We propose and prove the feasibility that the liquid-solid phase transition of water can be monitored based on FBG sensor. The supercooling phenomenon is observed during the phase transition process. On this basis, we show the phase transition signals of different concentrations of NaCl solution based on FBG sensor monitoring. The results show the correlation between the concentrations and the phase transition signals. This correlation is expected to provide a new scheme of solution concentration testing.

Spatial diversity reception can be used over wireless optical links to mitigate atmospheric turbulence. Based on the clear atmospheric channel model and the model of diversity coherent receivers for laser communication, considering the spatial correlation of received signals, the error rates of both equal gain combining (EGC) and maximum ratio combining (MRC) are analyzed, and the outage probability of them are compared with that of selection combining (SC). The impact of spatial correlation of received signals on the diversity of coherent laser communication system is studied. The less spatial correlation of received signals is, the better the diversity reception for coherent free-space laser communication is. Simulations show that diversity can improve the performance of coherent laser communication. The performance of MRC is much better than those of EGC and SC, but SC is simpler and more convenient. Both performance and feasibility should be considered in applications.

Aiming at the problem of GQA in sharpening image, an improved QGA is proposed. An adaptive quantum revolve door step adjustment strategy is used, different rotate angles are adopted for the evolution of different generations, and the same generation still has the same length. The Hamming distance of every quantum chromosome is compared in order to adjust its evolution speed. The solutions of quantum chromosome are updated to higher grades in the target range. The diagonal crossover mode is adopted for quantum crossover operation. The flow chart of the image sharpening algorithm is given. The simulation results show that the proposed algorithm is much better than other methods in sharpening edges and reducing noise, and image edges also get a very good enhancement.

Image matching is the foundation and key for obtaining lunar elevation information based on CCD data. We study the wavelet pyramid layered matching algorithms of lunar CCD image. CCD image is decomposed by wavelet according to the wavelet multiresolution analysis. Mismatch elimination strategy is constructed on the top of the pyramid level, and rapid searching strategy for matching points is constructed on the bottom of the pyramid level. Image matching is completed from low resolution to high resolution. Matching time and searching time for non-corresponding image points are reduced in this algorithm, accordingly, the calculation complexity is reduced greatly. So the searching efficiency and the registration precision are improved. The experimental results show that this algorithm has high precision and matching efficiency.

The advantage of manufacturing space mirror by SiC material is analyzed, and the key technologies of fabricating and testing SiC aspheric mirror are researched. The off-axis SiC aspheric surface is ground and polished by the FSGJ-2 numerical control machine, and the contour is measured by the profilometer of FSGJ-2. For the purpose of testing aspheric mirror by null-compensation, a computer-generated holographic instrument is specifically designed and developed. Finally, an example for fabricating and measuring an off-axis aspheric mirror with the aperture of 468 mm×296 mm is given. The peak-to-valley (PV) and root mean square (RMS) values of the surface error are 0.148λ and 0.017λ (λ is 632.8 nm), respectively. It could meet the requirements of the optical design.

A discrete complex pupil filter is proposed to create focused field using cylindrical beams in the high numerical aperture (NA) system. The radius of this filter is normalized to 1. It consists of six discrete transmitted annular zones with different amplitudes and there zones are shifted by a π phase retardation in neighboring zones except for the same retardation in the two outermost zones. The polarization pattern and intensity of the incident azimuthally polarized beam can be modified by the filter and then focused by the high NA lens. An ultra-long (longer than 8λ) diffraction limited three-dimensional optical tube with azimuthal polarization spiraling around z-axis can be created. The center of the optical tube field is null along the axial direction. And the radius of the tube determined by the transverse full width at half maximum (FWHM) of this focused field is 0.31λ in the focal plane and remains nearly constant throughout the total depth of the tube. This complex pupil filter will meet applications in three-dimensional tailoring of focused field and trapping and manipulation of particles.

To meet the requirement of high precision measurement (0.2×10-6) of refractive index homogeneity of optical glass, the uncertainty caused by temperature of measurement environment should be less than 0.05×10-6. Uncertainty analysis caused by temperature is taken for five error sources. The result shows that when the radial temperature difference of air, flats, oil, and component in the measurement cavity is ±0.01 ℃, the uncertainty caused by temperature is 0.031×10-6, which can satisfy the precision. Important data are offered for high precision measurement of refractive index homogeneity of optical glass, and useful advices are given for the improvement of laboratory enviroment.

The high power output of medical all-solid-state 561 nm yellow laser is achieved by the method of semiconductor-pump intracavity frequency doubling. After the comparison and analysis for laser parameters of the main lines parameters of the NdYAG laser crystal, the high-gain 1064, 1319 and 946 nm line operations suppressed by the membrane system design of the resonator cavity. Through the rational choice of the nonlinear crystal and the reasonable control of crystal placement angle and matched temperature, the single line of 561 nm output is obtained. The output power is 1.41 W at the incident pump power of 13.5 W, with the light to light conversion efficiency of 10.5%.

With the technique of laser rapid forming (LRF), tensile samples of 304 stainless steel are prepared, on which tensile test is done. The surface is observed by optical microscope, the fracture morphology of the specimens is observed by scanning electronic microscopy (SEM), and chemical compositions of sampling points are analyzed by energy dispersive spectrometer (EDS). The results show that the sample′s microstructure contains small grains with unidirectional solidification characteristic, which form micro-holes and micro-cracks inside the formed parts. In specimens of tensile fracture, there are ductile fracture characteristics, and the contents of oxygen and silicon in some area of fracture surface are higher. These worsen the mechanical properties of the specimens.

The deflection of focused beam propagation direction when the metal plate is cutting by numerical-control (NC) laser cutting machine is studied. Several incidence physical parameters affecting the direction of focused beam when the energy center lines of the laser beam and the optical axis of the convex lens are in different planes are found out. The relationship between them is given by geometrical optics. It is found that we can change the direction of focused beam by shifting the convex lens. The testing results show that the horizontal movement of the convex lens can change the direction of focused beam. This method is also applicable to other laser processing equipments which use convex lens. It provides a new selection on the direction-adjusting design of focused beam.

Scientific experiments show that damage to optical materials is related with factors like laser wavelength, material properties, laser pulse width, etc. The final stage of damage is various, which can be melting, crack and ablation. In an effort to explain these phenomena, we run a semi-quantitative discussion on the optical material damage mechanism regarding the thermal conduction equation, presenting a key parameter that determines the relationship between laser induced damage and laser pulse width τp—the time τ it takes for the inclusion within the optical material to transfer its heat to the body. When τpτ, the damage threshold is determined by laser radiation intensity; when τpτ, the damage threshold is determined by laser radiation energy density.

Through theoretical analysis and simulation test, we design and fabricate a 26 inch (1 inch=2.54 cm) liquid crystal display television set (LCD TV) with two side white light LEDs (WLEDs) as backlights. The structure of the WLED is simple and the WLEDs perform excellent. In the actual fabrication, a highly efficient circuit is used to drive the WLED units. The simulation results show that the brightness uniformity of the LCD TV is 91% and the color uniformity is 85%, which completely satisfies the requests of design.

In non-imaging optics, based on the characteristics of the transition of optical extension, the size of elements and beam aperture angles in light pipe illumination optical path of a new type of laser projection display system with the laser diode (LD) array as the light source are given. As an example, the light pipe illumination system design using standard optical design software Zemax is described. The source is 3×8 red LD array. The spatial light modulator (SLM) is a 0.45 inch (1 inch=25.4 mm) liquid crystal on silicon (LCOS). The design includes laser source beam shaping, light pipe uniformity system and the light pipe relay lens. Good performances of energy efficiency and beam uniformity are gotten. Then, the method to design light pipe illumination system with high quality of energy transition in the laser projection display system is shown.

Based on finite element method, simulation about the property of piezoelectricity film deformable mirror (PFDM) under three-point position-setting is done. The results show that the contact between mirror and frame can cause nonlinear response. For solving this problem, two methods are proposed. Simulation results show that both of them can weaken the nonlinear response.

A design of athermalized shortwave infrared optical system with wide field of view is introduced. The working wavelength is 0.9～1.7 μm, the resolution is 640 pixel×512 pixel, and total optical length is 55mm. The results show that the modulation transfer function (MTF) is above 0.6 at the spatial frequency of 20 lp/mm in the temperature range of -40 ℃～60 ℃. The system has the advantages of high image quality, wide temperature range, compact structure and low mass.

A simulating model of emissivity of infrared stealth coating based on Kubelka-Munk theory is put forward. Taking aluminum particles as pigments, using Maxwell-Garnett effective medium theory, the relationship between equivalent refractive index of coating and wavelength is calculated and analyzed. Based on the mutual interaction of the electromagnetic wave and pigments, adopting geometrical optical theory, scattering and absorption coefficients of the coating are calculated. Effects of aluminum particles′ parameters, such as size and volume, to the emissivity of coating are analyzed quantitatively. The result shows that the proposed model could be used to guide the preparation of infrared stealth coating.

In topology, an optical network is composed of multiple edges (optical transmission) and nodes (optical switch). The service features and the time structure of optical switch stream supporting the service are discussed based on the connection and connectionless patterns. Examples include the length of optical packet and burst, and the length of optical circuit with high dynamic degree, which is defined in the internet engineering task force (IETF) standard. The measured results imply the achievable shortest length of optical circuits. The space architecture of optical switch is discussed. Examples include three architectures in terms of large port number and capacity, i.e., the optical switching structures based on micro-electro-mechanical system (MEMS), wavelength-selective switch (WSS), and arrayed waveguide grating (AWG). The architectural scalability of three ones discussed above is addressed. Some other challenging issues are also discussed, including optical buffer and power consumption. Hopefully, the paper is helpful for understanding the essence of optical switching and the relationship with the counterpart electronic switching.

The cause, criterion and research method of small-scale self-focusing on high-power laser systems are reviewed. Small-scale self-focusing of lasers in Ndglass and frequency-conversion crystal are analyzed and discussed. Moreover, measurement of small-scale modulation growth is introduced. Then methods to suppress small-scale self-focusing are also presented, and damage of high-power lasers to optical components is reduced by controlling small-scale modulation growth. Finally, the future research in nonlinear effects of fused high-power laser technology is proposed.

A novel technology named microscale laser shock forming (μLSF) is rapidly developing. During the process of μLSF, micro plastic deformation is generated due to the high-amplitude shock wave pressure induced by the microscale laser-material interaction. It combines the advantages of laser forming, laser shock peening and plastic forming. The required micro geometry and satisfactory surface quality can be obtained by controlling the laser parameters and formulating a reasonable peening path. The μLSF has significant advantages in micro-plastic manufacture due to its flexibility. Based on the introduction of principle and features of μLSF, the pressure model, constitutive model and processing methods of μLSF are analyzed, and the key technologies in μLSF are discussed. After summarizing the research status about the quality and performance of the forming surface induced by μLSF, the problems existing in current research of μLSF are pointed out. Finally, expectations of future studies on μLSF are brought forward.

With the development of high power semiconductor pump technology and new fiber structures, high power fiber Raman lasers become a research focus nowadays. Starting with models of silicon germanium single-clad fiber Raman laser, double-clad fiber Raman laser and photonic crystal fiber Raman laser, the basic theories of high power fiber Raman lasers are introduced, the merits and defects of them are reviewed, and the latest developments are reported. The developments in the narrow linewidth fiber Raman amplifiers are advanced, and the technological difficulties and solution methods are discussed. Finally, the prospects of high power Raman technology in high power fiber Raman lasers are predicted.

The reported optical fiber sensors based on photonic crystal fiber loop mirrors are reviewed. We summarize various sensors based on photonic crystal fiber loop mirrors, including strain sensors, temperature sensors, curvature sensors, twist sensors and pressure sensors. The principles and advantages of these sensors are introduced. The prospect of development of optical fiber sensors based on photonic crystal fiber loop mirrors is addressed.

Laser ablation fast pulse discharge plasma spectroscopy (LA-FPDPS) technique is used to analyse aluminum alloy. The optical emission spectra are recorded using this technique. From the measured spectra, the signal-to-noise ratio (SNR) and the relative standard deviation of several elemental lines are derived. Compared with the spectrum obtained from laser induced breakdown spectroscopy, the optical emission intensity and SNR in the LA-FPDPS spectrum of aluminum alloy increase greatly. The measurement precision in terms of relative standard deviation is improved as well. In addition, several calibration curves for trace elements analysis in aluminum alloy are obtained using LA-FPDPS technique, which can be used for quantitative analysis of those corresponding elements.

We quantitatively analyze the content of the element Ni in the Chinese national standard soil samples by the method of X-ray fluorescence spectroscopy using XLt793 metal analyzer in ambient environment of the laboratory. The direct calibration curve of Ni is measured by studying the characteristics of X-ray fluorescence of Ni in the optimal experimental conditions. The experimental results demonstrate that the relation between concentration \[mass fraction (50~1000)×10-6\] of Ni element and the intensity of the characteristic spectrum is well linear, and the relative standard deviation (RSD) of intensity measurement from the standard value is 8.60%. Using the soil samples of the same type the relative deviation of element analysis of concentration measurement from the standard value is 4.43%. Using calibration curves to analyze the different soil types, the relative deviation between the measured concentration and the standard value is 7.13%.

Laser-induced breakdown spectroscopy is used in qualitative and quantitative analysis of trace amounts of heavy metals zinc in water, with 1064 nm NdYAG laser as the excitation light source and high resolution, wide spectral range echelle spectrometer and intensified charge-coupled device (ICCD) as the line separating and detecting devices. The characteristic line at 481.1 nm is chosen as the analysis line to measure the characteristic line intensities of different zinc concentrations. A solid state graphite round flat is used as matrix for element enrichment to reduce water splashing, extend the plasma lifetime and improve the detection sensitivity. The experimental sample is prepared by titrating a fixed volume of zinc chloride solution of different concentrations on a fixed area of the graphite matrix. The results show that the optimal detection delay time is about 1100 ns. The spectrum intensity rises with the concentration increasing, and a good linear relationship is found at low concentration region. The lower limit of detection of zinc in water of 4.108 mg/L is obtained. A measurement method for further study of trace heavy metals in water is provided with laser induced breakdown spectroscopy technique.

Filter is often used to interfere the spectral spectrum into different bands in free space laser communication. This article mainly introduces the research and preparation of a three-band near infrared optical filter. According to the design theory, TiO2 is selected as the material of high refractive index and SiO2 as the low one to realize high transmittance in two bands of 770~860 nm and 1530~1575 nm, and high reflection in the band of 1615~1700 nm. The film stack is designed by film design software, and electron gun and ion-assisted deposition system are used for film preparation. The process flow is optimized through the adjustment of process parameters to get a good thickness uniformity of less than 3% by adjusting the compensation bezel. Although the film is thick, it meets the use requirement as shown by the tests of optical properties, mechanical properties and resistance to the environment. In addition, the quality of the coating surface successfully passes the test of the surface profile instrument, meanwhile, the variation of profile peak-to-valley (P-V) value can meet the design requirements.

Based on plasmonic metal grating mechanism and multilayer theory, a subwavelength slit with metal-dielectric multilayer composite surface grating which can enhance focusing effect is proposed. According to the finite difference-time domain (FDTD) method, the numerical simulation results demonstrate that the focusing behaviors of the designed structure is related to the numbers of metal-dielectric layers and grooves. It is found that the focal length can be increased significantly by controlling the number of metal-dielectric layers. The maximum focal length and the maximum focus depth can reach 9.15 and 26.38 \mm, respectively. Therefore, the focusing performances are enhanced obviously compared with conventional mono-metal gratings.

SnO2 polycrystalline target with pure tetragonal phase is synthesized by solid-state reaction, and is employed to fabricate SnO2 thin films on sapphire substrates by pulsed laser deposition technique. X-ray diffraction (XRD) analysis shows that all the films are a-oriented and present good crystalline quality. Laser-induced voltage (LIV) effect is found in those films grown on the vicinal-cut substrates, and the influence of the substrate temperature on the LIV effect in SnO2 thin films is studied. With the temperature increasing from 500 ℃ to 800 ℃, the peak voltage of LIV signals in SnO2 thin films firstly increases, and then decreases. At the same time, the response time firstly decreases, and then increases. Meanwhile, the optimal temperature is found, at which the peak voltage of LIV signals reaches the maximum. The response time and the rise time reach 98 and 28 ns, respectively, which is comparable to the duration of the applied laser pulse.