Journals >Chinese Optics Letters
Contents
2004
Volume: 2 Issue 12
15 Article(s)
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Detectors
Bragg grating chemical sensor with hydrogel as sensitive element
Xiaomei Liu, Shilie Zheng, Xianmin Zhang, Jun Cong, Kangsheng Chen, and Jian Xu
A novel fiber Bragg grating (FBG) based chemical sensor using hydrogel, a swellable polymer, as sensitive element is demonstrated. The sensing mechanism relies on the shift of Bragg wavelength due to the stress resulted from volume change of sensitive swellable hydrogel responding to the change of external environment.A novel fiber Bragg grating (FBG) based chemical sensor using hydrogel, a swellable polymer, as sensitive element is demonstrated. The sensing mechanism relies on the shift of Bragg wavelength due to the stress resulted from volume change of sensitive swellable hydrogel responding to the change of external environment. A polyacrylamide hydrogel fiber grating chemical sensor is made, and the experiments on its sensitivity to the salinity are performed. The sensitivity is low due to the less stress from the shrinking or swelling of hydrogels. Reducing the cross diameter of the grating through etching with hydrofluoric acid can greatly improve the sensitivity of the sensor..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12683 (2004)
Fiber Optics and Optical Communications
Dual wavelength erbium-doped fiber laser with a lateral pressure-tuned Hi-Bi fiber Bragg grating
Lingyun Xiong, Guiyun Kai, Lei Sun, Xinhuan Feng, Chunxian Xiao, Yange Liu, Shuzhong Yuan, and Xiaoyi Dong
Tunable dual wavelength erbium-doped fiber laser (EDFL) with stable oscillation at room temperature is proposed and demonstrated. This laser utilizes a Bragg grating fabricated in a high birefringence fiber as the wavelength-selective component, and then achieves the stable dual wavelength oscillation by introducing thTunable dual wavelength erbium-doped fiber laser (EDFL) with stable oscillation at room temperature is proposed and demonstrated. This laser utilizes a Bragg grating fabricated in a high birefringence fiber as the wavelength-selective component, and then achieves the stable dual wavelength oscillation by introducing the polarization hole burning effect. Furthermore, by applying lateral strain upon the fiber Bragg grating (FBG), the space of the laser dual wavelengths can be tuned continuously..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12686 (2004)
Collision-induced timing jitter in dispersion-managed WDM soliton system with filtering
Jianxin Du, and Qihong Lou
Taking into account the randomicity of collision positions and the arbitrary encoding of data in channel, the influences of different dispersion management on collision-induced timing jitter in a filtered wavelength division multiplexing (WDM) soliton system are obtained statistically and numerically by applying a set Taking into account the randomicity of collision positions and the arbitrary encoding of data in channel, the influences of different dispersion management on collision-induced timing jitter in a filtered wavelength division multiplexing (WDM) soliton system are obtained statistically and numerically by applying a set of coupled ordinary differential equations which are derived through variational procedure. The optimal dispersion managements which can greatly reduce the collision-induced timing jitter are found. The multi-channel collision-induced timing jitters in a filtered WDM soliton system are given with an optimal dispersion management and constant dispersion..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12688 (2004)
A novel 40-Gb/s all-optical inverted wavelength converter based on a modified terahertz optical asymmetric demultiplexer
Xuetian Huang, Peida Ye, Min Zhang, and Ling Wang
A novel scheme for all-optical inverted wavelength conversion with 40-Gb/s pseudorandom bit sequences (PRBSs) based on a modified terahertz optical asymmetric demultiplexer (TOAD) is proposed. The performance of the proposed wavelength converter is analyzed in term of extinction ratio (ER) through numerical simulationsA novel scheme for all-optical inverted wavelength conversion with 40-Gb/s pseudorandom bit sequences (PRBSs) based on a modified terahertz optical asymmetric demultiplexer (TOAD) is proposed. The performance of the proposed wavelength converter is analyzed in term of extinction ratio (ER) through numerical simulations. For a typical ER of 10 dB, some key characteristic parameters of the semiconductor optical amplifier (SOA) are designed. With the properly designed parameters, a high quality eye diagram is achievable, indicating that the amplitude fluctuation of the output signal is effectively reduced..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12691 (2004)
Image Processing
Fusion of visible and infrared imagery for face recognition
Xuerong Chen, Zhongliang Jing, Shaoyuan Sun, and Gang Xiao
In recent years face recognition has received substantial attention, but still remained very challenging in real applications. Despite the variety of approaches and tools studied, face recognition is not accurate or robust enough to be used in uncontrolled environments. Infrared (IR) imagery of human faces offers a proIn recent years face recognition has received substantial attention, but still remained very challenging in real applications. Despite the variety of approaches and tools studied, face recognition is not accurate or robust enough to be used in uncontrolled environments. Infrared (IR) imagery of human faces offers a promising alternative to visible imagery, however, IR has its own limitations. In this paper, a scheme to fuse information from the two modalities is proposed. The scheme is based on eigenfaces and probabilistic neural network (PNN), using fuzzy integral to fuse the objective evidence supplied by each modality. Recognition rate is used to evaluate the fusion scheme. Experimental results show that the scheme improves recognition performance substantially..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12694 (2004)
Lasers and Laser Optics
LD-pumped passively Q-switched red laser at 660 nm
Qinghua Xue, Quan Zheng, Yikun Bu, and Longsheng Qian
A laser diode (LD) pumped Nd:YAG red pulse laser at 660 nm was presented by V:YAG passively Q-switching and LBO intracavity frequency doubling. With 1.6-W incident pump power, average output power of 46-mW, pulse duration (FWHM) of 23.3 ns, pulse repetition rate of 21.6 kHz, peak power of 91.4 W, and single pulse energA laser diode (LD) pumped Nd:YAG red pulse laser at 660 nm was presented by V:YAG passively Q-switching and LBO intracavity frequency doubling. With 1.6-W incident pump power, average output power of 46-mW, pulse duration (FWHM) of 23.3 ns, pulse repetition rate of 21.6 kHz, peak power of 91.4 W, and single pulse energy of 2.13 μJ were obtained. The beam quality factor M2 was less than 1.2. The fluctuations of pulse energy and repetition rate were less than 3% in 4 hours. The pulsed laser at 660 nm is expected to be used as the pump source of Cr^(3+):doped crystal to obtain the gain-switched tunable laser..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12708 (2004)
Frequency-locked tunable LD laser with a broad bandwidth
Hong Chang, Haibin Wu, Changde Xie, and Hai Wang
Using lock-in amplifer and proportional, integral, and derivative (PID) electric circuit, the frequency of diode laser is stabilized on a highly mechanical stable Fabry-Perot (FP) cavity transmission peak. When the frequency locking system is on, the frequency tunable range of the laser is about 4 GHz around the D1 traUsing lock-in amplifer and proportional, integral, and derivative (PID) electric circuit, the frequency of diode laser is stabilized on a highly mechanical stable Fabry-Perot (FP) cavity transmission peak. When the frequency locking system is on, the frequency tunable range of the laser is about 4 GHz around the D1 transition of Rb. The laser frequency tuning is implemented by scanning the FP cavity length. The fluctuation of frequency of the output laser is less than 1 MHz, and the drift of the center frequency is less than 1.5 MHz in 1.5 min. This system has great potential of the application in the experimental investigation of the interaction between light and atoms, especially, for the case of far off the atomic resonance..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12710 (2004)
Oxide-apertured VCSEL with short period superlattice
Lin Li, Jingchang Zhong, Yongming Zhang, Wei Su, Yingjie Zhao, Changling Yan, Yongqin Hao, and Xiaoguang Jiang
Novel distributed Bragg reflectors (DBRs) with 4.5 pairs of GaAs/AlAs short period superlattice (SPS) used in oxide-apertured vertical-cavity surface-emitting lasers (VCSELs) were designed. The structure of a 22-period Al_(0.9)Ga_(0.1)As (69.5 nm)/4.5-pair [GaAs (10 nm)-AlAs (1.9 nm)] DBR was grown on an n+ GaAs substrNovel distributed Bragg reflectors (DBRs) with 4.5 pairs of GaAs/AlAs short period superlattice (SPS) used in oxide-apertured vertical-cavity surface-emitting lasers (VCSELs) were designed. The structure of a 22-period Al_(0.9)Ga_(0.1)As (69.5 nm)/4.5-pair [GaAs (10 nm)-AlAs (1.9 nm)] DBR was grown on an n+ GaAs substrate (100) 2 deg. off toward <111>A by molecular beam epitaxy. The emitting wavelength was 850 nm with low threshold current of about 2 mA, corresponding to the threshold current density of 2 kA/cm2. The maximum output power was more than 1 mW. The VCSEL device temperature was increased by heating ambient temperature from 20 to 100 (Celsius degree) and the threshold current increased slowly with the increase of temperature..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12713 (2004)
Microstructure and properties of plastic deformed martensite induced by laser shock processing
Jichang Yang, Yinqun Hua, Ruifang Chen, Lan Cai, Yongkang Zhang, and Hong Yan
Firstly, 45# steel was quenched by the NEL-2500A rapidly axial flow CO2 laser. The experimental parameters were the laser power of 750 W, the laser beam diameter of 4 mm, the scanning velocity of 7 mm/s. The thickness of coating layer was 0.1 mm and the width was 8 mm. Secondly, the martensite induced by laser quench wFirstly, 45# steel was quenched by the NEL-2500A rapidly axial flow CO2 laser. The experimental parameters were the laser power of 750 W, the laser beam diameter of 4 mm, the scanning velocity of 7 mm/s. The thickness of coating layer was 0.1 mm and the width was 8 mm. Secondly, the martensite induced by laser quench was shocked by Nd:YAG laser. The parameters of laser shock processing were the wavelength of 1.06 μm, the pulse duration of 23 ns, and theoutput energy of 16-20 J. The laser was focused on a spot of φ7 mm. K9 optical glass was used as confinement. The sample was coated with black paint 86-1 (the thickness is about 0.025 mm). By testing and analysis of samples which were treated by laser quench and laser quench+shock with transmission electron microscope (TEM), it was discovered that the surface layer of martensite was deformed plastically by laser shock processing. In the secondary hardened zones, there were a lot of slender secondary twin crystal martensites, dislocation tangles, and cellular dislocations. Compared with that of the hardened zones through laser quench only, the residual stress and mechanical properties of the secondary hardened zones were improved and increased through laser compound method..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12715 (2004)
Nonlinear Optics
Experimental investigation on the improvement of SBS characteristics by purifying the mediums
Wuliji Hasi, Zhiwei Lv, Weiming He, Shuangyi Wang, and Sining Liu
The influence of optical breakdown on stimulated Brillouin scattering (SBS) process is investigated with purified CCl4, acetone, and CS2 mediums which are obtained through 0.22-μm pore-size filter. Experiments are conducted with a Nd:YAG Q-switched laser system. The optical breakdown threshold, the reflectivity and theThe influence of optical breakdown on stimulated Brillouin scattering (SBS) process is investigated with purified CCl4, acetone, and CS2 mediums which are obtained through 0.22-μm pore-size filter. Experiments are conducted with a Nd:YAG Q-switched laser system. The optical breakdown threshold, the reflectivity and the stability of SBS in both purified and unpurified mediums are determined and compared. The improvement of optical breakdown threshold is observed more or less in all purified mediums. In the condition that optical breakdown does not occur after the medium purified, the energy reflectivity and the stability of SBS both show improvement. Therefore, the characteristics of SBS can be improved by purifying the mediums to obtain higher optical breakdown threshold which reduces the influence of optical breakdown on SBS process..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12718 (2004)
Quantum Optics
Lasing with and without inversion due to spontaneously generated coherence in an open V-type system
Jingjuan Li, Chengpu Liu, Ni Cui, Hua Li, and Xijun Fan
It is shown that in an open V-type atomic system without incoherent pumping, the spontaneously generated coherence (SGC) can not only lead to lasing with inversion but also lead to lasing without inversion (LWI) including at resonance of the driving and probe fields. This conclusion is much different from that obtainedIt is shown that in an open V-type atomic system without incoherent pumping, the spontaneously generated coherence (SGC) can not only lead to lasing with inversion but also lead to lasing without inversion (LWI) including at resonance of the driving and probe fields. This conclusion is much different from that obtained in the corresponding closed V-type system..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12725 (2004)
Instrumentation, Measurement, and Metrology
A new quality map for quality-guided phase unwrapping
Yuangang Lu, Xiangzhao Wang, Xianghong Zhong, Guotian He, Yingming Liu, and Defeng Zheng
A new quality map for quality-guided phase unwrapping is presented. The quality map is derived from the wrapped phase map directly and can reflect phase quality accurately. It is demonstrated that the proposed quality map is a good phase-quality indicator, with which the quality-guided unwrapping algorithm can retrieveA new quality map for quality-guided phase unwrapping is presented. The quality map is derived from the wrapped phase map directly and can reflect phase quality accurately. It is demonstrated that the proposed quality map is a good phase-quality indicator, with which the quality-guided unwrapping algorithm can retrieve a reliable phase profile..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12698 (2004)
Non-contact thickness measurement for ultra-thin metal foils with differential white light interferometry
Yanli Du, Huimin Yan, Yong Wu, Xiaoqiang Yao, Yongjun Nie, and Baixuan Shi
A new differential white light interference technique for the thickness measurements of metal foil is presented. In this work, the differential white light system consists of two Michelson interferometers in tandem, and the measured reflective surfaces are the corresponding surfaces of metal foil. Therefore, the measurA new differential white light interference technique for the thickness measurements of metal foil is presented. In this work, the differential white light system consists of two Michelson interferometers in tandem, and the measured reflective surfaces are the corresponding surfaces of metal foil. Therefore, the measuring result is only relative to the thickness but not the position of metal foil. The method is non-contact and non-destructive, it has the advantages of high accuracy, fast detection, and compact structure. Theoretical analysis and preliminary experimental verifications have shown that the technique can be used to measure the thickness of foil in the range of 1 to 80 μm with accuracy better than 0.08 μm..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12701 (2004)
Estimation of measuring uncertainty for optical micro-coordinate measuring machine
Kang Song, and Zhuangde Jiang
Based on the evaluation principle of the measuring uncertainty of the traditional coordinate measuring machine (CMM), the analysis and evaluation of the measuring uncertainty for optical micro-CMM have been made. Optical micro-CMM is an integrated measuring system with optical, mechanical, and electronic components, whBased on the evaluation principle of the measuring uncertainty of the traditional coordinate measuring machine (CMM), the analysis and evaluation of the measuring uncertainty for optical micro-CMM have been made. Optical micro-CMM is an integrated measuring system with optical, mechanical, and electronic components, which may influence the measuring uncertainty of the optical micro-CMM. If the influence of laser speckle is taken into account, its longitudinal measuring uncertainty is 2.0 μm, otherwise it is 0.88 μm. It is proved that the estimation of the synthetic uncertainty for optical micro-CMM is correct and reliable by measuring the standard reference materials and simulating the influence of the diameter of laser beam. With Heisenberg's uncertainty principle and quantum mechanics theory, a method for improving the measuring accuracy of optical micro-CMM through adding a diaphragm in the receiving terminal of the light path was proposed, and the measuring results are verified by experiments..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12704 (2004)
OPTICAL DATA STORAGE
Experimental research on high density data storage using solid immersion lens
Jia Wang, and Tao Hong
We have set up a solid immersion lens (SIL) near-field static recording system for demonstrating preliminarily the feasibility of SIL technology in the higher density storage. The experimental result with recording mark size of 240 nm is obtained corresponding to a potential of density of tens of gigabits per square inWe have set up a solid immersion lens (SIL) near-field static recording system for demonstrating preliminarily the feasibility of SIL technology in the higher density storage. The experimental result with recording mark size of 240 nm is obtained corresponding to a potential of density of tens of gigabits per square inch. Some factors in the SIL near-field recording are discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 2, Issue 12, 12722 (2004)
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