A combined Raman/elastic backscatter lidar observations is carried out in the Pearl River Delta (PRD) China. The results show the largest lidar ratios of the order of 80 sr in the uplifting boundary layer in 2-3 km during the haze period. In the moderate pollution period, the lidar ratio has an average value of 58 sr. The Angstrom exponent exhibits high values around 1.82, indicating the presence of rather small particles. Different back air mass trajectories and the ambient atmospheric conditions are attributed to the distinct characteristics of aerosol optical properties in the haze and moderate pollution episodes. In the lower layer in the haze period, air masses are mostly advected from southeast coast China. In contrast, the air mass in the moderate pollution observing period passes through northwest China, indicating the combination of some pollution from the Tarim Basin in case of strong convection and the smoke from adjacent fire burning spot in PRD region.

We present the numerical simulation and analysis of the bandwidth estimation for adaptive optics (AO) systems based on stochastic parallel gradient descent (SPGD) optimization. Time-varying atmosphere turbulence due to wind velocity and turbulence structure constant is considered in the dynamic simulation. The performance of SPGD system with different iteration frequencies is studied in detail. A formula given that estimates the Strehl ratio degradation after SPGD adaptive control due to the increasing proportion of the number of deformable mirror actuator times Greenwood frequency to iteration frequency based on numerical analyses, can be used to roughly predict the required iteration frequency under the condition of various Greenwood frequencies.

A set of two-dimensional (2D) binary codes are created by the calculation of the speckle contrast in line scan laser display system. According to the 2D binary code, phase plates are fabricated by etched glass or photoresist with different thicknesses corresponding to the code. It is introduced on the intermediate image plane to reduce speckle in laser based line scan display system. The experimental results show that the phase plate with the 2D binary code of order 5 can successfully reduce speckle contrast to 17.5%.

Ultrasonic thermography or thermosonics is proved to be an effective non-destructive testing (NDT) method for inspecting carbon-fiber-reinforced polymer (CFRP) composites; however, the potential damages for the structure cannot be ignored, because of the contact vibration between the ultrasonic horn and the specimen. This work aims at developing a new excitation method for ultrasonic thermography—air-coupled ultrasonic excitation. CFRP laminates with impact damages are tested by air-coupled ultrasonic thermography, and the theoretical model of heat conduction is given. Results demonstrate good excitation performance for impact damages detection in CFRP composites. Moreover, the conventional ultrasonic thermography results are shown, and the prospect of air-coupled ultrasonic thermography is discussed.

We propose two design methods of concentric multi-belt pure phase apodizer and phase modulation functions for generating two ring-shaped focuses by focusing the linearly polarized doughnut-shaped beam with a high numerical aperture objective. The phase modulation functions for odd and even belt are verified effectively by numerical simulation. The distance of the two focuses and the position of each focus can be controlled or separately adjusted by the use of liquid crystal spatial phase modulation. It could be useful in optical trapping, particle stacking, alignment and transportation.

A novel temperature sensor based on a dual-core fiber (DCF) is proposed and theoretically analyzed. The DCF-based temperature sensor is simply formed by splicing a segment of DCF to two segments of single mode fibers, where the DCF is used as the sensing element. The mode coupling between two fiber cores of the DCF is sensitive to the temperature-induced index change of the silica in the DCF. Simulations show that there is a linear relationship between the temperature of the DCF and the wavelength shift of the output spectrum of the DCF-based temperature sensor when the broadband light is injected into one fiber core of the DCF. Temperature sensors based on DCFs with different parameters for temperature sensing are also investigated.

A novel web-like microstructure optical fiber (MOF) is fabricated which serves as a bundle of suspended submicron-thickness membranes as planar waveguides and their Y-type connection nodes as the secondary cores. The polarization dependent visible continuum coverage from 350 to 1 000 nm is generated from a 20-cm-long membrane of 0.55-μm-thickness pumped by 200-fs laser at 800 nm. We also obtain narrowband signal of blue dispersive wave around 410 nm with the up-conversion efficiency routinely beyond 20% in the Y-type secondary core in another smaller web-like MOF.

The impact of channel occupancies on polarization division multiplexed quadrature phase-shift keying (PDM-QPSK)/on-off keying (OOK) hybrid systems is investigated numerically over a dispersion-managed transmission link. In addition to keep large residual dispersion per span, we find that suitable channel occupancy also help to improve the nonlinear tolerance of such hybrid systems significantly. About 2.4-dBm more nonlinear threshold (NLT) and 75% increase of transmission reach can be obtained under suitable channel plan for 112-Gb/s PDM-QPSK/OOK hybrid systems.

An all fiber structure nanosecond pulse is realized through two stage amplifiers, which has 8.78 W in average power, 1 064 nm in wavelength, 11 kHz in repetition frequency, 125 ns in impulse duration, 0.8 mJ in single pulse power, 5.3 kW in peak power. The optic-optic conversion efficiency is 55.6%. Meanwhile, we setup another system, a nanosecond pulse is realized through just one stage amplifier, which has 10.10 W in average power, 1 064 nm in wavelength, 11 kHz in repetition frequency, 150 ns in impulse duration, 0.92 mJ in single pulse power, 6 kW in peak power. The optic-optic conversion efficiency is 67%. The only one stage of amplifier simplifies the system structure and reduces the cost.

In this letter, a modified grouped bit-flipping decoding algorithm for low-density parity-check (LDPC) coded pulse position modulation (PPM) signals is proposed. The improvement in performance is observed by Monte Carlo simulations. The coding gain is more than 1 and 2 dB for the order numbers of PPM of 4 and 16 respectively.

In flexible bandwidth optical networks, the dynamic lightpath setup and teardown inevitably lead to spectrum fragmentation which blocks the new connections. In order to effectively allocate the spectrum along a better route, a notion of available spectrum consecutiveness is introduced and three dynamic routing and spectrum assignment (RSA) algorithms are proposed in this letter accordingly. The novel algorithms retain the spectrum consecutiveness as much as possible when establishing a lightpath and reduce the spectrum fragmentation. Simulation results indicate that our proposed spectrum consecutiveness based RSA algorithms achieve lower blocking probability and higher adaptability to more line rates mixture.

The photonic crystal fiber-based surface plasmon resonance (SPR) refractive index sensor is demonstrated by using post-processing technique of photonic crystal fiber (PCF). The coupling of PCF mode field and SPR can be controlled by the air holes collapsing in PCF. The effects of metal film thickness and air hole diameter on the sensor at different wavelength are simulated by using finite element method. The simulation results are analyzed by using the modes matching theory. The amplitude based and spectrum based detection methods are discussed respectively. Refractive index sensitivity 1 700 nm/per refractive index unit (RIU) can be achieved for an aqueous analyte.

A switchable dual-wavelength erbium-doped fiber laser is proposed and experimentally demonstrated, which is constructed by a polarization-maintaining fiber Sagnac loop mirror (PMF-SLM) and two FBGs with different wavelengths. Wavelength switching operation is achieved by properly adjusting the polarization controller (PC) in the PMF-SLM. Stable single- or dual-wavelength lasing output can be realized. The maximum amplitude variation for every lasing wavelength is less than 1 dB, and the signal-to-amplified spontaneous emission (ASE) ratio is about 35 dB.

Laser linewidth is the important determinant of applying coherent optical orthogonal frequency division multiplexing (CO-OFDM) in optical transmission systems. The laser linewidth impairments in 100-Gb/s polarization division multiplexing CO-OFDM (PDM-CO-OFDM) system without optical dispersion compensation are compensated by the phase drift compensator (PDC) based onMth-power-law method located at the receiver. PDC is more effective to compensate the phase drift due to laser linewidth. Simulating results show that the maximum Q factor can be increased by almost >10.0 dB for back-to-back (BtoB). For the 100-kHz linewidth system of 800-km system, a benefit of about 4.9 dB is possible for the maximum Q factor.

A novel numerical algorithm is proposed to reconstruct the Laplacian of an object field from one single in-line hologram. This method uses two different reconstruction distances of z and z+\Delta z, or two different reconstruction wavelengths of \lambda and \lambda + \Delta to reconstruct one digital in-line hologram. Theoretical analysis shows that when the value of \Delta z or \Delta \lambda is sufficiently small, the difference of the two reconstructed fields is an approximation to the second-order Laplacian differentiation of the object wave, and the zero-order and "twin-image" noise can be almost eliminated simultaneously. Computer numerical simulations and optical experiments are carried out to validate the effectiveness of this algorithm.

Image matching is an important question in computer vision, however, due to the large viewpoint and similar regions, there exist false matches. A robust matching method-DelTri is proposed. Based on the initial matching of Scale Invariant Feature Transform, the matched keypoints are respectively triangulated to create the triangulation net, which can express the overlapped physical structure of the objects. The matched triangles can lead to the final matches. Compared with classical RANSAC, experiments show that DelTri can improve the match robustness, including matching accuracy and magnitude efficiency.

We illustrate an approach to statistical model and sequential hypothesis designed to the automatic target recognition (ATR) problem for active imaging LADAR. The key to this approach is using multihypothesis sequential tests to reduce the number of target hypotheses under consideration as more observed data are processed. The approach is potentially useful when sensor data are plentiful but computation time and processing capability are constrained. We experimentally demonstrate that the proposed recognition approach can resolve the military ground vehicle recognition problem of active imaging LADAR with a high recognition rate.

For many years, various local feature descriptors have been proposed. Among them, Lowe's scale invariant feature transform (SIFT) descriptor is the most successful one and has been proven to be performed better n the distinctiveness and robustness than other descriptors. However, SIFT descriptor is based on gray level images and pays little attention to the color information which can be a powerful cue in the distinction and recognition of objects. To increase the discriminative power, color features have been plugged into the feature descriptors only recently. In this letter, we study the photometric invariant properties of the Lowe's SIFT, HueSIFT, rgSIFT and CSIFT based on color diagonal offset model. Theoretical and experimental results show that the four descriptors are not fully invariant to photometric transformation. To solve this problem, a new color invariant framework based on color diagonal offset model is proposed in this letter. Experimental results validate our proposed framework.

Oil microleakage can cause the land surface vegetation to be abnormal. An oil and gas exploration method based on the vegetation information in the hyperspectral remote sensing images is proposed. It's used to probe the effectiveness of extracting the oil and gas microleakage information, with the vegetation anomalies in the remote sensing images. A decision tree based on the vegetation index is taken to extract the anomalies areas of vegetation in the CASI images. It's shown by the experiment that there are some potential for the exploration of oil and gas in the areas covered by sparse vegetations.

An unsupervised segmentation and its performance evaluation technique are proposed for synthetic aperture radar (SAR) image based on the mixture multiscale autoregressive (MMAR) model and the bootstrap method. The segmentation-evaluation techniques consist of detecting the number of image regains, estimating MMAR parameters by using bootstrap stochastic annealing expectation-maximization (BSAEM) algorithm, and classifying pixels into region by using Bayesian classifier. Experimental results demonstrate that the evaluation operation is robust, and the proposed segmentation method is superior to the traditional single resolution techniques, and considerably reduces the computing time over the EM algorithm.

By making use of the discrete fractional cosine transform, spectrum cutting and combining, rate-distortion control and color space transform, a joint compression and encryption scheme for multiple images and color images is proposed based on the multiple-order discrete fractional cosine transform (MODFrCT). The spectra coefficients of images gotten by the discrete cosine transform are scanned in a way of zigzag, cut at an appropriate position, and combined into a single spectrum image sequentially encrypted by the MODFrCT. Rate-distortion control is utilized during the spectrum cutting to balance the qualities of the multiple reconstructed images. A color image can be decomposed into Y, Cb, and Cr components prior to the encryption, and these three components are then encrypted in the same way as that for multiple images. The numerical simulations demonstrate the validity and efficiency of these schemes, and the robustness of the schemes against occlusion attack is examined.

In order to broaden the scope of application and ensure the calibration precision, a new method of linear calibration by making fully use of vanishing point attributes is proposed. The method dose not need any rigorous restrictions, and solves the self-calibration problem with only five vanishing points in two digital images, which are arbitrarily taken by a handheld digital camera. Furthermore, another approach for camera's pose estimation is also put forward without any strict controlled motions. The experimental results of both computer simulation and real images show that the calibration algorithm is effective, feasible, and robust.

A rational-dilation wavelet transform (RWT) based pan-sharpening method for multi-spectral (MS) images of various oscillatory nature is proposed. The previous multi-scale transforms, such as wavelets, curvelets and contourlets, decompose an image into channels with low constant Q-factors, and aren't suitable for pan-sharpening images with different behavior in frequency domain. The RWT as an over-complete scheme not only increases the sampling in spatial and frequency domain, but also provides a tunable Q-factor approach to be suitable for a given dataset. We studied its multi-scale decomposition scheme and the RWT based pan-sharpening method. The MS image pan-sharpening experiments show that this method using a better suitable parameter set can achieve a promising performance and often outperforms many other widely-used pan-sharpening methods both in visual quality and in term of evaluation indexes.

An effective image splicing algorithm based on phase correlation and speeded-UP robust features (SURF) operator is proposed which can sort the disordered sequence and stitch them into a super viewing field image without any human intervention. Phase correlation in frequency domain is used for images sorting and region ofinterest (ROI) estimation, and guiding features extracting and matching in spatial domain by SURF operator and bidirectional best bin first (BBF) strategy. The experimental results demonstrate that this algorithm not only can deal with the input images with translation, rotation and scale changes, but also outperforms the pre-existing methods on the aspect of repeatability, efficiency and accuracy.

Integer wavelet transform (IWT) could offer the lower computational complexity and the less storage spending for image compression than the discrete wavelet transform (DWT). But the most coefficients of the IWT image have smaller dynamic change ranges than discrete wavelet transform. In this letter, an efficient and low-complerity coding algorithm called embedded optimal coefficient scaling (EOCS) is proposed. It optimizes the distribution of the wavelet coefficients in every threshold plane and provides an efficient embedded quadtree-partitioning scheme to encode the image. Experimental results show that the presented method cannot provide peak signal-to-noise ratio (PSNR) performance up about 2–6 dB better than set partitioning in hierarohical trees (SPIHT) without the OCSF scheme, but also support both efficiently lossy and lossless compression in single bitstream.

An objective quality evaluation measure of asymmetric and symmetric distorted stereoscopic images is proposed. In the measure, stereoscopic features are first extracted from left and right images by using singular value decomposition. Then, the relationship between the stereoscopic features and subjective scores is established by using support vector regression. Finally, the objective evaluation scores are tested on symmetric and asymmetric databases. Experimental results show that the proposed measure is more effective in quantifying image quality, compared with other two relevant quality evaluation measures.

Polarization aberration of optical systems in imaging polarimetry affects the polarization detection accuracy, especially in wide field of view and large relative aperture systems. The polarization aberration of the imaging lens in imaging polarimetry is demonstrated and analyzed through the way of polarization ray tracing. The impact of polarization aberration on the polarization detection accuracy of imaging polarimetry is also discussed. The variation of Stokes parameters as functions of the field of view and the relative aperture is achieved. The polarization aberration can be reduced and calibrated at different field of view and the relative aperture of the optical systems, and the correct polarization information of the object can be derived.

To meet application requirements of high resolution and high frame rate for the aerial camera, a real-time high definition (HD) aerial camera imaging system is designed and developed. A KAI-01050 charge-coupled device (CCD), ADSP-BF561, and AD9920A are used in the system. ADSP-BF561 is used to configure registers of AD9920A for generating the timing-driven signals to meet CCD parameter needs, and image stitching through ping-pong operation of collected video signals is achieved, then the image is displayed correctly. In the end, the system is developed, 1 M pixels and 60 frame rate are realized, and running results on the system verify effectiveness of the design program.

A new bidirectional reflectance distribution function (BRDF) model of earth objects is established for the calibration of remote sensing image by the national metrology equipment. This model colligates the solar radiance, the atmosphere status, the object type, and the space camera parameter, etc. The output data of this model is the enter radiance data for the space camera. The remote sensing image can be appeared more “true” through this calibration. A kind of ground glass for architecture is measured and the correspond remote sensing image is simulated. After calibrated, the chromatism of this image is improved by 2 and the luminance contrast of that is improved by 3.

Digital image correlation has become an important and effective non-contact optical full-field strain measurement technique. The strain field obtained directly by image correlation algorithm is full of noise. In this letter, we explore a novel way of actively adding small amount of Gaussian random noise to original displacement field, subsequently utilizing the well-known thin-plate spline smoothing (TPSS) technique to smooth the noised displacement field, and finally differentiating smoothed displacement field to get reliable strain field. The resultant method, named as active noise thin-plate spline smoothing (ANTPSS), outperforms the conventional TPSS and spline least-squares approximation. Moreover, ANTPSS successfully smooths the displacement filed obtained from three-point bending experiment of foam block and generates a reliable inhomogeneous strain field.

A high power and good beam quality InGaAs/GaAs quantum well semiconductor disk laser at 1 015 nm wavelength is reported. The semiconductor wafer is grown in reverse order: substrate is on the window side and the distributed Bragg reflector is the last grown epilayer. Then the wafer is up-side-down and capillary bonded to a SiC heatsink, and the substrate is chemically etched. Because the total thickness of the substrate-removed structure is less than 10 μm, the thermal management of the laser is significantly improved, and the maximum output power over 0.6 W is obtained using a 3% output coupler and 3.2 W incident pump power. The M2 factors of 1.02 and 1.01 indicate a near-diffraction-limited beam quality. To further reveal the characteristics of this substrate-etched structure on the thermal management, the heat flux and the temperature distribution of the gain wafer are numerically analyzed, and the corresponding results are discussed.

Thermal depolarization caused by birefringence is a major factor that limits the output power of linearly polarized Nd:YAG laser. This paper theoretically analyzes the thermal depolarization of [111]- and [100]-cut Nd:YAG rods and output power of two diode-pumped Nd:YAG rods are compared experimentally. 3×80 mm sized [111]- and [100]- cut rods with doping concentration of 1.1±0.1at.% are used. With a pump power of 180 W, the ratio of linearly polarized output power versus unpolarized output power obtained with the [111]- and [100]- cut rods are 19% and 43% respectively, with a difference of 24%. The experiment demonstrates that in comparison with conventional [111]- cut Nd:YAG rod, [100]- cut Nd:YAG rod can improve the linearly polarized output power obviously. The thermal depolarization depends on the polarization direction for the [100]- cut Nd:YAG rod, and the linearly polarized output power can be improved by suitably modification of the polarization direction of linearly polarized laser to minimize thermal depolarization.

We demonstrate a diode-pumped master-oscillator/fiber-amplifier (MOFA) system consisting of a passively SESAM mode-locking Nd:YVO4 laser and a Yb-doped large-mode-area fiber amplifier, which generates total average power of 24.4 W at 1 064 nm center wavelength, 91.5 MHz repetition rate, and 21.9 ps pulse duration. Power scaling limitations that arise from nonlinear distortions such as self-phase-modulation (SPM) and stimulated Raman scattering (SRS) have not been observed during the whole experiments.

A fiber laser system emitting high-quality ultrashort powerful light pulses is reported. The photonic crystal fiber featuring high-gain large -mode-core and short absorption length is used, and the fiber laser is passively mode-locked by a semiconductor saturable absorber mirror. Its output greatly exceeds the power limitation of single-mode fiber oscillators with 1.4-W average power at 1 039-nm center wavelength, 6.9-ps pulse width, and 45.4-MHz repetition rate.

We report on extra cavity frequency doubling lasers for 266 nm with a compact, tunable extended cavity diode laser (ECDL) at 1 064 nm. The ECDL injected into a tapered amplifier yields a power of 290 mW. In a first frequency-doubling stage, about 47-mW green light at 532 nm is generated. Subsequent second-harmonic generation (SHG) employing a BBO crystal leads to about 30 μW of ultraviolet (UV) light at 266 nm. The tunable characteristic of this UV light source is discussed. The tuning span of quasi-phase matching of doubling cavity for 532 nm with PPKTP crystal is achieved with –3.5 nm by changing the temperature of PPKTP and is achieved with –1.186 nm by adjusting angle of PPKTP.

Axial multiple foci patterns of radially polarized hollow Gaussian beam (HGB) with radial wavefront distribution is investigated theoretically. The wavefront phase distribution is cosine function of radial coordinate. Simulation results show that the multiple foci patterns can be adjusted considerably by the beam order of HGB and cosine parameter that indicates the phase change degree. The foci number fluctuates on increasing cosine parameter for certain beam order. And when the beam order is small, there occur five foci in focal region, and the cases are more frequently than that under the condition of higher beam order. Gradient force distributions are also given to show that the multiple foci of radially polarized HCB may be applied to construct tunable optical traps.

Highly efficient passively Q-switched Yb:YAG ceramic laser with Cr4+:YAG crystal as saturable absorber is achieved. Maximum average output power of 0.96 W is obtained when the absorbed pump power of 3.8 W is used; corresponding optical-to-optical efficiency is about 25%. The slope efficiency is 30%. Laser pulses at 1 030 nm with pulse energy of 107 μJ and pulse width of 9 ns are achieved at repetition rate of 9 kHz, with corresponding peak power of 11.9 kW. Meanwhile the effects of absorbed pump power on the characteristics of passively Q-switched laser pulses are investigated systematically.

In order to investigate the effect of multi-micro laser shock peening on residual stress of copper materials, surface residual stress is measured, and distribution of residual stress under different overlapping rates and laser energies is explored. Surface mean residual stress is proposed as characteristic means according to the defect of test equipment in existence. Numerical simulation is carried out to display residual stress distribution on top surface and depth in the overlapping process of microscale laser peening. The results show that overlapping rate and laser energy greatly influence the distribution of residual stress, and the surface mean residual stress is an effective characteristic means according to the residual stress distribution along typical paths and mean stress formula.

Different distributed feedback (DFB) configurations in optically pumped polymer lasers, including the active Bragg grating structures, the dielectric grating structures spin-coated with polymeric semiconductors, and the actively waveguide dielectric grating structures (AWGS), are studied systematically. In the experiment, the F8BT polymer poly [(9,9- dioctylfluorenyl-2,7-diyl)-alt-co- (1,4-benzo-{2,1’,3} -thiadiazole)] is employed as the active medium in the three laser configuration. And all grating structures are fabricated though interference lithography or interference ablation. It is found that the AWGS design has advantages over the other two. The continuous and high-quality active waveguide in the AWGS enables low-threshold (115 \mu J/cm2) laser emission with narrow linewidth (~0.4 nm at full-width at half-maximum). The experimental verifications are in good agreement with the theoretical analysis. These results reveal some interesting mechanisms in optically pumped DFB polymer lasers, and it may be enlightening to the construction of electrically driven organic lasers.

A diode-pumped picosecond mode-locked Yb:YAG ceramic laser is realized with a slope efficiency of 44%. Output power up to 1.04 W is obtained with pulse duration of 10.4 ps at central wavelength of 1 049.5 nm. The standard deviation of maximum output power instability is 0.00453.

The single cavity all-dielectric thin film Fabry-Perot filter (s-AFPF) is investigated in this letter as a means of tuning the wavelength in an external cavity diode laser (ECDL), and the means of limiting longitudinal mode hopping is also investigated. When a TE or TM plane wave irradiates a s-AFPF, a quasilinear relationship is found in a certain wavelength range between the optical intensity peak-transmittance wavelength of s-AFPF and the cosine value of plane wave incident angle at s-AFPF. Based on this feature, we propose and investigate a configuration with a s-AFPF in a tunable ECDL. By theoretical calculation, a mode-hop-free wavelength tuning range of ~5 nm around 1 550 nm is achieved. The ECDL can be used in the application of environmental monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on.

The optical properties of disperse red 1 (DR1) dye molecules can be changed by controlling the molecular configurations using AlPO4-5 (AFI) and SAPO-47 (CHA) single crystals. Polarized and temperature dependent absorption spectra show that DR1 molecules exist as cis configuration in the cages of CHA crystals. The absorption band for cis-configuration is centered at 432 nm, which does not depend on polarization angle and temperature. However, DR1 molecules are well aligned in the channels of AFI crystal with trans configuration. Its absorption band is centered at 520 nm, which shows strongly anisotropic polarizability and shifts to long wavelength with increasing temperature. It can be used as polarizer and temperature sensor. The second harmonic generation (SHG) and photoluminescence (PL) investigations show that the DR1 trans isomers in AFI matrix have potential applications in nonlinear optics.

Potassium dideuterium phosphate (DKDP) with deuterium content of 60% and potassium dihydrogen phoshate (KDP) crystals are grown by "point-seed" rapid growth method. Optical property including transmittance spectra, conoscopic image, light scattering and laser damage threshold (LDT) are measured. The results show that although the infrared absorption edge of transmission spectra is obviously red-shifted, structure perfection and optical homogeneity of DKDP crystal became poorer. Light scattering have no obvious change. We also find that the value of LDT at 1 053 nm has a 2.5-3.8 \times increase compared with that tested at 526 nm and LDT of Z-cut samples is obviously higher than that of tripler-cut samples.

Determination of NO concentration in live cells is essential to evaluate its related cellular functions. In this letter, the concentration of NO in HeLa cells and rat dorsal root ganglion (DRG) neurons are studied by confocal laser scanning microscopy using DAF-2 DA as a fluorescence probe. The results show the fluorescence intensity of NO in HeLa cells is higher than that in DRG neurons, which indicats that the former exhibits higher NO concentration. Furthermore, the experimental conditions for low photobleaching and phototoxicity are optimized.

The influence of diffusive nonlinearity on mobility of photovoltaic lattice solitons is demonstrated. The dynamical evolution of collision between photovoltaic lattice solitons and nonlinear lattices are simulated numerically. The results show the lattice solitons with a transverse velocity have complicated behaviors and will not propagate with an oblique trajectory. When considering the diffusive nonlinearity, we find that diffusive nonlinearity can introduce a nonlinear chirped phase to lattice soliton and the lattice soliton with a special incident angle can become a "tilted soliton".

A fixed abrasive technology combined with computer controlled optical surfacing is discussed, and a removal function model for multi-pellet polishing pad is established based on the removal function theory of planar motion. The parameters of the model, such as the movement eccentricity of the polishing pad and the distance between pellets, are optimized by introducing a approaching factor and a curve RMS distance in the simulation. The comparison of the theoretical model and the experimental results indicate that the error between the theoretical maximum removal rate and the experimental data is 0.0073 \mu m/min, and its error ratio is 5.58%; the RMS distance error between the theoretical removal function curve and the experimental curve is 0.0849 μm and its error ratio is 7.01%. The veracity of the theoretical model is verified by experimental results, which predicts the feasibility of the fixed abrasive polishing technology and establishes a promising basis for the SiC mirror precision fabrication field.

The optimized oxygen inductively coupled plasma etching parameters are systematically studied to fabricate Poly (methyl-methacrylate-glycidly-methacrylate) inverse ridge waveguide with smooth vertical features. The etch rate, surface roughness and vertical profile are characterized by atomic force microscopy and scanning electron microscopy. The optimized etching parameters are found to be 400-W antenna-RF power, 30-W radio frequency (RF) bias power, 1-Pa-chamber pressure, and 40-sccm be O2-flow rate. Spincoating butyl acetate diluted polymer solution onto the channel waveguide is proved to be an effective method which can decrease the surface roughness. According the results, the RMS rouqhness of the film decreases 80%. Optical propagation loss can be reduced from 2.6 to 1.5 dB/cm for the above reason.

The Gaussian doping is used to optimize the performance of InP/InGaAs uni-traveling-carrier photodiode (UTC-PD) in this letter. The UTC-PD structure is modeled with drift-diffusion approach and the comparisons of the characteristics for four UTC-PDs with different doping schemes in absorption layer are made. According to the comparison, one optimized UTC-PD where the InP collection layer is partly replaced by a depleted InGaAs using Gaussian doping on top of lightly constant background doping in the absorption layer is presented, with f3dB of 79 GHz, which is more than 1.9 times higher than that with the constant doping in the absorption layer.

We design a T-Shaped wavelength division de-multiplexer in two-dimensional (2D) photonic crystal based on the coupling resonance characteristics. In this structure, three high effective and relative narrow bandwidths optical wavelengths (1 310, 1 440, and 1 550 nm) are obtained by changing the radius of the ring and cavity rods. The method of the finite-difference time-domain is used to investigate the characteristics of the coupling resonance characteristics of the ring and the cavity. The calculation results show that transmission rates of these three wavelengths are all reach up to 95% and achieve with 5-nm mean value of bandwidth.

We propose a surface plasmon resonance (SPR) sensor based on phase modulation and polarization interferometry, both of which provide a refractive index (RI) resolution of the same order as that of SPR sensors of the phase type. And it has a wide dynamic range and insensitivity of RI resolution to the thickness of metal films as that of the intensity type SPR sensors. In this letter, we choose electro-optic (EO) phase modulation instead of the angle modulation. We demonstrate theoretically that with the EO phase modulation, our sensor could provide a better RI resolution.

The relative coupling efficiency of top two-dimensional metal coupling grating for mid-wave quantum well infrared photodetector is calculated by finite difference time domain algorthms. The relative coupling efficiency with respect to the grating parameters, such as grating period, duty ratio, and grating depth, is computed. The calculated results show that the relative coupling efficiency will reach the largest value for the 4.1 μm incident infrared light when taking grating period as 1.3 μm, duty ratio as 0.75, grating depth as 0.4 \mu m.

Large-area metallic photonic crystals (MPCs) consist of two-dimensional (2D) periodical arrays of gold nano-holes are fabricated by solution-processible gold nanoparticles using interference lithography in combination with subsequent lift-off and annealing processes. By controlling the annealing temperature, the 2D nano-hole arrays are transformed into nano-island arrays, enabling easy achievements of two different photonic devices. The microscopic characterization shows convincingly the success of the fabrication techniques and verifies our proposed mechanisms for this kind of nanoscale morphology transformation. This kind of mechanisms can be applied extensively in the metallic nanofabrication and in the realization of plasmonic photonic devices.

The far-field analytical expressions for the electromagnetic fields of amplitude of vector-vortex beams having a Bessel–Gauss (BG) distribution propagating in free space are obtained based on the vector angular spectrum and the method of stationary phase. The far-field energy flux distributions and the beam quality by the power in the bucket (PIB) in the paraxial and nonparaxial regimes are investigated. The PIB of the vector-vortex BG beams depend on the ratio of the waist width to wavelength and the polarization order. The analyses show that vector-vortex BG beams with low polarization order have better energy focusability in the farfield.

The effects of counter-rotating terms on ground states (GS) of a lambda-type three-level atomic system coupled with two fields are examined. The GS, which are dark states in rotating wave approximation (RWA), can be expressed by a simple formula including the excited states. When the coupling strength is less than 0.2 of the maximum energy splitting in the atomic system, the component coefficients of excited states in the GS can be described by the formula similar as that in a two-level system and have linear relationship with their coupling constant. Further increasing the coupling strength will increase the excited components in the GS more rapidly, very different from the two-level system.

The discrete dipole approximation (DDA) method is used to calculate the scattering matrix elements and optical cross-sections for a wide variety of complex soot aggregates in random orientation at a visible wavelength of 0.628 \mu m. The effects of the material composition and the size of the larger particle that is in touch with soot cluster on scattering and radiative properties of complex soot aggregates are analyzed. It is shown that the material composition and the size of the larger particle can strongly influence or even dominate the overall scattering and radiative properties of the aggregates.

The influence of varied water distribution in different locations of the mesophyll and mid-vein of the same leaf on the absorption and refraction coefficient is described. And the further comparisons between green leaf and yellow leaf reveal that the complex permittivity of leaf can provide important information about the water content and can characterize the changes of the water distribution of the leaf. So our measurements tend to demonstrate that the dielectric material parameters will be employed to determine the leaf water status in plant leaves.

Time-resolved femtosecond coherent anti-Stokes Raman spectroscopy (fs-CARS) is utilized to measure the methane/oxygen/nitrogen flame temperature at atmospheric-pressure. The measurements are performed using the CARS signal of N2 with 40-fs laser pulses in the first few picoseconds after the initial in-phase excitation. Flame temperatures at 300 and 1 325 K are measured, the experimental results show good agreements with theoretical ones and present a good repeatability.

SiC coating for surface modification grows on reaction boned SiC (RB-SiC) substrate cannot have high quality because the material of RB-SiC has two phases. We apply a new method to improve the effect of surface modification. First the surface of RB-SiC is carbonized, and then a diamond like carbon (DLC) coating is prepared on it before the growth of SiC coating. Research and tests show that the SiC coating can grow denser and uniform because of the buffer function of the DLC coating, thus the effect of surface modification is improved. The roughness reduces from 1.397 to 0.478 nm (rms) after the surface modification using DLC buffer layer.

A Terahertz sensing method based on the resonant transmission characteristics through metallic aperture arrays is proposed. Here we present metallic aperture arrays of rectangular and H-shaped holes which induce localized resonance. High characterization sensitivity to surface condition is demonstrated. When applied with the liquid of 3-pentanone, arrays of rectangular and H-shaped holes have sensitivity of 158 and 172 GHz/RIU (refractive index unit), respectively. So the metal meshes based localized resonance can also be used as a sensor chip in terahertz region.

THz spectral properties of several of fresh animal tissues are investigated based on the time domain system. Terahertz pulse transmission spectra of different animal tissues slices with different thickness are obtained, and the refractive index, the absorption coefficient, and the extinction coefficient of these tissues are analyzed and discussed. According to the double Debye model, tissue parameters are simulated and calculated. The theoretical and experimental results are matched. These studies are helpful to make further research of the THz spectral performances of human tissues and cancers.

To improve the color reproduction accuracy of image among digital devices in spectral color reproduction, a novel profile connection space is proposed. The profile connection space is composed of three sets of tristimulus determined by the principal components of typical illuminants and CIE1931XYZ standard colorimetric observer. The spectral reflectance of three common used atlases is transformed to three deformations of the profile connection space, and then transformed back to the spectral reflectance. The color difference between the original and transformed reflectance are very small for the common used illuminants, which indicates that the profile connection space is a good candidate for spectral color reproduction.