During a 1 m solar telescope tracking process, the relative change between the telescope optical axis and its auto-guiding system optical axis decreases tracking accuracy. According to the structure of the telescope optical, mechanical and electric control systems, the tracking error of auto guider caused by the change of optical axes is analyzed, and the detection method of the optical axes change is provided. The test results show that the maximum relative change of the optical axes is 46″. It varies only with the telescope altitude angles, independent of telescope azimuth angles. The major factor to cause the telescope optical axes change is telescope structure distortion under its gravity. The software correction model of the telescope optical axes which changes in the auto-guiding system is introduced to improve the long-term tracking accuracy decreased by the optical axes change.

The developing of quantum information technology calls for single photon detector to have higher capability. As a new-style single photon detector, quantum-dot based single photon detector has good potential. A single photon detector based on quantum-dot field effect transistor (QDFET) is researched. The photoconductive gain mechanism of QDFET is introduced. Then the material is chosen and the structure is designed. It′s laid stress on the experimental analysis of photoconductance quantization and noise equations. The results indicate that the single photon detection based on QDFET has great characteristic in sensitivity, photon response and photon resolution ratio.

The results of comparison observation experiments between the 355 nm lidar and BAM-1020 particulate monitor laid on a 325 m tower of the Institute of Atmospheric Physics of the Chinese Academy of Sciences are given. Based on the data from 21 September 2011 to 21 October, good correlation between aerosol extinction coefficient by the lidar and PM2.5 particulate matter concentration is found. The linear regression model to establish the relationship between the extinction coefficient and the particulate matter concentration is used. The data of PM2.5 concentration measured by monitor laid on tower is used to study the inversion accuracy of the relational expression on the vertical height. The study results show that the correlation coefficients between lidar inversion PM2.5 and the measured values at 63, 80, 120 and 160 m are 0.9447, 0.9331, 0.9284 and 0.9308, respectively. The result shows that the lidar can detect the vertical distribution of particles. The lidar will be beneficial to study the spatial distribution and cross-border transportation problems of pollutants, as well as provide data to support policies and measurements of joint prevention and control of regional atmospheric.

The offline time-gated stimulated emission depletion (g-STED) microscopy, which is based on time-correlated single photon counting (TCSPC) algorithm, is proposed. As STED beam can eliminate the ratio of spontaneous fluorescent emission while reducing the fluorescence lifetime, the lifetime of fluorescent signals in the center of excitation focal spot and that in the surrounding doughnut area which are overlap by the STED focal spot are significant different. Based on this principle, in a general continuous wave STED (CW-STED), the fluorescent lifetimes of the whole imaging region are calculated by TCSPC, and the signals with shorter lifetime are discarded after all data recorded. The effective point spread function (PSF) of each fluorescent labels are shrinked in order to enhance the resolution. Compared with traditional ones, this offline g-STED not only decreases the incident intensity of laser to avoid the risk of fluorescence photobleaching and optical toxicity, but also increases the flexibility of time-gate manipulation. A spatial resolution of 80 nm is obtained in the experiment when only 45 mW STED beam is introduced. The potential influences of time-gate selection to the resolution and signal-to-noise ratio (SNR) are further discussed.

Cross-polarized image can provide both polarization-sensitive information and a more clear sub-surface structure of the sample. As a result, getting the cross-polarized image by using optical coherence tomography (OCT) becomes more and more popular. A novel fiber-based cross-polarized optical coherence tomography (CP-OCT) system is implemented, which is capable of acquiring both cross-polarized signal and co-polarized signal of a sample simultaneously. Forming principles of both cross-polarized and co-polarized signals are described, and the expressions of them are derived using Jones matrix. The images of a glass slide, a λ/4 wave plate at a wavelength of 1310 nm, and vivo skin obtained with the system confirm that CP-OCT can provide both polarization-sensitive and polarization-insensitive informations of the sample.

We synthesize CdTe quantum dots in aqueous solution and characterize the stability of quantum dots in different culture media and different pH environments. The impact of quantum dots on HeLa cellular proliferation inhibition rate is studied. The quantum dots conjugated with transferrin are used for HeLa cell labelling. Finally, the quantum dots are conjugated with dextran and applied in the transparent dorsal skin fold window chamber to observe the dynamics of the bioconjugations in blood vessels. The experimental results show that the quantum dots peaking at 660 nm are stable in cell culture media of DMEM and M1640. When the pH of the buffer solutions increases from 5 to 13, the fluorescence intensity of CdTe increases firstly and then reduces. The cell viability is higher than 80% even when the concentration of quantum dots is 13 μg/mL. The quantum dots conjugated with transferrin obviously target to the HeLa cells. What′s more, the clear dynamic flourescence images of quantum dots conjugated with dextran are observed under microscope. The study shows that such quantum dots can be used for living imaging research successfully.

Photonic crystal fibers (PCFs) have made a rapid development for the last several years since the first report in 1996. Consequently, all kinds of PCFs with different structures and characteristics have emerged in endlessly. Based on a main thread that the PCFs are used especially to femtosecond laser technologies, a brief overview of the experimental research in this field is presented. Especially the current status and perspective in the high-power/high-energy femtosecond laser systems is highlighted.

The functional devices based on the microstructured optical fiber infiltrated with liquids effectively combine the micro/nano structure with the physical effect of materials under different external fields. They provide a promising platform for novel photonic devices with the advantages of tunability, flexibility in design, all-in-fiber structure and integration. In this paper, the recent research statue of the liquid-filling microstructured optical fiber devices, such as optical switches/attenuators, filters, modulators and dispersion compensators, as well as optical fiber sensors, is reviewed. At the same time, the variety and physical characteristics of functional materials and the filling methods, which are the focus for future research in this area, are analysed. Finally, some prospects are given for the reference and research in the future.

Diode pumped alkali vapor laser (DPAL) has applications in many areas and is developed rapidly in recent years. A diode laser array with center wavelength of 780 nm is used as the pump source for the Rb laser, and a Littrow external cavity is built with a plane diffraction grating to narrow the linewidth of the diode laser to 0.13 nm. A chopper is used to change the continuous diode laser to pulsed laser. The diode laser is beam shaped, a lens group is used to twist the beam to nearly square shape. After linewidth narrowing and beam shaping, the diode laser is focused on a Rb vapor cell which is filled with Methane as buffer gas at the pressure of 79 kPa. With the maximum peak power of 13 W injected into the Rb laser resonator and the temperature of the cell kept at about 145 ℃, the linearly polarized Rb laser with peak power of 2.8 W is obtained, and the optical to optical efficiency is 21%.

To solve the bottleneck problem of deformation and cracks of laser metal deposition (LMD) parts and improve their mechanical properties, ultrasonic vibration is introduced to the LMD of titanium alloy processes to refine the grain size and to reduce residual stress based on its significant effect in the fields of casting, welding and laser cladding. So the paper applies ultrasonic vibration system to fabricate the samples and analyses its effect on its macroscopical appearances、microstructure and residual stress by experiments. The results show that the cladding layers thickness and the grain size change smaller, and also the reinforcement phase TiC in functionally graded materials samples is more uniform dispersion by metallographic photos. In addition, the residual stress is reduced, which shows that cavitation and mechanical effect of ultrasound break the solid crystal net connected by primary dendrite and refine the grain, and also the melt get supplement so as to the tensile stress is reduced. On the other hand, stirring acoustic stream in the molten pool make the reinforcement phase distribution uniform to reduce the solidification stress for different interphase solidification shrinkage stresses.

Ti-Fe alloy coatings with different Nb4Si additions are prepared by laser cladding on TA15 alloy. The influence of Nb4Si content on microstructures and properties of the coatings are investigated by means of X-ray diffraction, scanning electron microscopy (SEM), microhardness tester, nano-indenter, and frication wear testing machine. The results show that the coatings with different Nb4Si additions mainly consist of β-TiNb dendrite and β-TiNb+TiFe eutectic. However, what has changed is that with the increase of the Nb4Si addition, the content of the eutectic presents the trend of first increasing then decreasing, namely, the highest value is obtained when the atomic fraction of Nb4Si particles is 2.0%. Another change in the microstructure is that a small amount of β-(TiNb)5Si3 phase is formed when the atomic fraction of Nb4Si addition is beyond 0.5%. When the atomic fraction of Nb4Si addition is 2.0%, the hardness, friction and wear properties of the coatings all reach the highest, while the elastic module is the lowest, as a result of high eutectic content.

A 355 nm NdYVO4 nanosecond laser with output power of 8 W and a 1030 nm femtosecond laser with output power of 3 W are used for etching the single-crystal silicon. The effects of laser ablation parameters including laser fluence, pulse width spot overlap rate, and processing times on the processing accuracy and quality are investigated and analyzed. The heating effect of femtosecond laser is less than ultravialet nanosecond laser, and nanometer fringes are generated with the laser pulse of femtosecond level, but many cracks appear for the superposition of nanometer fringes as the processing times increases. The experimental results indicate that the advantage of femtosecond laser processing is not absolute, and relatively cheap ultraviolet nanosecond laser may be more suitable for the cases where plenty of materials need to be removed.

To study the relation between the surface morphology and the deformation mechanism of the target material under the shock, a flexible loading condition, in laser shock peening (LSP), the surface morphology of 304 austenite stainless steels treated by LSP is investigated using the optical microscope. The surface features observed present the characteristics of plastic deformation in the polycrystalline face centered cubic (FCC) metal. The surface microstructure can directly represent the deformation mechanism of the material under shock wave loading. The experimental results show that the surface morphology of the treated material corresponds to the deformation mechanism, which provides a new experimental method of studying the deformation mechanism in LSP.

The changes of three-dimensional (3D) laser cutting head′s orientation directly affect the cutting efficiency, security and stability of machine tool. A kinematic model of 3D laser cutting machine is established, and optional values are analyzed when geometric information of cutter location points on the cutting trajectory is transformed to space coordinates of five axes. Based on the friction between moving parts and the quality and the inertia of rotation axis, this paper establishes an energy model of the rotational motion of B, C-rotation axis between adjacent cutter location points. The optimization goal is the lowest total energy consumption of rotational motion of B, C-rotation axis on the complete cutting ring, then a minimum energy consumption path can be found by Dijkstra algorithm. Through example calculation, this method can avoid the momentary swing of B, C-rotation axis and enhance the movement smoothness of laser cutting head.

Experiments on YAG laser transmission welding of polymethylmethacrylate (PMMA) specimens are carried out to study laser welding technology, microstructure of welding zone and tensile property. The results show that transparent and black PMMA specimens can be well welded and there is no ablated mark at laser irradiated surface without optical absorbing material when laser power is above 200 W. In tensile experiments, the transparent PMMA specimens break at the edge of welding zone with the maximum load of 2110 N, and there is no crack at the welding zone. When laser power is below 200 W, the welding zone is fractured under the condition of single track welding, and the maximum load is 1170 N. Optical absorbing material can be used to improve the reliability of laser transmission welding of transparent and color PMMA specimens. The quality of laser transmission welding with black thermoplastic acrylic resin is better than that of other absorbing materials.

In order to grain refinement and improve the quality of laser cladding coating, the Fe60-base composite coatings are fabricated by rotating magnetic field auxiliary laser cladding on Q235 steel surface. The microstructures and phase composition of the coating are analyzed by means of scanning electron microscopy (SEM), X-Ray diffraction (XRD) and energy dispersive spectrometer (EDS). The cross-section micro-hardness of the cladding layer is measured by Vickers hardness tester, and the abrasion performance of the cladding is characterized through the friction and wear experiments. The results show that the phase of the laser cladding composite coatings is mainly composed of γ-(Ni,Fe) solid solution、silicides and borides. The Cr5Si3 grain is refined and uniform distributed. The average micro-hardness of the composite coating is 685HV0.5, which is 1.1 times of that of the coating without rotating magnetic field; the weight loss of laser cladding modified layer is only about 0.66 times of that of the coating without rotating magnetic field. The wear behaviors of the laser cladding composite coatings are improved significantly.

A high-power narrow-bandwidth all-fiber thulium-doped silica fiber master oscillator power amplifier (MOPA) system that consists of a low power thulium-doped continuous wave fiber laser seed and two-stage thulium-doped double-clad fiber amplifiers pumped by fiber-pigtailed multimode diodes at 790 nm is reported. The center wavelength of the fiber laser is 1963 nm and the 3 dB bandwidth is 0.24 nm. The maximum output power is 22 W at a slope efficiency of 44% with respect to the launched pump power.

In total reflection prism laser gyro, the combiner output characteristics directly affect the gyroscope′s accuracy. By using the laser mode theory, the combination spot patterns of clockwise and anti-clockwise beams in different rotation speeds are analyzed. The interference spot abnormalities caused by unsuitably assembled diaphragm or combining prism, passed higher-order transverse mode, too big y direction angle, as well as multi-longitudinal modes are discussed. The relationship between beam combination quality and navigation accuracy in ring laser is studied experimentally.

The characteristics of pulsed CO2 laser produced Sn plasma plume expansion under ambient air pressures are studied by shadowgraph technique. The dependences of Sn plume expansion position and plasma debris energy on delay time are obtained. The modified drag diffusion model is employed to fit the experimental data. Plasmas are generated by irradiating planar Sn targets using 400 mJ, 75 ns pulses from a CO2 laser. Our results show that the estimated expansion velocity of the plasma in the early stage (delay time is less than 100 ns) is almost 3 cm/μs, and decreases rapidly with delay time to about 0.3 cm/μs at later stage (delay time is larger than 800 ns) because of the thermalization collisions with buffer gas pressure of 1000 Pa. Fitting results of modified drag diffusion model indicate that the plasma plume maximum size is xst=15.2 mm, which is found to agree fairly well with the measured data of 16 mm.

Based on the specialties of small diffracted source and far field diffraction, the Rayleigh-Sommerfeld scalar diffraction integral formula is simplified to analyze the characteristics of the far field total power and the beam propagation factor of non-paraxial diffraction beam. Physically, as the spatial frequency spectrum of non-paraxial diffraction beam is confined to a finite spatial frequency, the calculated value of the far field total power fails to comply with the law of energy conservation. Besides, the calculated value of the beam propagation factor of non-paraxial diffraction beam is against the commonsense rule. Then, the spatial frequency spectrum in the mathematical concept is employed to analyze the above mentioned characteristics, and the two commonsense rules are put forward again. And it is clearly shown through the relative calculation errors of the far field total power and the beam propagation factor of non-paraxial TEM00 mode Gaussian beam.

Far field speckle characteristics of a broad area laser diode (LD) and a two-dimension (2D) laser diode array (LDA) made of single diode are measured respectively. A rectangular aperture close to diffuser is used to select different parts of laser light field as illumination spot. The speckle contrast measured for different illumination spots has no obvious trend (turn up or down) along the movement of rectangular aperture. It means that there′s no relationship between contrast and the laser light field selected. 2D LDA made of four LDs produces incoherent light and angular diversity. Adjusting the distance between array and diffuser to change the angular of adjacent incidence into diffuser. The distance from lens to diffuser is fixed. The experimental results shows that, only when the angular is larger than that of imaging lens seen from the diffuser, the contrast of the speckle is reduced by a factor of 1/M.

Enhancement of Cr,Yb∶YAG self-Q-switched microchip laser by bonding Yb∶YAG ceramic is investigated. Yb∶YAG/Cr,Yb∶YAG self-Q-switched microchip lasers is demonstrated. Average output power of 0.53 W is obtained under absorbed pump power of 7.1 W. Laser pulses with pulse energy over 25 μJ, pulse width shorter than 3 ns and peak power over 9 kW are achieved. The effect of transmission of output coupler on the laser performance is also addressed.

A diode-pumped solid-state laser at 1.5 μm by use of the Er3+,Yb3+YAl3(BO3)4 crystal is presented. Initially, the laser efficiency is quite low and can not be operated continuously owing to the serious thermal effect. To solve these problems, the oven design and pumping source parameters including operation frequency, duty cycle and waist radius are optimized for reducing the crystal′s thermal deposition. A more efficient quasi continuous-wave (CW) laser which can produce output power of 2.6 W at 1.5 μm is realized when the pumping source is set as modulated frequency of 40 Hz, duty cycle of 10%, pumping waist radius of 80 μm and incident power of 17.6 W. Furthermore, a CW single-transverse-mode laser with output power of 290 mW and slope efficiency of 8.5% is also demonstrated under pumping power of 5 W.

In high power excimer laser system, the signal contrast ratio is decreased severely by the amplified spontaneous emission (ASE), which decreases the laser pulse signal contrast severely, leads to waveform broadening and distortion, and impacts on the accurate physical experiment. In this paper, based on the principle of the short pulse generation by electro-optical switch, study on ultraviolet electro-optical switch is made, and a method for ASE suppression of the laser amplifier chain is established. In the waveform clipping experiment of the first pre-amplifier in master oscillator power amplifier (MOPA) system, the extinction ratios of the single and cascaded dual electro-optical switches reach 103 and 104 level, and the laser pulse signal contrast ratios are promoted to 105 and 106 level after clipping, respectively. In the experiment of single channel MOPA system, the cascaded dual electro-optical switch is adopted to control the ASE, and an amplified narrow pulse is obtained on the target surface, providing an effective solution to the problem of waveform amplification in the high power excimer laser system.

The technology of epitaxy growth GaN/Si (111) with high temperature AlN buffer is investigated. The state of strain and crystalline quality of GaN epitaxial layer on Si(111) substrate is investigated by high resolution X-ray double crystal diffraction (HRXRD). The influence of the high temperature AlN buffer thickness on the surface morphologies of GaN films is characterized by the atomic force microscopy (AFM). The experimental results show that the Al pre-treatment time and the thickness of AlN buffer have a significant influence on the crystalline quality, state of strain and surface morphology of GaN. The optimal Al pre-treatment time is 10 s, and the thickness of AlN buffer is 40 nm. The good surface morphology of GaN epitaxial layer is obtained with the full width at half maximum (FWHM) of GaN (0002) of 452″, and (10-12) of 722″ by X-ray (XRD) double crystal diffraction.

As cylinder-segment scatters have the features of anisotropy and multiple controllable degrees of freedom. With the plane-wave expansion method, the slow light effect with high group refractive index and low dispersion can be generated by optimizing the structures of photonic crystal waveguide with line defect, such as changing the length of major axis or minor axis, or rotating scatterers relative to the direction of line defect. Simulation results show that slow lights with band width from 10.1 nm to 1.1 nm and group refractive index from 36.5 to 287.5 are achieved by changing the lengths of major axis or minor axis; slow lights with band width from 11.4 nm to 0.8 nm and group refractive index from 45.5 to 293.7 are gained by rotating scatterers. Moreover, slow lights with ultralow dispersion, even near zero dispersion, can also be obtained by these methods, which shows that choosing suitable scatterers and adjusting their parameters can efficiently achieve slow light effect with high group refractive index and low dispersion.

Dependence of Mg doped InN characteristics on the rapid thermal annealing (RTA) temperature is investigated. The mosaic tilt, twist and correlation lengths of InN film are determined by using X-ray diffraction (XRD) symmetrical and asymmetrical reflections as well as reciprocal spacing mapping (RSM), which will then lead to the screw and edge dislocations. Comparing with the dislocations and mobility in different RTA temperatures, the crystal qualities are greatly improved at 400 ℃. We suggest that Mg atoms are activated by the RTA treatment, along with the reduction of carrier concentration. At the same time, N vacancies, which act as donors, are partly compensated when annealing in N2 atmosphere, leading to the reduction of defects and dislocations as well as carrier concentration. Such results also corroborate with the full width of half maximum (FWHM) of ω scans of InN (002) plane.

Visible and infrared control and guide system as one of controling means receives extensive attention increasingly in terms of military. In order to meet the requirements of infrared optical instruments, a visible and infrared triple waveband filter film system is designed according to the theory of thin film. Through the comparative study on serveral kinds of the common materials used in visible and infrared area, ZnS and YbF3 are selected as the materials. On the substrate of Ge, coating with average reflectance 91% at 450~950 nm while average transmittance 86% at 3.7~4.8 μm and 7.5~9.0 μm, eletron beam and ion assisted deposition technique is used in this process. More requirements are integrated into the coatings,and the structures of optical instruments can be simplified. Results of test show that all the parameters meet the requirements.

A measurement system of refractive index of air (RIA) based on surface plasmon resonance (SPR) and phase detection is presented. A heterodyne interference optical path is built and a SPR sensor with self-adaptive structure for angle shift is applied. Theoretical analyses indicate that the variation of the phase difference between p and s polarization components of the measurement signal versus that of the reference signal is almost linear with RIA fluctuation. Thus the formula of RIA measurement is derived. The application of the self-adaptive SPR sensor reduces the measurement error by an order of magnitude and greatly improves the sensitivity. The comparison experiments with the method of Edlen equations show that the measurement accuracy reaches less than 5×10-6 at the phase detection precision of 0.1° and the incident angle of 44.0° (which is close to the resonance angle). Furthermore, the measurement system can provide an initial estimate of RIA accurate enough for other measuring instruments with higher precision.

The alignment method of dual-grating Moiré fringe has characteristics of high-accuracy and reliability, which is mainly fit for contact and proximity lithography. For the realization of high-accuracy measurement, the parallelism between mask grating mark and wafer grating mark is practically required. Generally, mask grating mark imaged in CCD has a tiny inclined angle. Therefore, an improved method is proposed, based on the previously proposed calibration method for inclined fringes through phase slope. The improved method makes full use of phase information in directions of 45° and 135° to revise the imaging position of CCD. By this mean, the mask grating fringes are also calibrated. Through comparison between the two methods, the results imply that the improved method is provided with large-measurement scope, strong anti-noise and high-accuracy, and measurement accuracy is better than 0.001° level.

Picosecond diagnostics system is used to provide parameters of laser facility and help it to achieve designed technical aim. This system will diagnose parameters of compressed pulse for petawatt laser such as energy, pulse width, farfield, and pulse contrast. Root-mean-square (RMS) error is adopted to describe stability of diagnostics system in order to test its performance. Energy measurement range is 10~1000 J, RMS error of calibration data is 2.2%. Pulse width measurement range is 0.5~18.0 ps, temporal resolution is 0.07 ps for Gaussian type pulse, and data RMS error is 3%. Farfield measurement range is 150 diffraction limitation (DL), spatial resolution is 0.3 DL, and RMS error is 0.15%. Pulse contrast measurement range is 30 ps, temporal resolution is 0.3 ps, and dynamic range is 106. In experiments on petawatt laser, picosecond diagnostics system provides these parameters instantaneously and successfully to analyze petawatt laser facility′s performance.

Statistical properties of the Rayleigh backscattered light power and phase caused by a highly coherent semiconductor laser from single-mode fiber are presented. Based on the random phasor model, the results show that the probability density function (PDF) of Rayleigh backscattered light power from single-mode fiber follows the modified Rician distribution. The phase distribution of Rayleigh scattered light is approximately Gaussian distribution. The experimental results are shown to correspond to theoretical derivation, and the maximum power of scattered light from different lengths increases linearly with the mean intensity.

Intra-channel four-wave mixing (IFWM) affects system performance in 160 Gb/s optical time division multiplexing (OTDM) communication systems. The effect of IFWM on the performance of a 160 Gb/s OTDM transmission system is analyzed. Strong dispersion management to suppress the detrimental effects of IFWM is theoretically presented and experimentally verified. The results show that amplitude fluctuation at "1" bit and ghost pulses at "0" bit are well suppressed by strong dispersion management in transmission link. The whole system performance is improved. Stable error-free (bit error rate less than 10-12) transmission over 107.6 km after more than 2 h is achieved without forward-error correction, and the power penalty is about 3.6 dB.

An approach to generate a microwave signal with multiplication frequency is studied and verified theoretically and experimentally. Based on big signal phase modulation and the dispersion of a single-mode fiber, the high order of microwave harmonic signal is generated. A tunable single passband microwave photonic filter is used to select a specific harmonic signal by tuning the sliced space of broadband optical source. Based on the theoretic analysis, an experimental system is established, and the harmonic signals at 10 GHz and 15 GHz are produced by applying a low-frequency signal at 5 GHz. It can be seen the 10 dB bandwidth of the signal is a few tens hertz, and the power fluctuation is 1 dB～2 dB.

The fabrication method for novel polymer imaging fiber is developed. The theory of light propagation in fiber and fiber design is expatiated, which is the guide for developing imaging fiber. The material of polymethyl methacrylate (PMMA) is heated and extruded in a hexagon mold as microstructured fiber preform. The holes in it are filled with polystyrene (PS) fibers. It is the first preform used for heat-stretch and stack-fusion to form a second preform. Then the second preform is heat-stretched to obtain imaging fiber with diameter of 0.22 mm and single fiber diameter of 3 μm. It is ultrahigh resolution imaging fiber, by which the microscale of 10 μm can be discerned. The method of one-step stack is used to stack 7200 pieces of customized polymer fibers as the multicore imaging fiber preform. The customized fiber with diameter of 0.25 mm and coating thickness of 20 μm is fused together. The preform is heat-stretched to form imaging fiber of 2 mm diameter and 20 μm single fiber diameter. It is found that the dust adsorbed on the fiber face seriously affects fiber′s structure and image quality.

The inner light baffle is introduced due to the layout of coaxial two reflect mirror system for stray light elimination. Different point source transmittance (PST) curves of the system are gained by changing diameter and height of the inner photomask which is quite useful for optimization of the inner photomask. By stray light analysis and finite element analysis (FEA), it′s ascertained the diameter of the inner photomask is 44.8 mm and the height is 100 mm, then great suppression effectiveness for infrared stray radiation is achieved together with required mechanical capability for the coaxial two reflect mirror system with an aperture of 320 nm.

Based on the study background for structural health monitoring (SHM), fiber Bragg grating (FBG) sensor is researched. The study on FBG starts and matures in the field of telecommunication, and the corresponding study in the field of civil engineering is in a development stage even. To improve its further developments and promote its application in engineering, two kinds of quasi-distributed FBG sensors placements are considered, one for the fiber reinforced plastics (FRP) package and the other for without package. The sensors are pasted on the bottom of the beam. Study on the detecting effectiveness and damaqe locating of the quasi-distributed FBG sensor when the reinforced concrete beam specimen cracks appear are carried out. The experimental results show that the crack can be roughly located, and the strain sensitivity of the FBG sensor with FRP package declines relative to the rare FBG sensor.

Compared with traditional point-scanning laser radar, the imaging laser radar based on range gating and gain-modulation ranging principles has faster ranging speed, but at the same time, signal noise ratio (SNR) of single-frame image is lower. According to principles of imaging laser radar, the ranging accuracy model under the influence of shot noise is built. Based on the model and the characteristics of airborne imaging laser radar, a new method which employs the techniques of gray image registration and superposition to improve ranging accuracy is put forward. Then the factors, such as the flight attitude, light uniformity and superposition frame number that influence the application of gray registration and superposition, are analyzed theoretically. The results show that flight attitude has no effect on the method and the light uniformity′s effect is small when the uniformity is better than 40%. There will not be other errors between the targets when superposition frame number is within a certain range. A ground of dynamic experiments and aerial experiment are conducted to verify the validity of the method.

To improve the scale factor stability of fiber optic current sensors, effects of azimuth which is the fiber welding azimuth between a sensing fiber and a fiber quarter-wave plate are studied, so as to restrain the linear birefringence by optimizing the azimuth. Effects of optical rotatory angle which are ignored by existing azimuth optimization theory are considered and a more accurate Jones matrix model is proposed with this new variable. It is theoretically shown that the present optimization theory has some errors with the consideration of optical rotatory angle when analyzing the simulation results. The scale factor is immune to the variable linear birefringence with some optical rotatory angles. The combined optimization of the azimuth and optical rotatory angles is proposed. It can reduce the technical requirements of fibers and effectively enhance the stability of scale factors.

This paper reports an external fluorescence seeding technology which can enhance the stimulated Raman scattering (SRS) in liquid-core optical fiber (LCOF). By surrounding a small section of LCOF with a glass capillary and a solution of Rhodamine 6G filled between them, fluorescent dye and Raman medium are seperated. The initial intensity of SRS is linearly amplified by external fluorescence seeding, and then the SRS of LCOF can be enhanced pollution-free and effectively. Experimental results show that the maximum enhancement of Stokes lines is obtained when the concentration of dye solution is optimized at about 10-6 mol/L.

To improve the quality and the detection capability on soil samples of laser induced breakdown spectroscopy, the effect of different heights of carbon sheets from the target surface on the soil plasma radiation intensity is investigated. Moreover, the electron temperature and electron density of plasmas are measured through the Boltzmann graph method and Stark broadening. Experimental results indicate that the plasma radiation intensity is significantly enhanced when the plasma is confined by carbon sheets, compared with no carbon sheets confinement. As the height of carbon sheets from the sample surface increases, the plasma radiation intensity gradually increases, peaks at 11 mm and then decreases. The calculated results show that the spectral line intensity of elements Fe, Mn, K and Ti with carbon sheets confinement at 11 mm from the target surface are enhanced by about 179.88%, 117.02%, 123.21% and 91.24%, respectively, than those without carbon sheets confinement; spectral signal-to-noise ratios are increased by about 107.30%, 92.26%, 68.48% and 67.66%, respectively; the electronic temperature and electronic density of plasmas are increased by 2800 K and 2.16×1016 cm-3, respectively. It provides a simple and easy method for the detection of trace elements in soil.

A real-time, on-line gaseous detection system with high-resolution spectrum is built based on LabVIEW. It employs off-axis cavity enhanced absorption spectroscopy technology, and uses an external cavity diode laser (ECDL) as a laser light source. Two kinds of scan mode, one in roughness, the other in fineness for spectral measurement are achieved. A weak absorption spectrum of CO2 molecule as well as the relationship among the spectral intensity, line width and gaseous concentration is obtained at wave number of 6358.65 cm-1. The minimum detection sensitivity is 1.1×10-6 cm-1 for the entire system when using the 6358.65 cm-1 spectral line. Vibration-rotation spectra of CO2 molecule from experiment is basically consistent with the simulation results in the wave number range of 6450~6530 cm-1. Experimental results indicate that this system is not only feasibility but also has high detection sensitivity and spectral resolution, and meets the different spectral detection requirements of gas.