Journals >Chinese Optics Letters
Contents
2006
Volume: 4 Issue 7
19 Article(s)
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Research Article
Variation analysis of turbulence resistance and angular spreading for partially coherent beam in turbulence
Wei Lu, Liren Liu, and Jianfeng Sun
A new factor M is proposed to characterize the similarity of the behavior of a partially coherent beam (PCB) to its coherent counterpart when propagating through atmospheric turbulence. It is shown that there exists a boundary in the range of the source coherent length. The decreasing rates of free space angular spreadA new factor M is proposed to characterize the similarity of the behavior of a partially coherent beam (PCB) to its coherent counterpart when propagating through atmospheric turbulence. It is shown that there exists a boundary in the range of the source coherent length. The decreasing rates of free space angular spreading and of turbulence distance with the source coherent length are different before and after the coherent length arriving at the boundary value, by which the change trend of M can be concluded..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 373 (2006)
Collisional broadening of some 2^1Delta_g<--B^1Pi_u lines in Na2 molecules by optical-optical double resonance spectroscopy
Jing Liu, Kang Dai, and Yifan Shen
Using the optical-optical double resonance (OODR) technique, we have studied the collisional broadening of some 2^1Delta_g<--B^1Pi_u lines in Na2 molecules. A single line Ar+ laser is used to pump the sodium dimers from thermally populated ground state X^1Sigma+_g level to the intermediate B^1Pi_u state. Then, a sinUsing the optical-optical double resonance (OODR) technique, we have studied the collisional broadening of some 2^1Delta_g<--B^1Pi_u lines in Na2 molecules. A single line Ar+ laser is used to pump the sodium dimers from thermally populated ground state X^1Sigma+_g level to the intermediate B^1Pi_u state. Then, a single-mode diode laser is used to probe the doubly excited 2^1Delta_g state. The broadening rate coefficient is determined from the slope of the total linewidth versus Ne density curve. We obtain the average value k_(br)=(1.1+-0.5)*10^(-8) cm3/s. The collisional excitation transfer between rotational levels of the B^1Pi_u state (i.e., B^1Pi_u(2,83/84)<--B^1Pi_u(2,82)) is also investigated. The rates can be determined from the relative intensities of the main peak and satellite lines, combined with a rate equation model. The rates of 1.25*10^(6) and 1.07*10^(6) /s are obtained, respectively..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 376 (2006)
Bias phase and light power dependence of the random walk coefficient of fiber optic gyroscope
Jian Mi, Chunxi Zhang, Zheng Li, and Zhanjun Wu
Taking account of shot noise, thermal noise, dark current noise, and intensity noise that come from broad band light source, the dependence of the random walk coefficient of fiber optic gyroscope (FOG) on bias phase and light power is studied theoretically and experimentally. It is shown that with different optical andTaking account of shot noise, thermal noise, dark current noise, and intensity noise that come from broad band light source, the dependence of the random walk coefficient of fiber optic gyroscope (FOG) on bias phase and light power is studied theoretically and experimentally. It is shown that with different optical and electronic parameters, the optimal bias phase is different and should be adjusted accordingly to improve the FOG precision. By choosing appropriate bias phase, the random walk coefficient of the aim FOG is reduced from 0.0026 to 0.0019 deg./h^(1/2)..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 379 (2006)
Tracking speckle displacement by double Kalman filtering
Donghui Li, and Li Guo
A tracking technique using two sequentially-connected Kalman filter for tracking laser speckle displacement is presented. One Kalman filter tracks temporal speckle displacement, while another Kalman filter tracks spatial speckle displacement. The temporal Kalman filter provides a prior for the spatial Kalman filter, anA tracking technique using two sequentially-connected Kalman filter for tracking laser speckle displacement is presented. One Kalman filter tracks temporal speckle displacement, while another Kalman filter tracks spatial speckle displacement. The temporal Kalman filter provides a prior for the spatial Kalman filter, and the spatial Kalman filter provides measurements for the temporal Kalman filter. The contribution of a prior to estimations of the spatial Kalman filter is analyzed. An optical analysis system was set up to verify the double-Kalman-filter tracker's ability of tracking laser speckle's constant displacement..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 382 (2006)
Automatic multi-resolution image registration based on genetic algorithm and Hausdorff distance
Famao Ye, Lin Su, and Shukai Li
Image registration is a crucial step in all image analysis tasks in which the final information is gained from the combination of various data sources, and it is difficult to automatically register due to the complexity of image. An approach based on genetic algorithm and Hausdorff distance to automatic image registratImage registration is a crucial step in all image analysis tasks in which the final information is gained from the combination of various data sources, and it is difficult to automatically register due to the complexity of image. An approach based on genetic algorithm and Hausdorff distance to automatic image registration is presented. We use a multi-resolution edge tracker to find out the fine-quality edges and utilize the Hausdorff distance between the input image and the reference image as similarity measure. We use wavelet decomposition and genetic algorithm, which combine local search methods with global ones balancing exploration and exploitation, to speed up the search of the best transformation parameters. Experimental results show that the proposed approach is a promising method for registration of image..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 386 (2006)
Study on validation method of visible imagery spatial resolution of imager on geostationary platform
Qiang Guo
Based on the analysis for the main elements of the total modulation transfer function (MTF) of imager on geostationary platform, the precise evaluation for its low spatial frequency spectrum has been achieved. Meanwhile, it is pointed out that the main cause of imagery spatial resolution lower than the designed value iBased on the analysis for the main elements of the total modulation transfer function (MTF) of imager on geostationary platform, the precise evaluation for its low spatial frequency spectrum has been achieved. Meanwhile, it is pointed out that the main cause of imagery spatial resolution lower than the designed value is the "slight defocus" of imager focal plane array (FPA). The validation method for visible imagery spatial resolution is proposed based on the analysis of defocused optical system model and edge-spread-function (ESF), the relative error is less than 7% after alleviating stray light effects. This method has been applied in the in-orbit ground testing of FY-2C geostationary meteorological satellite successfully..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 389 (2006)
Polarization-dependent characteristics of a racetrack waveguide resonator fabricated by ion exchange in K9 glass
Xiuyou Han, Feng Liu, Fufei Pang, Fenghong Chu, Haiwen Cai, Ronghui Qu, and Zujie Fang
A racetrack waveguide resonator filter was fabricated by ion exchange technology in K9 optical glass. The filter responses of the waveguide resonator were measured with two polarized input lightwaves. The polarization-dependent characteristics of the waveguide resonator were analyzed, and the results of effective indicA racetrack waveguide resonator filter was fabricated by ion exchange technology in K9 optical glass. The filter responses of the waveguide resonator were measured with two polarized input lightwaves. The polarization-dependent characteristics of the waveguide resonator were analyzed, and the results of effective indices of n_(TE)=1.5721 and n_(TM)=1.5548, coupling ratios of r_(TE)=0.731 and r_(TM)=0.761, and losses of 'alpha'_(TE)=4.35 dB/cm and 'alpha'_(TM)=6.05 dB/cm were obtained for transverse electric (TE) and transverse magnetic (TM) modes, respectively. The causes of large loss and effective index differences between TE and TM modes were discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 393 (2006)
Effects of cross-correlated noises on the intensity fluctuation of the single-mode laser system
Bing Wang, Shuwen Dai, and Shuping Ge
A single-mode laser model with cross-correlated additive and multiplicative noise terms is considered, and the effects of correlation between noises on the relaxation time and the intensity correlation function are studied. Using the projection operator method and taking into account the effects of the memory kernels oA single-mode laser model with cross-correlated additive and multiplicative noise terms is considered, and the effects of correlation between noises on the relaxation time and the intensity correlation function are studied. Using the projection operator method and taking into account the effects of the memory kernels of the intensity correlation function, the analytic expressions for the relaxation time and the correlation function are derived. Based on numerical computations, it is found that the self-correlation time and the cross-correlation time have the same effects on the single-mode laser system..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 397 (2006)
Influence of net gain on the statistical fluctuation in a single-mode laser system
Qinghua Cheng, Dahai Xu, Li Cao, and Dajin Wu
Using linear approximation method, we calculate the intensity correlation time of a single-mode laser driven by both colored pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts, and analyze the influence of the net gain coefficient a0 on the statistical flUsing linear approximation method, we calculate the intensity correlation time of a single-mode laser driven by both colored pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts, and analyze the influence of the net gain coefficient a0 on the statistical fluctuation of the laser system. It is found that for the case that the colored pump noise is long time correlated, the main factor influencing the statistical fluctuation of the laser system is a0, and the frequency of the modulation signal has negligible effect on the statistical fluctuation of the laser system..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 401 (2006)
High-efficiency 1598.5-nm third Stokes Raman laser based on barium nitrate crystal
Huiting Chen, Qihong Lou, Jingxing Dong, and Wanchun Chen
A high-efficiency eye-safe Raman laser was demonstrated by use of the third Stokes radiation in a Ba(NO3)2 crystal pumped by a 1064-nm Nd:YAG laser. The output wavelength of the Raman laser was 1598.5 nm with a full-width at half-maximum (FWHM) of 1.5 nm. With an incident pump energy of 140 mJ, a maximum of 18-mJ RamanA high-efficiency eye-safe Raman laser was demonstrated by use of the third Stokes radiation in a Ba(NO3)2 crystal pumped by a 1064-nm Nd:YAG laser. The output wavelength of the Raman laser was 1598.5 nm with a full-width at half-maximum (FWHM) of 1.5 nm. With an incident pump energy of 140 mJ, a maximum of 18-mJ Raman output energy was generated at a repetition rate of 30 Hz, corresponding to an optical-to-optical conversion efficiency of 12.9%. The Raman pulse duration was shortened to 2.9 ns compared with that of the pump pulse of 19.3 ns. The eye-safe solid-state Raman laser is expected to have wide applications in range-finding, telemetry, laser radar, and other aspects..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 404 (2006)
Diode-pumped passively Q-switched and mode-locked Nd:YLF laser with Cr4+:YAG saturable absorber
Shudi Pan, Kezhen Han, Hongmei Wang, Xiuwei Fan, and Jingliang He
A diode-pumped passively Q-switched Nd:YLF laser was demonstrated by using saturable absorber of Cr4+:YAG. At the incident power of 7.74 W, pure passively Q-switched laser with per pulse energy of 210 'mu'J and pulse width of 19.6 ns at repetition rate of 1.78 kHz was obtained by using Cr4+:YAG with initial traA diode-pumped passively Q-switched Nd:YLF laser was demonstrated by using saturable absorber of Cr4+:YAG. At the incident power of 7.74 W, pure passively Q-switched laser with per pulse energy of 210 'mu'J and pulse width of 19.6 ns at repetition rate of 1.78 kHz was obtained by using Cr4+:YAG with initial transmission of 80%. At the incident power of 8.70 W, a Q-switched mode-locking with average output power of 650 mW was achieved, the overall slope efficiency was 16%, corresponding to the initial transmission of 85% of Cr4+:YAG..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 407 (2006)
Suppression of mode competition in fiber lasers by using a saturable absorber and a fiber ring
Jing Yang, Ronghui Qu, Guoyong Sun, Jianxin Geng, Haiwen Cai, and Zujie Fang
An erbium-doped fiber (EDF) laser was configured with a fiber grating, a fiber ring resonator, and a saturable absorber by using un-pumped EDF as mode selection element. The laser showed single mode operation with a narrow linewidth of 5 kHz. The mode selection mechanisms of the un-pumped EDF and the ring resonator areAn erbium-doped fiber (EDF) laser was configured with a fiber grating, a fiber ring resonator, and a saturable absorber by using un-pumped EDF as mode selection element. The laser showed single mode operation with a narrow linewidth of 5 kHz. The mode selection mechanisms of the un-pumped EDF and the ring resonator are theoretically and experimentally analyzed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 410 (2006)
Room temperature continuous wave operation of 1.33-micron InAs/GaAs quantum dot laser with high output power
Qin Han, Zhichuan Niu, Haiqiao Ni, Shiyong Zhang, Xiaohong Yang, Yun Du, Cunzhu Tong, Huan Zhao, Yingqiang Xu, Hongling Peng, and Ronghan Wu
Continuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots (QDs) embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-mW output power at ground state of 1.33-1.35 microns for a 20-micron ridge-waveguide laser without facet coContinuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots (QDs) embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-mW output power at ground state of 1.33-1.35 microns for a 20-micron ridge-waveguide laser without facet coating is achieved. By optimizing the molecular beam epitaxy (MBE) growth conditions, the QD density per layer is raised to 4*10^(10) cm^(-2). The laser keeps lasing at ground state until the temperature reaches 65 Celsius degree..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 413 (2006)
Integration of GaN thin films with silicon substrates by fusion bonding and laser lift-off
Ting Wang, Xia Guo, Yuan Fang, Bin Liu, and Guangdi Shen
GaN thin films grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD) are successfully bonded and transferred onto Si receptor substrates using fusion bonding and laser lift-off (LLO) technique. GaN/Al2O3 structures are joined to Si substrates by pressure bonding Ti/Au coated GaN surface onto TiGaN thin films grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD) are successfully bonded and transferred onto Si receptor substrates using fusion bonding and laser lift-off (LLO) technique. GaN/Al2O3 structures are joined to Si substrates by pressure bonding Ti/Au coated GaN surface onto Ti/Au coated Si receptor substrates at the temperature of 400 Celsius degree. KrF excimer laser with 400-mJ/cm2 energy density, 248-nm wavelength, and 30-ns pulse width is used to irradiate the wafer through the transparent sapphire substrates and separate GaN films from sapphire. Cross-section scanning electron microscopy (SEM) combined with energy dispersive X-ray spectrometer (EDS) measurements show that Au/Si solid solution is formed during bonding process. Atomic force microscopy (AFM) and photoluminescence (PL) measurements show that the qualities of GaN films on Si substrates degrade little after substrates transfer..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 416 (2006)
Precise calculation of the KTP crystal used as both an intracavity electro-optic Q-switch and a second harmonic generator
Yuye Wang, Jianquan Yao, Degang Xu, Pu Zhao, and Peng Wang
A method of precisely calculating the external applied voltage and the optimum type-II phase matching angles for KTP crystal, which is used as both an intracavity electro-optic (EO) Q-switch and a frequency doubler, is presented. The effective EO coefficient along the phase-matching direction is defined to calculate thA method of precisely calculating the external applied voltage and the optimum type-II phase matching angles for KTP crystal, which is used as both an intracavity electro-optic (EO) Q-switch and a frequency doubler, is presented. The effective EO coefficient along the phase-matching direction is defined to calculate the half-wave voltage and the quarter-wave voltage, and the precise calculation for the phase matching angles in the condition of KTP crystal optimum second harmonic phase matching is theoretically realized..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 419 (2006)
A novel hybrid surface micromachined segmented mirror for large aperture laser applications
Jie Li, Haiqing Chen, and Hongbin Yu
A novel hybrid surface micromachined segmented mirror array is described. This device is capable of scaling to large apertures for correcting time-varying aberrations in laser applications. Each mirror is composed of bottom electrode, support part, and mirror plate, in which a T-shaped beam structure is used to supportA novel hybrid surface micromachined segmented mirror array is described. This device is capable of scaling to large apertures for correcting time-varying aberrations in laser applications. Each mirror is composed of bottom electrode, support part, and mirror plate, in which a T-shaped beam structure is used to support the mirror plate. It can provide mirror with vertical movement and rotation around two horizontal axes. The test results show that the maximum deflection along the vertical direction of the mirror plate is 2 microns, while the rotation angles around x and y axes are +-2.3 deg. and +-1.45 deg., respectively..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 422 (2006)
An improved algorithm for cloud multiple scattering
Guibin Yuan, Xiaogang Sun, and Jingmin Dai
Clouds' radiation characteristics are very important in clouds scene simulation, weather forecasting, pattern recognition, and other fields. Radiation of a cloud mainly comes from its multiple scattering. A new algorithm to calculate multiple scattering, called build-up factor algorithm, is proposed in this paper. Clouds' radiation characteristics are very important in clouds scene simulation, weather forecasting, pattern recognition, and other fields. Radiation of a cloud mainly comes from its multiple scattering. A new algorithm to calculate multiple scattering, called build-up factor algorithm, is proposed in this paper. In this algorithm, a modified gamma distribution is assumed to describe droplets distribution inside a cloud, then the radiation transport equation is calculated to get the solution of single scattering, and finally, a build-up factor is defined to estimate the multiple scattering contributions. This algorithm considers both single scattered radiance and multiple scattered radiance and needs shorter computing time. It can be used in real time simulations..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 425 (2006)
A new approach to measure the ocean temperature using Brillouin lidar
Wei Gao, Zhiwei Lv, Yongkang Dong, and Weiming He
An approach of lidar measurements of ocean temperature through measuring the spectral linewidth of the backscattered Brillouin lines is presented. An empirical equation for the temperature as a function of Brillouin linewidth and salinity is derived. Theoretical results are in good agreement with the experimental data.An approach of lidar measurements of ocean temperature through measuring the spectral linewidth of the backscattered Brillouin lines is presented. An empirical equation for the temperature as a function of Brillouin linewidth and salinity is derived. Theoretical results are in good agreement with the experimental data. The equation also reveals the dependence of the temperature on the salinity and Brillouin linewidth. It is shown that the uncertainty of the salinity has very little impact on the temperature measurement. The uncertainty of this temperature measurement methodology is approximately 0.02 Celsius degree..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 428 (2006)
Colorimetric characterization of liquid crystal display using an improved two-stage model
Yong Wang, and Haisong Xu
An improved two-stage model of colorimetric characterization for liquid crystal display (LCD) was proposed. The model included an S-shape nonlinear function with four coefficients for each channel to fit the tone reproduction curve (TRC), and a linear transfer matrix with black-level correction. To compare with the simAn improved two-stage model of colorimetric characterization for liquid crystal display (LCD) was proposed. The model included an S-shape nonlinear function with four coefficients for each channel to fit the tone reproduction curve (TRC), and a linear transfer matrix with black-level correction. To compare with the simple model (SM), gain-offset-gain (GOG), S-curve and three-one-dimensional look-up tables (3-1D LUTs) models, an identical LCD was characterized and the color differences were calculated and summarized using the set of 7*7*7 digital-to-analog converter (DAC) triplets as test data. The experimental results showed that the model was outperformed in comparison with the GOG and SM ones, and near to that of the S-curve model and 3-1D LUTs method..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 7, 432 (2006)
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