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Contents
2007
Volume: 5 Issue 6
19 Article(s)
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Research Article
Aharonov-Bohm effect in spherical billiard
Dehua Wang
Using Gutzwiller's periodic orbit theory, we study the quantum level density of a spherical billiard in the presence of a magnetic flux line added at its center, especially discuss the influence of the magnetic flux strength on the quantum level density. The Fourier transformed quantum level density of this system Using Gutzwiller's periodic orbit theory, we study the quantum level density of a spherical billiard in the presence of a magnetic flux line added at its center, especially discuss the influence of the magnetic flux strength on the quantum level density. The Fourier transformed quantum level density of this system has allowed direct comparison between peaks in the level density and the length of the periodic orbits. For particular magnetic flux strength, the amplitude of the peaks in the level density decreased and some of the peaks disappeared. This result suggests that Aharonov-Bohm effect manifests itself through the cancellation of periodic orbits. This phenomenon will provide a new experimental testing ground for exploring Aharonov-Bohm effect..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 311 (2007)
Multiphoton ionization and dissociation of CH3I at 266 and 355 nm
Li Li, Xianghe Kong, and Shudong Zhang
The mechanisms of multiphoton ionization (MPI) and dissociation of CH3I have been studied using time-of-flight (TOF) mass spectrometer at 266 and 355 nm. MPI mass spectrum at 266 nm consists mostly of fragment ions. This is consistent with a neutral-fragment photoionization mechanism in which rapid one-photon dissociatThe mechanisms of multiphoton ionization (MPI) and dissociation of CH3I have been studied using time-of-flight (TOF) mass spectrometer at 266 and 355 nm. MPI mass spectrum at 266 nm consists mostly of fragment ions. This is consistent with a neutral-fragment photoionization mechanism in which rapid one-photon dissociation occurs from the repulsive potential energy surface followed by MPI of neutral photofragments. The observation of parent ions at 355-nm excitation is indicative of parent-ionic ladder mechanism in which the parent ions are produced directly by two-photon excitation resonantly excited to Rydberg C state and then ionized through additional one-photon absorption to produce CH3I+. Fragment ions are produced by dissociation of CH3I+..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 315 (2007)
Optimizing the optical field distribution of solid immersion lens system by a continuous phase filter
Xuehua Ye, Yaoju Zhang, and Junfeng Chen
In solid immersion lens (SIL) microscopy systems with high numerical aperture (NA), there always exists the aberration produced by Fresnel effects at the interface between SIL and the sample. This aberration may cause the degradation of the image of sample. We design a continuous phase filter and optimize the optical fIn solid immersion lens (SIL) microscopy systems with high numerical aperture (NA), there always exists the aberration produced by Fresnel effects at the interface between SIL and the sample. This aberration may cause the degradation of the image of sample. We design a continuous phase filter and optimize the optical field distribution of SIL system. The numerical results show that when the continuous phase filter is used, the field distribution of SIL system can be optimized, and the focal depth and intensity of transmitted light can be increased. At the same time, the intensity of side-lobe and the resolution are kept almost unchanged..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 318 (2007)
7.3-W single-frequency master-oscillator fiber power amplifier with China-made double-clad fiber
Fangpei Zhang, Qihong Lou, Jun Zhou, Hongming Zhao... and Zhijiang Wang|Show fewer author(s)
A narrow-linewidth master-oscillator fiber power amplifier system was presented, in which an ultrastable, continuous-wave, single-frequency laser was adopted as the master oscillator and a China-made Yb-doped large-mode-area fiber was used as the power amplifier medium. The system generates single-frequency radiation uA narrow-linewidth master-oscillator fiber power amplifier system was presented, in which an ultrastable, continuous-wave, single-frequency laser was adopted as the master oscillator and a China-made Yb-doped large-mode-area fiber was used as the power amplifier medium. The system generates single-frequency radiation up to 7.3 W at 1064-nm wavelength with 39% slope efficiency and 26% optical-optical power conversion efficiency. The spectral characteristics as well as the suppression of amplified spontaneous emission were discussed in detail..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 322 (2007)
Improved adaptive-threshold burst assembly in optical burst switching networks
Jiuru Yang, Gang Wang, and Shilou Jia
An improved adaptive-threshold burst assembly algorithm is proposed to alleviate the limitation of conventional assembly schemes on data loss and delay. The algorithm will adjust the values of assembly factors according to variant traffic regions. And the simulation results show that, by using the adaptive-factor adaptAn improved adaptive-threshold burst assembly algorithm is proposed to alleviate the limitation of conventional assembly schemes on data loss and delay. The algorithm will adjust the values of assembly factors according to variant traffic regions. And the simulation results show that, by using the adaptive-factor adaptive assembly scheme, the performance of networks is extensively enhanced in terms of burst loss probability and average queuing delay..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 325 (2007)
Study on welded seam recognition using circular laser vision sensor
Peiquan Xu, Xinhua Tang, Ri Na, and Shun Yao
A novel visual robotic arc welding system based on circular laser vision sensor is developed. After image de-noising, image segmentation, and image thinning, the relation of depth value of workpiece and off-axis angle 'gamma', three-dimensional (3D) calculation, and seam tracking experiments are carried out. FiA novel visual robotic arc welding system based on circular laser vision sensor is developed. After image de-noising, image segmentation, and image thinning, the relation of depth value of workpiece and off-axis angle 'gamma', three-dimensional (3D) calculation, and seam tracking experiments are carried out. Finally, the error for seam tracking system is analyzed. The results show that 1) 3D information can be obtained using the proposed visual robotic arc welding system and the real-time seam tracking is realized; 2) the seam tracking error is small enough for gas tungsten arc welding (GTAW) process, and this system can be used for seam location and seam tracking or seam finder..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 328 (2007)
Geometrically robust image watermarking using scale-invariant feature transform and Zernike moments
Leida Li, Baolong Guo, and Kai Shao
In order to resist geometric attacks, a robust image watermarking algorithm is proposed using scale-invariant feature transform (SIFT) and Zernike moments. As SIFT features are invariant to rotation and scaling, we employ SIFT to extract feature points. Then circular patches are generated using the most robust points. In order to resist geometric attacks, a robust image watermarking algorithm is proposed using scale-invariant feature transform (SIFT) and Zernike moments. As SIFT features are invariant to rotation and scaling, we employ SIFT to extract feature points. Then circular patches are generated using the most robust points. An invariant watermark is generated from each circular patch based on Zernike moments. The watermark is embedded into multiple patches for resisting locally cropping attacks. Experimental results show that the proposed scheme is robust to both geometric attacks and signal processing attacks..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 332 (2007)
Scalable distributed video coding based on block SW-SPIHT
Anhong Wang, Yao Zhao, Zhenfeng Zhu, and Hao Wang
Nowadays, distributed source coding (DSC) and distributed video coding (DVC) have been receiving more and more attention due to the distinct contributions to the easy encoding. At the same time, with more new requirements coming forth in the current network communication, the scalability of bit stream has been a new foNowadays, distributed source coding (DSC) and distributed video coding (DVC) have been receiving more and more attention due to the distinct contributions to the easy encoding. At the same time, with more new requirements coming forth in the current network communication, the scalability of bit stream has been a new focus in the real applications. A scalable DVC scheme is presented without requiring layered coding in which the main attributions of DVC, namely the capabilities of easy encoding and robustness, are inherited remarkably and the property of scalability is also integrated simultaneously. Based on the block Slepian-Wolf set partitioning in hierarchical trees (SW-SPIHT), the Wyner-Ziv frames are encoded to get the scalable bit stream. In addition, the binary motion searching is explored at the decoder with the help of a rate-variable 'hash' from the encoder to improve the performance of the whole system. The final experimental results show that our system has higher peak signal-to-noise ratio (PSNR) than the pixel-domain DVC at the high bit rate. What is more, the scalability in signal-to-noise ratio (SNR) is also achieved satisfactorily..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 336 (2007)
A computed tomography reconstruction algorithm based on multipurpose optimal criterion and simulated annealing theory
Hui Li, Xiong Wan, Taoli Liu, Zhongshou Liu, and Yanhua Zhu
Although emission spectral tomography (EST) combines emission spectral measurement with optical computed tomography (OCT), it is difficult to gain transient emission data from a large number of views, therefore, high precision OCT algorithms with few views ought to be studied for EST application. To improve the reconstAlthough emission spectral tomography (EST) combines emission spectral measurement with optical computed tomography (OCT), it is difficult to gain transient emission data from a large number of views, therefore, high precision OCT algorithms with few views ought to be studied for EST application. To improve the reconstruction precision in the case of few views, a new computed tomography reconstruction algorithm based on multipurpose optimal criterion and simulated annealing theory (multi-criterion simulated annealing reconstruction technique, MCSART) is proposed. This algorithm can suffice criterion of least squares, criterion of most uniformity, and criterion of most smoothness synchronously. We can get global optimal solution by MCSART algorithm with simulated annealing theory. The simulating experiment result shows that this algorithm is superior to the traditional algorithms under various noises..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 340 (2007)
Micro-Gal laser absolute gravimeter based on high precision heterodyne interferometer
Zhiping Zhang, Zhaogu Cheng, Zhaoyu Qin, and Jianqiang Zhu
A micro-Gal absolute gravimeter based on high-precision and high-stability heterodyne interferometer is presented. The distance measuring technology of the gravimeter is studied in detail. The experimental results of distance measuring for a free-falling motion show that the high-precision heterodyne interferometer desA micro-Gal absolute gravimeter based on high-precision and high-stability heterodyne interferometer is presented. The distance measuring technology of the gravimeter is studied in detail. The experimental results of distance measuring for a free-falling motion show that the high-precision heterodyne interferometer described in this paper can meet the demand of a micro-Gal absolute gravimeter with relative uncertainty of 6.4*10^(-9). Moreover, the heterodyne interferometer is more stable than the Mach-Zehnder interferometer (MZI) which is widely used in present absolute gravimeters..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 344 (2007)
Lasing characteristics of strongly pumped Yb-doped photonic crystal fiber laser
Kang Li, Yishan Wang, Wei Zhao, Guofu Chen... and Zuyan Xu|Show fewer author(s)
A strongly pumped Yb-doped large-mode-area photonic crystal fiber (LMA-PCF) laser is analyzed. The lasing characteristics of an improved Fabry-Perot (F-P) cavity fiber laser using LMA-PCF are studied theoretically based on a rate equation model and the exact numerical solution of the rate equations is in excellent agreA strongly pumped Yb-doped large-mode-area photonic crystal fiber (LMA-PCF) laser is analyzed. The lasing characteristics of an improved Fabry-Perot (F-P) cavity fiber laser using LMA-PCF are studied theoretically based on a rate equation model and the exact numerical solution of the rate equations is in excellent agreement with the experimental result..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 347 (2007)
Experimental spectra study of Tm:GdVO4 microchip laser at room temperature
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A high efficient diode-pumped Tm:GdVO4 microchip laser is demonstrated. Output power of 310 mW at 1917 nm with slope efficiency of 22% is produced when pumped by 2 W of power at 802 nm. Unpolarized fluorescence spectra near 1800 nm pumped by laser diode are measured. In addition, the most important upconversion fluoresA high efficient diode-pumped Tm:GdVO4 microchip laser is demonstrated. Output power of 310 mW at 1917 nm with slope efficiency of 22% is produced when pumped by 2 W of power at 802 nm. Unpolarized fluorescence spectra near 1800 nm pumped by laser diode are measured. In addition, the most important upconversion fluorescence from 1D2 to 3F4 and 3H6 levels is discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 351 (2007)
All solid-state sum-frequency generation of 1.12-W continuous-wave laser at 588 nm
Yanfei Lu, Xihe Zhang, and Zhihai Yao
A new resonator design for doubly resonant continuous-wave (CW) intracavity sum-frequency mixing (SFM) is reported. 1.12 W of coherent radiation at 588 nm is generated by mixing 1062-nm Nd:GdVO4 laser and 1319-nm Nd:YAG laser. The optical-to-optical conversion efficiency is up to 3.7%.A new resonator design for doubly resonant continuous-wave (CW) intracavity sum-frequency mixing (SFM) is reported. 1.12 W of coherent radiation at 588 nm is generated by mixing 1062-nm Nd:GdVO4 laser and 1319-nm Nd:YAG laser. The optical-to-optical conversion efficiency is up to 3.7%..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 353 (2007)
Effect of MAE on the properties of phosphate edge-cladding glasses
Fenggang Zhao, Guonian Wang, and Lili Hu
Edge-cladding is a key factor in improving saturated small signal gain coefficient 'beta's of large laser disc glass. In this paper, the glasses were melted with traditional method. The influences of mixed alkali effect (MAE) on refractive index, thermal expansion coefficient 'alpha', glass transition tEdge-cladding is a key factor in improving saturated small signal gain coefficient 'beta's of large laser disc glass. In this paper, the glasses were melted with traditional method. The influences of mixed alkali effect (MAE) on refractive index, thermal expansion coefficient 'alpha', glass transition temperature Tg, dilatometer softening temperature Td, and relative chemical durability of phosphate edge-cladding glasses were studied. The results reveal that when Li/(Na+Li)=0.5, Tg, Td, and dissolution rate (DR) reach a minimal value. These results are preferred in phosphate edge-cladding glasses..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 355 (2007)
Metamorphic In0.53Ga0.47As p-i-n photodetector grown on GaAs substrates by low-pressure MOCVD
Qi Wang
Top-illuminated metamorphic In0.53Ga0.47As p-i-n photodetectors are grown on the ultrathin low-temperature InP buffered GaAs substrates. Photodetectors with the 300-nm-thick In0.53Ga0.47As absorption layer show a typical responsivity of 0.12 A/W to 1.55-micron optical radiation, corresponding to an external quantum effTop-illuminated metamorphic In0.53Ga0.47As p-i-n photodetectors are grown on the ultrathin low-temperature InP buffered GaAs substrates. Photodetectors with the 300-nm-thick In0.53Ga0.47As absorption layer show a typical responsivity of 0.12 A/W to 1.55-micron optical radiation, corresponding to an external quantum efficiency of 9.6%. Photodetectors with the active area of 50*50 (microns) exhibit the -3 dB bandwidth up to 6 GHz. These results are very encouraging for the application of this metamorphic technology to opto-electronic integrated circuit (OEIC) devices..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 358 (2007)
All angle negative refraction with the effective phase index of -1
Tao Geng, Tingyu Liu, and Songlin Zhuang
We theoretically studied a left-hand structure based on a two-dimensional (2D) photonic crystal (PC) with a negative refractive index. The propagation of electromagnetic waves in the proposed PC structure is investigated through dispersion characteristic analysis and numerical simulation of field pattern. The designed We theoretically studied a left-hand structure based on a two-dimensional (2D) photonic crystal (PC) with a negative refractive index. The propagation of electromagnetic waves in the proposed PC structure is investigated through dispersion characteristic analysis and numerical simulation of field pattern. The designed PC structure can exhibit all angle negative refraction, and the corresponding effective refractive indices along all directions are almost same and close to the ideal value of -1. A flat lens formed from such a PC has been designed and its imaging properties have been investigated systematically..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 361 (2007)
Generation of cluster states in thermal cavity
Meifeng Chen, Songshe Ma, and Xiaolan Zhang
A scheme is reported for generating a multi-atom cluster state in thermal cavities, which is based on the simultaneous interaction of two two-level atoms with a single-mode cavity field driven by a classical field. The photon-number-dependent parts in the evolution operator are cancelled with the assistant of a strong A scheme is reported for generating a multi-atom cluster state in thermal cavities, which is based on the simultaneous interaction of two two-level atoms with a single-mode cavity field driven by a classical field. The photon-number-dependent parts in the evolution operator are cancelled with the assistant of a strong classical field, so the scheme is insensitive to the thermal field. In the present scheme, the detuning between the atoms and the cavity is equal to the atom-cavity coupling strength, thus the operation speed is greatly improved, which is important in view of decoherence..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 364 (2007)
A simple data assimilation method for improving the MODIS LAI time-series data products based on the object analysis and gradient inverse weighted filter
Binbin He
A simple data assimilation method for improving estimation of moderate resolution imaging spectroradiometer (MODIS) leaf area index (LAI) time-series data products based on the gradient inverse weighted filter and object analysis is proposed. The properties and quality control (QC) of MODIS LAI data products are introdA simple data assimilation method for improving estimation of moderate resolution imaging spectroradiometer (MODIS) leaf area index (LAI) time-series data products based on the gradient inverse weighted filter and object analysis is proposed. The properties and quality control (QC) of MODIS LAI data products are introduced. Also, the gradient inverse weighted filter and object analysis are analyzed. An experiment based on the simple data assimilation method is performed using MODIS LAI data sets from 2000 to 2005 of Guizhou Province in China..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 367 (2007)
Study on vibrational modes by group theory and infrared spectra by DFT for calcite crystal
Danhua Lou, Fengjiu Sun, and Lijuan Li
The factor group symmetry analysis (FSA) method and position symmetry analysis (PSA) method are used to analyze the vibrational modes of calcite (CaCO3) crystal, respectively. With the activated results of infrared and Raman spectra presented, strong points of each method are concluded. The infrared spectra are studiedThe factor group symmetry analysis (FSA) method and position symmetry analysis (PSA) method are used to analyze the vibrational modes of calcite (CaCO3) crystal, respectively. With the activated results of infrared and Raman spectra presented, strong points of each method are concluded. The infrared spectra are studied by using dynamics calculations based on density-functional theory (DFT) with the supercell model of calcite crystal. The frequencies of 27 normal modes are achieved, which are consistent with that by the group symmetry analysis very well, and fit with the experimental results better than the lattice dynamical methods..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 6, 370 (2007)
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