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Chinese Optics Letters 第6卷 第1期

Author Affiliations
Abstract
School of Physical Electronic, University of Electronic Science and Technology of China, Chengdu 610054
A multi-conjugate adaptive optics (MCAO) can offer a possibility of widening field of view (FOV) characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle’s expressions of two deformable mirrors (DMs) MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.
自适应光学 大气湍流 激光雷达 多层共轭 共轭高度 等晕角 010.1080 Active or adoptive optics 010.1330 Atmospheric turbulence 010.3640 Lidar 
Chinese Optics Letters
2008, 6(1): 0101
Author Affiliations
Abstract
The Intelligence Measure-Control Technique Research Center, Anhui Normal University, Wuhu 2410002Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu 241000
Laser induced breakdown spectroscopy (LIBS) is a potential technique for rapid analysis of samples present in solids, gases and liquids. In the last two decades it was an object of extensive studies. Controlled calibration method used to analysis the LIBS spectra is investigated. Compared with the inner calibration and calibration-free (CF) methods, this new method overcomes “matrix effect”, and demonstrates a better ability to cope with the spectra. It is used to analyze natural soil, and errors of the concentration are decreased about 5%. The result shows that the new method is feasible and accurate.
激光诱导击穿光谱 定量分析 光谱 可控定标 140.3440 Laser-induced breakdown 020.0020 Atomic and molecular physics 350.5400 Plasmas 300.0300 Spectroscopy 
Chinese Optics Letters
2008, 6(1): 0105
Author Affiliations
Abstract
School of Information Science and Technology, Southwest Jiaotong University, Chengdu 610031
Via a cascaded structure, the peak-to-trough ratio is considerably improved for sampled fiber Bragg gratings (SFBGs) based on multiple-phase-shift (MPS) technique. This cascaded filter is composed of two identical SFBGs which are inserted with the increasing or decreasing arrangement of phase shifts. With this inverse arrangement of MPS in grating design, the phase fluctuation of individual SFBG can be compensated, and as a result an excellent phase matching condition is realized. In this way, the peak-to-trough ratio in reflection spectra is improved from 6 to 12 dB when multiplication factor m=4, and from 5 dB to 10 dB when m=8.
光通信 光滤波器 光纤光栅 多相移 050.2770 Gratings 050.5080 Phase shift 060.2340 Fiber optics components 
Chinese Optics Letters
2008, 6(1): 0109
Author Affiliations
Abstract
Institute of Acoustics, Chinese Academy of Sciences, Beijing 100080
Optical fiber interferometric sensors based on [3×3] couplers have been used in many fields. A new technique is proposed to demodulate output signals of this kind of sensors. The technique recovers the signal of interest by fitting coefficients of elliptic (Lissajous) curves between each fiber pair. Different from other approaches, this technique eliminates the dependence on the idealization of [3×3] coupler, provides enhanced tolerance to the variance of photoelectric converters, and is anti-polarization in a certain extent. The main algorithm has been successfully demonstrated both by numerical simulation and experimental result.
光纤传感器 解调 3×3耦合器 干涉仪 060.2370 Fiber optics sensors 070.6020 Continuous optical signal processing 060.1810 Buffers, couplers, routers,switches, and multiplexers 120.3180 Interferometry 
Chinese Optics Letters
2008, 6(1): 0112
Author Affiliations
Abstract
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 2018002Fiberhome Telecommunication Tech Co. Ltd., Wuhan 430073
A pulsed master-oscillator fiber power amplifier system with near diffraction-limited output by use of China-made large-mode-area fiber and a (2+1)×1 multimode combiner is reported. The effect of the seed power on the amplification performance is found. For the seed power, there exists a range within which the pulsed fiber amplifier can operate safely and reliably at a certain pump power. With the seed average power of 70 mW, the amplification performances of the fiber amplifier are investigated.
脉冲光纤放大器性能 种子光功率 国产大模场面积双包层光纤 (2+1)×1多模泵浦耦合器 060.2320 Fiber optics amplifiers and oscillators 140.3280 Laser amplifiers 
Chinese Optics Letters
2008, 6(1): 0119
Author Affiliations
Abstract
Wuhan National Laboratory for Optoelectronics, Wuhan 4300742School of Optoelectronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 4300743Yangze Optic Fiber and Cable Company Ltd., Wuhan 430073
We present a novel broadband dispersion compensating photonic crystal fiber with defected core in this paper. The small central defect of air hole can flexibly control the chromatic dispersion properties of this kind of photonic crystal fiber. This kind of fiber has broadband large negative chromatic dispersion, and the chromatic dispersion coefficient varies from -440 to -480 ps/(nm·km) in the measured wavelength range of 1500-1625 nm. The calculated chromatic dispersion curve is well matched to the measured chromatic dispersion coefficient in the range of 1500-1625 nm. The proposed photonic crystal fiber can be used to design the dispersion compensating fiber in the desired wavelength range by adjusting its structural parameters.
光子晶体光纤 色散补偿光纤 宽带色散补偿 060.2280 Fiber design and fabrication 060.2340 Fiber optics components 060.4510 Optical communications 260.2030 Dispersion 
Chinese Optics Letters
2008, 6(1): 0122
Author Affiliations
Abstract
Department of Physics/Applied Physics, University of Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany2Département de chimie, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R13COPL, Département de physique, génie physique et optique, Université Laval, Québec, Canada G1K7P4
Photo-induced processes in organic materials mostly occur on molecular levels. Excited molecules may split to form radicals, starting a polymerization process with diffusing monomers. The azo-dyes perform an optically induced cis-trans isomerization. During pattern formation like a holographic grating, the local temperature increase, especially in thin films, is up to date a subject of estimation from absorption and dissipation data. However, the exact knowledge of the surface temperature would help a lot in understanding the resulting refractive index and thickness patterns during holographic exposure. In this paper, in-situ pyrometer measurements are presented. As examples, different photosensitive materials, varying from a photopolymer to polycrystalline azo dyes, are used in order to outline the magnitude of this effect and demonstrate the feasibility of this technique.
高温计 黑体辐射 衍射效率 氮基染料 光敏聚合物 050.1940 Diffraction 090.2900 Optical storage materials 160.2900 Optical storage materials 350.5340 Photothermal effects 
Chinese Optics Letters
2008, 6(1): 0125
Author Affiliations
Abstract
College of Electronic Science and Technology, Shenzhen University, Shenzhen 5180602Research Center for Space Optical Engineering, Harbin Institute of Technology, Harbin 150001
Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped far-infrared laser is used as the illumination source, and a 124×124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.
太赫兹 THz成像 热释电相机 实时 110.2970 Image detection systems 110.6820 Thermal imaging 040.1240 Arrays 140.3070 Infrared and far-infrared lasers 
Chinese Optics Letters
2008, 6(1): 0129
Author Affiliations
Abstract
College of Information, Guangdong Ocean University, Zhanjiang 5240252College of Science, University of Shanghai for Science and Technology, Shanghai 200093
Attenuated total reflection (ATR) ratio is usually utilized to study the properties of surface plasmon resonance (SPR) sensors. The relationship between normalized light intensity and ATR ratio is investigated, and a modification coefficient is put forward to describe the relationship. A mathematical expression is built up for the coefficient based on Fresnel principle. The result shows that the ATR ratio, which cannot be measured directly in experiments, can be determined with the coefficient and the normalized intensity of light. The characteristic of the coefficient is also discussed.
表面等离子共振 衰减全内反射 归一化光强 偏振光 130.6010 Sensors 120.0120 Instrumentation, measurement, and metrology 230.0230 Optical devices 
Chinese Optics Letters
2008, 6(1): 0132
Author Affiliations
Abstract
Image Processing Department, Changchun Institute of Optics, Fine Mechanics and Physics,Chinese Academy of Sciences, Changchun 1300332Graduate University of Chinese Academy of Sciences, Beijing 100039
To cope with the occlusion and intersection between targets and the environment, location prediction is employed in the visual tracking system. Target trace is fitted by sliding subsection polynomials based on least absolute deviation (LAD) estimation, and the future location of target is predicted with the fitted trace. Experiment results show that the proposed location prediction algorithm based on LAD estimation has significant robustness advantages over least square (LS) estimation, and it is more effective than LS-based methods in visual tracking.
电视跟踪 最小偏差估计 预测跟踪 330.4150 Motion detection 100.0100 Image processing 120.0120 Instrumentation, measurement, and metrology 150.0150 Machine vision 
Chinese Optics Letters
2008, 6(1): 0135
Author Affiliations
Abstract
College of Precise Instrument and Optical Electronic Engineering, Tianjin University, Tianjin 3000722Key Laboratory of Opto-Electronics Information Technical Science, Ministry of Education, Tianjin University, Tianjin 3000723Department of Applied Physics, Tianjin University, Tianjin 300072
Traditional speckle fringe patterns by electronic speckle pattern interferometry (ESPI) are inherently noisy and of limited visibility, so denoising is the key problem in ESPI. We present the variational denoising method for ESPI. This method transforms the image denosing to minimizing an appropriate penalized energy function and solving a partial differential equation. We test the proposed method on computer-simulated and experimental speckle correlation fringes, respectively. The results show that this technique is capable of significantly improving the quality of fringe patterns. It works well as a pre-processing for the fringe patterns by ESPI.
散斑图像 变分方法 去噪 110.6150 Speckle imaging 030.6140 Speckle 100.0100 Image processing 
Chinese Optics Letters
2008, 6(1): 0138
Author Affiliations
Abstract
Department of Electronic Engineering, Xiamen University, Xiamen 361005
A highly efficient cascaded P-doped Raman fiber laser (RFL) pumped by a 1064-nm continuous wave (CW) Nd:YVO3 solid-state laser is reported. 1.15-W CW output power at 1484 nm is obtained while the input pump power is 4 W, corresponding to the power conversion efficiency of 28.8%. The threshold pump power for the second-order Stokes radiation is 1.13 W. The slope efficiency is as high as 42.6%. The experimental results are in good agreement with theoretical ones. Furthermore, the power instability of the P-doped RFL at 1484 nm in an hour is observed to be less than 5%.
级联掺磷拉曼光纤激光器 掺钕钒酸钇激光器 1484 nm 1064 nm 140.0140 Lasers and laser optics 140.3550 Lasers, Raman 140.3580 Lasers, solid-state 
Chinese Optics Letters
2008, 6(1): 0141
Author Affiliations
Abstract
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800
High-power operation of diode-pumped fiber lasers at wavelength near 2 μm are demonstrated with short length of heavily Tm3+-doped silica glass fibers. With 7-cm long fiber, a laser at near 2 μm is obtained with the threshold of 135 mW, maximum output power of 1.09 W, and slope efficiency of 9.6% with respect to the launched power from a laser diode at 790 nm. The output stability of this fiber laser is within 5%. The dependence of the performance of fiber lasers on the operation temperature and cavity configuration parameters is also investigated.
光纤激光器 掺铥 短长度 高功率 140.3510 Lasers, fiber 140.3480 Lasers, diode-pumped 140.3070 Infrared and far-infrared lasers 
Chinese Optics Letters
2008, 6(1): 0144
Author Affiliations
Abstract
State Key Laboratory of Materials Modification &
The influences of laser defocusing amount Δz, laser power P, space distance DLA between laser and arc on weld penetration, arc modality and stability are investigated in low power YAG laser and metal active gas (laser-MAG) hybrid welding process. The experimental results indicate that the effects of laser-induced attraction and contraction of MAG arc are emerged in hybrid welding process, which result in the augmentation of hybrid welding energy. When DLA=-0.5-2 mm, Δz=-2-2 mm and P≥73 W, the synergic efficiency between laser and MAG arc is obvious, the cross section at the root of hybrid arc is contracted and the hybrid weld penetration is increased. The maximal ratio of hybrid/MAG weld penetration is 1.5 and the lowest YAG laser power that augments MAG arc is 73 W. The input of YAG laser makes the stabilities of arc ignition and combustion prominent in hybrid welding process.
激光-电弧复合焊接 电弧吸引及压缩效应 能量增强 焊接稳定性 350.2660 Fusion 350.3390 Laser materials processing 350.5400 Plasmas 140.3390 Laser materials processing 
Chinese Optics Letters
2008, 6(1): 0147
Author Affiliations
Abstract
1 Ultrafast Laser Laboratory, School of Precision Instruments and Optoeletronics Engineering
2 Key Laboratory of Optoelectronic Information Technical Science, Ministry of Education, Tianjin University, Tianjin 3000722Electronic Engineering Department, Tianjin University of Technology and Education, Tianjin 300222
Lines are induced on the surface of a photosensitive (FOTURAN) glass by focused femtosecond laser transverse writing with scanning velocity in a wide range of 40-1800 μm/s. The formed lines are analyzed using scanning electron microscope (SEM) and optical microscope (OM). It is observed that three distinct morphologies of lines are produced depending on the scanning velocity. Lines written in low velocity level (40-100 μm/s) and high velocity level (1000-1800 μm/s) are uniform and regular, while those written in moderate velocity level (150-600 μm/s) are rough. The influence of scanning velocity is explained based on different pulses overlapping or cumulative dose of laser exposure in irradiated area. Fabrication of shallow groove on the surface is also demonstrated.
诱导线 飞秒激光 扫描速度 FOTURAN 光敏玻璃 140.3390 Laser materials processing 140.7090 Ultrafast lasers 230.4000 Microstructure fabrication 130.3120 Integrated optics devices 
Chinese Optics Letters
2008, 6(1): 0151
Author Affiliations
Abstract
Department of Postgraduate, Changchun University of Science and Technology, Changchun 1300222School of Science, Changchun University of Science and Technology, Changchun 130022
Frequency-selective surface (FSS) is a two-dimensional periodic structure consisting of a dielectric substrate and the metal units (or apertures) arranged periodically on it. When manufacturing the substrate, its thickness and dielectric constant suffer process tolerances. This may induce the center frequency of the FSS to shift, and consequently influence its characteristics. In this paper, a bandpass FSS structure is designed. The units are the Jerusalem crosses arranged squarely. The mode-matching technique is used for simulation. The influence of the tolerances of the substrate’s thickness and dielectric constant on the center frequency is analyzed. Results show that the tolerances of thickness and dielectric constant have different influences on the center frequency of the FSS. It is necessary to ensure the process tolerance of the dielectric constant in the design and manufacturing of the substrate in order to stabilize the center frequency.
频率选择表面 传输特性 模匹配 加工公差 160.0160 Materials 260.2110 Electromagnetic optics 310.0310 Thin films 
Chinese Optics Letters
2008, 6(1): 0154
Author Affiliations
Abstract
Department of Physics, Zhenjiang Watercraft College, Zhenjiang 2120032THz-Technology Research Center of Shenzhen University, Shenzhen 5180603Shenzhen Key Laboratory of Micro-Nano-Photonic Information Technology, Shenzhen 5180604College of Electronic Science and Technology of Shenzhen University, Shenzhen 518060
A method to realize absolute negative refraction index [EQUATION] with a two-dimensional (2D) photonic crystal is presented by introducing dielectric anisotropy in the photonic crystal material. The band structures of E-polarization mode and H-polarization mode can be adjusted by changing the parameters of materials. Thus the two modes with different polarizations have the same negative refraction index [EQUATION] for the same frequency. The results are demonstrated by numerical simulation based on the finite-difference time-domain (FDTD) method.
光子晶体 绝对负折射率 各向异性 成像 250.0250 Optoelectronics 160.4670 Optical materials 260.1180 Crystal optics 110.2990 Image formation theory 
Chinese Optics Letters
2008, 6(1): 0157
Author Affiliations
Abstract
Photonic Chinese Medicine Lab, South China Normal University, Guangzhou 5106312School of Physics and Electronic Information Science, Gannan Teachers College, Ganzhou 3410003Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510631
A·C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na+, pH7.0. Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7. The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.
A·C碱基错配对 喇曼光谱 多聚腺嘌呤核苷酸 多聚胞嘧啶核苷酸 170.5660 Raman spectroscopy 300.6170 Spectra 300.6330 Spectroscopy, inelastic scattering including Raman 300.6450 Spectroscopy, Raman 300.6390 Spectroscopy, molecular 
Chinese Optics Letters
2008, 6(1): 0161
Author Affiliations
Abstract
The finding of nonlinear nanometric-sized probes is of key importance for the development of nonlinear microscopy in physical as well as biological sciences. We isolate nonlinear KTiOPO4 nanocrystals and study them by second-harmonic generation microscopy (SHGM) and atomic force microscopy (AFM) independently. With both polarization analysis and defocused imaging of the emitted second harmonic field, we extract the Euler angles of the crystalline axes of a single nanocrystal. A balanced coherent optical homodyne detection shows the coherent nature of the nanocrystal nonlinear emission and allows a phase measurement of the emitted second-harmonic field. These features make the KTiOPO4 nanocrystal a good candidate for a vectorial probe of electromagnetic near fields.
190.3970 Microparticle nonlinear optics 170.5810 Scanning microscopy 160.4330 Nonlinear optical materials 
Chinese Optics Letters
2008, 6(1): 0164
Author Affiliations
Abstract
National Key Lab of Tunable Laser Technology, Harbin Institute of Technology, Harbin 150001
A doubly resonant ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a novel Tm,Ho:GdVO4 laser was demonstrated. Cryogenic Tm(5 at.-%), Ho(0.5 at.-%):GdVO4 laser with high pulse repetition frequency (PRF) of 10 kHz at 2.05 μm was employed as pumping source of ZGP OPO. The 15-mm-long ZGP crystal, 55° cut for I-type phase-matching with low absorption coefficient less than 0.05 cm-1 at 2 μm, was placed in a plano-plano cavity with resonator length of 30 mm. The ZGP OPO generated a total combined output power of 1.2 W at 3.75 and 4.52 μm under pumping power of 5.3 W, corresponding to slope efficiency of 40% from incident 2-μm laser power to mid-infrared (Mid-IR) output. A widely tunable range from 3.0 to 6.5 μm was achieved by changing the crystal angle only 3.5°.
光学参量振荡器 ZnGeP2 Tm Ho:GdVO4 190.4970 Parametric oscillators and amplifiers 190.2620 Harmonic generation and mixing 140.3480 Lasers, diode-pumped 140.3580 Lasers, solid-state 
Chinese Optics Letters
2008, 6(1): 0168
Author Affiliations
Abstract
National Key Lab of High Power Semiconductor Lasers, Changchun University of Science and Technology, Changchun 130022
The growth parameters affecting the deposition of self-assembled InAs quantum dots (QDs) on GaAs substrate by low-pressure metal-organic chemical vapor deposition (MOCVD) are reported. The low-density InAs QDs (~5×108 cm-2) are achieved using high growth temperature and low InAs coverage. Photoluminescence (PL) measurements show the good optical quality of low-density QDs. At room temperature, the ground state peak wavelength of PL spectrum and full-width at half-maximum (FWHM) are 1361 nm and 23 meV (35 nm), respectively, which are obtained as the GaAs capping layer grown using triethylgallium (TEG) and tertiallybutylarsine (TBA). The PL spectra exhibit three emission peaks at 1361, 1280, and 1204 nm, which correspond to the ground state, the first excited state, and the second excited state of the QDs, respectively.
InAs量子点 低密度 光荧光谱 250.5230 Photoluminescence 310.1860 Deposition and fabrication 120.6660 Surface measurements, roughness 
Chinese Optics Letters
2008, 6(1): 0171
Author Affiliations
Abstract
State Key Laboratory of Precision Spectroscopy, and Department of Physics, East China Normal University, Shanghai 200062
Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.
飞秒激光器 多脉冲 光孤子 自相位调制 320.0320 Ultrafast optics 320.7120 Ultrafast phenomena 060.5530 Pulse propagation and temporal solitons 140.0140 Lasers and laser optics 
Chinese Optics Letters
2008, 6(1): 0176
Author Affiliations
Abstract
Department of Physics, University of Science and Technology of China, Hefei 230026
Multimode dispersion is the main obstacle for high bandwidth in multimode optical fiber (MMF) communication system. Mode selection is an effective method to oppress multimode dispersion. We propose and investigate a kind of polymer optical fiber polished coupler. Beam propagation method (BPM) is employed to calculate the coupling coefficient of transmission modes in MMF coupler, and an output pattern from coupling branch is obtained. Analysis and experiment show that this coupler can select certain modes by changing polished depth, contact area, and intersection angle of two branches, which means that the device can be employed both as a mode selector and a sensor. In addition, simulation shows that five times bandwidth enhancement may be realized by selecting modes with the polymer fiber polished coupler.
多模塑料光纤 耦合器 模式选择 带宽 060.2310 Fiber optics 060.1810 Buffers, couplers, routers,switches, and multiplexers 230.1360 Beam splitters 
Chinese Optics Letters
2008, 6(1): 16