Elastic lidar observations of profiles of the aerosol extinction, backscattering coefficients, and the lidar ratio have been performed in Beijing. The elastic lidar transmitts wavelengths of 532 and 355 nm. The measurement altitude can reach up to 6 km. The similarity of the extinction and backscattering profiles suggests a close relation between the mean transmission and reflection properties. The lidar ratio on July 22, 2008 varied from 10 to 30 sr with the mean value of 20 sr. The profiles of the aerosol properties indicate the cirrus at 6–km altitude and a well-mixed boundary layer from July 22 to 24, 2008. The detected boundary layer also agrees well with the high and stable ozone concentration obtained from the differential optical absorption spectroscopy (DOAS) system.

A new method for calibration of sun photometers based on Bouguer-Beer law is proposed. The developed basic equation of calibration makes it possible to formulate the derivative methods of calibration on the basis of photometric measurements upon optical air masses, the ratio of which is an integer number.

The theory of speckle formation in laser scanning display system is established based on the averaging effect of eye response as laser beam scanning through an eye resolution spot. It is analyzed that speckle reduction can be obtained by averaging states of speckle during scanning. The theoretical results show that a smaller correlation length of screen surface and the narrowing of laser beam in scanning direction can reduce speckle contrast for this system.

When using normalized dispersion method for the dispersion design of photonic crystal fibers (PCFs), it is vital that the group velocity dispersion of PCF can be seen as the sum of geometrical dispersion and material dispersion. However, the error induced by this way of calculation will deteriorate the final results. Taking 5 ps/(km·nm) and 5% as absolute error and relative error limits, respectively, the structure parameter boundaries of PCFs about when separating total dispersion into geometrical and material components is valid are provided for wavelength shorter than 1700 nm. By using these two criteria together, it is adequate to evaluate the simulated dispersion of PCFs when normalized dispersion method is employed.

The material dispersion of a tapered fiber is described by Sellmeier's equation. The dependence of refractive index on wavelength and doping concentration is discussed. A He-Ne laser with the output wavelength of 632.8 nm is used in the experiment. When the cutoff frequency of the fiber is less than the laser frequency, the guiding modes of a single-mode fiber (at 1550 nm) are investigated. The results show that the original single-mode fiber becomes a multi-mode waveguide. The propagation and mode coupling of the light in the taper region are analyzed. By controlling the taper end size of the fiber, the unique tapered fiber can convert a multi-mode beam into a single-mode one.

The mode-spacing of the fiber Bragg grating Fabry-Perot (FBG F-P) cavity is calculated by using the effective cavity length which contains the effective length of the FBG. The expression of the effective length, defined by using the phase-time delay, is obtained and simplified as a function of the peak reflectivity at the Bragg wavelength, the band edges, and the first zero-reffectivity wavelength. The effective length is discussed from the energy penetration depth point of view. Three FBG F-P cavities are fabricated in order to validate the effective length approach. The experimental data fits well with the theoretical predictions. The limitation of this method is also pointed out and the improved approach is proposed.

An improved Pan-sharpening algorithm appropriate to vegetation applications is proposed to fusea set of IKONOS panchromatic (PAN) and multispectral image (MSI) data. The normalized difference vegetation index (NDVI) is introduced to evaluate the quality of fusion products. Compared with other methods such as principal component analysis (PCA), wavelet transform (WT), and curvelet transform (CT), this algorithm has a better trade-off between keeping the spatial and spectral information. The NDVI performances indicate that the fusion product of this method is more suitable for vegetation applications than the other methods.

According to the color constancy theory, a modified variation Retinex is proposed for improving the visibility of the dark regions in images under insufficient and/or non-uniform lighting conditions. A new penalty functional based on nonlinear diffusion and correlation between the reflectance and the given image is designed for the intensity image enhancement, followed by adaptive color compensation. With high computational efficiency achieved by an improved multi-resolution algorithm, simulation results prove that the proposed method shows more colorful and vivid visual performance, and achieves wider dynamic range with higher objective standard values.

Traditional speckle fringe patterns of electronic speckle pattern interferometry (ESPI) are obtained by adding, subtracting, or multiplying the speckle patterns recorded before and after the deformation. However, these speckle fringe patterns are of limited visibility, especially for addition and multiplication fringe patterns. We propose a novel method to obtain speckle fringe patterns of ESPI from undeformed and deformed speckle patterns. The fringe pattern generated by our method is of high contrast and has better quality than subtraction fringe. The new method is simple and does not require more computational effort. The proposed method is tested on the experimentally obtained undeformed and deformed speckle patterns. The experimental results illustrate the performance of this approach.

The active control of 30-m ring interferometric telescope (RIT) needs edge sensing and tip sensing when its primary mirror is composed by trapezoid-shaped segments, and the imaging performance of the RIT is determined by the accuracy of these two detecting approaches. Considering the detecting accuracy available in current segmented telescope active control systems, the effect of these detecting approaches on the surface error of the RIT primary mirror is calculated from the point of error propagation. The corresponding effect on imaging performance (modulation transfer functions (MTFs) and point spread functions (PSFs) at several typical wavelengths) of the RIT primary mirror is also simulated. The results show that tip sensing is very important for increasing the active control quality of the RIT primary mirror under the present techniques.

Liquid crystal thermography is a high-resolution, non-intrusive optical technique for full-field temperature measurement. We present the detailed calibration data for the thermochromic liquid crystal (TLC) with a useful range of 41-60 \circ C. The calibration is done with true color image processing by using an isothermal calibrator. The hue-temperature curve of the TLC is obtained, and the measurement uncertainty is analyzed. Combined with the image noise reduction technique of a 5×5 median filter, the measurement accuracy of the liquid crystal thermography can be significantly improved by approximately 57.1%.

A novel microring resonator accelerometer is proposed. It is realized by a suspended straight waveguide coupled with a microring resonator. Under the external acceleration, the coupling coefficient is a function of gap spacing between the two waveguides. The mathematical model of the sensing element is established. Both the finite element method and coupled mode theory are adopted to analyze and optimize the proposed structure. Simulation results show that the mechanical sensitivity is 0.015 \mu m/g with the working frequency below 500 Hz and cross-axis sensitivity less than 0.001%, which is promising in seismic related applications.

Continuous-wave green laser with a maximum power of 34 W has been obtained by intracavity frequency doubling with KTP in diode-side-pumped Nd:YAG. The Nd:YAG/KTP green laser has a simple three-mirror V-fold cavity structure. The optical-to-optical conversion efficiency is 9.5%. The instability of the laser is measured when the output powers are near 16, 21, 30, and 34 W after the beam is filtered. At the maximum output power, the M<sup>2</sup> factor is measured to be 8.

A passively Q-switched side-pumped laser with folded resonator is specially constructed for singlelongitudinal-mode smooth pulse output. Nd:YAG is chosen as the laser active medium and Cr<sup>4+</sup>:YAG as the saturable absorber medium. Additionally, the method of frequency selection by grating with 1200 line/mm and Fabry-Perot (F-P) etalon is used in the twisted-mode cavity. The single-frequency smooth pulses are produced with 10-Hz repetition rate, 20-ns pulse width, and 1.064-\mu m wavelength. The probability of single-frequency laser output measured is over 99% by using the methods of Fourier analysis and F-P etalon multiple-beam interferometry at the threshold voltage. The measured near-field and far-field angles of divergence are 1.442 and 1.315 mrad, respectively. The values of M<sup>2</sup> are 1.32 and 1.31 separately with the knife-edge method. Single pulse at 1.064 \mu m with the energy of 8.8 mJ is achieved in TEM<sub>00</sub> mode.

A 1.3-\mu m wavelength vertical-mesa ridge waveguide mulitple-quantum-well (MQW) distributed feedback (DFB) laser with high directly modulated bandwidth and wide operation temperature range is reported. With the optimization of the strained-layer MQWs in the active region, the surrounding graded-index separated-confinement-heterostructure waveguide layers, together with the optimization of the detuning and coupling coefficient of the DFB grating, high directly modulation bandwidth of 16 GHz at room temperature and wide working temperature range from ?40 to 85 \circ C are obtained. The mean time to failure (MTTF) is estimated to be over 2×10<sup>6</sup> h. The device is suitable as light source of high-bit-rate optical transmitters with small size and reduced cost.

A diode-end-pumped electro-optic (EO) Q-switched green laser operating at the repetition rate of 20 kHz is reported. A block of La<sub>3</sub>Ga<sub>5</sub>SiO<sub>14</sub> (LGS) single crystal is used as a Q-switch and the type I phase-matching LiB<sub>3</sub>O<sub>5</sub> (LBO) is used as the nonlinear crystal in the second harmonic generation. The 2.3-Waverage power of 532-nm green laser is obtained at the repetition rate of 20 kHz with the pulse width as short as 10 ns. When the output power is about 1.5 W, the measured power fluctuation is less than 1.4% (root-mean-square, RMS) with the beam quality factor of M<sup>2</sup><2 in both orthogonal directions.

To obtain high power 589-nm yellow laser, a T-shaped thermal-insensitive cavity is designed. The optimal power ratio of 1064- and 1319-nm beams is considered and the fundamental spot size distribution from the output mirror to the two laser rods are calculated and simulated, respectively. As a result, a 589-nm yellow laser with the average output power of 5.7 W is obtained in the experiment when the total pumping power is 695 W. The optical-to-optical conversion efficiency from the fundamental waves to the sum frequency generation is about 15.2% and the pulse width is 150 ns at the repetition rate of 18 kHz. The instability of the yellow laser is also measured, which is less than 2% within 3 h. The beam quality factors are M<sup>2</sup><sub>x</sub>=4.96 and M<sup>2</sup><sub>y</sub>= 5.08.

With the development of high power ultrafast laser passively mode-locked by a semiconductor saturable absorber mirror (SESAM), the damage threshold and degeneration mechanism of the SESAM become more and more important. One way to reduce the maximum electric field inside the active part of the SESAM is the use of a dielectric coating on the top of the semiconductor structure. With Fresnel formula, optical transfer matrix, and optical thin film theory, the electric field distribution and reflectance spectrum can be simulated. We introduce the design principles of SESAM including the dependence of reflectance spectrum on dielectric function of absorber, and investigate the dependences of the electric field distribution, modulation depth, reflectance spectrum, and the relative value of incident light power at the top quantum well of SESAM on the number of SiO<sub>2</sub>/Ta<sub>2</sub>O<sub>5</sub> layers.

During the mass formation of aggregates of molecules in a gelatin film dyed with the mixture of chrysophenine and acridine yellow dyes, photo-reorientation, photo-disorientation, and photo-orientation of the molecules are observed. Based on these observations, the photo-induction of granular aniso tropy may be realized.

SiO<sub>2</sub> thin films containing Si<sub>1-x</sub>Ge<sub>x</sub> quantum dots (QDs) are prepared by ion implantation and annealing treatment. The photoluminescence (PL) and microstructural properties of thin films are investigated. The samples exhibit strong PL in the wavelength range of 400?470 nm and relatively weak PL peaks at 730 and 780 nm at room temperature. Blue shift is found for the 400-nm PL peak, and the intensity increases initially and then decreases with the increase of Ge-doping dose. We propose that the 400?470 nm PL band originates from multiple luminescence centers, and the 730- and 780-nm PL peaks are ascribed to the Si=O and GeO luminescence centers.

The feasibility of fenestration operation in middle ear bone with pulsed infrared laser is evaluated. Healthy male New Zealand rabbits in vivo are used in the experiment. Middle ear mastoid bone of animal model is completely exposed with conventional methods, and then a pulsed CO<sub>2</sub> laser (10.6 \mu m) and an Er:YAG laser (2.94 \mu m) are used to perform the fenestration operation. Diamond drill is also used as a control group. The total operation time and light irradiation time are recorded and the opening efficiency is assessed. The morphological changes and thermal damage around the opening window on the middle ear bone are examined. It is shown that both laser systems are suitable for the fenestration operation in middle ear bone, and this no-touch technique has a lot of benefits compared with traditional methods. The bleeding during operation has an important effect on operation time and thermal injury and needs to be controlled efficiently in further study.

The evolution characteristics of a matter-wave bright soliton are investigated by means of the variational approach in the presence of spatially varying nonlinearity. It is found that the atom density envelope of the soliton is changed as a result of the spatial variation of the s-wave scattering length. The stable soliton can exist in appropriate initial conditions. The movement of the soliton depends on the sign and value of the coefficient of spatially modulated nonlinearity. These theoretical predictions are confirmed by the full numerical simulations of the one-dimensional Gross-Pitaevskii equation.

Considering an optical bistable system with cross-correlated additive white noise and multiplicative colored noise, we study the effects of correlation between the noises on the correlation function C(s) using the unified colored noise approximation and the Stratonovich decoupling ansatz formalism. The effects of the self-correlation time \tau of the multiplicative colored noise and the correlation intensity \lambda between the two noises are studied with numerical calculation. It is found that C(s) increases with the increase of the self-correlation time \tau, but decreases with the increase of the correlation intensity \lambda. At large value of \tau, there is almost no change for C(s) when  changes.

A simple approach based on six transfer cells and simulated annealing algorithm for analyzing and tailoring the spectra of arbitrary microring resonator arrays is presented. Coupling coefficients, ring sizes, and waveguide lengths of microring resonator arrays can be arbitrary in this approach. After developing this approach, several examples are demonstrated and optimized for various configurations of microring resonator arrays. Simulation results show that this approach is intuitive, efficient, and intelligent for applications based on microring resonator arrays.

The analytical expression for the complex amplitude of light reflected from a wedge-shaped thin film is derived. For plane wave incidence, a simple ray tracing approach is used to calculate Goos-H?nchen (GH) shifts; and for non-plane wave incidence, for example, a Gaussian beam, the angular spectrum approach of plane wave is used in simulation. The two approaches predict that a wedge-shaped thin film can produce large negative longitudinal GH shifts. Although the reflectivity is small near the condition of resonance, the large negative GH shifts can be more easily detected in comparison with the shift from a plane-parallel film in vacuum.

Negative refraction and subwavelength imaging properties of a two-dimensional (2D) photonic crystal (PC) slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air holes immersed in a dielectric. For a certain frequency range in the third photonic band, the directions of the group velocities and the phase velocities can be opposite, so the PC can work as a kind of negative refractive-index material. The light radiated from a point source can form a subwavelength image spot through the PC slab. Negative refraction and an effective refractive index of the PC slab n=?1 can be achieved for the incident wave with its incident angle within a certain range.

The correct calibration of coefficients in the inversion model for aerosol mass concentration is the precondition of obtaining highly precise results. The concept of the fractal dimension of scattering equivalent section is presented, and the calibration mechanism of the fractal dimension is discussed. Based on the calibration mechanism, the stability of the fractal dimension is analyzed. Theoretical analysis and experimental results indicate that the fractal dimension obtained by the intersection point calibration method is stable, while that calibrated by the Gauss-Newton method is instable, which only describes the shape characteristic of a small sample. The study of the calibration mechanism for the fractal dimension markedly enhances the present model for aerosol mass concentration.

A modified asymmetrical Czerny-Turner arrangement with a fixed plane grating is proposed to correct aberrations over a broadband spectral range by analyzing the dependence of aberrations for different wavelengths. The principle of design is deduced in detail. We compare the performance of this modified Czerny-Turner imaging spectrometer with that of the existing Czerny-Turner arrangement by using a practical Czerny-Turner imaging spectrometer example. The excellent performance of the modified imaging spectrometer is confirmed by simulation with ZEMAX software.

The propagation of picosecond deep ultraviolet laser pulse at wavelength of 193 nm in air is numerically investigated. Long plasma channel can be formed due to the competition between Kerr self-focusing and ionization induced defocusing. The plasma channel with electron density of above 10<sup>13</sup>/cm<sup>3</sup> can be formed over 70 m by 50-ps, 20-mJ laser pulses. The fluctuation of laser intensity and electron density inside ultraviolet (UV) plasma channel is significantly lower than that of infrared pulse. The linear absorption of UV laser by air is considered in the simulation and it is shown that the linear absorption is important for the limit of the length of plasma channel.

We assess the color appearance of the samples with different inks on glossy substrates, five kinds of paper with different gloss levels. The color samples are measured using spectrophotometers under different illuminating/viewing geometries and visually estimated using the psychophysical method of magnitude estimation. The results of the two approaches are compared through the color appearance model of CIECAM02. The experimental data analysis indicates that the 0/45 and 15/0 geometries can be used to describe the two major aspects of gloss effect, the enlargement of color gamut, and the reduction of lightness. The agreement for hue attribute between instrumental measurement and visual assessment is better than those for colorfulness and lightness.

To improve the accuracy of color image reproduction from displays to printers, an adaptively spatial color gamut mapping algorithm (ASCGMA) is proposed. In this algorithm, the compression degree of out-of-reproduction-gamut color is not only related to the position of the color in CIELCH color space, but also depending on the neighborhood of the color to be mapped. The psychophysical experiment of pair comparison is carried out to evaluate and compare this new algorithm with the HPMINDE and SGCK gamut mapping algorithms recommended by the International Commission on Illumination (CIE). The experimental results indicate that the proposed algorithm outperforms the algorithms of HPMINDE and SGCK except for the very dark images.

A novel composite model is put forward for humidity-sensitive material based on Maxwell-Garnett and effective medium theory. The analytical expression of the relation between effective refractive index and relative humidity is shown with different absorption factors and porosities. The larger the absorption factor is, the higher the refractive index is. The refractive index of humidity-sensitive SiO<sub>2</sub> film decreases with the increase of ceramic material porosity. The sensitivity of optical humidity sensor can reach the magnitude of 10<sup>?3</sup>. In comparison with the experimental humidity-sensing curve by the method of p-polarized reflectance and the analysis of mechanism, theoretical simulation is in agreement with experimental results. Therefore, this composite model is proved to be reasonable which lays new theoretical foundation in further research on optical humidity sensor.

A simple all optical system for stopping and storing light pulses is demonstrated. The system consists of an erbium-doped fiber amplifier (EDFA), a semiconductor optical amplifier (SOA), and a fiber ring resonator. The results show that the multisoliton generation with a free spectrum range of 2.4 nm and a pulse spectral width of 0.96 nm is achieved. The memory time of 15 min and the maximum soliton output power of 5.94 dBm are noted, respectively. This means that light pulses can be trapped, i.e., stopped optically within the fiber ring resonator.

In order to improve the performance of reflectance diffuse optical imaging (rDOI), a novel polynomial geometry (PG) of optical fibers arrangement is proposed. Polynomial geometry is based on the hexagonal geometry (HG) and multicentered double-density (MD) mode. The overlapping sensitivity matrix, area ratio (AR), reconstruction image, two-absorber model, and contrast-to-noise ratio (CNR) in different depths are used to evaluate the performance of PG. The other three geometries including HG, rectangular geometry (RG), and MD mode are also compared with PG. The deformation of the reconstruction images is evaluted by circular ratio (CR). The results prove that the proposed PG has high performance and minimum deformation in quality of reconstruction image in rDOI.