Journals >Chinese Journal of Lasers
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2012
Volume: 39 Issue 5
44 Article(s)
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Biomedical Photonics and Laser Medicine
Study on Phase Characteristics of White Blood Cells and Their Optical Models
Xu Yuanyuan, Wang Yawei, Jin Weifeng, Jiang Shouwang, Yue Quwei, Bu Min, Shang Xuefu, and Lü Cuihong
Identification and analysis of five different types of white blood cells (WBCs) have a very important application in many fields, such as clinical medicine and life science. In recent years, the digital phase microscopy techniques of red blood cells are remarkably expanded in their observing application. However, due tIdentification and analysis of five different types of white blood cells (WBCs) have a very important application in many fields, such as clinical medicine and life science. In recent years, the digital phase microscopy techniques of red blood cells are remarkably expanded in their observing application. However, due to special optical phase structures of WBCs, the techniques of phase microscopy have difficulty in studying them. Based on this, the analysis of optical characteristics of five types of WBCs is done, and optical models of them are built in this paper. Distribution characteristics of WBCs under these phase models are obtained with numerical simulation techniques. It is found that phase distribution of WBCs is not only related to interference, but also to the scattering of nucleus by analyzing the relationship between phase distributions and classifications of them, but it has certainty to some extent..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 504001 (2012)
Flow Velocity Measurement Based on Speckle in Optical Coherence Tomography
Yang Liu, Hong Wei, Wang Chuan, and Ding Zhihua
Flow velocity measurement based on speckle in optical coherence tomography (OCT) images is developed. Similar to traditional laser speckle signal, time-varying fluctuations in OCT speckle intensity is related to the average velocity of scattering particles within the sampling volume. Fluctuated signal of the speckle inFlow velocity measurement based on speckle in optical coherence tomography (OCT) images is developed. Similar to traditional laser speckle signal, time-varying fluctuations in OCT speckle intensity is related to the average velocity of scattering particles within the sampling volume. Fluctuated signal of the speckle intensity is obtained from the detected OCT signal by filtering and demodulation. Then the spectrum of the speckle is deduced through Fourier transform of the fluctuated signal, and quantitative measurement of flow velocity can be conducted according to the calculated ratio of high to low (HLR) spectrum. The method of flow measurement based on speckle intensity in OCT instead of phase information is introduced. Investigation on the relationship of the calculated HLRs with the flow velocities is experimentally conducted. Flowing particles in a tube in mimic of capillary is visualized by the proposed method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 504002 (2012)
Discrimination of Nasopharyngeal Carcinoma and Normal Nasopharyngeal Cell Lines Based on Confocal Raman Microspectroscopy
Ye Yuhuang, Chen Yang, Li Yongzeng, Feng Shangyuan, Su Ying, Zou Changyan, and Ou Lin
Raman microspectroscopy can provide molecular-level finger-print information about the biochemical composition and structure of cells and tissues with excellent spatial resolution. Raman spectroscopy of nasopharyngeal carcinoma cell lines C666-1, CNE2 and normal nasopharyngeal cell line NP69 are presented to investigatRaman microspectroscopy can provide molecular-level finger-print information about the biochemical composition and structure of cells and tissues with excellent spatial resolution. Raman spectroscopy of nasopharyngeal carcinoma cell lines C666-1, CNE2 and normal nasopharyngeal cell line NP69 are presented to investigate the differences between them. The ratio of I1449/I1657(1.10) seems to very easily divide tumor and normal cell lines into two groups, and this result is coincident with the existing report about the study of normal and malignant bronchial tissue. Principal component analysis (PCA) and linear discriminant analysis (LDA) are also used to classify different cell lines and achieve an exciting result with a sensitivity and specificity of 90% and 100%, respectively. The results of the work may be helpful to the discrimination of normal and tumor cells, which show that Raman spectroscopy can be one of the diagnostic methods of nasopharyngeal carcinoma and do favor to the early diagnosis..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 504003 (2012)
Surface Enhanced Raman Scattering Spectrum Analysis of Nude Mouse Serum with Au Nanoparticles Active Substrate
Liu Shupeng, Zhu Hongfei, Chen Na, Chen Zhenyi, and Hu Ling
Raman spectrum and surface enhanced Raman scattering (SERS) spectrum of the nude mouse serum are measured using laser Raman confocal micro-spectrometry. The results show that the Au nanoparticles active substrate can enhance the Raman spectra dramatically. A lot of information which conventional Raman spectroscopy failRaman spectrum and surface enhanced Raman scattering (SERS) spectrum of the nude mouse serum are measured using laser Raman confocal micro-spectrometry. The results show that the Au nanoparticles active substrate can enhance the Raman spectra dramatically. A lot of information which conventional Raman spectroscopy fails to detect emerges. This is due to the chemical adsorption and interactions between the gold nanoparticles and the substances in serum. The information is important for the analysis of the most components and structures of the serum proteins. With SERS spectrum, even micro-sample can also reflect the molecular structure information of the serum proteins, lipids, carbohydrates, ribonucleic acid and other components. Information of the serum components can reflect physiological and pathological metabolism changes of the cells and tissues in the body. So SERS spectrum of the serum would provide an effective means for the diagnosis and therapy of diseases..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 504004 (2012)
Holography and Information Processing
Method to Effective Inhibit Digital Sum Value of the Optic Disc Data
Liu Tao, and Ruan Hao
Digital sum value (DSV) for the data of the optic discs needs to be effectively suppressed, a method based on enumerating to effective inhibit the digital sum value of the optic disc data is proposed. This method cuts the raw data into pieces to get modulation, enumerates all possible bit streams, calculates the DSV ofDigital sum value (DSV) for the data of the optic discs needs to be effectively suppressed, a method based on enumerating to effective inhibit the digital sum value of the optic disc data is proposed. This method cuts the raw data into pieces to get modulation, enumerates all possible bit streams, calculates the DSV of each bit stream. This method can completely show the DSV characteristics in all of possible bit streams, thus can select the appropriate stream as the modulation data stream. This method is tested in laboratory and production line, that can be completely verified and is a very good suppression of the DSV..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 509001 (2012)
Laser Manufacturing
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502007 (2012)
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502010 (2012)
Computer-Aided Optimization of the Process Parameters for Fabricating Overhanging Structure by Selective Laser Melting
Liu Jie, Yang Yongqiang, Wang Di, Xiao Dongming, and Su Xubin
To improve the fabricating quality of overhanging structure in selective laser melting (SLM), the computer-aided optimization of process parameters is studied, which focuses on the fabrication orientation and the power input. The optimization model of the fabrication orientation, which is aiming at reducing the difficuTo improve the fabricating quality of overhanging structure in selective laser melting (SLM), the computer-aided optimization of process parameters is studied, which focuses on the fabrication orientation and the power input. The optimization model of the fabrication orientation, which is aiming at reducing the difficultly fabricating overhanging surface area, is proposed. The genetic solution for the model is studied. The static lookup table to adjust the energy input duly is built by traversing all the triangles in the stereo lithography (STL) file. The experimental results show that the difficultly fabricating overhanging surface area reduces from 555.12 mm2 to 16.211 mm2 after the optimization of the fabrication orientation, which leads to the less support needs, and the fabrication quality is obviously improved without so much overhang and deformation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 503001 (2012)
Investigation of the Ultrafast Process of Femtosecond Laser Ablation of Highly Oriented Pyrolytic Graphite
Zhang Nan, Yang Jinghui, and Zhu Xiaonong
Pulsed laser ablation of highly oriented pyrolytic graphite (HOPG) is one of the most important methods for fabricating fullerene, carbon nanotube and other carbon nano-materials. Investigation of the ultrafast process of femtosecond laser ablation of HOPG can provide important insights for exploring the method of prodPulsed laser ablation of highly oriented pyrolytic graphite (HOPG) is one of the most important methods for fabricating fullerene, carbon nanotube and other carbon nano-materials. Investigation of the ultrafast process of femtosecond laser ablation of HOPG can provide important insights for exploring the method of producing carbon nano-materials with femtosecond laser. Using the pump-probe technique, the ultrafast processes of 50 fs laser ablation of HOPG at different laser fluences from 0.33 J/cm2 to 20 J/cm2 are investigated within the time window of 0~9 ns after the laser pulse strikes the target. The differences between the ablation processes of HOPG and aluminum under the strike of laser pulses with the same parameters are studied. It is found that as the pump laser fluence changes from 20 J/cm2 to 0.33 J/cm2, the HOPG target material removed by the photothermal mechanism gradually decreases; however the ejected material composed of larger particles induced by the photomechanical mechanism gradually increases. It is also found that the absorption coefficient of the ablated target is the main factor that causes the differences between the ablation processes of HOPG and aluminum..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 503002 (2012)
Analysis on Mechanical Property of 6061-T6 Aluminum Alloy by Laser Shot Peening Based on Strain Rate
Zhou Jianzhong, Zuo Lidang, Huang Shu, Xu Zengchuang, Yang Jing, Ji Xinglu, and Xie Xiaojiang
In order to investigate the effects of laser shot peening (LSP) on mechanical properties of 6061-T6 aluminum alloy under different strain rates, standard tensile specimens are tested under different conditions like single-side LSP and two-side LSP, followed by the tensile property tests under four different strain rateIn order to investigate the effects of laser shot peening (LSP) on mechanical properties of 6061-T6 aluminum alloy under different strain rates, standard tensile specimens are tested under different conditions like single-side LSP and two-side LSP, followed by the tensile property tests under four different strain rates from 0.0001 to0.1 s-1. The distribution of surface residual stress is measured, and surface roughness before and after LSP is observed. Furthermore, the relation between surface roughness and elongation is also investigated. The grain size and microstructure before and after LSP are analyzed. The results show that the ultimate tensile strength (UTS) and yield strength increases but the elongation decreases with the increment of strain rate. Compared with the untreated sample, the UTS and yield strength after single-side LSP increase slightly, and the elongation decreases by about 1%. After two-side LSP, the UTS increases by 10.8%, and the yield strength increases by 12.5%, the elongation decreases by about 2%. A large amount of grain is refined and the dislocation density also increases in the laser-peened area, which improves the mechanical properties of 6061-T6 aluminum alloy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 503003 (2012)
Process Parameters Analysis on Surface Texturing under Laser Shock Peening
Huang Zhihui, Liu Huixia, Shen Zongbao, Li Pin, Hu Yang, Liu Hui, Du Daozhong, and Wang Xiao
Laser surface texturing (LST) is widely used in surface micro-forming, but its main problem is that the ablation process causes melting, cracking and changing of the surface microstructure. By using laser shock processing (LSP) micro dents are fabricated on Al7075 surface, which not only overcomes the weakness of LST, Laser surface texturing (LST) is widely used in surface micro-forming, but its main problem is that the ablation process causes melting, cracking and changing of the surface microstructure. By using laser shock processing (LSP) micro dents are fabricated on Al7075 surface, which not only overcomes the weakness of LST, but also inherits the advantage of LSP. Choosing AxioCSM700 true color confocal scanning microscopy and Vecco WYKO surface morphology, the geometry morphology of micro dents are observed. With HXD-1000TMSC/LCD MH-VK double press heads, the interior and surface micro-hardness of micro dents are measured. Experimental results show that the diameter and the depth of micro dents change with laser pulse energy, the times of laser shock, focal length and thickness of confined layer K9 glass. The hardness of micro dent increases gradually along radial direction and the biggest hardness occurs in the center, which effectively improves the wear resistance of material..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 503004 (2012)
Monitoring Mechanism of Plasma Generated by Laser Welding Galvanized Steel with Powder Feeding
Zhang Yi, Duan Linyong, Zhou Dianwu, Li Shichun, and Wang Cunshan
Experiments of laser welding of 1.6 mm thick galvanized steel B340/590DPD+Z with different amounts of copper are performed by using a CO2 laser. Based on the light emission from the plasma plume acquired by spectrometer in the welding process, the effects of adding copper powder on the plasma optical signal and the relExperiments of laser welding of 1.6 mm thick galvanized steel B340/590DPD+Z with different amounts of copper are performed by using a CO2 laser. Based on the light emission from the plasma plume acquired by spectrometer in the welding process, the effects of adding copper powder on the plasma optical signal and the relationship between the pores and the plasma optical signal is analyzed. Then the average content of copper element and the distribution of the main elements around the pores are detected by using a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that compared to laser welding without adding copper powder, the oscillation of plasma temperature is significantly reduced and the average temperature drops about 5000 K. In addition the solid solution alloy of copper and zinc distributes around the pore wall and the porosity has a correlation with the intensity of spectrum at CuI324.8 nm as well. The researches provide a theoretical basis for monitoring on laser welding galvanized steel with powder feeding and a new method for the plasma control technology..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 503005 (2012)
Laser Physics
Module of Fiber Coupled Diode Laser Based on 808 nm Single Emitters Combination
Zhu Hongbo, Hao Mingming, Peng Hangyu, Zhang Zhijun, Liu Yun, Qin Li, Ning Yongqiang, and Wang Lijun
Because of the good beam quality and heat dissipation of single emitter diode laser, it is more suitable to be used in the source of electro-optic countermeasure. Aim at the response curve of charge-coupled device (CCD) spectrum, 808 nm single emitter is used as unit source and 24 single emitters are divided into four Because of the good beam quality and heat dissipation of single emitter diode laser, it is more suitable to be used in the source of electro-optic countermeasure. Aim at the response curve of charge-coupled device (CCD) spectrum, 808 nm single emitter is used as unit source and 24 single emitters are divided into four groups. In order to increase the output power intensity, space combination and polarization combination are used in the experiment. Combined beam is focused in an optical fiber through the focused lens group designed by ourself. All the single emitters are connected in series. When the drive current is 8.5 A, 162 W output power is obtained from a 300 μm fiber core with a numerical aperture of 0.22 at 808 nm and coupling efficiency of 84%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502001 (2012)
Stability Impact and Optimization Analysis of Temperature Field of Switchyard Mirror Box in ICF Target Area
Zhou Yi, Yang Pin, Liao Yunfei, Liu Pengwei, and Zuo Dong
In order to achieve minimum deformation of optical components and ensure beam quality, temperature control of switchyard mirror box in target area of the laser inertial confinement fusion (ICF) devices is very important. Mathematical and physical models of switchyard box in target area are established. FLUENT software In order to achieve minimum deformation of optical components and ensure beam quality, temperature control of switchyard mirror box in target area of the laser inertial confinement fusion (ICF) devices is very important. Mathematical and physical models of switchyard box in target area are established. FLUENT software is used to analyze the temperature field inside mirror box and analysis result is consistent with the measured result. The temperature field distribution and stability time inside mirror box impacted by different wind velocities and angles are analyzed, the results show that the greater the speed, the faster the temperature field inside mirror box stabilized. And when wind velocity v is greater than 1.3 m/s, the decrease of stability time is not obvious. Wind angle shows great impact on the steady of temperature inside mirror box and the best value is obtained. When wind velocity v is 1.3 m/s and wind angle θ is 20°, the stability time inside mirror box is the shortest with the value of 77 min. And within 32 min after the blower turned off, the temperature difference between the mirror is in the allowable range, with a maximum of 0.009 K..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502002 (2012)
Optimization of n-DBR in High Power Vertical-Cavity Surface-Emitting Laser under a Short Pulsed Operation
Zhang Lisen, Ning Yongqiang, Zhang Xing, Liu Di, Qin Li, Zhang Jinlong, Liu Yun, and Wang Lijun
The dependent of threshold current, output power and wall-plug efficiency on the reflectivity of n-distributed Bragg reflector (DBR) is simulated theoretically. The vertical-cavity surface-emitting laser (VCSEL) single device and arrays are fabricated and tested using waveform analysis method. The pulse width and repetThe dependent of threshold current, output power and wall-plug efficiency on the reflectivity of n-distributed Bragg reflector (DBR) is simulated theoretically. The vertical-cavity surface-emitting laser (VCSEL) single device and arrays are fabricated and tested using waveform analysis method. The pulse width and repetition rate are 60 ns and 100 Hz, respectively. The peak output power of single device with an aperture of 500 μm is up to 102 W, corresponding to a power density of 52 kW/cm2, when the injection current is 110 A. The peak powers of 4×4 and 5×5 arrays are 98 W and 103 W at 100 A. The output power and the spectra of single device are compared at different injection currents under continuous wave (CW), quasi-CW (QCW), and pulsed operation, respectively. It is also concluded that the red shift rate of lasing wavelength is 0.92 nm/A and 0.3 nm/A, the temperature rise is 85 ℃ and 180 ℃ under CW and QCW operation, respectively. While it is only 0.0167 nm/A under pulsed operation, the corresponding temperature rise at 6 A is 1.5 ℃, which is far less than that under the other two conditions. That is why the peak power is so high under pulsed operation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502003 (2012)
Influence of Metal Particles on Damage Threshold of Fused Silica at 3ω
Wang Libin, Ma Weixin, Ji Lailin, and Zhao Dongfeng
In high-power laser, as a kind of contamination on the surface of fused silica, the metal particles has been long concerned. In order to measure the influence of metal particles on damage threshold of fused silica quantitatively, damage threshold of uncontaminated and contaminated (by Al, Cu, Fe) Corning7980 fused siliIn high-power laser, as a kind of contamination on the surface of fused silica, the metal particles has been long concerned. In order to measure the influence of metal particles on damage threshold of fused silica quantitatively, damage threshold of uncontaminated and contaminated (by Al, Cu, Fe) Corning7980 fused silica is tested on the standard damage test platform in Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences. Research finds that, the damage threshold of contaminated fused silica is reduced to 20%~30% compared to the uncontaminated, the higher-absorption-coefficient metal particles induce damage more easily, and damage morphology is very different. The uncertain behavior and probability of damage is offline observed from microscopics point of view. Refer to the damage explosion model, the temperature changes over time is roughly simulated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502004 (2012)
Effect of Oxide Aperture on Temperature Rise in High Power Vertical-Cavity Surface-Emitting Laser
Liu Di, Ning Yongqiang, Qin Li, Zhang Jinlong, Zhang Xing, Liu Yun, and Wang Lijun
Thermal characteristics of single vertical-cavity surface-emitting laser (VCSEL) devices with different oxide apertures are studied experimentally in order to get better beam quality and higher output power by choosing appropriate size of the oxide aperture. Single devices with oxide apertures of 415, 386, and 316 μm aThermal characteristics of single vertical-cavity surface-emitting laser (VCSEL) devices with different oxide apertures are studied experimentally in order to get better beam quality and higher output power by choosing appropriate size of the oxide aperture. Single devices with oxide apertures of 415, 386, and 316 μm are made by controlling the oxidation time. Diameters of the mesa and the P type contact are 450 μm and 400 μm, respectively. Thermal resistances of three kinds of devices are measured experimentally based on their different output characteristics under continuous-wave (CW) operation at room temperature. It is found that the smaller the oxide aperture is, the larger the thermal resistance of the device becomes. Temperature rise caused by self heating of injection current is obtained by comparing the relationship of current, wavelength and temperature. At a current of 1 A, the temperature of devices are 32.4 ℃, 35.2 ℃ and 76.4 ℃ corresponding to the oxide aperture of 415, 386, and 316 μm, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502005 (2012)
"Smile" Effect on the Beam Quality for Diode Laser Arrays
Lang Chao, Yao Shun, Chen Bingzhen, Jia Guannan, and Wang Zhiyong
By establishing the near-field and far-field models of the diode laser arrays with the "Smile" effect, and combining optical near-field scanning method with Gaussian beam propagation theory, the conclusion that the value of "Smile" effect and the distribution decide the beam quality of diode laser aBy establishing the near-field and far-field models of the diode laser arrays with the "Smile" effect, and combining optical near-field scanning method with Gaussian beam propagation theory, the conclusion that the value of "Smile" effect and the distribution decide the beam quality of diode laser arrays together is proved theoretically and experimentally. Except that, the beam parameters products of diode laser arrays under different "Smile" effect in the fast axis are calculated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502006 (2012)
Experimental Study on Eliminating Self-Mode Locking of Nd:YAG Laser
Tian Fei, Luo Jia, Hu Daping, and Ye Yidong
The phenomena of self-mode locking in Q-switched Nd:YAG laser used for pumping Tisapphire will result in instability of laser pulse peak power output and mangle the optical devices. In order to eliminate this phenomena availably, the reason caused for self-mode locking is investigated, and Fabry-Perot (F-P) etalon withThe phenomena of self-mode locking in Q-switched Nd:YAG laser used for pumping Tisapphire will result in instability of laser pulse peak power output and mangle the optical devices. In order to eliminate this phenomena availably, the reason caused for self-mode locking is investigated, and Fabry-Perot (F-P) etalon with different parameters is employed. By using one piece of 20 mm-thick F-P etalon with a reflectivity of 60%, which can not only reduce inserting loss but also avoid the damage of F-P etalon′s coatings, a smooth pulse waveform in pulse width of 70 ns and pulse energy of 600 mJ at 1064 nm is realized, the reason for it may be as follows: though there are probably five longitudinal modes in a full width at half maximum (FWHM) of F-P etalon theoretically, only one longitudinal mode may be able to oscillate considering the loss; though there are several transmission peaks in the gain bandwidth of Nd:YAG, incontiguous longitudinal modes can not meet the condition of mode locking..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502007 (2012)
Single-Ended Fiber Coupled Acousto-Optic Q-Switched All-Fiber Laser
He Jing, Zhao Hongming, Zhou Jun, Du Songtao, Dong Jingxing, and Wei Yunrong
A single-ended fiber coupled actively acousto-optic Q-switched all-fiber laser with high-repetition-rate, short pulse duration, narrow line-width and high efficiency is experimentally demonstrated. Based on the combination of fiber grating and plane mirror providing a linear Fabry-Perot (F-P) cavity, the fiber laser isA single-ended fiber coupled actively acousto-optic Q-switched all-fiber laser with high-repetition-rate, short pulse duration, narrow line-width and high efficiency is experimentally demonstrated. Based on the combination of fiber grating and plane mirror providing a linear Fabry-Perot (F-P) cavity, the fiber laser is working on the backward-pump scheme by use of laser diode and (2+1)×1 pump coupler, achieving all-fiber structured pulse ytterbium-doped double-clad fiber laser by adopting single-ended fiber coupled acousto-optic modulator (AOM). AOM operates in the first direction and inversely outputs, inverted output Q-switched pulse with repetition rate of 20~100 kHz adjustable. At the repetition rate of 50 kHz and pump power of 5.7 W, laser system outputs highly efficient, stable, narrow line-width short pulse of 2.64 W average power, corresponding to single pulse energy of 528 μJ, pulse duration of 56 ns and peak power of 943 W. The center wavelength of laser is around 1080 nm with line-width of 0.06 nm, and the optical-optical conversion efficiency is as high as 46%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502008 (2012)
100 kHz Repetition Rate Picosecond Regenerative Amplifier with High Pulse Stability
Huang Yutao, Fan Zhongwei, Niu Gang, Yan Ying, Wang Xiaofa, Huang Ke, Lian Fuqiang, and Yu Jin
A laser diode-pumped picosecond Nd:YVO4 regenerative amplifier system is reported, which produces high stable pulses at 100 kHz repetition rate. RTP crystal is chosen as electro-optical switches to control the output of regenerative amplifier. The amplifier is a symmetrical W type resonator with 1.8 m total length. TheA laser diode-pumped picosecond Nd:YVO4 regenerative amplifier system is reported, which produces high stable pulses at 100 kHz repetition rate. RTP crystal is chosen as electro-optical switches to control the output of regenerative amplifier. The amplifier is a symmetrical W type resonator with 1.8 m total length. The effects of round trips number and cavity losses on period doubling bifurcation and maximum output power are analyzed. When pump power is 30 W, the amplifier provides the output power of 5.3 W with pulse stability root mean square (RMS) is less than 2% by choosing the optimal round trips number. The amplified pulse has a pulse duration of 13.78 ps, a peak power of 3.84 MW. The beam quality factor M2 after amplification is less than or equal to 1.5..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502009 (2012)
MOCVD Growth of AlGaInAs/AlGaAs Quantum Well for 852 nm Laser Diodes Studied by Reflectance Anisotropy Spectroscopy
Xu Huawei, Ning Yongqiang, Zeng Yugang, Zhang Xing, Zhang Jianwei, Zhang Jian, and Zhang Lisen
The influence of the growth temperature and interruption time on the crystal quality of AlGaInAs/AlGaAs quantum well is investigated. The AlGaInAs/AlGaAs quantum well and whole 852 nm laser structures are grown by metal organic chemical vapor deposition (MOCVD). Reflectance anisotropy spectroscopy (RAS) and photolumineThe influence of the growth temperature and interruption time on the crystal quality of AlGaInAs/AlGaAs quantum well is investigated. The AlGaInAs/AlGaAs quantum well and whole 852 nm laser structures are grown by metal organic chemical vapor deposition (MOCVD). Reflectance anisotropy spectroscopy (RAS) and photoluminescence (PL) spectra are applied to measure the AlGaInAs/AlGaAs interfaces crystalline quality. The results show that high growth temperature will lead to indium segregation from AlGaInAs quantum well to AlGaAs barrier. By lowering the growth temperature and using of interruption time between AlGaInAs quantum well and AlGaAs barriers, the indium segregation effect can be effectively suppressed. The AlGaInAs/AlGaAs quantum well shows an abrupt interface and good crystalline quality under this growth conditions. With optimizing growth conditions, whole laser structures are grown. All the epilayer and growth process can be distinguished in situ by RAS transient spectra..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502010 (2012)
Bandwidth Investigation of Optical Parametric Amplifier in Different Noncollinear Geometries
Liu Tao, Jia Huibin, Xiang Hongyin, Yu Song, Zhang Hua, and Wang Yundi
The tunable bandwidth and the parametric bandwidth of periodically poled LiNbO3 (PPLN) based on picosecond optical parametric amplifier with different noncollinear geometries are investigated theoretically and numerically. By utilizing an noncollinear geometry recommended by ourself and setting both the noncollinear anThe tunable bandwidth and the parametric bandwidth of periodically poled LiNbO3 (PPLN) based on picosecond optical parametric amplifier with different noncollinear geometries are investigated theoretically and numerically. By utilizing an noncollinear geometry recommended by ourself and setting both the noncollinear angle θ between the wave vectors of the pump and the quasi-phase-matching grating and the grating period of PPLN at optimal values, broad and stable tunable bandwidth can be obtained. An expression is proposed to calculate the optimal grating period for PPLN. By expanding the wave-vector mismatch in a Taylor series and retaining terms through first order, second order and third order, respectively, three equations are presented to determine the parametric bandwidth. The results calculated from these equations are analyzed and compared with that calculation by employing the wave-vector mismatch directly, and then the effect of high order series on the parametric bandwidth is studied. At the end, a feasible scheme is presented to determine the working temperature and noncollinear angle α, maximize the tunable bandwidth and parametric bandwidth, and simplify the experimental operation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502011 (2012)
Phase Perturbation of Large Aperture KDP Crystal Manufacture and Effects on Third Harmonics Generation
Ji Lailin, Liu Chong, Tang Shunxing, Chen Ming, Feng Wei, Zhu Baoqiang, Ma Weixin, Zhu Jian, Dai Yapin, and Lin Zunqi
The effects of period phase perturbation of large aperture KDP crystal in middle spatial frequency are analyzed based on the results of experiments of Shenguang II. The period of phase perturbation of crystal reflection wavefront is near 20 mm, and the modulation amplitude is about 35 nm, the period of the third harmonThe effects of period phase perturbation of large aperture KDP crystal in middle spatial frequency are analyzed based on the results of experiments of Shenguang II. The period of phase perturbation of crystal reflection wavefront is near 20 mm, and the modulation amplitude is about 35 nm, the period of the third harmonics near field is about 12 mm, the contrast of strip is between 0.1 and 0.3, which leads to 3ω far field distortion and the probability of self-focusing increase. This cycle modulation at medium high frequency is possible caused by vacuum siphon in the process of crystal manufacture, and it needs to be verified in the follow-up experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502012 (2012)
Analysis of Optical Parametric Chirped Pulse Amplification Spectrum and Conversion Efficiency Resulting from Time Characteristics of Signal Pulse Based on YCOB Crystal
Wang Nannan, Sun Meizhi, Xu Tingting, Kang Jun, and Xie Xinglong
The impact of time-domain properties about the signal pulse on spectrum and conversion efficiency after optical parametric chirped pulse amplification (OPCPA) is studied, based on coupled equations in YCOB crystal, when pump energy and pulse shape are certain. The energies of pump and signal pulse are 45 J and 500 mJ, The impact of time-domain properties about the signal pulse on spectrum and conversion efficiency after optical parametric chirped pulse amplification (OPCPA) is studied, based on coupled equations in YCOB crystal, when pump energy and pulse shape are certain. The energies of pump and signal pulse are 45 J and 500 mJ, and beam diameters are 60 mm and 50 mm, respectively, during the calculation. Pulse width of pump pulse is 3 ns, while signal′s is 1.2 ns. The numerical results show that signal spectrum amplified and conversion efficiency are related to time-domain properties of input signal pulse. The spectral full width at half maximum (FWHM) after OPCPA is broadened from 36 nm to 61 nm when the signal pulse as one order Gaussian pulse, but that of two order Gaussian pulse is just broadened to 47 nm. The order is higher, broadening is less. The FWHM keeps almost unchanged at 36 nm, compared with that before OPCPA when the signal pulse as five even higher order Gaussian function. And when the length of YCOB crystal is constant, conversion efficiency reaches 32% when the signal pulse as one order Gaussian pulse, with that of two order Gaussian pulse is only 25%. That of eight order Gaussian pulse or above changed little, remaining approximately 19%. Temporal characteristics of signal pulse make great fluence on the spectrum and conversion efficiency of the amplified pulse when the pump pulse and the length of the crystal are certain..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502013 (2012)
Advancing Precision of Grating Tiling with Modified Single Neuron Adaptive PID Control Algorithm
Wang Cong, Du Li, Zhang Junwei, Zhou Hai, Wang Xiao, Chen Liangming, Fu Xuejun, Lin Donghui, Wu Wenlong, and Zhu Qihua
Grating tiling which is considered as a feasible technology can be used to obtain multiple-meter-sized large-aperture gratings, and stability control is one of key problems. So, it is important to find available and fit proportion integration differentiation (PID) closed loop control in required high accuracies conditiGrating tiling which is considered as a feasible technology can be used to obtain multiple-meter-sized large-aperture gratings, and stability control is one of key problems. So, it is important to find available and fit proportion integration differentiation (PID) closed loop control in required high accuracies condition (submicroradian orientations and nanometer positions). In this paper, by means of the principle of back propagation (BP) nerve net modified PID controller, the first value that a system in zero initial conditions using step response produces is replaced with sign function to achieve single neuron adaptive PID control, and based on that, in order to improve the risetime of the system at the beginning of the response, a changeable neuron proportionality coefficient replaces the constant K value. Simulation result indicates that the proposed control algorithm will not bring greater overshoot with quicker risetime than the traditional PID controller; and the experimental result indicates that the proposed control algorithm can guarantee the precision of the grating-tiling..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502014 (2012)
Research on Langmuir Flow Patterns in Laser Gyros
Wang Zhiguo, Long Xingwu, and Wang Fei
In order to reduce errors cause by Langmuir flow in ring laser gyros, controlling effect of bypass tube between cathode and anode on the Langmuir flow in discharge tube is investigated. Langmuir flow patterns in discharge tube as a function of bypass tube radius, discharge current and gas pressure are simulated numericIn order to reduce errors cause by Langmuir flow in ring laser gyros, controlling effect of bypass tube between cathode and anode on the Langmuir flow in discharge tube is investigated. Langmuir flow patterns in discharge tube as a function of bypass tube radius, discharge current and gas pressure are simulated numerically with gas glow discharge theory. It is found that Langmuir flow pattern varies with the said parameters. What′s more, average Langmuir flow across the fundamental mode section in discharge tube can be adjusted to zero. These foundings not only explain some experimental phenomena but also are useful in reducing Langmuir flow drift and consequently thermal sensitivity in ring laser gyros..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 502015 (2012)
Materials and Thin Films
Spectrum and Laser Properties of Nd:Lu3Al5O12 Crystal
Wang Xiaodan, Xu Xiaodong, Wang Jingya, Ma Chunlan, and Xu Jun
High quality Nd:Lu3Al5O12(Nd:LuAG) crystal doped with 1% Nd (atom fraction) is grown by the Czochralski method. The spectrum properties of the crystal are characterized. Compared with Nd:YAG with the same Nd concentration, Nd:LuAG single crystal has similar shape of absorption peak and fluorescence peak, but the positiHigh quality Nd:Lu3Al5O12(Nd:LuAG) crystal doped with 1% Nd (atom fraction) is grown by the Czochralski method. The spectrum properties of the crystal are characterized. Compared with Nd:YAG with the same Nd concentration, Nd:LuAG single crystal has similar shape of absorption peak and fluorescence peak, but the position of peaks has 1 nm red-shift. Nd:LuAG single crystal has longer fluorescence lifetime and wider absorption line than Nd:YAG and NdGGG single crystals. Under Ti sapphire laser pumping with 900 mW power, the maximum output power, the slope efficiency, and the lasing threshold of Nd:LuAG crystal are 420 mW, 47.5% and 22 mW, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 506001 (2012)
Study on Nonequilibrium Heat Transfer in Au Nano Metal Films by Femtosecond Laser Pump and Probe Method
Zhu Lidan, Sun Fangyuan, Zhu Jie, and Tang Dawei
After femtosecond laser exciting the metals, photons excite electrons into higher energy levels, and then the excited electrons thermalize rapidly. The higher-temperature electrons transmit energy to the lattice through the electron-phonon scattering process, the electron-phonon coupling factor is used to govern the raAfter femtosecond laser exciting the metals, photons excite electrons into higher energy levels, and then the excited electrons thermalize rapidly. The higher-temperature electrons transmit energy to the lattice through the electron-phonon scattering process, the electron-phonon coupling factor is used to govern the rate of electron-phonon thermal relaxation process. So far, the size effects of the electron-phonon coupling factor are still in controversial. We explore the femtosecond laser pump and probe method to study the nonequilibrium heat transfer in Au nano metal films, and explore the parabolic two-step radiation heating model to fit the experimental data. By studying on the different thicknesses of Au films′ electron-phonon coupling factors, we find that with the thin film thickness increases, the electron-phonon coupling factor decreases. The experimental data is in agreement with the theory model, which is based on the mean free path forwarded..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 507001 (2012)
Microstructure and Performance of the Integrated Filter Film on InGaAs Detector
Wang Yunji, Tang Hengjing, Li Xue, Duan Weibo, Liu Dingquan, and Gong Haimei
For compact, low-cost and high-precision consideration, the filter films centered on 1.38 μm are fabricated on InP substrates and InGaAs detector by thermal evaporation. The optical properties, surface and interface morphology of the films are investigated by polarized light microscope, atomic force microscope (AFM) ,sFor compact, low-cost and high-precision consideration, the filter films centered on 1.38 μm are fabricated on InP substrates and InGaAs detector by thermal evaporation. The optical properties, surface and interface morphology of the films are investigated by polarized light microscope, atomic force microscope (AFM) ,scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). It shows that the filter film contains a three-cavity Fabry-Perot structure, the same with the design, the centralwavelength of the passband is 1.38 μm and the peak of transmission is around 60%. Tested electrical performance results reveal that the fabrication process has no effect on current-voltage characteristics and noise of the device. The optical response testing shows that the integrated device has a better performance than the device separated with the filter film..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 507002 (2012)
Influence of Heat Treatment on the Microstructure and Properties of Pulsed Laser Deposited Hydroxyapatite Thin Films
Wu Jian, Xu Lili, and Yang Sen
Pulsed laser deposition is used to prepare hydroxyapatite (HA) thin films onto Ti6Al4V (TC4) substrate, and the influence of the annealing temperature on the microstructure and properties is investigated. The morphology, composition and microstructure of the HA films are detected by the scanning electron microscope (SEPulsed laser deposition is used to prepare hydroxyapatite (HA) thin films onto Ti6Al4V (TC4) substrate, and the influence of the annealing temperature on the microstructure and properties is investigated. The morphology, composition and microstructure of the HA films are detected by the scanning electron microscope (SEM), the energy disperse spectroscopy (EDS), X-ray diffraction and the Fourier transform infrared (FTIR) spectroscopy, respectively. The surface roughness and wettability are investigated separately by the profilometer and the contact angle measurement. The experimental results demonstrat that the as-deposited film is compact and defect-free, which is mainly composed of amorphous phase. After heat treatment, the film has a higher crystallinity and roughness, and the ratio of Ca/P is closer to that of HA, and the surface becomes more hydrophilia compared with the bare substrate and the as-deposited one. However, the exorbitant annealing temperature (700 ℃) can result in microcracks on the film..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 507003 (2012)
Measurement and Metrology
Research on the Randomly Phase Shifting Algorithm with Wavelength Tuning
Guo Renhui, Li Jianxin, Zhu Rihong, and Chen Lei
The wavelength tuning interferometer is applied to test large optical components. In order to calculate the phases using the algorithms with certain phase steps, the steps should be calibrated. When testing is done at long cavity lengths, the calculating precision using algorithms with certain steps is low. It is becauThe wavelength tuning interferometer is applied to test large optical components. In order to calculate the phases using the algorithms with certain phase steps, the steps should be calibrated. When testing is done at long cavity lengths, the calculating precision using algorithms with certain steps is low. It is because of the limited resolution of the laser controller, environment vibration and airflow disturbance, etc.. On the basis of the randomly phase shifting algorithm, the randomly phase shifting algorithm with wavelength tuning is presented. And it is applied to the large aperture wavelength tuning interferometer. The algorithm is simulated and it is proved correct and with high precision. The experimental results show that it can obtain the phases in the wavelength tuning interferometer. The precision is proved high comparing to the ideal phases..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 508002 (2012)
On-Line Three-Dimensional Inspection Based on Orthogonal Two-Frequency Grating Projection
Wu Yingchun, Cao Yiping, Shi Shunping, and Chen Deliang
An orthogonal two-frequency grating designed for the on-line inspection is proposed. The higher frequency fringes are introduced in the orthogonal direction of the original single frequency fringes, which are used to extract modulation and complete pixel matching in the inspection. The proposed grating can resolve the An orthogonal two-frequency grating designed for the on-line inspection is proposed. The higher frequency fringes are introduced in the orthogonal direction of the original single frequency fringes, which are used to extract modulation and complete pixel matching in the inspection. The proposed grating can resolve the problem of pixel matching and phase calculation requiring different frequencies. In addition, the higher frequency fringes don′t influence the low frequency fringes used for the phase calculation, and the higher frequency fringes don′t need to be filtered. So the influence of filtering in phase calculation can be eliminated. Both numerical simulations and experiments prove the feasibility and validity of the proposed method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 508003 (2012)
An Online Detection System for Atomic Beam
Wang Xiaojia, Feng Yanying, and Xue Hongbo
An online detection system is developed for measuring the longitudinal velocity spectrum, flux and populations in specific states of an atomic beam, through the fluorescence and the time of flight (TOF) method. A fluorescence collection optical system with a plug and play and focal length adjustable mechanical structurAn online detection system is developed for measuring the longitudinal velocity spectrum, flux and populations in specific states of an atomic beam, through the fluorescence and the time of flight (TOF) method. A fluorescence collection optical system with a plug and play and focal length adjustable mechanical structure is designed to improve the system integration and the signal to noise ratio (SNR). The system is used to measure and analyze on-line performance of an atomic beam, with a program based on LabView for the control of the photomultiplier tubes (PMT), the timing of TOF, the sweep range of the probe laser, and smoothing the results. The experimental results show that the SNR up to 571 (in 20 ms) can be obtained in this system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 508004 (2012)
Wavefront Acquirement of Single Interferogram Using the Virtual Grating Moiré Fringe Method with Gaussian Filter in the Spatial Domain
Wang Jun, Chen Lei, and Wu Quanying
The virtual grating Moiré fringe is a method to acquire the test wavefront using single interferogram. The Gaussian function is used to filter Moiré interferogram in the spatial domain. The Moiré interferogram is blurred by Gaussian filter in the spatial domain, thus the high frequency component is filteThe virtual grating Moiré fringe is a method to acquire the test wavefront using single interferogram. The Gaussian function is used to filter Moiré interferogram in the spatial domain. The Moiré interferogram is blurred by Gaussian filter in the spatial domain, thus the high frequency component is filtered out, leaving the low frequency component which contains the test phase information. The relationship between the window of Gaussian filter and the carrier frequency of the interferogram is given. The amount of calculation of the method is low and it is easy to select the filter window. The wavefront of a plane is measured using Zygo phase shifting interferometer, whose result (dPV=0.080λ, xRMS=0.020λ, λ=632.8 nm) coincides with the one obtained by the virtual grating Moiré fringe method (dPV=0.079λ，xRMS=0.017λ)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 508005 (2012)
Measurement and Metrology
Simulation and Crosstalk Analysis of 360° Three-Dimensional Display System Based on Rotating LED Line Array
Cao Zisheng, Li Haifeng, Yao Zhenning, Liu Xu, and Liu Xiangdong
In order to improve the display of 360° three-dimensional display system based on rotating linear light-emitting diode array, a simulation program is established. The causes of crosstalk are analyzed in detail: design parameters and system error. And their effects on the display is simulated with the results that In order to improve the display of 360° three-dimensional display system based on rotating linear light-emitting diode array, a simulation program is established. The causes of crosstalk are analyzed in detail: design parameters and system error. And their effects on the display is simulated with the results that the generation of crosstalk can be effectively inhibited by the rational optimization of design parameters and controlling the precision of manufacture. Various perspective views can be reproduced in the simulation program, and the effects of perspective crosstalk caused by design flaws and errors can be simulated, and thus the design of the system parameters is optimized..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 508001 (2012)
Optical Communication
Air-Hole Type Photonic Crystal Add-Drop Filters Based on Total-Internal-Reflection Ring Resonators
Jiang Junzhen, Qiang Zexuan, Xu Xiaofu, Chen Zhiyong, and Qiu Yishen
A hexagonal-lattice air-hole photonic crystal add-drop filter (OADF) is proposed combing the hybrid effect of total-internal-reflection (TIR) ring resonators and photonic crystal band gap. The mode profile of line defect waveguide can be effectively operated in single mode by either compressing or dislocating the two rA hexagonal-lattice air-hole photonic crystal add-drop filter (OADF) is proposed combing the hybrid effect of total-internal-reflection (TIR) ring resonators and photonic crystal band gap. The mode profile of line defect waveguide can be effectively operated in single mode by either compressing or dislocating the two rows of photonic crystal above and below the line defect waveguide, which further affects the dropped efficiency. Dropped efficiencies of proposed filter with different widths of Bus-waveguide and disiocations δ are then numerically analyzed by using two-dimensional finite-difference time-domain (FDTD) numerical technique. The results show that -0.11 dB dropped efficiency and 1100 quality factor Q can be obtained with 1464 nm signal channel when the width of Bus-waveguide, coupling strength and dislocation are 0.83 periodicity, 0 periodicity and 0.5 periodicity. On the other hand, dropped efficiency of 0.89 dB and quality factor of 2100 can be also provided when the width of Bus-waveguide, coupling strength and displacement are 0.83 periodicity, 1 periodicity and 0 periodicity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 505001 (2012)
Glucose Evanescence Absorption Sensor by Using Plastic Optical Fiber
Chu Fenghong, and Wang Jiyuan
Glucose concentration is detected by using evanescent absorption method. Plastic optical fiber is used as sensor head and light transmit element. A high brightness blue LED modulated with sine signal is used as excitation source with spectrum centered at 470 nm. The sensitivity of the system under different shaped sensGlucose concentration is detected by using evanescent absorption method. Plastic optical fiber is used as sensor head and light transmit element. A high brightness blue LED modulated with sine signal is used as excitation source with spectrum centered at 470 nm. The sensitivity of the system under different shaped sensor heads (U-shaped, biconical-shaped, spiral-shaped) is measured, and the spiral-shaped sensor head shows the highest sensitivity to glucose. The relationship between the spiral-shaped output light power and glucose concentration is linearly and the linear coefficient is 0.986. The sensitivity of the sensor head is 0.1 μg/mL. The system shows excellent reversibility when the sensor is tested by alternately cycling between 0 mg/100 mL and 25 mg/100 mL glucose solution in five cycles..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 505002 (2012)
Characteristics of All-Fiber Gas Raman Light Source Based on Hydrogen-Filled Hollow-Core Photonic Crystal Fiber
Chen Xiaodong
The characteristics of all-fiber gas Raman light source based on hydrogen-filled hollow-core photonic crystal fiber pumped with Q-switched fiber laser are investigated theoretically and experimentally. The wavelength of the Stokes frequency-shift wave is 1135.7 nm with the Q-switched pump pulses at 1064.7 nm. Both our The characteristics of all-fiber gas Raman light source based on hydrogen-filled hollow-core photonic crystal fiber pumped with Q-switched fiber laser are investigated theoretically and experimentally. The wavelength of the Stokes frequency-shift wave is 1135.7 nm with the Q-switched pump pulses at 1064.7 nm. Both our theoretical and experimental results show that the generated Stokes pulse is much narrower than the pump pulse, and the generated Stokes pulse duration increases with the single pulse energy of the pump pulses. Moreover, by choosing narrower pump pulses, the Raman threshold pump energy may decrease and the conversion efficiency may increase. For the 125 ns pump pulses with the repetition rate of 5 kHz, the Raman threshold pump energy and the conversion efficiency at the Raman threshold are measured to be 2.13 μJ and 9.82% in experiments..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 505003 (2012)
Space Laser Communications Based on Quasi-Orthogonal Space-Time Block Coding
Xing Xuefeng, and Li Hongzuo
Quasi-orthogonal space-time block coding (QOSTBC) is a transformational structure of orthogonal space-time coding. It is a time and space diversity technique. It has a highly efficient diversity utilization and coding efficiency. Over atmospheric turbulence channels, QOSTBC is an optical communication solution. By the Quasi-orthogonal space-time block coding (QOSTBC) is a transformational structure of orthogonal space-time coding. It is a time and space diversity technique. It has a highly efficient diversity utilization and coding efficiency. Over atmospheric turbulence channels, QOSTBC is an optical communication solution. By the study of the atmospheric channel characteristics, a QOSTBC model based on spatial diversity optical communication is proposed. The principle of QOSTBC is introduced. The channel capacity and bit error rate (BER) are analyzed. Using Monte Carlo simulation method, the channel capacity and the BER between diversity and no diversity coding system are compared. The results show that by using of QOSTBC the system′s channel capacity increases with the number of transmit antennas. The error performance is improved effectively. The system signal noise ratio (SNR) reduces 9 dB comparing QOSTBC and Alamouti coding system, which indicates that the coding system has provided a well channel capacity and error performance. The coding system can effectively inhibit optical intensity fluctuation of optical communication affected by atomspheric turbulance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 505004 (2012)
Experimental Study on All-Optical Clock Recovery of All-Fiber Mode-Locking Cavity Configuration
Wang Shunyan, Jiang Yang, Wu Cinan, Wang Ju, Yu Jinlong, Zhou Zhuya, Xu Jing, and Li Hengwen
A scheme of all-optical clock recovery based on an all optical fiber mode-locking cavity configuration is analyzed and demonstrated. In the scheme, the semiconductor optical amplifier (SOA) in traditional structures is displaced by a segment of highly nonlinear optical fiber (HNLF). Through the cross-phase modulation eA scheme of all-optical clock recovery based on an all optical fiber mode-locking cavity configuration is analyzed and demonstrated. In the scheme, the semiconductor optical amplifier (SOA) in traditional structures is displaced by a segment of highly nonlinear optical fiber (HNLF). Through the cross-phase modulation effect (XPM) in optical fiber, the nonlinear modulation is implemented in the cavity, which is able to overcome the limitation of date rate caused by the carrier recovery time of SOA in traditional methods and break through the "electronics bottleneck". The theory of cross phase modulation effect in optical fiber and the principle of clock recovery in mode-locking ring cavity are analyzed. In addition, a high quality clock signal is successfully extracted from a 40 Gbit/s optical return-to-zero (RZ) signal experimentally. This scheme can work straightway with higher bit rate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 505005 (2012)
Terahertz Technology
Laser Line Competition in Optically Pumped D2O Cavity Terahertz Wave
Liang Pingyuan, Meng Meng, and Luo Xizhang
Based on the theory of semi-classical density matrix, a model of double three-energy-level system for terahertz laser line competition is built. The mathematical expressions of absorption coefficient for pump signal and gain coefficients for terahertz laser signals are deduced, and the competitions between 66 μm and 11Based on the theory of semi-classical density matrix, a model of double three-energy-level system for terahertz laser line competition is built. The mathematical expressions of absorption coefficient for pump signal and gain coefficients for terahertz laser signals are deduced, and the competitions between 66 μm and 116 μm spectral lines in CO2-9P (32) optically pumped D2O cavity terahertz laser are calculated numerically by means of iteration. The general rules for laser line competition under different operating conditions (including pump power, operating gas pressure and length of cavity) are summarized..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 511001 (2012)
Optical Design and Fabrication
Multilayer Diffraction Element with Wide Field of View and High Diffractive Efficiency
Fan Changjiang, Zhao Yahui, Ying Chaofu, and Wu Haowei
A novel multilayer diffractive optical element (MLDOE) composed with different optical materials is investigated and the materials combination principle is discussed. The results show that the first layer, the last layer and the middle layer should be high refractive index and low dispersion optical material, low refraA novel multilayer diffractive optical element (MLDOE) composed with different optical materials is investigated and the materials combination principle is discussed. The results show that the first layer, the last layer and the middle layer should be high refractive index and low dispersion optical material, low refractive index and high dispersion optical material, and smaller Abbe number optical material, respectively. The diffractive efficiency of the MLDOE at each wavelength in designed band is larger than 90% and the full angle of view can reach 110°, which can effectively improve energy utilization ratio and image quality of the hybrid refractive-diffractive optical system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 516001 (2012)
Remote Sensing and Sensors
Inversion of Micro-Pulse Lidar Signals with a New Calibration Method
Chen Tao, Zhao Yujie, Liu Dong, Yu Jie, Xu Lingzhi, Wang Yingjian, and Zhou Jun
A new self-adaptive method to determine the calibration value in the effective distance of micro-pulse lidar (MPL) is proposed. A profile of aerosol backscatter coefficient, which is retrieved from MPL signal with the boundary value determined using the new method, is compared with the one retrieved from another lidar A new self-adaptive method to determine the calibration value in the effective distance of micro-pulse lidar (MPL) is proposed. A profile of aerosol backscatter coefficient, which is retrieved from MPL signal with the boundary value determined using the new method, is compared with the one retrieved from another lidar signal with the boundary value assumed around the troposphere. The comparison shows that the two profiles seem to be consistent with each other well. A group of lidar signal, observed continuously 12 hours, is retrieved with this method, which can accurately indicate the weather conditions. The result shows that the method has a good stability..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 5, 514001 (2012)
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