Journals >Chinese Optics Letters
Contents
2007
Volume: 5 Issue 8
20 Article(s)
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Research Article
Combinational-deformable-mirror adaptive optics system for compensation of high-order modes of wavefront
Huafeng Yang, Guilin Liu, Changhui Rao, Yudong Zhang, and Wenhan Jiang
A new kind of adaptive optics (AO) system, in which several low spatial frequency deformable mirrors (DMs) with optical conjugation relationship are combined to correct high-order aberrations, is proposed. The phase compensation principle and the control method of the combinational AO system are introduced. The numericA new kind of adaptive optics (AO) system, in which several low spatial frequency deformable mirrors (DMs) with optical conjugation relationship are combined to correct high-order aberrations, is proposed. The phase compensation principle and the control method of the combinational AO system are introduced. The numerical simulations for the AO system with two 60-element DMs are presented. The results indicate that the combinational DM in the AO system can correct different aberrations effectively as one single DM with more actuators, and there is no change of control method. This technique can be applied to a large telescope AO system to improve the spatial compensation capability for wavefront by using current DM..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 435 (2007)
Calculations of Rydberg energy levels for Ni XVIII using the weakest bound electron potential model theory
Chao Zhou, Liang Liang, and Ling Zhang
Martin expression about the quantum defect of single-valence atoms is extended to many-valence atoms by identifying the weakest bound electron (WBE) under the weakest bound electron potential model (WBEPM) theory. Six Rydberg series energy levels of 2p6np2Po_(1/2) (n>3), 2p6np2Po_(3/2) (n>3), 2p6nd2D_(3/2Martin expression about the quantum defect of single-valence atoms is extended to many-valence atoms by identifying the weakest bound electron (WBE) under the weakest bound electron potential model (WBEPM) theory. Six Rydberg series energy levels of 2p6np2Po_(1/2) (n>3), 2p6np2Po_(3/2) (n>3), 2p6nd2D_(3/2) (n>3), 2p6nd2D_(5/2) (n>3), 2p6nf2Fo_(5/2) (n>4), and 2p6nf2Fo_(7/2) (n>4) for Ni XVIII are calculated by this method. The calculated results are in good agreement with the experimental results..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 438 (2007)
Influence of group-delay ripple on timing jitter induced by SPM and IXPM in systems with dispersion compensated by CFBG
Xi Qin, Jihong Cao, Yong Chen, Feng Zhang, and Shuisheng Jian
An analytical expression was proposed to analyze the influence of group-delay ripple (GDR) on timing jitter induced by self-phase modulation (SPM) and intra-channel cross-phase modulation (IXPM) in pseudo-linear transmission systems when dispersion was compensated by chirped fiber Bragg grating (CFBG). Effects of ripplAn analytical expression was proposed to analyze the influence of group-delay ripple (GDR) on timing jitter induced by self-phase modulation (SPM) and intra-channel cross-phase modulation (IXPM) in pseudo-linear transmission systems when dispersion was compensated by chirped fiber Bragg grating (CFBG). Effects of ripple amplitude, period, and phase on timing jitter were discussed by theoretical and numerical analysis in detail. The results show that the influence of GDR on timing jitter changes linearly with the amplitude of GDR and whether it decreases or increases the timing jitter relies on the ripple period and ripple phase. Timing jitter induced by SPM and IXPM could be suppressed totally by adjusting the relative phase between the center frequency of the pulse and the ripples..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 441 (2007)
Performance comparison between sampling methods using DOP as feedback signal for higher-order PMD compensator
Min Yao, Huanyou Wang, and Lin Chen
We numerically analyzed the performance of the two polarization-mode dispersion (PMD) compensation methods of the single degree of polarization (DOP) sampling and DOP ellipsoid sampling methods. The numerical results show that the single DOP sampling method can generate the maximum DOP, and may result in a small overalWe numerically analyzed the performance of the two polarization-mode dispersion (PMD) compensation methods of the single degree of polarization (DOP) sampling and DOP ellipsoid sampling methods. The numerical results show that the single DOP sampling method can generate the maximum DOP, and may result in a small overall differential group delay (DGD) or the principal state of polarization (PSP) launching. By the PSP launching, just the first-order PMD is compensated while second-order PMD not. When the DOP ellipsoid sampling method is used the performance is evidently better, because the effect of high-order PMD on PMD compensation is reduced..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 445 (2007)
Dominant color extraction based color correction for multi-view images
Feng Shao, Mei Yu, and Gangyi Jiang
Color information is very important in setting the style of images. In this paper, a color correction method based on dominant color extraction is proposed to eliminate the color inconsistence between multi-view images. With the theory of basic color categories, dominant colors from the categories are extracted for refColor information is very important in setting the style of images. In this paper, a color correction method based on dominant color extraction is proposed to eliminate the color inconsistence between multi-view images. With the theory of basic color categories, dominant colors from the categories are extracted for reference image and input image, and then the corresponding color mapping relationships are built. Experimental results show that the proposed method is quite effective..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 449 (2007)
Multi-focus image fusion based on spatial frequency and morphological operators
Bin Yang, and Shutao Li
A new multi-focus image fusion method using spatial frequency (SF) and morphological operators is proposed. Firstly, the focus regions are detected using SF criteria. Then the morphological operators are used to smooth the regions. Finally the fused image is constructed by cutting and pasting the focused regions of theA new multi-focus image fusion method using spatial frequency (SF) and morphological operators is proposed. Firstly, the focus regions are detected using SF criteria. Then the morphological operators are used to smooth the regions. Finally the fused image is constructed by cutting and pasting the focused regions of the source images. Experimental results show that the proposed algorithm performs well for multi-focus image fusion..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 452 (2007)
Target models for range performance prediction of infrared imaging system
Yinghua Zhang, and Zhongnan Wan
This paper describes a commonly used target model and two improved models for range performance prediction of infrared imaging system in an original explicit way. We conclude the basic assumptions of each model, define the temperature difference, and give the mathematical equation to calculate the measurement of resolvThis paper describes a commonly used target model and two improved models for range performance prediction of infrared imaging system in an original explicit way. We conclude the basic assumptions of each model, define the temperature difference, and give the mathematical equation to calculate the measurement of resolvable target details. The flow path for using the measurement to evaluate the range performance is briefly introduced. The features of these models are compared..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 454 (2007)
Method for changing brightness temperature into true temperature based on twice recognition method
Yang Song, Xiaogang Sun, and Hong Tang
The channel output of a multi-wavelength pyrometer is the brightness temperature rather than the true temperature. Twice recognition method is put forward to change the brightness temperatures of a multi-wavelength pyrometer into the true temperatures of targets. Using the data offered by Dr. F. Righini, the experimentThe channel output of a multi-wavelength pyrometer is the brightness temperature rather than the true temperature. Twice recognition method is put forward to change the brightness temperatures of a multi-wavelength pyrometer into the true temperatures of targets. Using the data offered by Dr. F. Righini, the experimental results show that the difference between the calculated true temperature based on twice recognition method and the real true temperature is within +-20 K. The method presented in this paper is feasible and effective for the true temperature measurement of targets..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 457 (2007)
Generation of a hollow laser beam by a multimode fiber
Hongyu Ma, Huadong Cheng, Wenzhuo Zhang, Liang Liu, and Yuzhu Wang
A simple method to generate a hollow laser beam by multimode fiber is reported. A dark hollow laser beam is generated from a multimode fiber and the dependence of the output beam profile on the incident angle of laser beam is analyzed. The results show that this hollow laser beam can be used to trap and guide cold atomA simple method to generate a hollow laser beam by multimode fiber is reported. A dark hollow laser beam is generated from a multimode fiber and the dependence of the output beam profile on the incident angle of laser beam is analyzed. The results show that this hollow laser beam can be used to trap and guide cold atoms..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 460 (2007)
Analysis of directional emission in square resonator lasers with an output waveguide
Wei Zhao, and Yongzhen Huang
Square microcavity laser with an output waveguide is proposed and analyzed by the finite-difference time-domain (FDTD) technique. For a square resonator with refractive index of 3.2, side length of 4 microns, and output waveguide of 0.4-micron width, we have got the quality factors (Q factors) of 6.7*10^(2) and 7.3*10^Square microcavity laser with an output waveguide is proposed and analyzed by the finite-difference time-domain (FDTD) technique. For a square resonator with refractive index of 3.2, side length of 4 microns, and output waveguide of 0.4-micron width, we have got the quality factors (Q factors) of 6.7*10^(2) and 7.3*10^(3) for the fundamental and first-order transverse magnetic (TM) mode near the wavelength of 1.5 microns, respectively. The simulated intensity distribution for the first-order TM mode shows that the coupling efficiency in the waveguide reaches 53%. The numerical simulation shows that the first-order transverse modes have fairly high Q factor and high coupling efficiency to the output waveguide. Therefore the square resonator with an output waveguide is a promising candidate to realize single-mode directional emission microcavity lasers..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 463 (2007)
808-nm fiber coupled module with a CW output power up to 130 W
Xiaowei Wang, Xiaoyu Ma, Gaozhan Fang, Xiaoming Feng, and Suping Liu
A fiber coupled module is fabricated with integrating the emitting light from four laser diode bars into multimode fiber bundle. The continuous wave (CW) output power of the module is about 130 W with a coupling efficiency of around 80%. The output power is very stable after the temperature cycling and vibration test. A fiber coupled module is fabricated with integrating the emitting light from four laser diode bars into multimode fiber bundle. The continuous wave (CW) output power of the module is about 130 W with a coupling efficiency of around 80%. The output power is very stable after the temperature cycling and vibration test. No apparent power decrease has been observed as the device working continuously for 500 h..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 466 (2007)
Investigation of pulsed laser ablation process of Hg0.8Cd0.2Te
Xinling Zhou, Chuansong Chen, Baoyuan Man, and Juan Guo
The vaporization threshold was measured under the irradiation of 1064-nm, 10-ns pulsed laser. Then we calculated the vaporization temperature based on the conservation law of energy and analyzed the vaporization time based on our established model. These results coincided well with the information from the micrograph oThe vaporization threshold was measured under the irradiation of 1064-nm, 10-ns pulsed laser. Then we calculated the vaporization temperature based on the conservation law of energy and analyzed the vaporization time based on our established model. These results coincided well with the information from the micrograph of scanning electron microscope (SEM) and the spectra of the plasma. Besides, the laser ablation rate was also computed and discussed theoretically..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 468 (2007)
Two-dimensional optical tomography of hemodynamic changes in a preterm infant brain
Feng Gao, Yuan Xue, Huijuan Zhao, Takashi Kusaka, Masanori Ueno, and Yukio Yamada
Our preliminary results on two-dimensional (2D) optical tomographic imaging of hemodynamic changes in a preterm infant brain are reported. We use the established 16-channel time-correlated single photon counting system for the detection and generalized pulse spectrum technique based algorithm for the image reconstructiOur preliminary results on two-dimensional (2D) optical tomographic imaging of hemodynamic changes in a preterm infant brain are reported. We use the established 16-channel time-correlated single photon counting system for the detection and generalized pulse spectrum technique based algorithm for the image reconstruction. The experiments demonstrate that diffuse optical tomography may be a potent means for investigating brain functions and neural development of infant brains in the perinatal period..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 472 (2007)
Feasibility of photoacoustic tomography for ophthalmology
Tao Lu, Zhiyuan Song, Yixiong Su, Fan Zhang, and Jianquan Yao
For the eyeball composed of membrane and liquid, the contrast of ultrasound imaging is not high due to its small variance in acoustic impedance. As a new imaging modality, photoacoustic tomography combines the advantages of pure optical and ultrasonic imaging together and can provide high resolution, high contrast imagFor the eyeball composed of membrane and liquid, the contrast of ultrasound imaging is not high due to its small variance in acoustic impedance. As a new imaging modality, photoacoustic tomography combines the advantages of pure optical and ultrasonic imaging together and can provide high resolution, high contrast images. In this paper, the feasibility of photoacoustic tomography for ophthalmology is studied experimentally. A Q-switched Nd:YAG pulsed laser with 7-ns pulse width is used to generate photoacoustic signal of a porcine eyeball in vitro. The two-dimensional (2D) optical absorption image of the entire eyeball is reconstructed by time-domain spherical back projection algorithm. The imaging results agree well with the histological structure of the eyeball and show a high imaging contrast..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 475 (2007)
Improving contrast and sectioning power in confocal imaging by third harmonic generation in SiOx nanocrystallites
Gilbert Boyer, and Karsten Plamann
We present a new optical microscope in which the light transmitted by a sample-scanned transmission confocal microscope is frequency-tripled by SiOx nanocrystallites in lieu of being transmitted by a confocal pinhole. This imaging technique offers an increased contrast and a high scattered light rejection. It is demonsWe present a new optical microscope in which the light transmitted by a sample-scanned transmission confocal microscope is frequency-tripled by SiOx nanocrystallites in lieu of being transmitted by a confocal pinhole. This imaging technique offers an increased contrast and a high scattered light rejection. It is demonstrated that the contrast close to the Sparrow resolution limit is enhanced and the sectioning power are increased with respect to the linear confocal detection mode. An experimental implementation is presented and compared with the conventional linear confocal mode..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 477 (2007)
All-optical conversion scheme from binary to its MTN form with the help of nonlinear material based tree-net architecture
Anup Kumar Maiti, Jitendra Nath Roy, and Sourangshu Mukhopadhyay
In the field of optical computing and parallel information processing, several number systems have been used for different arithmetic and algebraic operations. Therefore an efficient conversion scheme from one number system to another is very important. Modified trinary number (MTN) has already taken a significant roleIn the field of optical computing and parallel information processing, several number systems have been used for different arithmetic and algebraic operations. Therefore an efficient conversion scheme from one number system to another is very important. Modified trinary number (MTN) has already taken a significant role towards carry and borrow free arithmetic operations. In this communication, we propose a tree-net architecture based all optical conversion scheme from binary number to its MTN form. Optical switch using nonlinear material (NLM) plays an important role..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 480 (2007)
Entanglement dynamics of non-interacting two-qubit system under a squeezed vacuum environment
Jun Qian, Xunli Feng, and Shangqing Gong
Entanglement dynamics of two non-interacting atoms in a squeezed vacuum reservoir is studied. Several examples with different initial entangled states are investigated, and it is found that entangled atoms become disentangled faster in squeezed vacuum than in ordinary vacuum, and larger squeezing results in faster entaEntanglement dynamics of two non-interacting atoms in a squeezed vacuum reservoir is studied. Several examples with different initial entangled states are investigated, and it is found that entangled atoms become disentangled faster in squeezed vacuum than in ordinary vacuum, and larger squeezing results in faster entanglement decay. The time evolution of the concurrence and the separability "distance" 'Lambda' can be used to explain this novel entanglement sudden death phenomenon..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 484 (2007)
Effects of water vapor in high vacuum chamber on the properties of HfO2 films
Bo Ling, Hongbo He, and Jianda Shao
The influence of water vapor content in high vacuum chamber during the coating process on physical properties of HfO2 films was investigated. Coatings were deposited on BK7 substrates by electron beam evaporation and photoelectric maximum control method. An in situ residual gas analyzer (RGA) was used to monitor the reThe influence of water vapor content in high vacuum chamber during the coating process on physical properties of HfO2 films was investigated. Coatings were deposited on BK7 substrates by electron beam evaporation and photoelectric maximum control method. An in situ residual gas analyzer (RGA) was used to monitor the residual gas composition in the vacuum chamber. The optical properties, microstructure, absorption and laser-induced damage threshold (LIDT) of the samples were characterized by Lambda 900 spectrophotometer, X-ray diffraction (XRD), surface thermal lensing (STL) technique and 1064-nm Q-switched pulsed laser at a pulse duration of 12 ns respectively. It was found that a cold trap is an effective equipment to suppress water vapor in the vacuum chamber during the pumping process, and the coatings deposited in the vacuum atmosphere with relatively low water vapor composition show higher refractive index and smaller grain size. Meanwhile, the higher LIDT value is corresponding to lower absorbance..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 487 (2007)
Pulse compression and supercontinuum at different powers of femtosecond pulses in water
Feng Xu, Jiansheng Liu, Ruxin Li, and Zhizhan Xu
Propagation of femtosecond light pulses in water is investigated. By changing input power from slightly above to highly above threshold for self-focusing, it is shown that either group velocity dispersion (GVD) or multi-photon ionization (MPI) and multi-photon absorption (MPA) may arrest the collapse. When MPI and MPA Propagation of femtosecond light pulses in water is investigated. By changing input power from slightly above to highly above threshold for self-focusing, it is shown that either group velocity dispersion (GVD) or multi-photon ionization (MPI) and multi-photon absorption (MPA) may arrest the collapse. When MPI and MPA dominate the propagation, the pulse can be self-compressed to a few optical cycles. In spectral domain, MPI alone induces a strong blue shift. MPA can restrain this strong blue shift..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 490 (2007)
Birefringent plate design for broadband spectral shaping in a Ti:sapphire regenerative amplifier
Xiaoming Lu, Chuang Li, Yuxin Leng, Cheng Wang, Chunmei Zhang, Xiaoyan Liang, Ruxin Li, and Zhizhan Xu
A method to design a birefringent plate (BP) for broadening spectrum in a regenerative amplifier is presented. Using this method, we design a quartz BP with thickness of 761 microns inserted into a Ti:sapphire regenerative amplifier. The gain narrowing effect is reduced efficiently, and the experimental results agree wA method to design a birefringent plate (BP) for broadening spectrum in a regenerative amplifier is presented. Using this method, we design a quartz BP with thickness of 761 microns inserted into a Ti:sapphire regenerative amplifier. The gain narrowing effect is reduced efficiently, and the experimental results agree with the calculation well. The bandwidth is broadened from 28 to 62 nm using the designed quartz BP and the pulses are compressed to ~23 fs..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 8, 493 (2007)
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