Journals >Chinese Optics Letters
Contents
2007
Volume: 5 Issue 9
20 Article(s)
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Research Article
An adaptive laser beam shaping technique based on a genetic algorithm
Ping Yang, Yuan Liu, Wei Yang, Minwu Ao, Shijie Hu, Bing Xu, and Wenhan Jiang
A new adaptive beam intensity shaping technique based on the combination of a 19-element piezo-electricity deformable mirror (DM) and a global genetic algorithm is presented. This technique can adaptively adjust the voltages of the 19 actuators on the DM to reduce the difference between the target beam shape and the acA new adaptive beam intensity shaping technique based on the combination of a 19-element piezo-electricity deformable mirror (DM) and a global genetic algorithm is presented. This technique can adaptively adjust the voltages of the 19 actuators on the DM to reduce the difference between the target beam shape and the actual beam shape. Numerical simulations and experimental results show that within the stroke range of the DM, this technique can be well used to create the given beam intensity profiles on the focal plane..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 497 (2007)
Characterization of planar photonic crystals using surface coupling techniques at large wavelengths
Y. Benachour, and N. Paraire
We report a non-destructive characterization of planar two-dimensional (2D) photonic crystals (PhCs) made in silicon on insulator (SOI) wafers using ellipsometric or Fourier transformed infrared (FTIR) spectroscope. At large wavelengths, devices behave as homogeneous isotropic materials defined by an effective filling We report a non-destructive characterization of planar two-dimensional (2D) photonic crystals (PhCs) made in silicon on insulator (SOI) wafers using ellipsometric or Fourier transformed infrared (FTIR) spectroscope. At large wavelengths, devices behave as homogeneous isotropic materials defined by an effective filling factor. The experimental results related to the PhC limited dimensions confirm this characterization..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 501 (2007)
Dynamics of dark-bright vector solitons in a birefringent fiber
Hong Li, and Dongning Wang
Coupled dark-bright vector solitons are considered in a birefringent fiber, and their dynamics are studied by the variational approach. The stationary states are analyzed, and it is found that their intensity distribution depends strictly on the ratio of the group-velocity delay strength to the effective total energy. Coupled dark-bright vector solitons are considered in a birefringent fiber, and their dynamics are studied by the variational approach. The stationary states are analyzed, and it is found that their intensity distribution depends strictly on the ratio of the group-velocity delay strength to the effective total energy. Finally, the propagation of the coupled dark-bright vector solitons is investigated by the numerical method..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 504 (2007)
Fiber Bragg grating pressure sensor with enhanced sensitivity
Wentao Zhang, Lihui Liu, Fang Li, and Yuliang Liu
A novel fiber Bragg grating (FBG) pressure sensor with the enhanced sensitivity has been demonstrated. A piston-like diaphragm with a hard core in the center is used to enhance the sensitivity. Both the theoretical analysis and the experimental result show that the radius of the hard core has significant effect on the A novel fiber Bragg grating (FBG) pressure sensor with the enhanced sensitivity has been demonstrated. A piston-like diaphragm with a hard core in the center is used to enhance the sensitivity. Both the theoretical analysis and the experimental result show that the radius of the hard core has significant effect on the pressure sensitivity. When the radius of the hard core is 1.5 mm, a pressure sensitivity of 7.23 nm/MPa has been achieved..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 507 (2007)
Speckle reduction of SAR images using ICA basis enhancement and separation
Yutong Li, and Yue Zhou
An approach for synthetic aperture radar (SAR) image de-noising based on independent component analysis (ICA) basis images is proposed. Firstly, the basis images and the code matrix of the original image are obtained using ICA algorithm. Then, pointwise Holder exponent of each basis is computed as a cost criterion for An approach for synthetic aperture radar (SAR) image de-noising based on independent component analysis (ICA) basis images is proposed. Firstly, the basis images and the code matrix of the original image are obtained using ICA algorithm. Then, pointwise Holder exponent of each basis is computed as a cost criterion for basis enhancement, and then the enhanced basis images are classified into two sets according to a separation rule which separates the clean basis from the original basis. After these key procedures for speckle reduction, the clean image is finally obtained by reconstruction on the clean basis and original code matrix. The reconstructed image shows better visual perception and image quality compared with those obtained by other traditional techniques..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 509 (2007)
Rotation-invariant texture analysis using Radon and Fourier transforms
Songshan Xiao, and Yongxing Wu
Texture analysis is a basic issue in image processing and computer vision, and how to attain the rotation-invariant texture characterization is a key problem. This paper proposes a rotation-invariant texture analysis technique using Radon and Fourier transforms. This method uses Radon transform to convert rotation to tTexture analysis is a basic issue in image processing and computer vision, and how to attain the rotation-invariant texture characterization is a key problem. This paper proposes a rotation-invariant texture analysis technique using Radon and Fourier transforms. This method uses Radon transform to convert rotation to translation, then utilizes Fourier transform and takes the moduli of the Fourier transform of these functions to make the translation invariant. A k-nearest-neighbor rule is employed to classify texture images. The proposed method is robust to additive white noise as a result of summing pixel values to generate projections in the Radon transform step. Experiment results show the feasibility of the proposed method and its robustness to additive white noise..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 513 (2007)
Parallel finite difference beam propagation method based on message passing interface: application to MMI couplers with two-dimensional confinement
Chaojun Yan, Wenbiao Peng, and Haijun Li
The alternate-direction implicit finite difference beam propagation method (FD-BPM) is used to analyze the two-dimensional (2D) symmetrical multimode interference (MMI) couplers. The positions of the images at the output plane and the length of multimode waveguide are accurately determined numerically. In order to reduThe alternate-direction implicit finite difference beam propagation method (FD-BPM) is used to analyze the two-dimensional (2D) symmetrical multimode interference (MMI) couplers. The positions of the images at the output plane and the length of multimode waveguide are accurately determined numerically. In order to reduce calculation time, the parallel processing of the arithmetic is implemented by the message passing interface and the simulation is accomplished by eight personal computers..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 516 (2007)
Stable multi-wavelength erbium-doped fiber laser based on dispersion-shifted fiber and Sagnac loop filter
Ying Gao, Daru Chen, and Shiming Gao
A multi-wavelength erbium-doped fiber laser (MEDFL) with simple line structure is experimentally demonstrated by using a Sagnac interferometer as a comb filter. It is shown that the multi-wavelength lasing is quite stable at room temperature due to the four-wave mixing (FWM) effect among different laser channels in theA multi-wavelength erbium-doped fiber laser (MEDFL) with simple line structure is experimentally demonstrated by using a Sagnac interferometer as a comb filter. It is shown that the multi-wavelength lasing is quite stable at room temperature due to the four-wave mixing (FWM) effect among different laser channels in the dispersion-shifted fiber cooperated in the laser cavity..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 519 (2007)
An acousto-optic Q-switched fiber laser using China-made double-cladding fiber
Hongming Zhao, Qihong Lou, Jun Zhou, Fangpei Zhang, Jingxing Dong, Yunrong Wei, Libo Li, and Zhijiang Wang
A simple laser-diode pumped acoustic-optic Q-switched fiber laser is reported by using China-made large-mode-area ytterbium-doped fiber. Q-switched pulses with a beam quality factor of M2 about 2 and several hundred nanoseconds pulse duration are achieved at the repetition rate of 1-50 kHz. When the repetition rate is A simple laser-diode pumped acoustic-optic Q-switched fiber laser is reported by using China-made large-mode-area ytterbium-doped fiber. Q-switched pulses with a beam quality factor of M2 about 2 and several hundred nanoseconds pulse duration are achieved at the repetition rate of 1-50 kHz. When the repetition rate is 1 kHz, the pulse energy is 0.93 mJ with the pulse duration of 132 ns. Meanwhile, the profile of laser pulses shows some mode-locking phenomena, the mechanism of the phenomena is discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 522 (2007)
Transverse-mode controlling of a large-mode-area multimode fiber laser
Libo Li, Qihong Lou, Jun Zhou, Jingxing Dong, Yunrong Wei, Bing He, and Jinyan Li
Coiling technique is used to control the transverse mode of a large-mode-area (LMA) multimode fiber laser. By winding the fiber to a coil with different radius, high-order modes of a multimode fiber laser are suppressed one by one and finally 15.4-W single-transverse-mode output is achieved when the coil radius is 20 mCoiling technique is used to control the transverse mode of a large-mode-area (LMA) multimode fiber laser. By winding the fiber to a coil with different radius, high-order modes of a multimode fiber laser are suppressed one by one and finally 15.4-W single-transverse-mode output is achieved when the coil radius is 20 mm. It is found that as the coil radius decreases, the beam quality of a multimode fiber laser gets better but the slope efficiency drops for higher-order modes are discriminated. During the experiment, as the coil radius of multimode fiber changes, output characteristic of the laser has been measured. Meanwhile, the mode loss of different modes is calculated theoretically. It is proved that the experimental measured results fit well with the theoretically calculated results..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 524 (2007)
Self-collimation in photonic crystals with anisotropic constituents
J. W. Haus, M. Siraj, P. Prasad, and P. Markowicz*
In a photonic crystal composed of anisotropic constituents we quantify the range of input angles and the degree of collimation of the beam inside the crystal. The optical properties of a photobleached 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) crystal are used in our model to demonstrate the efficacy of thIn a photonic crystal composed of anisotropic constituents we quantify the range of input angles and the degree of collimation of the beam inside the crystal. The optical properties of a photobleached 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) crystal are used in our model to demonstrate the efficacy of the self-collimation features..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 527 (2007)
Tissue scattering parameter estimation through scattering phase function measurements by goniometer
Ying Zhu, Zhihua Ding, and Martial Geiser
An automated optical system is built up to perform goniometric measurement of scattering phase function. Measurements of typical samples including monodisperse polystyrene micro-spheres solution, and mutlidisperse polystyrene micro-spheres solution are carried out in a dark room. The possibility of estimating the averaAn automated optical system is built up to perform goniometric measurement of scattering phase function. Measurements of typical samples including monodisperse polystyrene micro-spheres solution, and mutlidisperse polystyrene micro-spheres solution are carried out in a dark room. The possibility of estimating the average particle size of phantom through analyzing its scattering phase function is demonstrated..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 531 (2007)
Effects of group-velocity mismatch and cubic-quintic nonlinearity on cross-phase modulation instability in optical fibers
Xianqiong Zhong, and Anping Xiang
The synthetic effects of group-velocity mismatch and cubic-quintic nonlinearity on cross-phase modulation induced modulation instability in loss single-mode optical fibers have been numerically investigated. The results show that the quintic nonlinearity plays a role similar to the case of neglecting the group-velocityThe synthetic effects of group-velocity mismatch and cubic-quintic nonlinearity on cross-phase modulation induced modulation instability in loss single-mode optical fibers have been numerically investigated. The results show that the quintic nonlinearity plays a role similar to the case of neglecting the group-velocity mismatch in modifying the modulation instability, namely, the positive and negative quintic nonlinearities can still enhance and weaken the modulation instability, respectively. The group-velocity mismatch can considerably change the gain spectrum of modulation instability in terms of its shape, peak value, and position. In the normal dispersion regime, with the increase of the group-velocity mismatch parameter, the gain spectrum widens and then narrows, shifts to higher frequencies, and the peak value gets higher before approaching a saturable value. In the abnormal dispersion regime, two separated spectra may occur when the group-velocity mismatch is taken into account. With the increase of the group-velocity mismatch parameter, the peak value of the gain spectrum gets higher and shorter before tending to a saturable value for the first and second spectral regimes, respectively..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 534 (2007)
Experiment study of wavelength conversion in a dispersion-flattened photonic crystal fiber
Qiuguo Wang, Bojun Yang, Lan Zhang, Hu Zhang, and Li He
Wavelength conversion based on four-wave mixing (FWM) has been demonstrated using a 40-m dispersion flattened highly nonlinear photonic crystal fiber (HNL-PCF). A conversion efficiency of -26 dB for a pump power of 19.5 dBm and a conversion bandwidth of 28 nm have been obtained, which are limited by the continuous waveWavelength conversion based on four-wave mixing (FWM) has been demonstrated using a 40-m dispersion flattened highly nonlinear photonic crystal fiber (HNL-PCF). A conversion efficiency of -26 dB for a pump power of 19.5 dBm and a conversion bandwidth of 28 nm have been obtained, which are limited by the continuous wave (CW) laser wavelength range and tunability of optical band pass filters (OBPFs)..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 538 (2007)
Characteristics of a PLZT electro-optical deflector
Zuoren Dong, Qing Ye, Ronghui Qu, and Zujie Fang
A beam deflector was designed and fabricated by using a lead lanthanum zirconate titanate (PLZT) ceramic with high quadratic electro-optic (EO) effect, based on refraction at an interface between areas with and without applied voltage. Its EO coefficients of R33=2.1*10^(-16) V2/m2 and R13=-0.37*10^(-16) V2/m2 were obtaA beam deflector was designed and fabricated by using a lead lanthanum zirconate titanate (PLZT) ceramic with high quadratic electro-optic (EO) effect, based on refraction at an interface between areas with and without applied voltage. Its EO coefficients of R33=2.1*10^(-16) V2/m2 and R13=-0.37*10^(-16) V2/m2 were obtained. Moreover, the hysteresis characteristics of the EO deflection were observed, and the effects of temperature on the characteristics of beam deflector were also investigated in detail..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 540 (2007)
Strong guiding of light in hollow nanowire structures
Liang Chen, James De Leon, and Xiaomin Jin
We have theoretically investigated the guiding mode patterns of hollow nanowires. Two types of nanowires, round shape and hexagonal shape, are examined with different combination of outer and inner radii. Because of electric field discontinuity at hollow interfaces and evanescent modes overlap in low refractive index rWe have theoretically investigated the guiding mode patterns of hollow nanowires. Two types of nanowires, round shape and hexagonal shape, are examined with different combination of outer and inner radii. Because of electric field discontinuity at hollow interfaces and evanescent modes overlap in low refractive index region, strong light guiding and confinement are achieved in both hollow wire structures..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 543 (2007)
Study of white light emission from ZnS/PS composite system
Caifeng Wang, Qingshan Li, Lei Lu, Lichun Zhang, and Hongxia Qi
ZnS films were deposited by pulsed laser deposition (PLD) on porous silicon (PS) substrates formed by electrochemical anodization of p-type (100) silicon wafer. The photoluminescence (PL) spectra of ZnS/PS composites were measured at room temperature. Under different excitation wavelengths, the relative integrated inteZnS films were deposited by pulsed laser deposition (PLD) on porous silicon (PS) substrates formed by electrochemical anodization of p-type (100) silicon wafer. The photoluminescence (PL) spectra of ZnS/PS composites were measured at room temperature. Under different excitation wavelengths, the relative integrated intensities of the red light emission from PS layers and the blue-green emission from ZnS films had different values. After samples were annealed in vacuum at different temperatures (200, 300, and 400 Celsius degree) for 30 min respectively, a new green emission located at around 550 nm appeared in the PL spectra of all ZnS/PS samples, and all of the ZnS/PS composites had a broad PL band (450-700 nm) in the visible region, exhibiting intensively white light emission..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 546 (2007)
Image recognition of laser radar using linear SVM correlation filter
Jianfeng Sun, Qi Li, Wei Lu, and Qi Wang
Through deducing the relationship between support vector machine (SVM) and correlation principle, the optimal hyperplane is proved as a correlation filter when the kernel function is the linear kernel. So a new correlation filter, named linear SVM correlation filter (LSCF), is proposed. The filter has not only shift-inThrough deducing the relationship between support vector machine (SVM) and correlation principle, the optimal hyperplane is proved as a correlation filter when the kernel function is the linear kernel. So a new correlation filter, named linear SVM correlation filter (LSCF), is proposed. The filter has not only shift-invariance, but also SVM properties. The real images of laser radar are used as experiment data, and LSCF is used to solve the in-plane rotation invariance. The results show that the filter can recognize the different rotated objects, and the correlation output is stable. The filter is insensitive to the noise and gray change, and has good discrimination ability. In the same design way, LSCF is also suitable to solve other problems of correlation distortion..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 549 (2007)
Behaviors of harmonic signals in wavelength-modulated spectroscopy under high absorption strength
Yuntao Wang, Haiwen Cai, Jianxin Geng, Zhengqing Pan, Dijun Chen, and Zujie Fang
Behaviors of harmonic signals in wavelength modulation spectroscopy (WMS) for gas detection with Lorentzian line under high absorption strength are investigated. Approximate analytic expressions of the second, fourth, and sixth harmonics on the strength are presented in concise forms. Simulations show that the expressiBehaviors of harmonic signals in wavelength modulation spectroscopy (WMS) for gas detection with Lorentzian line under high absorption strength are investigated. Approximate analytic expressions of the second, fourth, and sixth harmonics on the strength are presented in concise forms. Simulations show that the expressions are in agreement with the Fourier expansion by numerical integration. It is expected theoretically and experimentally in a WMS system for methane detection that there are not only a maximum, but also a null point in the harmonics versus strength relations, which should be of practical importance in methane sensing applications..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 552 (2007)
Influence of coating material on laser damage threshold of TiO2 films
Jianke Yao, Zhengxiu Fan, Hongbo He, and Jianda Shao
The optical property, structure, surface properties (roughness and defect density) and laser-induced damage threshold (LIDT) of TiO2 films deposited by electronic beam (EB) evaporation of TiO2 (rutile), TiO2 (anatase) and TiO2+Ta2O5 composite materials are comparatively studied. All films show the polycrystalline anataThe optical property, structure, surface properties (roughness and defect density) and laser-induced damage threshold (LIDT) of TiO2 films deposited by electronic beam (EB) evaporation of TiO2 (rutile), TiO2 (anatase) and TiO2+Ta2O5 composite materials are comparatively studied. All films show the polycrystalline anatase TiO2 structure. The loose sintering state and phase transformation during evaporating TiO2 anatase slice lead to the high surface defect density, roughness and extinction coefficient, and low LIDT of films. The TiO2+Ta2O5 composite films have the lowest extinction coefficient and the highest LIDT among all samples investigated. Guidance of selecting materials for high LIDT laser mirrors is given..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 9, 556 (2007)
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