of vehicle velocimeter, the state-space model of system is built, and the adaptive adjustment of acceleration variance is realized by the deviation between measured and predicted value of speed. The adaptive algorithm for measuring noise variance, which can eliminate outliers and reflect the real-time characteristics of road, is given according to the orthogonal properties of innovation and speed estimation error in Kalman filter algorithm. Simulated results show that the algorithm is better than CSM algorithm in the convergence speed of filtering and estimation accuracy. Experimental results show that this algorithm can significantly improve the accuracy and robustness of velocimeter.

Ni-Based alloy coatings with different contends of rare-earth La2O3 are prepared on the surface of 6063 aluminum alloy by using laser cladding. The effects of rare earth La2O3 on microstructure, phase structure and composition of laser cladding Ni-Based alloy coatings on 6063 Al alloys are investigated by means of optical microscope (OM), X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that with increasing the amount of La2O3 (above 5%)，the cladding layer tends to form gas-holes. When the amount of La2O3 is in the range of 0%~2% the same below, the cladding layer tends to form cracks, and coating can′t bind tightly with the matrix. Gas-holes and cracks in the coatings reduced with the addition of 5% La2O3. The main phase structures of Ni-based alloy coatings with different contends of rare-earth La2O3 are β-NiAl (Cr) and a small amount of Al3Ni, AlNi3, Al, etc. After adding rare earth, a little of rare earth compounds La2O3、Al4La is found in XRD diagrams, and NiAl phase (100) crystallographic orientation peak almost disappeared, grain orientation towards (110), (200) and (211), and (110) crystallographic orientation peaks appear different degrees of migration; Compared with Ni60 cladding layer without adding rare earth, Ni60 cladding layer with 5% of rare-earth La2O3 has a uniform element distribution, a lower dilution rate, which significantly reduce the porosity and refine the grain size; The cladding layer mainly composed of NiAl-Cr eutectic structure, rare earth elements segregate at the grain boundary and form some stable rare earth compound such as Al4La.

The microstructures, tensile strength and fractures of TC4 titanium alloys, fabricated by laser solid forming (LSF), are investigated experimentally in different heat treatment states. The results show that LSF Ti alloy TC4 contains layer bands which stress relief annealing and solid solution aging can help eliminate so that the microstructures become more homogeneous, while the former makes less contribution to the improvement of strength and ductility, the latter can get comprehensive mechanical properties. The tensile fracture shows that the fractures of solution-aging specimens are almost ductile fractures while the as-deposited and stress relief annealing specimens are all mixed fractures. The formation mechanism of cleavage is explained by researching microstructures and fractures which is that cracks propagation along the interface of α/β forms the cleavage plane and the pores joined to the crack forms the dimples.

Aiming at the problem that the large-aperture optical component exists difference in temperature between the top and the bottom surfaces in precision finishing, the temperature property of the polishing pad and the workpiece, taking the annular lapping system for example, have been investigated. Significant temperature difference between the top and the bottom surfaces of the optical component is measured even at low rotating speed polishing applying the 1.6 m annular polishing machine. Two effective methods are proposed, one is adjusting the technological parameters, the other is adiabatic polishing. The feasibility of the methods is confirmed by the temperature measurement experiments using control variable and adiabatic polishing. The proposed methods lay the foundation of precision finishing.

Dense spectral combining (DSC) based on reflection volume Bragg grating (VBG) is an important method to improve brightness of fiber-coupled diode laser modular. Accounting for laser divergence, spectral bandwidth, wavelength and angle shifts from ideal Bragg condition, a diffraction efficiency model of reflection VBG is presented. Based on the new numerical model of diffraction efficiency, design principles and technical approach for DSC of two channels by reflection volume Bragg grating are investigated. The results show if wavelength shift is less than ±0.49 nm and angle shift is less than ±16 mrad from ideal Bragg condition, the DSC combining efficiencies are over 98.7% when the spectral full width at half-maximum (FWHM) is 0.3 nm, and the divergence angle with over 90% energy is 14 mrad.

Laser Raman spectroscopy (LTRS) is used to monitor the Raman spectroscopic changes of Cryptococcus humicolus cells and mitochondria stressed by aluminum (Al). The results show that the characteristic Raman peaks of C. humicolus cells and mitochondria are significantly decreased with the increase of aluminum concentration and treatment time, the intensity of Raman peaks associated to nucleic acid, protein and lipid respectively exhibits significant decreasing tendency with the extension of treatment time, indicating that the content of nucleic acid, protein and lipid in the cells and mitochondria is reduced during the apoptosis process. The intensity of characteristic peaks related to cytochrome c (Cyt c) in mitochondria significantly decreases with the increase of aluminum concentration and treatment time, suggesting that the yeast mitochondrial membrane rupture leads to Cyt c release into outer of mitochondria. With the increase of aluminum concentration and treatment time, the respiratory peak is observed to decrease gradually, indicating that the mitochondrial activity becomes weaker, energy metabolism has been hampered. LTRS is used for real-time monitoring of the dynamic process of cell apoptosis and physiological and biochemical changes of in vitro mitochondria under aluminum stress, and revealing the release behavior of Cyt c during the apoptosis process of C. humicolus cells induced by aluminum. The results help understand the biological mechanism of aluminum toxicity in acidic soils on organisms.