The model-based wavefront sensorless adaptive optics (AO) system has a great potential in real-time correction because of its fast convergence and good correction. The linear relationship between imaging masked detector signal SMDand mean square gradient of wavefront phase SMG is the theoretical basis of the system control algorithm. To verify the linear relationship, we establish an AO system experiment platform with a 37-element piezoelectric deformable mirror(DM), a CCD camera and a Shack Hartmann sensor, in which the DM is used to generate wavefront aberration, the CCD camera is used to grab the distribution of far-field intensity and the Hartmann is used to get the information of wavefront. Based on the collected information of far-field intensity and the wavefront aberration, we calculate values of SMD and SMG, respectively. Experiment results show that SMD is linear to SMG and the slop is 0.018, which is very close to the theoretical value 1/(4π 2).

Self-focused array Airy beam has properties of high strength and large beam density, which makes it have strong inhibition for atmospheric turbulence and atmospheric scattering. Thus it can be used to receive much stronger signals on the receiver side and greatly improve the quality of atmospheric laser communication. A plurality of cubic phase masks that can produce Airy beams are orderly arranged to produce a multiphase diaphragm, which then can produce an array Airy beam with self-focusing. The simulation and experiment explain the auto-focusing process of Airy beams and the effect of spot size on its auto-focusing performance. The experimental results show that the array Airy beam, based on multiphase diaphragms, can be auto-focus, and the auto-focusing size gets larger as the spot size gets larger. Thus, by means of adjusting the spot size of each Airy beam in the array, the Airy's auto-focusing position can be controlled effectively.

The non-paraxial vector propagation characteristics of low order Laguerre-Gaussian beam (LGB) in space are analyzed by the space vector angular spectrum method, and the analytic expression of vectorial far-field distribution of LGB is obtained. Based on the generalized Lorenz-Mie theory, the scattering property of LGB by a single homogeneous spherical particle is analyzed. The research results show that, with the increase of topological charge of LGB, its hollow spot area increases while its on-axis differential scattering cross section decreases. With the increase of particle size, there exist peaks for the absorption, scattering and extinction efficiency factors, meanwhile these peaks shift towards the increase direction of particle size when the topological charge increases.

A mathematical model of the far-field beam distribution is built after the transmitted beam passes through the telescope with wave-front error. The effect of root mean square (RMS) value of wave-front error on the divergence angle of the transmitted beam is analyzed by numerical calculation combined with Monte Carlo method. Based on this, the tolerance of the telescope wave-front error required by the far-field divergence angle of the transmitted beam is determined. The analysis results show that for the laser communication system which the transmitted beam is off-axis on the telescope pupil, the far-field divergence angle is smaller than 10 μrad when the RMS of wave-front error is smaller than 0.13λ(λ is the light wavelength). The far-field divergence angle is smaller than 16.2 μrad when the RMS is smaller than 0.2λ and the probability of the divergence angle smaller than 10 μrad is 60%. The testing results of the wave-front errors of the telescope at different temperatures and the corresponding far-field divergence angles of the transmitted beams are well coincided with the analysis results.

In order to improve the beam quality of the laser diode and make it meet the requirement of high precision interferometric measurement for large distance, we propose a beam shaping method by using spatial light modulator based on the complex amplitude modulation algorithm. The laser diode beam is shaped to the non-astigmatic fundamental mode Gaussian beam, which has the advantages of good collimation and symmetrical spot shape. Experiment for analyzing the beam quality of the shaped beam is performed, and the results show that the M2 factors in the x and y directions of the shaped beam are close to 1 and the astigmatism of the shaped beam is close to 0, which verify the effectiveness of the proposed beam shaping method. The beam shaping method is applied to large distance interferometric measurement. Displacement measurement with micrometer steps is carried out at a distance of 8 m, and sub-wavelength accuracy is achieved compared with a nanometer stage. Experimental results indicate that the shaped beam can meet the requirement of large distance interferometric measurement, which verify the feasibility of the proposed beam shaping method.

As basic units of structure and function of the biological nervous system, neurons encode, transmit, and integrate information through discharge activities neuron, plays an important role in life activities. Based on the dynamic nature of neuronal discharge activity and phase imaging technique, we discuss nondestructive and label free imaging method for living cells and their inner substructure. According to phase information of neuron model, we study the characteristics of static morphology and dynamic discharge activities. The optical imaging simulation technique is used to establish the neuron phase model and obtain the information of its phase distribution. Starting from the physical meaning of the phase function, the substructure of the model is analyzed. Considering dynamic effect of the change of intracellular ion concentration in discharge activities on refractive index and phase information, the method of visualizing the dynamic process with phase information is discussed preliminarily. For the complex heterogeneous phase volume model, the local static morphological information on the substructure and phase characterization result of dynamic discharge activity on the sample are obtained without phase decoupling by introducing the heterogeneous contrastive compensation idea. The availability of the method is verified by simulation analysis. The results show that the optical phase characterization method for neuronal discharge characteristics and morphology is nondestructive, label-free, and quantifiable.

High resolution tomography images of human ex vivo kidney and colon tissues are obtained by using full-field optical coherence tomography (FFOCT) system. The experimental setup is based on a Linnik-type interferometer illuminated by a low coherence lamp. The theoretical resolution of the system is 0.5 μm. Series of interferometric images of sample and reference mirror are obtained by a charge-coupled device (CCD) and four-step phase-shifting algorithm. This experimental setup is used to image human kidney, and kidney tissue structures are successfully identified based on characteristic of histological slices of the kidney. The system is used to image human colon tissue and colonic adenocarcinoma tissue. On the basis of histological slices images, the ability of the FFOCT system identifying human cancer tissue is verified with the analysis of the colonic tissue and colonic adenocarcinoma tissue tomography images. The results of the study lay the foundation for future clinical diagnosis and application for FFOCT.

Bioluminescence tomography (BLT) is a new optical molecular imaging technique that utilizes the light intensity information on the surface of biological tissues to reconstruct the three-dimensional distribution of the internal bioluminescent source. The source reconstruction of BLT has serious morbidity due to the limited measurements of light intensity and the complicated structure of biological tissue. A multilevel adaptive finite element method for BLT is proposed, which is combined with the permissible regional-shrinking strategy to improve the quality of the reconstruction. Simulations of single-source and double-source based on the digital mouse model are designed to assess the localization ability of light source and the quantification ability of energy density of the method, respectively. The results show that the proposed method can significantly improve the positioning accuracy and energy density of the light source.

Absolute blood flow velocity and orientation are measured by a dual-mode imaging technology using photoacoustic microscopy and optical coherence tomography (PA/OCT). The blood flow velocity perpendicular to the direction of the probe beam is measured by photoacoustic correlation spectroscopy. The blood flow velocity parallel to the direction of the probe beam is measured by the Doppler OCT. Then the absolute velocity and orientation of blood flow are obtained. For the same fluid sample with different tilt angles, the standard deviation of the absolute blood flow velocity which is 1 mm·s-1 measured by PA/OCT is 0.02 mm·s-1 and the correlation coefficient between the blood flow orientation measured by PA/OCT and the actual flow orientation is 0.997. The experimental results show that the PA/OCT is suitable for measuring absolute blood flow velocity and orientation.

A spectral calibration method for optical coherence tomography (OCT) is proposed. The method is implemented by introducing an interference signal with a fixed optical path difference (OPD) in the Fourier domain OCT system. The sample interference signal and the fixed OPD signal are acquired simultaneously. Then the fixed OPD signal is obtained from the mixed signals through a filter step, and its phases are calculated to calibrate the interference signal of the sample in the system. We theoretically analyze the feasibility of the proposed method. In a 100 kHz swept source OCT system, the spectral calibration experiments with a mirror as the sample are performed at different depth positions. The point spread functions and the axial resolutions are obtained. Compared with the results using the light source clock, the proposed method has a better effectiveness.

Evaluation for decision threshold corresponding to the minimum bit error rate (BER) of modulating retro-reflector (MRR) free space optical communication (FSOC) system is presented. And based on this threshold, the closed form expression of the BER for MRR FSOC system is obtained, considering the effects of adaptive threshold noise and photodetector noise. According to the derived expressions, the effects of adaptive decision threshold parameters and modulation extinction ratio on BER are analyzed. Results show that the BER of MRR FSOC system with adaptive threshold precedes to that with fixed threshold 17.5 dB (BER is 10-5, weak turbulence), and when the number of training data bits is greater than 3, the BER performance of the adaptive decision threshold system is similar to the BER performance of the decision threshold system based on instantaneous channel state information.

On the basis of typical optoelectronic oscillator (OEO) chaotic system, the output of chaotic laser is fed back to the Mach-Zehnder modulator (MZM), so that the gain coefficients of the original system can change dynamically and a second time delay is introduced into the system. Then we study the effects of the feedback time and the feedback intensity of the improved chaotic system on the time-delay characteristics and complexity of the system theoretically. The simulation results show that the chaotic laser generated by the optoelectronic oscillator with optical feedback has higher complexity and lower delay characteristics. The system exhibits the better chaotic dynamic characteristics when the delay time of the optical feedback is the same as the delay time of the photoelectric delay. The results show that this method can produce more complex chaotic signals and reduce the delay characteristics of signals without increasing the system costs, and it is helpful to improve the security of the system.

Based on light induced thermal effect, all-optical intensity modulation characteristics of optical microfiber coupler (OMC) are studied. The theoretical analysis shows that, the modulation response efficiency of OMC is proportional to the waist length, loss coefficient, and pump modulation intensity, and is inversely proportional to the radius of the OMC waist coupling fiber. In the experiment research, the intensity modulated 980 nm pump light is injected into the OMC to heat the waist region, and the all-optical control function of the 1550 nm working light transmitted by OMC is obtained. The results show that, the OMC can realize intensity modulation with a whole cycle and a large modulation depth under modulation pump power of hundreds of microwatts. In addition, the amplitude of the modulation response signal has a linear response to the amplitude of intensity modulated 980 nm pump light in a low power region. The threshold of the required modulated pump light power is as low as several dozens of micro watts. The research has provide experimental data for the development of all-optical functional devices, such as optical attenuation, optical switch, intensity modulator, and it also provides a reference scheme for the control of the thermal stability of photonics integrated equipment and the security of quantum communication system.

An online synchronization measurement method for loss and refractive index growth of fiber Bragg grating (FBG) is demonstrated. The dynamic evolution of loss in FBG during the inscription process is studied in detail. The results show that the loss coefficient α of FBG linearly increases with its coupling coefficient κ. In order to optimize the loss performance of FBG, we propose the loss-coupling slope coefficient α/κ to evaluate the loss characteristics of FBG. The results show that we can make the FBG loss-coupling slope coefficient larger by increasing the distance between the optical fiber and the phase mask or using the phase mask with higher diffraction efficiency of 0 order diffracted light, which may be caused by the increase of the background refractive index which is independent of coupling coefficient. And loss-coupling slope coefficient α/κ of the FBG in D2-loading fiber is 50% lower than at 1550 nm, compared with it in H2-loading fiber.

Optical system for measuring the fluorescence lifetime is built up according to the principle of time correlation single photon counting, and the characteristics of single photon emission of single quantum dots are verified experimentally. The fluorescence lifetime of quantum dots with single photon emission properties on different substrates of quartz glass slide, silicon wafer and gold film is measured and compared for different effective distances between quantum dots and substrates. The experimental results are explained with theoretical simulation results of correlation of fluorescence decay rate and quantum yield with effective distance. The blinking properties of single quantum dots on different substrates are recorded and analyzed. The experimental results show that different substrates can effectively modify the fluorescence blinking and fluorescence decay rate of single photon emission of single quantum dots.

The traditional phase retrieval of in-line digital holography is invalid to eliminate the twin image and to get accurate phase when the object does not conform the sparsity, while the resolution of the off-axis digital holography is low due to the limitation of the minimum of the recording distance. An in-line and off-axis hybrid digital holography is proposed. The off-axis and in-line holograms are recorded respectively. The approximate phase distributions in the recording plane are obtained by constrained optimization approach from the off-axis hologram, and they are used as the initial value in the iterative procedure of the reconstruction of the in-line hologram, then the high quality amplitude and phase images are reconstructed. The ideal resolution of the hybrid digital holography is analyzed. The experimental results show that the proposed method can utilize the full spatial bandwidth of the image sensor, it can realize a large field of view and high resolution digital holographic imaging without the interference of the twin image when the objects have complex shape, and the resolution in the experiments approach the ideal resolution.

Basic structure of Raman scattering lidar in northern suburb of Nanjing is introduced. Treatment method of the data of stratospheric atmospheric aerosol extinction coefficient profiles inversed by Raman scattering lidar principle is described. Stratospheric aerosol observational data on December 8 and 9, 2011 in northern suburb of Nanjing are emphatically processed. The Raman scattering lidar distance correction signal is denoised by wavelet under four different thresholds. Appropriate threshold is used to obtain the stratospheric atmospheric aerosol extinction coefficient profile by the formula of inversion principle. Variation characteristics of aerosol extinction coefficients in the stratosphere are analyzed at the same time.

In order to eliminate a large amount of speckle noise and parasitic interference fringes noise caused by high coherence light source (laser), as well as the effects from the mechanical vibrations and air fluctuations which typically affect any uncommon-path interferometric system, we design and establish a white-light (halogen-light) common-path digital holographic microscope based on the grating diffraction. First, the parameters of the selected optical elements and the optical system are derived by theoretical analysis and calculation. Then, a common-path off-axis digital holographic microscope based on grating diffraction, which uses a halogen lamp as the illumination light source, is constructed. At last, the imaging accuracy and the spatiotemporal noise of the system are measured. Experimental results demonstrate that the established digital holographic microscope has a very high accurate imaging performance and spatiotemporal sensitivity with the spatial noise of 0.6 nm and the temporal noise of 0.04 nm.

A kind of electro-optic Q-switched laser in the form of pulse group output with short pulse interval and high subpulse peak power is proposed. The Nd∶YAG crystal is pumped by the diode laser (LD) module, and the single energy storage of resonant cavity is achieved. On the basis of controlling the Q-switch steps open repeatedly, single pump energy can be divided into multiple times Q-switched outputs and the short pulse interval and pulse group laser output are obtained, providing a research way for high repetition frequency and high peak power laser. Results show that with a group of half ring laser diode module as the source for Nd∶YAG crystal, lithium niobate (LN) crystal as the Q-switch, storage material is single pumped by laser diode module, and the Q-switch is stepped opened, the laser can be stably operation in the range of 1-20 Hz, minimum subpulse interval of 100 ns is obtained and subpulse frequency ranges in 1.1-10.0 MHz, subpulse energy is greater than 23 mJ and energy fluctuation is less than 10%, single pulse width is less than 37 ns, subpulse peak power is close to 1 MW, and the optical-optical conversion efficiency is 22.5%.

An ultrashort pulse laser system based on ultra-large-mode-field fiber amplification is reported. The laser system adopts fiber chirped pulse amplification amplification structure. The pulses with 500 fs are stretched to 500 ps by volume Bragg grating (VBG). The seed laser with average output power of 10 mW and repetition of 40 MHz is amplified by Yb-doped fiber amplifier. The repetition is adjusted to 500 kHz through the acousto-optic modulator. Then we use the large-mode field core diameters of 40 μm and 85 μm photonic crystal fibers as power amplifiers. Finally the laser with center wavelength of 1030 nm is compressed by VBG. The average output power is 104 W, and the near-diffraction-limit 767 fs pulse with maximum peak power of 0.271 GW is achieved.

In view of the low frequency stabilization accuracy of prism laser gyros, the characteristics of frequency stabilization control system of prism laser gyros are systematically studied. The light intensity tuning curve and the frequency stabilizing actuator are analyzed theoretically. The mathematical model of the frequency stabilization control system of the prism laser gyros is established. The steady state performance and dynamic performance of the system are further analyzed. The analysis results show that the system has different steady-state errors and the adjustment time is too long under the influence of constant temperature and slow temperature change, which leads to the decline of the stability frequency accuracy. We optimize the controller parameters to provide optimal damping ratio and rapidity for second-order system. And the feedforward control system with temperature compensation is adopted to realize the full compensation of the frequency stability error caused by the temperature and improve the frequency stability accuracy of the system. The experimental results show that the optimized frequency stabilization control system can improve the frequency stability accuracy by one order of magnitude compared with the original frequency stabilization control system, and the gyro accuracy can be improved by more than 30%.

A narrow-linewidth, low-noise hybrid integrated external cavity laser at 1550 nm is fabricated, the polarization maintaining fiber Bragg grating (FBG) as optical feedback component is coupled with the semiconductor gain chip, and the laser linewidth is reduced by the large group delay characteristics at the sloping side of the FBG reflectance spectrum. The butterfly-packaged laser realizes a single longitudinal mode and polarization-maintaining output of the single polarization laser, including the output power ≥30 mW with integral linewidth of 15.9 kHz at 1 kHz, the Lorentz linewidth of 4.85 kHz, the intrinsic linewidth of 4.06 kHz, the relative intensity noise ≤-155 dB·Hz -1 at 1 MHz, the polarization extinction ratio >25 dB, the current tuning range without mode hopping ≥8 GHz, the temperature tuning range without mode hopping ≥14 GHz, the power stability of 1.7% within 6 h, and the frequency variations <50 MHz.

As a non-coherent light source,the amplified spontaneous emission (ASE) sources play an important role in biomedical field. The pulsed ASE light source is used as a pumping source to stimulate the supercontinuum generated by the nonlinear medium, which has low temporal coherence and broad spectral characteristics, making it have a broader application prospects. The generation and amplification processes of a pulse ASE source are investigated . The nanosecond pulse ASE light source at a watt level is obtained. A fiber loop mirror structure is used to promote the in-band power, which resulting in a 280 mW continuous narrowband ASE output. And using an acousto-optic modulator and an electro-optic modulator to modulate a continuous narrowband ASE, with a pulse width of 8 ns, a repetition frequency of 50 kHz and an average power of 50 μW. The amplification process of ASE with different pulse shapes is studied in detail.

High-order harmonics generation (HHG) and isolated attosecond pulse generation of H2+ in a few-cycle 800 nm chirped laser field are theoretically studied. Calculation results show that the HHG can limit the harmonics emitted by two nuclei at the same time through choosing the proper chirped parameters, which decreases the interference in the space and helps to obtain a smooth and continuous HHG flat supported only by single nucleus. An isolated 98 attosecond pulse is generated by synthesizing a spectrum width of 100 orders in the smooth and continuous region with the chirped parameters β=6 and the full width at half maximum τ0=5 fs. Calculation results also verify that when there are two nuclei contributing to the HHG, it is harmful to generate the isolated attosecond pulse. In the discussion, the classical returning energy maps and time frequency analysis are performed to explain the physical mechanism of HHG.

By the laser overlap welding experiments, the tensile-shear and fatigue properties of different joint specimens are investigated and the experimental results are analyzed by combining the weld cross-sections and fracture morphologies. The results show that, as for the non-penetrating joint with a width of 80 mm, the residual stress makes the tensile-shear strength decrease by 4.1% and the fatigue limit value decrease by 26.4%. The 0.2 mm overlap gap makes the tensile-shear strength of the joint decrease by 8.8% and the fatigue limit value decrease by 6.25%. The incidence angle of 20° makes the tensile-shear strength of the joint increase by 3.8% and the fatigue limit value increase by 18.7%. As for the same thickness combination, the cold rolling state of base metals has a certain impact on the mechanical properties of joints.

The MC carbide reinforced Inconel625 composites are prepared by the laser additive manufacturing technology, and the effects of TiC addition mass on the microstructures, micro-hardness and wear properties of the composites are investigated. The results show that the microstructure of composite with the addition of TiC is composed of dendritic γ matrix and interdendritic reinforcements with a dispersive distribution. With the increase of TiC addition, the primary dendritic spacing of the composites decreases, while the content of MC carbide as well as the micro-hardness increases gradually. The wear resistance properties of all the composites are improved by over 80%. When the TiC has a mass fraction of 1%, the yield strength and tensile strength of the composites are increased by 21.9% and 27.5%, respectively, but their elongation is reduced.

The dissimilar weldment of P92/Inconel 625 is realized by the ultra-narrow-gap laser welding with filler wire and the microstructures and mechanical properties of the welded joints are systematically investigated. The results show that the quality of the welded joints have smooth welds, nice sidewall fusion, no pores and other defects. The welds possess a typical characteristic of solidification structure. The microstructure in the heat affected zone of P92 steels is martensite, which is divided into the coarse grain and fine grain zones. The micro-hardness in the fine grain zone of P92 steel at the welded joint interface is the largest, but it decreases after heat-treatment. The specimens fracture at Inconel 625 alloy in the tensile tests at the room temperature, but fracture at P92 steel in the tensile and stress-rupture tests at high temperature. The impact toughness of welded joints is between those of the two kinds of base materials.

A numerical simulation model based on the cross-linked distribution of mitigated pits in the fused silica elements is proposed. The modulation effect of the mitigation area on the downstream light transport under the 351 nm laser irradiation is studied by the scalar diffraction theory and the fast Fourier transform algorithm. The results indicate that the modulation of the cross-linked mitigation area on the downstream light transport is mainly determined by the cross-linking degree of mitigated pits. With the increase of cross-linking degree, the local maximum of light modulation first increases rapidly and then decreases very fast, and the corresponding location first approaches and then is far away from the output surface of the mitigated element. With the increase of propagation distance, the light modulation first increases rapidly and then decreases very fast. The parameter optimization of the morphological structure of the mitigation area can avoid effectively the cascading damages among the downstream elements.

The laser cladding of CoCrW powder on 38MnVS6 steel substrate is conducted, and the effects of active elements in substrate on the morphology and microstructure of laser cladding layer are investigated. The results show that, when the powder feeding rate is 5.60 g·min-1 and the scanning speed is smaller than 5 mm·s-1, the melt pool of cladding layer is relatively deep and the fusion line of cladding layer and substrate is concave downwards. When the scanning speed is higher than 6 mm·s-1, the melt pool is relatively shallow and the fusion line is smooth. The increase of the powder feeding rate makes the change of cladding layer morphology. The sulfur content in substrate determines the temperature coefficient of surface tension, which changes the direction of Maragoni convection and thus influences the final compositions and microstructures of cladding layers.

The Si powders of different contents are added into the TC4 powders and the laser cladding deposition experiment is conducted. The influence of induction heating on the microstructures of samples is investigated. The results show that, as for the as-deposited samples without the introduction of induction heating, Si can effectively refine the columnar crystals and thus their widths decrease from 285.5 μm to 12.1 μm. In contrast, after the introduction of induction heating, the widths of the columnar crystals do not change, but part of the columnar crystals in the direction of deposition are broken and thus the throughout growth does not form. In addition, the crystals consist of a large number of α colony, and the irregular and dispersed silicide precipitations occur in α lamellar.

The Tm2O3-doped 55GeO2-15PbO-5PbF2-10BaO-10ZnO-5K2O germanate glass is fabricated by using the high temperature melt-quenching method. The thermal stability and structures of this glass are measured, and the thermal stability coefficient of this glass is greater than 180 ℃. The hydroxyl content of this glass is measured by a infrared spectroscopy and the hydroxyl absorption coefficient is less than 0.51 cm-1. The absorption and fluorescence spectra are obtained under different Tm2O3 doping concentrations. The research results show that the cross-relaxation rate increases with the increase of Tm2O3 mass fraction. When the mass fraction of Tm2O3 is 5%, the fluorescence intensity at a wavelength of 1880 nm reaches the maximum, and the peak emission cross section of3F4→3H6 energy transition is up to 5.84×10-21 cm2.

The surface state density of gallium arsenide (GaAs) materials can be significantly lowered by surface sulfur passivation. After passivation, a 14-fold enhancement in the photoluminescence intensity of GaAs films is observed and the photocurrent and responsivity also increase. The performance improvement is analyzed from the perspective of energy bands and the results indicate that the passivation treatment is helpful for the adjustments of the surface density and the Schottky barrier height, which further improves the material performances.

The preparation of p-type heavily-doped 4H-SiC is conducted by using the laser irradiation of solid Al film. The effects of the Al film thickness and the laser pulse number on the doping results are analyzed and the control of different process parameters to the electrical properties of p-type doped layers is verified. The results show that the maximum carrier concentration is 6.613×1017 cm-3, the minimum volume resistivity is 17.36 Ω·cm, and the doping concentration (particle number concentration) is 6.6×10 19 cm-3, when the Al film thickness is 120 nm and the pulse number is 50. The Al doping modification mechanism of 4H-SiC can be described as the formation of p-type doped layer as a result of the Si—C bond breaking and the replace of Si by Al under the ultraviolet laser irradiation.

A white-light interference algorithm based on spatial frequency-domain analysis is described, which permits a high-resolution surface measurement by removing 2π ambiguity contained in phase information. In the frequency domain analysis, we can extract the coherence and phase profiles simultaneously, where the coherence profile is free of 2π ambiguity but contains the measurement errors caused by background noises, while the phase profile is precisely the opposite. By combining the coherence and phase information, we remove the 2π ambiguity contained in phase information successfully. In addition, a differential analysis method between adjacent pixels is adopted to deal with the local 2π phase-jump errors, which are caused by the background noises and the light source fluctuations. This technique is highly efficient since it does not require enormous computation. Both theories and experiments are elaborated in detail to verify the validity and stability of this method.

Active light measurement based on structured light is widely used in industrial measurement for its several advantages, while the Gamma nonlinearity, vibration, and noises easily lead to phase error and effect accuracy of three-dimensional measurement. Due to Gamma nonlinear problem for measurement system and different brightness distributions of projector, the system has different Gamma values. An image is projected on a standard whiteboard with smooth surface, and partitioned by using grayscale feature by histogram statistics. According to sub-regional information target area of the projector sub-area information is obtained to establish different regions modelling, which is used to compensate initial phase. To avoid system jitter and noise, original image is pre-processed before solving the phase. Applying this method to actual measurement, precision and accuracy of phase are greatly improved, and the method is simple and convenient, compared with existing methods of eliminating the nonlinearity of Gamma.

For the pulse laser ranging system commonly used in flight target trajectory measurement, the variation of echo waveforms has significant effect on the ranging accuracy. In order to study the range error caused by the variation of echo waveforms,we analyze the echo characteristics of the complex three-dimensional flying target. Based on the typical Q-switched pulsed laser ranging, the mathematical model of transmitted pulse of Q-switched laser is analyzed, and a theoretical model is presented with echo power distribution calculated by the reflection characteristics, surface shape and orientation information of the flying target. On the basis of the above, the target model is built with a typical target, and the characteristics of pulsed laser echo are studied by simulation. The influence of target orientation on echo characteristics and echo distortion range error is analyzed. The pulse laser ranging experiment system is built and the simulated target is processed for verification experiment. The experimental results show that the echo pulse broadening and distortion range error caused by attitude angles variation of flight target are consistent with the basic theory, which verifies the effectiveness of the model.

A dual core single channel photonic crystal optical fiber surface plasma resonance biosensor based on TiO2 film is proposed to enhance the sensitivity. A layer of TiO2 film is added on the surface of the sensor silver film, which can isolate oxygen to prevent the oxidation of silver and improve the sensitivity of the sensor. The coupling characteristics and performance of the sensor are numerically analyzed based on the full vector finite element method. It is shown that there is a highly linear relationship between the analyte refractive index and the resonant wavelength of the sensor in the sensing range of 1.33-1.38, the adjusted linear correlation value is 0.9806, and the average sensitivity is 4200 nm·RIU-1. In addition, the effects of photonic crystal fiber air hole size, silver film thickness, TiO2 thickness and other parameters on the performance of the sensor are further carried out. The result shows that changing the structure parameters can optimize the output spectrum of the biosensor and improve the sensor performance.

Aiming at the demand of in-situ online monitoring of heavy metals in industrial wastewater, a continuous online determination method of heavy metals in water based on laser-induced breakdown spectroscopy (LIBS) is proposed. We adopt the enrichment type of graphite substrate evaporation to realize rapid and automatic detection of heavy metal elements in water by studying the enrichment mode of sample solution, method for quantitative addition of sample solution, and evaporation and enrichment type of sample solution, which can improve detection efficiency and capacity. The standard solutions with different mass concentrations of six heavy metal elements including Cd, Cr, Cu, Ni, Pb, and Zn are tested to establish the calibration curves and obtain the corresponding detection limits. The relative standard deviations of multiple measurements of spectral intensity are 9.24%, 10.45%, 12.59%, 11.58%, 15.24%, and 6.87%, respectively. The detection limits are 0.03, 0.012, 0.0047, 0.033, 0.071, and 0.0376 mg/L, respectively. The proposed method provides an effective measure for online monitoring of heavy metals in water.

A kind of terahertz metamaterial with a near-zero magnetic permeability (μ) which uses a metal-dielectric composite structure as the basic unit cell is proposed. Under the condition that the terahertz wave is incident perpendicularly, the optimal value of the real part of μ is 0 near the resonance frequency of 1.44 THz with a bandwidth (|μ|<0.05) of about 0.2 THz when the electric field is transverse-magnetic polarized. However, when the electric field is transverse-electric polarized, the optimal value of the real part of μ is 0 near the resonance frequency of 0.978 THz with a bandwidth (|μ|<0.05) of about 0.1 THz. Under the fixed geometric parameters, the μ-near-zero effect can be achieved in different frequency bands via the adjustment of polarization direction. The influences of the thickness of polyimide dielectric layer, metal layer number, and incident angle on the μ-near-zero effect are analyzed, and the tolerance error range of this structure is discussed.