For 3 kW diode laser used in robot surface modification system, the focal spot is uneven. A kind of focus and homogenization method by using the Fresnel lens for the focusing system of high power diode laser has been put forward, and a uniform rectangular spot of 10 mm×2 mm has been designed. Through the simulation analysis of Zemax and Matlab, the influences of the pitch of Fresnel lens and the divergence angle of incident rays on the homogeneity of the focal spot have been studied. The results show that the best uniformity of the focal spot is about 94.90% when the pitch of Fresnel lens is less than 1mm and the uniformity gets worse and worse with the increase of the pitch of Fresnel lens. As the pitch increases to 2.5 mm, it has less influence on the uniformity of the focal spot, and the uniformity basically stables at around 93.85%. Meanwhile, the uniformity will be improved with the increase of divergence angle, but large divergence angle will increase the difficulty of focusing and make the uniformity get worse and worse. When the pitch of Fresnel lens is 1mm and the divergent angle is from 12.5 mrad to 20 mrad, the best uniformity of the focal spot is 95.22%.

The pure phase modulation characteristics of a liquid crystal spatial light modulator are measured at oblique incidence using Zygo interferometer. The establishment of a mathematical model of pure phase modulation of liquid crystal spatial light modulator at oblique incidence, the effects of oblique incident angle of the phase modulation characteristics, structures based Zygo interferometer measurement system, and phase modulation characteristics under various incident angles are measured. The measurement results show that, at various incident angles, phase modulation increases approximately linearly, and the larger the incident angle, the smaller the increasing slope. With the same gray scale value the phase modulation amount decreases when the incident angle increases. When the incident angle is less than 5°, phase modulation curves almost coincide, and the maximum phase difference of the phase modulation amount is 0.032l with the same grayscale value.

Based on Fernald method, the function relation between the set value of the lidar ratio and the optical depth of aerosols within the lidar detection range is studied. In view of the continuity of the function, the new algorithm for retrieving low layer arosol slidar ratio is proposed, in which the dichotomy is used and the optical depth of aerosols is the convergent criterion. In late July 2014, the sun photometer and the self-developed Raman-Mie lidar are used to detect the atmosphere in Xi′an. Then the proposed algorithm is used to retrieve the lidar ratio and the extinction coefficient. The experimental results show that, the lidar ratio of aerosols in Xi'an is relatively stable during the observation period, the value is 44 or 45. Due to the impact of atmospheric humidity the lidar ratio is larger in the day of rain, the value is 51. The fine retrieving of aerosols lidar ratio is accomplished by iteration, and in the iteration only the Mie scattering signal of lidar and the detection data of sun photometer are used. This is very important for studying the fine retrieve algorithm of aerosol′s optical characteristics.

In order to realize the narrow-gap welding of 20 mm thick plate 16MnDR steel, experiments are designed to study the effect of root faces and groove angles on welding process stability, weld appearances and welding efficiency, then optimize the size of the groove, on this basis, using autogenous laser as bottom welding, multi-pass multi-layer laser-MIG hybrid welding to fill the gap. The results indicate that the weld appearance is pretty good and there is no defects of internal weld. Comparing the welding heat input and welding efficiency of laser-MIG hybrid welding with traditional arc welding, the welding heat input of laser-MIG hybrid welding decreases by 45%, and the welding efficiency of laser-MIG hybrid welding increases by 155%. The tensile strength of the joint is slightly higher than that of the base metal, satisfying the strength requirement, and there is no crack while the joints are bent to 180°, meeting the yield strength.

Tensile strength 700 MPa Nb-Ti microalloyed C-Mn steel is welded using high power fiber laser. The effects of heat input (162、175、187、226 J/mm2) on microstructure, tensile properties, microhardness, impact toughness are studied. The results show that the microstructure of welded seam (WS) and coarse grain heat affected zone (CG-HAZ) are mainly lath martensite, and a little of bainite and ferrite. The original austenite grain size of CGHAZincreases with heat input increasing. The effects of heat input on microstructure of fine grain heat affected zone (FG-HAZ) and mixed grain heat affected zone (MG-HAZ) are not obvious. The average hardness of WS and HAZ are greater than that of base material (BM), and the hardness of WS and peak hardness of weld joint decrease with the heat input increase because of the formation of ferrite and bainite with the increase of heat input. The tensile strength of welded joint are higher than that of BM at four different heat inputs. The impact toughness of weld joint is better than that of BM at four different heat inputs, and both weld joint and BM fracture mode are ductile fracture. The effect of heat input on weld joint impact energy is not obvious.

The thin surface layers of 316 L stainless steel with different mass fractions (5%, 10%, 13.26%) and sizes (nano, micro) SiC composite powder are deposited on Q235 steel substrates by laser cladding process. Sections of such coatings are examined to reveal their microstructure and properties and to analyze the strengthen mechanism, by using optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD). The distribution of the hardness on the cross section of cladding layer and wear resistance of the coatings also are tested by microhardness tester and frictional wear tester. The results show that 316L stainless steel with 10% of the SiC is appropriate. With the same proportion, micro SiC just dissolve partly, but some SiC phase exists; while nano SiC will be dissolved totally, producing new strengthening phase M7C and FeSi, which can effectively inhibit the growth of the columnar crystal, and change the microstructure of the cladding layer for cellular crystal, also restrain the growth of g-CrFeNi grain in the overlapping remelting area, the coating hardness reaches 527HV increase by 132% compare with the pure 316L coating; the coating hardness is higher than 100HV, compare with the cladding layer with the addition of 10% micro SiC, and the friction coefficient and wear weight loss are minimal, which leads excellent wear resistance.

Using the substrate of mild steel with thickness of 2 mm, Fe-Si-B amorphous ribbon with thickness of about 25 μm is cladded on substrate surface by pulse laser. The effects of pulse power P, pulse width W, pulse frequency F, beam diameter f of the pulse laser on the formation, the dilution rate, microstructure and microhardness of the coatings are investigated. The results show that the coating with well formation, the lowest dilution rate, lower pore density, and chemical bonding with substrate is obtained, when P=18.4 W, T=3.2 ms, F= 3.0 Hz, f=0.3 mm. With the increase of laser power, the crystallization in coating happens easily, and the contents and categories of crystallization phase of α-Fe, Fe2B and Fe3Si are increased, moreover, the thickness of coating increases while the microhardness of coating decreases. The highest microhardness in central coating is about 1400 HV , exceeding extensively that of mild steel with 100 HV.

Rolled AA7020-T651 with 2 mm thickness are welded by a hybrid laser arc heat source system with the ER5356 filler. The microstructure and mechanical performance of hybrid welded joint are investigated by optical microscope, scanning electron microscope, Shanghai synchrotron radiation X-ray micro-tomography, electron backscattered diffraction, micro-hardness, tensile properties and finite element simulation. The results show that the weld zone, fusion line and base mental exhibit cast equiaxial dendrites, large columnar crystal and stretching rolling structure, respectively. Moreover, a fine grain zone with about 100 μm in width near the heat affected zone is observed clearly. The tensile strength, yield strength, elongation and welding coefficient are 260 MPa, 213 MPa, 4.8% and 0.7, respectively. Central hybrid weld has the lowest hardness (75 HV), which is about 62.5% of base metal, presenting a serious strength loss. This is mainly due to serious evaporation losses and redistribution of strengthening element Zn as well as the precipitate particles modifications during the hybrid welding process. Finite element analysis suggests that the undercut similar to a notch near weld toe rather than central weld zone with the lowest hardness is the fundamental reason to the fatigue failure of in-service hybrid welded joints.

Heat treatment is an important method to improve the mechanical property of laser deposition repair GH4169 alloy. The effects of different heat treatment methods and aging heat treatment temperature on high temperature tensile properties of laser deposition repair GH4169 alloy are investigated. As compared with asdeposited (AD) samples, after the local heat treatment and vacuum heat treatment for laser deposition repair GH4169 alloy, microstructure of laser deposition repair GH4169 alloy changes little, the interdendritic Laves phase slightly dissolved. The high temperature tensile strength and yield strength of vacuum heat treatment samples are slightly higher, reaching over 86% and 95% of the wrought standard of Q/3B548-1996, however, the elongation after fracture decreases slightly. After increasing the temperature of aging heat treatment, the Laves phase slightly dissolved further, the high temperature tensile strength and yield strength of repaired specimen are improved, reaching over 92% and 98% of the wrought standard.

Single-polarization, single-longitudinal-mode (SLM) erbium-doped fiber laser based on the twisting of polarization-maintaining fiber Bragg gratings (PMFBGs) is proposed and demonstrated. Two uniform FBGs directly written in a homemade polarization-maintaining and photosensitive erbium-doped fiber (PMPEDF) without hydrogen loading by using ultraviolet light from a 248 nm KrF excimer laser as the wavelength-selective component are used in a linear cavity. Owing to the polarization-dependent loss enhanced by the PMFBGs, stable SLM and stable single- polarization operation of the fiber laser are achieved by controlling the birefringence through appropriately twisting the fiber laser cavity.

In combination with characteristics of cavity spatial filter far-field alignment on SG-II-Up facility, a serial- parallel alignment control method based on combination of feed forward compensation and feedback regulation is presented by establishing coupling models between pinholes. The reference centers are stable and reliable extracted out by position predication and gray gradient extremum search. The feedback regulation quantity is determined by image Jacobian matrix for each pinhole. Regulation of previous pinhole is regarded as disturbance to the next one, and the feed forward compensation control quantity is calculated according to the established coupling model between pinholes. The serial- parallel alignment controls for multi- pinholes are implemented simultaneously by synthesizing the feedback and feed forward control quantities. Experimental results show that the reference center extraction accuracy reaches above 97%, collimating time reduces from 1 min to 30 s, and the collimating efficiency improves greatly.

A new delayed self-heterodyne technique using an unbalanced Michelson interferometer (MI) composed of a 3×3 optical fiber coupler is proposed. The principle of the technique to measure the laser phase and frequency noise are analyzed theoretically. The experimental setup is introduced. Also, the technique is used to characterize the phase noise power spectral density (PSD), frequency noise PSD and linewidth of two typical kinds of lasers, distributed feedback (DFB) semiconductor laser (Emcore) and super-narrow linewidth DFB fiber laser (NKT). The results show that the technique can measure the noise characters of different kinds of lasers and it confirms the correction and robustness of the proposed technique.

Heat management has become one of the key techniques for diode pumped solid state laser′s (DPSSL) performances, such as compact, plug-in efficiency and beam quality. The heat management technology for DPSSL based on low-melting-point Gallium alloys phase change material (PCM) is studied. Experimental result proves that, compared with air-cooled heat radiator, PCM heat radiator can extend laser working hours to six times longer, decrease cooling power to 46% and radiator′s volume to 53%, and improve the plug efficiency from 3.02% to 3.77%. Furthermore, the finite element software ANSYS has been used to simulate the temperature distribution of PCM radiator. The simulated result indicates that PCM has advantages such as low cooling power and small volume. The results provide the theoretical and experimental basis in laser heat management using liquid metal, and has important engineering application value.

In order to study the effect of laser shock processing (LSP) on mechanical properties of magnesium alloys, the tensile stress-strain curves and microstructures of AZ31 and AZ80D-T6 magnesium alloys are investigated by electronic universal tensile machine and with Nd: glass laser with the wavelength of 1064 nm and pulse width of 20 ns. The results show that after LSP, the tensile strength of AZ80-T6 and AZ31 alloys are increased by 4.6% and 15.7%, the surface hardness are increased by 22.7% and 31.8%, respectively. The strengthening effect of LSP on AZ31 is more significant than AZ80D-T6. The LSP generates high value residual compressive stress and high-density twins as well as the lamellar or short columnar or dynamic precipitation b phases. The grains are refined and the ultrafine grains are formed. The effect of pre - aged β precipitates on LSP strengthening effect and tensile fracture characteristics are discussed.

The effect of temperature on laser wavelength from a dye-doped cholesteric liquid crystal (CLC) is studied. It is found that the laser wavelength is red shifted with the temperature rise. For a thin dye-doped CLC sample, the laser wavelength abruptly jumps at a certain temperature and then slightly decreases with the temperature rise within a certain temperature range. When the sample is thick enough, i.e. the sample thickness is more than 25 μm, the laser wavelength almost increases linearly with the temperature rise. The physical mechanism of this phenomenon is analyzed, theoretical simulation is performed, and the simulation result is consistent with the experimental result. The property that the laser wavelength increases linearly with the temperature rise can be used for temperature sensors.

The dissimilar metals of copper alloy and stainless steel are joined by single friction stir lap welding. Ni-based alloy coating with WC is deposited on the transition layer of stainless steel by laser cladding. Optical microscope (OM), scanning electron microscopy (SEM) equipped with energy disperse spectroscopy (EDS), X-ray diffraction (XRD) and micro hardness tester are used to investigate the microstructure, phase and hardness. The results show that a reliable connection is formed in the transition layer of stainless steel and copper matrix, the homogeneous layers of stainless steel and copper are formed in the middle and lower part of the welded zone(SZ)； intercalations NiCu4 are observed in the layered structure, for which untypically high hardness value 277 HV is registered; the microstructure of Ni-based alloy is compact and the coating is composed of γ-Ni，Ni3Fe，WC，W2C and Cr23C6. The average hardness of the coating is increased, which is 5.7 times as high as that of copper alloy.

The line defect waveguide structure of triangular lattice photonic crystal with air ring is studied. The influence of scatter inner radius Rin and outer radius Rout on the slow light properties is studied. These results indicate that the ratio of Rin/Rout in 0.15~0.35 is favorite to obtain the broadband slow light. The outer radius Rfout of the air ring rows next to the waveguide channel has the more impact on the properties than the inner radius Rfin of the air ring rows next to the waveguide channel. The air holes scattering element on both sides of the waveguide are benefit to reduce the group velocity, while the air rings are helpful to get wider slow light bandwidth. However, the ideal slow light phenomenon is obtained in the asymmetric line defect waveguide which is combined air holes with air rings. The group velocity 0.0086 c which has low dispersion is obtained with the wavelength range of 6.588 nm.

Novel high quality factor Q terahertz metamaterials based on asymmetric double split ring resonator as unit cells are reported. When the incident electric field is polarized perpendicular to the ring gaps, the proposed structure simultaneously sustains, the trapped- mode resonance, the mixed- mode resonance and the dipole resonance in different terahertz frequency ranges. The quality factor and center resonance frequency of the resonances can be tuned by changing the gap position and vertical distance between the horizontal metal microstrip lines of the metamaterials unit cells. Numerical simulation results show that the stop band of trapped- mode resonance can reach almost narrow line width of 11.1 GHz and the corresponding quality factor is about 40; the line width of mixed-mode resonance is about 62.4 GHz and the corresponding quality factor is about 16. The proposed high-Q metamaterials have extensive applications in the fields of terahertz research, such as for the high-resolution thin-film sensors, high-performance narrow-band terahertz filters and high frequency modulators.

Multifunctional Fe3O4@Gd2O3∶Eu3+ hollow nanospheres are prepared via a urea-based homogeneous precipitation method. The multifunctional layers are designed to a shell- shell structure to avoid the magnetic nanoparticles clustering. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images indicate that the as-obtained Fe3O4@Gd2O3∶Eu3+ sample consists of uniform nanospheres with an average diameter of 390 nm, and the thicknesses of magnetic and fluorescent layers are about 55 nm and 15 nm, respectively. The shell thickness and the size of the hollow nanospheres can easily be controlled via adjusting the concentration of raw materials and the size of silica template. The sample of Fe3O4@Gd2O3∶Eu3+ shows high saturation magnetization of 17.1 emu/g and strong red emission under ultraviolet excitation, which may be applied in targeted therapy, immune detection, magnetic separation, luminescence detection and so on. This synthesis route is of great significance in the controllable synthesis of other multifunctional hollow nanospheres as well.

Random phase-shifting algorithm based on principal component analysis has important application in dynamic interferometry. At present, the sign ambiguity and the reliability of the extracted phase by principal component analysis are still not be solved and valued in the exiting references. To solve these problems, we firstly extract the phase and phase shifts simultaneously from interferograms with random phase shifts by principal component analysis. Then we analyze the relationship between the extracted phase shifts and the global sign and the accuracy of the extracted phase. Finally, the sign ambiguity and the reliability of extracted phase are determined and valued by analyzing the extracted phase shifts. Numerical simulations and experiments are implemented to verify the effectiveness of this method. The simulation result shows that the global sign and the reliability of the extracted phase depend on the slope and the statistic characteristics of the phase shifts, respectively.

The dynamic Allan variance (DAVAR) is a new method for analyzing stochastic error of gyroscope. However, it has difficulty in making a good tradeoff between tracking capabilities and variance reduction due to the window with fixed length. An improved algorithm based on kurtosis and time-variant window is proposed to quickly track variations in the signal and obtain a low variance of the estimate. The kurtosis is introduced into analysis of gyroscope output, and the window length function to truncate signal is built by taking kurtosis as variables,which can make window length change with the non-stationary of the signal automatically. Then the length of truncation window is estimated according to the function, the values of Allan variance is obtained in the windows, and the error coefficients can also be identified and extracted at the same time. The above data are expressed by three or two-dimensional to describe the dynamic characteristics of gyro. Simulation and experimental data analysis results show that the proposed algorithm can track the non-stationary of gyroscope more effectively and obtain a good confidence in stationary random process, and the method can be more effective for the extraction and identification of stochastic error coefficients.

The double-helix chiral fiber grating is a polarization and wavelength selective, which is very potential for applications in the field of optical fiber sensing. However, the spin pitch of the reported chiral fiber grating with circularly polarizing property is only tens of micrometers. The high insertion loss and low mechanical strength limit its application scope. The polarization filtering properties of the normally used coated fiber, whose refractive index of the jacket is higher than that of the cladding, are studied using the complex coupled mode equations. It is revealed that not only the mechanical strength increases in the coated fiber, but also the spin pitch increases to hundreds of micrometers. For this reason, loss can be reduced to meet the transmission requirement of a medium length of fiber. Influence of the parameters of the double- helix circularly polarizing fiber on the polarization filtering properties is analyzed. It is shown that increasing the coupling coefficient of the core mode and the cladding leaky mode is an effective way to improve the polarization filtering performance of the fiber. The results are instructive for the research and developing of the double-helix circularly polarizing fibers.

With mode coupling theory and finite element solving method, a photonic crystal fiber (PCF) coupler basing on selective infiltration and its response to bending are investigated. The bended coupler is treated as a straight waveguide by introducing an equivalent refractive index (RI). The coupling wavelength is simulated and the bend sensing characters are analyzed. The coupling wavelength shift has linear response to bending curvature with directional indication; the coupling wavelength is decided by the RI of infiltrated liquid and the diameter of air-holes; while the bending sensitivity is affected by the distance between the infiltrated hole and the fiber core. With these characters, a two-dimensional bending vector sensor is designed based on selectively infiltrated PCF. Two orthogonal air-holes on the cross-section of the PCF are selected to be filled with different RI liquids. The two liquid waveguides couple with fiber coreseparately. The shift of two coupling wavelengths indicates the bending curvature in two orthogonal directions. The bending curvature and two- dimensional direction can be solved simultaneously by inspecting the shift of two coupling wavelengths. The flexible design and controllable fabrication of the sensor has been demonstrated and a promising sensing application could be seen.

A novel structural en/decoder using wavelength selective switch and optical delay line is proposed to reconfigure and achieve high chip rate in two-dimensional wavelength-hopping/time-spreading (2-D WH/TS) optical codedivision multiple access (OCDMA) system. This study expounds the operation principle, presents experimental results from a network tested with user operating at 2.5 Gbit/s, and realizes the experiment of 40 km transmission. Features of group delay and insertion loss about en/decoder are measured and performance of 500 GChip/s rate en/decoder is reached with VPI simulation software. The experimenal results demonstrate that the novel method can recover the waveform, and moreover, the bit error rate of the system can be less than 1.00 × 10-9.

In order to achieve one-way absorber, a one-dimensional photonic crystal including magnetic material layer and metal layer is designed. The transmission properties of the structure are studied using a modified transfer matrix method. Based on the coupling of magnetic surface plasmonic resonances, the structure achieves perfect nonreciprocal absopbtion. For a special wavelength of 409.725 nm, the electromagnetic wave is totally absorbed from left incidence with incident angle of +45°, whereas it is totally reflected from right incidence with incident angle of -45°. The results are demonstrated through simulations based on finite element method.

Polarization imaging detection based on continuous terahertz (THz) wave is studied. THz real-time polarization imaging system,which using the SIFIR-50 THz laser as radiation source and a NEC IRV-T0831C THz imager as array detector, is demonstrated. According to the polarization characteristics from transmitted light of the target, THz transmission images for three kinds of typical targets—metallic structures, watermark of cashes and hidden objects—are obtained using the uncooled microbolometer THz camera. The Stokes vector images and polarization images are calculated and analyzed. Experimental results show that THz polarization imaging not only have the advantage of THz noninvasive imaging, but can also improve the performance of target recognition effectively and maximize the differences between the images of different target objects.

The advantages and disadvantages of several kinds of three-mirror system and four-mirror system are clear, a kind of high quality space detailed survey camera in the middle or high orbit is formed. According to the same technical target, we analyse the key parameters of space detailed survey camera, six kinds of optical systems: on-axis three-mirrors system, two imaging off-axis three-mirrors system, one imaging three-mirror system, onaxis four-mirrors system, two imaging off-axis four-mirrors system and one imaging four-mirror system has been designed by Zemax software, and all of them can satisfy the requirements of the indicators. The advantages and disadvantages of six systems are given, on consideration of the fabrication, testing, calibration and the technology development of high resolution camera, the one imaging off-axis four-mirrors system has been chosen, gets a effective focus length 29 m, F number 9.7, wide of field 1°×0.3°, shape size 3200 mm×6489 mm×8194 mm space detailed survey camera optical system. The property of the optical system is simulated and validated, the results suggest that the resolution, transfer function, aberration and distortion of system are excellent.

Combining the Bloch theory and Maxwell equations, the Bloch surface wave forming on the surface defect of one-dimensional photonic crystal is analyzed theoretically. The local characteristics of Bloch surface wave and the influences of incident angles and incident wavelengths on the Bloch surface are discussed. On this basis, the sensing performance of the surface defect photonic crystal structure is studied. When the incident TE polarization component travels through the photonic crystal at a certain angle, the surface wave resonance occurs in the defect layer forming by the detected solution, and the electromagnetic field is located and enhanced. The Bloch surface wave has a high sensitivity with the change of the refractive index of the solutions. The simulation results show that the Q value can up to about 2620.29, and the sensitivity S is about 62°RIU-1. Therefore, the Bloch surface wave has good sensing performance in the one-dimensional photonic crystal structure. It can provide certain theoretical references for the design and application of refractive index sensors.

Shapes of a water- jet in different regimes are analyzed on the basis of fluid theory. High speed photography is used to record the turbulence of the water-air interface. The water-jet contours are detected and reconstructed by using digital image processing algorithms. The ray tracing method is employed to investigate the optical losses produced by the surface perturbation. The results show that the amplitude and frequency of turbulence have a great impact on light propagation under the effect of total internal reflection. At the stage of incipient turbulence, no optical losses is caused since the wave amplitude and frequency are the relatively small. But when the amplitude and frequency of turbulence exceed certain threshold values, the power losses tend to increase so that it weakens the ability to guide light of water-jet in this kind of situation.

Considering the problems of long detection time, poor reproducibility and limited resistance to light and temperature interference of equipment used for on-site detection of pesticide residues in the current market, a portable pesticide residue detector is designed based on enzyme inhibition and the data fusion algorithm. The system mainly includes an absorbance sensing module and a signal data fusion conditioning module. The absorbance sensing module uses front optical compensation path to eliminate common optical signal interference. The signal data fusion conditioning module groups and fuses the electrical signal in order to enhance signal authenticity. The test shows that the sensor system has good stability and reproducibility (relative standard deviation is lower than 2.5%), and the introduction of front optical compensation path eliminates the common optical signal interference effectively. Validation rate of samples whose inhibition rate is higher than 70% is up to 85%. When the sample inhibition rate reaches 50%, the pesticides in the concentration range of 0.5~5.0 mg/kg can be detected, which meets the demand of on-site detection.

A remote imaging radar system based on ultra-wideband chaotic signal generation and radio over fiber is proposed and demonstrated experimentally. The radar system consists of a central station, optical fiber links and a base station. At the central station, an ultra-wideband chaotic signal is generated by an improved Colpitts oscillator and then is up-converted as a probe signal. The probe signal is converted into an optical signal by using the external modulation technique of laser diode. Optical fiber links are used to transport optical signals to the remote base station or back to the central station. At the base station, the optical signal is transformed into the microwave signal and then transmitted by a horn antenna. At the receiving end, the echo signal from a target is converted to be in optical domain and then transported to the central station, where it is collected after optical-to-electrical conversion and down conversion. The target imaging is obtained by utilizing the correlation method and back projection algorithm. Experimental results show that the proposed radar system can achieve remote imaging for single and multiple free-space targets with a distance of 10 km. The range resolution of 6 cm and the azimuth resolution of 8 cm are obtained, respectively.

Three- dimensional fluorescence spectroscopy is one of the most important techniques to analyze substance. The adulterated edible oil is detected, and Rayleigh scattering, spectral intensity and position of characteristic peak are analyzed through three-dimensional fluorescence spectroscopy. It is found that the Rayleigh scattering, emission wavelength and spectral intensity vary with the increase of concentration of fried oil. In order to exactly analyze the impact of the fried oil on edible oil, the fluorescence peak of vitamin E is discussed. The experimental results show that the redshift of the fluorescence peak of vitamin E is observed and the fluorescence intensity declines with the dosage concentration increasing. The sensitivity and reliability of the three-dimensional fluorescence spectroscopy technique is demonstrated. As the results show, the detection of fried oil in edible oil based on three-dimensional fluorescence spectroscopy is feasible and effective.

Time-resolved spectra of Zn plasma induced by a femtosecond laser are acquired and analyzed with an intensified charge-coupled device (ICCD) spectral system. The time-evolution characteristics of the plasma spectra and parameters are investigated. Through analyzing the continuous and characteristic spectra of the Zn plasma, it is found that the continuous spectrum appears firstly and its life time is only about 100 ns, subsequently the characteristic spectrum emerges. The different characteristic spectra show different intensities. Meanwhile the evolution regularities of the electron density and temperature are obtained. Furthermore, the line shift of the spectrum at 481.0 nm is analyzed. The results show that there are red shifts for the spectrum at the original region and its maximum value is up to 0.23 nm. Then the red shift becomes quite small after 300 ns. The line shift changes with the electron density almost linearly.

Hemoglobin concentrations of single red blood cells are measured by single cell laser tweezers Raman spectroscopy. Hemoglobin solution with different concentrations is prepared and the linear relationship between Raman intensity and hemoglobin concentration is obtained. By detecting the Raman spectrum of a single red blood cell, the hemoglobin concentration of a single red blood cell is calculated according to the linear formula. Raman spectra of 70 red blood cells are measured. The calculated hemoglobin concentration of single red blood cells is from 270 g/L to 500 g/L. Mature erythrocytes account for more than 90% of the red blood cells and its hemoglobin concentration is 350~450 g/L. The hemoglobin concentration of reticulocyte is 300 g/L or less, and the hemoglobin concentration of old red blood cells is higher than 450 g/L. The conclusion conforms to the standard of mean corpuscular hemoglobin concentration (MCHC) 310~370 g/L. Using this method to measure hemoglobin concentration of single red blood cells is quick, non-destructive, simple and accurate. This shows the advantages of Raman spectroscopy on single cell analysis.