A new polarization lidar has been developed for detecting depolarization characteristics of aerosol and cirrus over Hefei (31.90N, 117.16E), China. The fundamental principle of polarization lidar is briefly introduced. Overall structure and specifications of the polarization lidar, as well as measurement method, are described. The observational results of depolarization ratio for cirrus over Hefei from February to May in 2005-2007 are presented and discussed. The exploring temperatures by radiosonde during the spring of 2005 are also presented and analyzed. The results show that the cirrus generally presents in the altitude from 7 to 12 km, and the depolarization ratio varies from 0.2 to 0.5. At the meanwhile, depolarization ratio appears a climbing tendency with the increasing height and the decreasing temperature.

An efficient scheme for photon statistics measurement is presented based on the Hanbury-Brown-Twiss configuration. We set the sampling time Ts to satisfy the relationship of Ts<Td<Tm, where Td is the dead time of each detector and Tm is the laser pulse repetition period. And each single photon detector cannot detect more than one photon in each pulse. The approach can sufficiently eliminate the influences of the detector’s dead time on photon statistics. At last, the photon statistics of coherent field is experimentally determined.

Design and operation of a practical, accurate alignment diagnostic system is important for the grating tiling technology, which is supposed to be applied in a chirped-pulse amplification system to increase the output power. A diagnostic method is proposed and demonstrated for grating tiling. Provided that the wavelength and incident angle of the diagnostic beam are properly set, the far-field of the main laser beam and that of the diagnostic beam can vary in the same way with the tiling errors between the sub-aperture gratings. Therefore, rotational and translational errors can be controlled and compensated according to the far-field of the diagnostic beam. The real-time monitoring and alignment can be achieved without disturbing the main beam.

A new integrated scheme based on resource-reservation and adaptive network flow routing to alleviate contention in optical burst switching networks is proposed. The objective of the proposed scheme is to reduce the overall burst loss in the network and at the same time to avoid the packet out-of-sequence arrival problem. Simulations are carried out to assess the feasibility of the proposed scheme. Its performance is compared with that of contention resolution schemes based on conventional routing. Through extensive simulations, it is shown that the proposed scheme not only provides significantly better burst loss performance than the basic equal proportion and hop-length based traffic routing algorithms, but also is void of any packet re-orderings.

A multiscale information measure (MIM), calculable from per-pixel wavelet coefficients, but relying on global statistics of synthetic aperture radar (SAR) image, is proposed. It fully exploits the variations in speckle pattern when the image resolution varies from course to fine, thus it can capture the intrinsic texture of the scene backscatter and the texture due to speckle simultaneously. Graph spectral segmentation methods based on MIM and the usual similarity measure are carried out on two real SAR images. Experimental results show that MIM can characterize texture information of SAR image more effectively than the commonly used similarity measure.

A new method to protect the copyright of digital museum based on digital holography is proposed. The Fresnel hologram of watermark image is embedded in the object to be protected through discrete wavelet transform (DWT). After the watermark detection, the copyright information appears in the reconstructed hologram. With the higher redundancy feature in the hologram, the proposed technique can actually survive several kinds of image processing. Experimental results prove that the presented method has good robustness in image protection.

In the real-world application of face recognition system, owing to the difficulties of collecting samples or storage space of systems, only one sample image per person is stored in the system, which is so-called one sample per person problem. Moreover, pose and illumination have impact on recognition performance. We propose a novel pose and illumination robust algorithm for face recognition with a single training image per person to solve the above limitations. Experimental results show that the proposed algorithm is an efficient and practical approach for face recognition.

A novel and precise micron-scale nanosecond laser spot measurement based on film-scanning method is presented. The method can be used to measure the spot size, beam profile, and intensity distribution of the pulse. The central spot radius of the pulsed Bessel beams with pulse width of 25 ns is measured to be 94.86+-5 \mum in our experiment through the analysis of the digital image by film scanning, and the result is consistent with the theoretical value of 92.33 \mum. Compared with charge-coupled device/complementary metal oxide semiconductor (CCD/CMOS) laser beam profilers, the film-scanning method shows higher measurement accuracy, single shot ultrashort pulse measurable, larger measurable size, and wider measurable wavelength range.

A novel coherent Doppler lidar (CDL) system based on single-mode fiber (SMF) components and instruments is presented to measure the speed of target. A fiber interferometer used in CDL system is reported. This fiber mixer is employed as a coherent receiver to resolve the shifts of signal-to-noise ratio (SNR) and mixing efficiency induced by backscattered field’s wavefront error. For a certain wavelength, the maximum coupling efficiency between signal and SMF is determined by the ratio of pupil diameter to focal length of the coupling lens. The legible interference patterns and spectrum signals show that fiber interferometer is suitable to compensate for amplitude and phase vibrations. This robust coherent receiver can achieve improved CDL system performance with less transmitter power.

A method for automatically identifying the order of fringe pattern traces is presented. It uses the simplified Otsu algorithm for obtaining the threshold, the angular scan in the range of 45 angle for searching the trace positions, and the zone search technique for identifying different traces. Experimental results show that the proposed method may reliably obtain the order of fringe pattern traces orientating from almost 45 angle to 90 angle.

The 810-nm InGaAlAs/AlGaAs double quantum well (QW) semiconductor lasers with asymmetric waveguide structures, grown by molecular beam epitaxy, show high quantum efficiency and high-power conversion efficiency at continuous-wave (CW) power output. The threshold current density and slope efficiency of the device are 180 A/cm2 and 1.3 W/A, respectively. The internal loss and the internal quantum efficiency are 1.7 cm2 and 93%, respectively. The 70% maximum power conversion efficiency is achieved with narrow far-field patterns.

An intracavity frequency-doubled vertical external cavity surface emitting laser (VECSEL) with green light is demonstrated. The fundamental frequency laser cavity consists of a distributed Bragg reflector (DBR) of the gain chip and an external mirror. A 12-mW frequency-doubled output has been reached at 540 nm with a nonlinear crystal LBO when the fundamental frequency output is 44 mW at 1080 nm. The frequency doubling efficiency is about 30%.

The Ca2SiO4:Dy3+ phosphor was synthesized by the high temperature solid-state reaction method in air. The emission spectrum of Ca2SiO4:Dy3+ phosphor shows several bands at 486, 575, and 665 nm under the 365-nm excitation. The effects of Li+, Na+, and K+ on the emission spectrum of Ca2SiO4:Dy3+ phosphor were studied. The results show that the emission spectrum intensity is greatly influenced by Li+, Na+, and K+. The charge compensation concentration corresponding to the maximum emission intensity is different with different charge compensations.

Er3+-doped phosphor-tellurite glass for broadband short-length Er3+-doped fiber amplifier (EDFA) is fabricated and characterized. The differential value (\DeltaT] of onset crystalline temperature (Tx) and glass transition temperature (Tg) is 206 oC. The stimulated emission cross section of Er3+ is calculated from absorption spectrum by McCumber theory and is 0.87\time 10^(-20) cm2 at 1532 nm. A broad 1.5-\mum fluorescence spectrum with 54-nm full-width at half maximum (FWHM) is demonstrated. Especially, the maximum phonon energy of undoped phosphor-tellurite glass is 1100 cm-1, which restricts the upconversion luminescence. It is possible to pump efficiently at 980 nm. These results indicate Er3+-doped phosphor-tellurite glass is suitable for fabricating broadband short-length EDFA.

The relative band gap for a rhombus lattice photonic crystal is studied by plane wave expansion method and high frequency structure simulator (HFSS) simulation. General wave vectors in the first Briliouin zone are derived. The relative band gap as a function of air-filling factor and background material is investigated, respectively, and the nature of photonic band gap for different lattice angles is analyzed by the distribution of electric energy. These results would provide theoretical instruction for designing optical integrated devices using photonic crystal with a rhombus lattice.

Nitridated \beta-Ga2O3 (100) substrate was investigated as the substrate for GaN epitaxial growth. The effects of nitridation temperature and surface roughness of \beta-Ga2O3 wafers on the formation of GaN were studied. It was found that the most optimized nitridation temperature was 900 oC, and hexagonal GaN with preferred orientation was produced on the well-polished wafer. The nitridation mechanism was also discussed.

A periodically poled lithium niobate (PPLN) optical parametric generator (OPG) pumped by a laser diode (LD)-pumped Q-switched Tm,Ho:GdVO4 laser operated at 2.048 \mum with pump pulse of 25 ns and repetition rate of 10 kHz is reported. A continuous tunable middle-infrared (mid-IR) spectrum of 3.88~4.34 \mum is obtained by changing the crystal temperature from 50 to 124 oC. When the incident pump power is 3 W, the total OPG output power is 95 mW, corresponding to optical conversion efficiency of 3.2%.

Considering a single-mode laser system with cross-correlated additive colored noise and multiplicative colored noise, we study the effects of correlation among noises on the normalized intensity correlation function C(s). C(s) is derived by means of the projection operator method. The effects of the self-correlation time \tau1 of the additive colored noise, \tau2 of the multiplicative colored noise, and the effect of the cross-correlation time \tau0 between the two noises on C(s) are discussed by numerical calculation. For the case of positive correlation (\lambda>0), it is found that when a0>0 the normalized intensity correlation function C(s) increases with the increase of \tau0 or \tau2, and with value of \tau0 or \tau2 becoming larger, C(s) comes to saturation. With increasing the self-correlation time \tau1 of the additive noise, a minimum and a maximum will appear on curve of C(a) as a0>0. If a0<0, C(s) decreases with the increase of \tau0, \tau1, and \tau2.

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.

BiOx films are prepared by reactive direct current (DC) magnetron sputtering from a metallic bismuth target in Ar + O2 with different O2/Ar ratios. It is found that the optical property of BiOx films is sensitive to O2/Ar ratios and the films deposited at O2/Ar ratio of 0.5 have the best reflectivity contrast under the same conditions. The structure and optical characteristics of the films are studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and spectrophotometer. As revealed by investigations, the phase transition is mainly responsible for the change of optical properties. The static test results indicate that the BiOx films have good writing sensitivity for blue laser beams. A high reflectivity contrast of about 52% at a writing power of 11 mW and writing pulse width of 800 ns is obtained. In addition, the films demonstrate good stability after being read for 10000 times.

Porous anodic alumina (PAA) templates with branch structure are fabricated by the two-step anodic oxidation processes, and then the Y-branched Cu nanowires are synthesized in the templates using an alternating current (AC) deposition method. We observe the morphology image of the samples by scanning electron microscopy (SEM), and measure the transmission spectrum and the polarization spectrum of the samples by the spectrophotometer. The results show that PAA films with Y-branched Cu nanowires have better transmittance in the near infrared region. An extinction ratio of 15~18 dB and an insertion loss of 0.1~0.4 dB are obtained in this region. Therefore PAA with Y-branched Cu nanowires can be used as a near-infrared micropolarizer, and this kind of micropolarizer would have a promising future in the field of photoelectricity integration.

We fabricate slightly deformed fused-silica microspheres in which whispering gallery modes possess remarkably directional escape emission from the microsphere boundary. With efficient free-space excitation and collection, the lateral spatial distribution of whispering gallery modes with different azimuthal mode numbers, m, is directly observed through modal coupling and directional emission. Excellent agreement with theory is obtained.

We propose a scheme for generation of three-mode W-type entangled coherent states (ECSs) in free-travelling optical fields by using a single-photon source, coherent state sources, beam splitters, photodetectors, and three-mode cross-Kerr media. The scheme consists of a Mach-Zehnder interferometer (MZI) in which each arm contains a cross-Kerr medium. We calculate the success probability of the generated W-type ECSs, and the total success probability is unity under the ideal conditions.

A simple method based on Sagnac interferometric spectroscopy (SIS) is applied for frequency stabilization of diode lasers. Sagnac interferometric spectra of rubidium vapor are investigated both theoretically and experimentally. The interference signal at the output of the Sagnac interferometer displays a sharp dispersion feature near the atomic resonance. This dispersion curve is used as the feedback error signal to stabilize the laser frequency. Linewidth of a diode laser is stabilized down to 1 MHz by this modulation-free method.

The chirped Mo/Si multilayer mirror in the extreme ultraviolet region is designed to obtain sub-femtosecond pulses from high-order harmonics. Numerical simulations of temporal profile of the pulses are made for superposition of incident high-order harmonics and that of reflected ones by the chirped multilayer mirror. The normal incidence reflectivity and chirp in the wavelength range of 12.5-16.5 nm are 6.7%+-0.5% and -3617+-171 as2, respectively. Simulation results indicate that the designed chirped multilayer mirror can be used for producing 104-as pulses.