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2012
Volume: 39 Issue 9
38 Article(s)
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Research Article
Properties of High Order Bessel Gaussian Beam Propagation in Non-Kolmogorov Atmosphere Turbulence
Chen Feinan, Chen Jingjing, Zhao Qi, Chen Yanru, Wang Yongqing, and Xin Yu
Extended Huygens-Fresnel principle is used to analyze the optical intensity transverse distribution of higher-order Bessel Gaussian beam (BGB) propagation through non-Kolmogorov (NoK) atmosphere turbulence model. In NoK turbulence model, the distance and power law effect the strength of phase perturbed by turbulence. SExtended Huygens-Fresnel principle is used to analyze the optical intensity transverse distribution of higher-order Bessel Gaussian beam (BGB) propagation through non-Kolmogorov (NoK) atmosphere turbulence model. In NoK turbulence model, the distance and power law effect the strength of phase perturbed by turbulence. So the result by numerical integral shows that the intensity distribution of BGB beam gets more severe changes at large distance. The higher order beam is less effected by turbulence than lower order beam. The lager transverse parameter of the source can get more spreads when it propagates through turbulence..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 913001 (2012)
Directionality of Apertured Partially Coherent Beams Propagating through Atmospheric Turbulence
Chen Xiaowen, Li Binzhong, and Tang Mingyue
Based on the extended Huygens-Fresnel principle, the expressions for the mean-squared width and the angular spread of apertured Gaussian Shell-model (GSM) beam propagating through atmospheric turbulent are derived by using the quadratic approximation of Rytov′s phase structure function. Compared with unapertured GSM beBased on the extended Huygens-Fresnel principle, the expressions for the mean-squared width and the angular spread of apertured Gaussian Shell-model (GSM) beam propagating through atmospheric turbulent are derived by using the quadratic approximation of Rytov′s phase structure function. Compared with unapertured GSM beam, the directionality of apertured GSM beams propagating through atmospheric turbulence is studied by using angular spread and normalized far-field average intensity distribution. It is found that under a certain condition apertured GSM beams with different truncation parameter δ may have the same directionality as the corresponding unapertured GSM beam in free space and turbulence, if the angular spread in far-field is chosen as the characteristic parameter of beam directionality. On the other hand, if the beam directionality expressed in terms of the normalized far-field average intensity distribution, the directionality of different apertured GSM beams and the corresponding unapertured GSM beams in free space is not the same even if they have the same angular spreads, but the same in turbulence..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 913002 (2012)
Optimization of Link Analysis and Design for Long-Range Non-Line-of-Sight Atmospheric Scattering Communication
Song Chao, Xu Zhiyong, Wang Jingyuan, and Wei Yimei
The average scattering phase function is proposed, to present the angular scattering properties of cloud droplets more accurately than Henyey-Greenstein (H-G) phase function. The theoretically multiple scattering model is founded in the form of Markov chains, which is based on probabilistic theory and stochastically miThe average scattering phase function is proposed, to present the angular scattering properties of cloud droplets more accurately than Henyey-Greenstein (H-G) phase function. The theoretically multiple scattering model is founded in the form of Markov chains, which is based on probabilistic theory and stochastically migrating theory. The characteristics of path loss under given communication configurations are obtained by Monte Carlo simulation algorithm. The best communication configurations for non-light-of-sight (NLOS) atmospheric aerosols scattering and cloud-droplets scattering are analyzed, considering whether there are clouds suspending in the atmosphere. The rationality of analysis is validated by the consistency between experimental data and simulation results. The conclusions referred in this paper are wavelength-dependent, and laser diode (LD) with wavelength 808 nm is chosen as the source light of experiment and simulation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 913003 (2012)
Holography and Information Processing
Alignment Scheme Research Based on Equivalent Overlapped Gratings for Reflective Lithography Alignment
Zhu Jiangping, Hu Song, Yu Junsheng, Tang Yan, Zhou Shaolin, Liu Qi, and He Yu
According to the technology characteristics of proximity and contact lithography, a practical reflective lithography alignment scheme is proposed. The differential Moiré fringe alignment technology is adopted in the scheme and alignment signal is carried in phase of Moiré fringe. Two sets of grating marks witAccording to the technology characteristics of proximity and contact lithography, a practical reflective lithography alignment scheme is proposed. The differential Moiré fringe alignment technology is adopted in the scheme and alignment signal is carried in phase of Moiré fringe. Two sets of grating marks with placed oppositely direction and similar periods are designed on the mask and wafer, respectively. Charge coupled device imaging system is used to receive Moiré fringe image. Then, the relative position relationship can be obtained using Fourier transform to extract Moiré fringe phase. The designed marks could also detect position offset on the vertical and horizontal directions. The reasonable designed scheme of optical path is schematically given, the internal mechanism of the whole system alignment is analyzed in details, and the feasible mathematical model is established. This research results show that the maximum error is less than 0.002 pixel when alignment offset is less than 1 pixel. Compared with light path of transmission-type, the scheme is more practical, satisfying the requirements of the practical alignment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 909001 (2012)
Arbitrary Waveform All-Optical Analog-to-Digital Conversion Based on Phase-Shifted Optical Quantization
Wang Yang, Zhang Hongming, Ma Chao, and Yao Minyu
All optical analog-to-digital converters (ADC) are key devices in high speed signal processing. The frequency response characteristic of all optical ADC based on polarization-differential interference and phase-shifted optical quantization (PSOQ) is experimentally demonstrated. Different frequency sinusoidal signals arAll optical analog-to-digital converters (ADC) are key devices in high speed signal processing. The frequency response characteristic of all optical ADC based on polarization-differential interference and phase-shifted optical quantization (PSOQ) is experimentally demonstrated. Different frequency sinusoidal signals are quantized by a 4 bit photonic ADC. The frequency spectra of digital signals are obtained and analyzed by discrete Fourier transform. The results show that the rang of frequency response is from 74.07 dB to 74.22 dB. The fluctuation of the frequency response is less than 0.15 dB. Then a 1 GHz triangular waveform is sampled and all-optical quantized, and the effective number of bits (ENOB) of 3.31 bit is obtained. The experimental results show that the frequency response of the PSOQ is better, and the application of PSOQ in arbitrary waveform is feasible..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 909002 (2012)
Comparison between 2.52 THz Off-Axis Digital Holography and Focal-Plane Imaging
Li Qi, Ding Shenghui, Li Yunda, and Wang Qi
Performance of focal-plane imaging and off-axis digital holography is studied by the way of the resolution measurement and imaging of watermark and words in pencil with the built 2.52 THz focal-plane imaging and off-axis digital holographic devices. The results validate that the common focal-plane imaging can not achiePerformance of focal-plane imaging and off-axis digital holography is studied by the way of the resolution measurement and imaging of watermark and words in pencil with the built 2.52 THz focal-plane imaging and off-axis digital holographic devices. The results validate that the common focal-plane imaging can not achieve relatively high resolution because of the long wavelength of terahertz. The imaging quality is determined by the placed position. Terahertz off-axis digital hologram can improve the resolution of the imaging system; however, the imaging object size is limited by the system resolution. It can be inferred that the focal-plane imaging is more suitable for large object and low resolution imaging..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 909003 (2012)
Color Reproduction Mechanism Analysis of Computer-Generated Color Rainbow Holography
Shi Yile, Wang Hui, Wu Qiong, Li Yong, and Jin Hongzhen
The relationship between color quantity in color computer-generated holography (CCGH) and computer display colorimetric system is discussed based on color transmission and matching theory. In addition, the relationship between color quantity in computer display colorimetric system and amplitude of object light field inThe relationship between color quantity in color computer-generated holography (CCGH) and computer display colorimetric system is discussed based on color transmission and matching theory. In addition, the relationship between color quantity in computer display colorimetric system and amplitude of object light field in (CCGH) is estabilished. Based on this research, the color reproduction mechanism of computer-generated color rainbow holography (CGCRH) is discussed. Then the calculation method of three primary colors and color quantity of holographic image is given..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 909004 (2012)
Laser Manufacturing
Research on Paint Removal with 1064 nm Quasi-Continuous-Wave Laser
Shi Shudong, Du Peng, Li Wei, Song Feng, Wang Chao, and Chen Nianjiang
As an environment-friendly low energy-consumptional green cleaning method, laser cleaning has important applications in paint removal. The removal of paint from steel substrate with a 1064 nm acoustic optical Q-switched quasi-continuous-wave Nd:YAG laser is reported. The influences of laser peak power density on the clAs an environment-friendly low energy-consumptional green cleaning method, laser cleaning has important applications in paint removal. The removal of paint from steel substrate with a 1064 nm acoustic optical Q-switched quasi-continuous-wave Nd:YAG laser is reported. The influences of laser peak power density on the cleaning result and substrate damage are investigated by numerical simulations and experiments. And the effect of the overlap ratio of laser spots on the cleaning result is investigated. The results show that, during the process of steel substrate paint stripping, the effective mechanism is vibration effect under the condition of threshold cleaning, and it is the combination of vibration effect and ablation effect under the condition of damage cleaning. For the paint with a thickness of 50 μm on the steel substrate, average power of 20 W and more than 80% overlap ratio of laser spot are effective to remove the paint while keeping the substrate undamaged. With the increase of laser power, repetition rate and the radius of laser spot, the cleaning efficiency increases and the cleaning becomes more effective..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 903001 (2012)
Study on Microstructure and Properties of Laser Welding Dual Phase Steel Joints for an Auto-Body
Dong Danyang, Wang Guanjun, Ma Min, and Jiang Tao
It is imperative to increase the service reliability of the laser welding dual phase (DP) steel joints for an auto-body which are subjected to dynamic loading during their manufacturing processes, as well as in an accident. Laser butt welding of DP600 is performed by using a pulsed NdYAG laser. Microstructures of the wIt is imperative to increase the service reliability of the laser welding dual phase (DP) steel joints for an auto-body which are subjected to dynamic loading during their manufacturing processes, as well as in an accident. Laser butt welding of DP600 is performed by using a pulsed NdYAG laser. Microstructures of the welding joints are analyzed. Microhardness and mechanical properties at various strain rates of the welding joints are tested. The results show that welds with good appearance can be obtained under the proper welding conditions. The microstructure of weld zone (WZ) is mainly martensite, and the microhardness is higher than that of base metal. And the heat affected zone (HAZ) is narrow, and there exists HAZ softening that occurs in welding because of the tempering of the martensite phase. The mechanical property of the DP600 welding joint is sensitive to the strain rates. After welding, the yield and tensile strength of DP600 increase as the strain rate increases, while the fracture elongations are all lower than that of the base metal. All tensile fracture of DP600 welding joints are typical ductile fracture characterized by dimples at various strain rates ranging from 10-3 to 103 s-1..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 903002 (2012)
Laser Physics
High-Power Passively Mode-Locked Thulium-Doped Femtosecond Fiber Laser at 2.0 μm
Liu Jiang, and Wang Pu
High pulse-energy semiconductor saturable absorber mirror passively mode-locked thulium-doped femtosecond fiber laser is reported. Based on a linear Fabry-Perot cavity by the combination of semiconductor saturable absorber mirror and broadband reflective mirror, the thulium-doped fiber is pumped by a home-made Er-dopedHigh pulse-energy semiconductor saturable absorber mirror passively mode-locked thulium-doped femtosecond fiber laser is reported. Based on a linear Fabry-Perot cavity by the combination of semiconductor saturable absorber mirror and broadband reflective mirror, the thulium-doped fiber is pumped by a home-made Er-doped fiber laser at 1550 nm. Stable mode-locked laser pulse train occurs at 312 mW incident pump power and the pulse repetition rate is 53 MHz in such a linear cavity configuration. When the incident pump power is 472 mW, the maximum output power is 50 mW, corresponding to the maximum single pulse energy of 0.94 nJ. The pulse width is measured to be 907 fs; the laser center wavelength and the 3 dB spectral bandwidth are 1939.5 nm and 4.6 nm, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902001 (2012)
Simultaneous Multi-Wavelength Pulsed Laser in Diode-End-Pumped Nd:YLF/Nd:YAG
Lu Tingting, Wang Juntao, Huang Minjie, Liu Dan, and Zhu Xiaolei
Simultaneous multi-wavelength pulsed laser is achieved in dual-end-pumped composite laser slab composed of Nd:YLF and Nd:YAG crystals. As much as 6 mJ of laser output at 1064 nm and 1053 nm wavelengths is obtained with an incident pump pulse energy of 40.5 mJ at 500 Hz repetition rate, corresponding to an optical-opticSimultaneous multi-wavelength pulsed laser is achieved in dual-end-pumped composite laser slab composed of Nd:YLF and Nd:YAG crystals. As much as 6 mJ of laser output at 1064 nm and 1053 nm wavelengths is obtained with an incident pump pulse energy of 40.5 mJ at 500 Hz repetition rate, corresponding to an optical-optical conversion efficiency of 14.8%. By inserting a LBO crystal in the cavity, three green wavelengths of 526.5, 529.0 and 532.0 nm lasing is detected simultaneously. The total pulse energy is about 3.6 mJ under 40.5 mJ of incident pump pulse energy at 500 Hz repetition rate. The optical-optical conversion efficiency is 8.9%. The beam quality factors are M2x=1.61, M2y=1.25..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902002 (2012)
Supermode analysis of the 18-core photonic crystal fiber laser
Yuan Wang, Jianquan Yao, Yibo Zheng, Wuqi Wen, Ying Lu, and and Peng
The modal of 18-core photonic crystal fiber laser is discussed and calculated. And corresponding far-field distribution of the supermodes is given by Fresnel diffraction integral. For improving beam quality, the mode selection method based on the Talbot effect is introduced. The reflection coefficients are calculated, The modal of 18-core photonic crystal fiber laser is discussed and calculated. And corresponding far-field distribution of the supermodes is given by Fresnel diffraction integral. For improving beam quality, the mode selection method based on the Talbot effect is introduced. The reflection coefficients are calculated, and the result shows that an in-phase supermode can be locked better at a large propagation distance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902003 (2012)
Large Aperture Plasma Electrode Pockels Cell for Multi-Pass Amplified Scheme
Wu Dengsheng, Zhang Xiongjun, Zhang Jun, Wang Rengui, Tian Xiaolin, Gu Kan, and Zhu Jian
Large aperture plasma electrode Pockels cell (PEPC) is the key unit of the multi-pass amplified scheme of SGⅡ upgrading laser. The PEPC in this scheme should achieve the status switching between on and off in a very short time. The response time of the PEPC driven by positive-negative switching pulses is not as short aLarge aperture plasma electrode Pockels cell (PEPC) is the key unit of the multi-pass amplified scheme of SGⅡ upgrading laser. The PEPC in this scheme should achieve the status switching between on and off in a very short time. The response time of the PEPC driven by positive-negative switching pulses is not as short as the demand of the multi-pass amplified scheme. In the single-pulse process, the low-impedance high voltage generator based on Blumlein pulse-forming line is used to drive the PEPC, and the response time can be reduced greatly. The theoretical charge time of the plasma switch with 350 mm×350 mm aperture is about 54 ns, and the response time can be less than 90 ns in single-pulse process. The experimental results of the switching efficiency of full aperture are higher than 99.7%. The extinction rate exceeds 381. The top width of the time window is larger than 160 ns, and the bottom width is less than 400 ns. All these experimental results can meet the specification of SGⅡ upgrading laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902004 (2012)
Short Linear Cavity Single-Frequency Fiber Laser with Active Frequency Stabilization by Fiber Bragg Grating
Yang Fei, Chen Dijun, Pan Zhengqing, Ye Qing, Cai Haiwen, Qu Ronghui, and Gong Shangqing
A short-linear-cavity all-fiber laser configured with 1.8 cm Er3+/Yb3+ co-doped phosphate glass fiber is demonstrated experimentally with single frequency and high frequency stabilization. The fiber laser is composed of a high-reflectivity fiber Bragg grating (FBG) and a polarization-maintaining FBG. The pump is from aA short-linear-cavity all-fiber laser configured with 1.8 cm Er3+/Yb3+ co-doped phosphate glass fiber is demonstrated experimentally with single frequency and high frequency stabilization. The fiber laser is composed of a high-reflectivity fiber Bragg grating (FBG) and a polarization-maintaining FBG. The pump is from a semiconducter laser of single mode at 976 nm. When the pump power into the cavity is 360 mW, the output power of the laser reaches more than 65 mW; the signal-to-noise ratio is higher than 70 dB; the laser linewidth is about 3 kHz and the polarization extinction ratio is about 40 dB. Moreover, the length of the active fiber is tuned by a piezoelectric transducer (PZT), and the laser frequency tunable slope is 14.2 MHz/V. Then the laser frequency is stabilized on FBG by using side frequency locking method. The long term frequency fluctuation is reduced from 25 MHz/10 s to 2.5 MHz/h..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902005 (2012)
Analysis of the Defocusing Tolerance of Spatial Filtering in High Power Laser Systems
Shan Quanyuan, Zhang Junyong, Zhang Yanli, Jiao Zhaoyang, and Zhu Jianqiang
In the inertial confinement fusion high power laser systems, the severe low frequency wavefront distortion will result in laser beam cutoff, and reduce laser beam quality due to the pinhole of the spatial filter. Based on the spherical wave factor with phase ripples, the defocusing tolerance of spatial filtering has beIn the inertial confinement fusion high power laser systems, the severe low frequency wavefront distortion will result in laser beam cutoff, and reduce laser beam quality due to the pinhole of the spatial filter. Based on the spherical wave factor with phase ripples, the defocusing tolerance of spatial filtering has been studied in detail. In this model, the calculation result shows that the shift distance of the actual frequency-plane in the spatial filter is in inverse proportion to the curvature radius. In addition, the beam quality will reduce with the curvature radius decreasing. For a specified spatial filter with parfocal length of 11.8 m and filtering pinhole radius of 200 μrad, the curvature radius absolute value of the spherical wave factor should not be small than 3.5 km for the critical frequency. When the curvature radius grows to 3 km, the beam quality will deteriorate rapidly as the spatial frequency of phase ripples become smaller than 1.57 mm-1..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902006 (2012)
Femtosecond Laser-Induced Color Centers in KCl Crystal
Yin Chuanlei, and Zhao Quanzhong
The space-selective formation of a series of color center defects in bulk transparent potassium chloride (KCl) crystal induced by 1 kHz and 200 kHz, 800 nm near-IR femtosecond laser which is focused via low-aperture objectives are reported, respectively. Absorption spectra before and after femtosecond laser irradiationThe space-selective formation of a series of color center defects in bulk transparent potassium chloride (KCl) crystal induced by 1 kHz and 200 kHz, 800 nm near-IR femtosecond laser which is focused via low-aperture objectives are reported, respectively. Absorption spectra before and after femtosecond laser irradiation indicate that five kinds of color centers are induced. With the increment of laser power, the concentration of color centers also increases. From the absorption spectra, it is found that the corresponding peak values of absorption bands of color centers induced by two different repetition rates femtosecond laser have slight shift. It is speculated that this phenomenon is resulted from the heat accumulation of the high repetition rate femtosecond laser. Theoretical analysis confirms that the point defects in bulk transparent KCl crystal and multiphoton absorption induced by high power density femtosecond laser-KCl crystal interaction are the main reasons of the formation of color centers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902007 (2012)
Transmission Laser Bonding Characteristics of Ti Coated Glass and PET
Liu Huixia, Wang Kai, Li Pin, Zhang Cheng, Gao Yangyang, Yan Zhang, and Wang Xiao
Transmission laser bonding of dissimilar and biocompatible materials has a potential application in biomedical implants and their encapsulation processes. PET and glass are bonded together by employing micro-scale titanium on glass using a near infrared continuous wave (CW) diode laser. Radio frequency magnetron sputteTransmission laser bonding of dissimilar and biocompatible materials has a potential application in biomedical implants and their encapsulation processes. PET and glass are bonded together by employing micro-scale titanium on glass using a near infrared continuous wave (CW) diode laser. Radio frequency magnetron sputtering deposition method is used to prepare Ti coating on glass substrates. The effect of main process parameters including laser power, scanning speed and film thickness of Ti coating on bond strength and bond width is investigated through the experiments based on single process parameters. The effect of surface roughness of glass substrate on the roughness of Ti coating and the bond strength is discussed. The bond strength between Ti coating glass and PET is obtained by lap-shear test. The information of failure analysis of laser bonded specimens after mechanical lap-shear test are gathered by true colour confocal microscopy for materials. The information of chemical bond for Ti coated glass and PET is collected from laser transmission bonding process by using X-ray photoelectron spectroscopy (XPS). Experimental results show that the main process parameters including laser power, scanning speed have a significant impact on bond strenghth, and the bond strength increases with the thickness of Ti coating and the surface roughness of glass substrates. Based on this research, it will be helpful for transmission laser bonding between Ti coated glass and polymer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902008 (2012)
CO2 Laser of Energy Transfer by a Discharge Driven Continuous Wave DF(v)
Zhong Wei, Yuan Shengfu, Luo Wei, and Sun Xu
By using the manner of the energy transferring from excited DF(v) to CO2(0000), CO2 spectral lines of 10P20(944.27 cm-1) and 10P12(955.26 cm-1) have been observed on the CO2 gain module of the dual-band laser. Research is focused on flux controlling, fuels injecting methods, optimized position of the optical axis, poweBy using the manner of the energy transferring from excited DF(v) to CO2(0000), CO2 spectral lines of 10P20(944.27 cm-1) and 10P12(955.26 cm-1) have been observed on the CO2 gain module of the dual-band laser. Research is focused on flux controlling, fuels injecting methods, optimized position of the optical axis, power stability and beam profile. The max power of the DF-CO2 laser is 2.3 W, and the cavity pressure of this laser is about 2 kPa..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902009 (2012)
Adaptive Path Length Control Technique for Four-Mode Differential Laser Gyro
Wang Zhiguo, Long Xingwu, Wang Fei, and Liu Xiaohu
In order to reduce the sensitivity to external disturbance of four-mode differential laser gyro (FMDLG), an adaptive path length control system is designed to make the FMDLG run at optimal operating point. Path length of the FMDLG is modulated with small amplitude sine wave. The amplitudes of 1st and 2nd harmonic signaIn order to reduce the sensitivity to external disturbance of four-mode differential laser gyro (FMDLG), an adaptive path length control system is designed to make the FMDLG run at optimal operating point. Path length of the FMDLG is modulated with small amplitude sine wave. The amplitudes of 1st and 2nd harmonic signals in light intensity are extracted with phase sense detector technique. The above two signals along with light intensity are used to realize adaptive path length control, which consist of automatic gain control, automatic modulation control and path length control. Experimental results show that adaptive path length control reduces the influence of variations of optical and electronic components parameters as well as light intensity on control system. It is important that it can make the FMDLG run at optimal operating point steadily. The adaptive path length control helps to reduce FMDLG′s sensitivity to magnetic field..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902010 (2012)
Thin Disk TiSapphire Regenerative Amplifier
Zhao Huan, Wei Zhiyi, Teng Hao, Han Hainian, and Wang Zhaohua
A regenerative amplifier taking a thin disk Tisapphire crystal (2 mm thick) as gain medium is presented. The front face of crystal is anti-reflection (AR) coated at 532 nm and 750~850 nm, the other face is high reflection (HR) coated at 532 nm and 750~850 nm, and the total absorbing efficiency of the crystal is over 80A regenerative amplifier taking a thin disk Tisapphire crystal (2 mm thick) as gain medium is presented. The front face of crystal is anti-reflection (AR) coated at 532 nm and 750~850 nm, the other face is high reflection (HR) coated at 532 nm and 750~850 nm, and the total absorbing efficiency of the crystal is over 80% at 532 nm for double passes. In the regenerative cavity, the Tisapphire crystal also acts as a flat reflective mirror, which reduces the complexity of amplifier. The crystal is end-cooled to reduce the thermal effects and improve the beam quality of amplified laser pulses, as a result, the output energy of the amplified laser is about 5.2 mJ, the corresponding conversion efficiency is 11.5%, and the beam quality factor M2 is less than 1.2..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 902011 (2012)
Materials and Thin Films
Etching Characteristics of MgO Doped Lithium Niobate in Inductively Coupled Plasma
Zhou Yujie, Feng Liqun, and Sun Junqiang
MgO doped lithium niobate (MgLiNbO3) is a relatively hard crystal and is difficult for dry etching. Dry etching rate and morphology control of MgLiNbO3 are key technologies in fabricating optoelectronic devices based on lithium niobate. Etching characteristics of MgLiNbO3 crystal are studied by using Plasmalab System 1MgO doped lithium niobate (MgLiNbO3) is a relatively hard crystal and is difficult for dry etching. Dry etching rate and morphology control of MgLiNbO3 are key technologies in fabricating optoelectronic devices based on lithium niobate. Etching characteristics of MgLiNbO3 crystal are studied by using Plasmalab System 100 (Oxford Instruments) with mixture gases of SF6/Ar. The etching rates of different working parameters including inductively coupled plasma (ICP) power, reactive ion etching (RIE) power, working pressure and SF6/Ar flow ratio are evaluated. The surface profile is also affected by various ratios of SF6/Ar gas mixture. The optimal etching conditions for MgLiNbO3 ridge-shaped waveguide are found to be ICP power of 1000 W, RIE power of 150 W, total gas flux of 52 mL/min (standard condition of 0 ℃, 1 atm), chamber pressure of 0.532 Pa and the gas volume ratio of SF6/(Ar+SF6) of 0.077. Optical ridge-shaped waveguide with approximately 2.5 μm depth, 74.8° etching sidewalls and smooth top surface is successfully fabricated using the optimized etching conditions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 906001 (2012)
Optical Constants of Antimony-Bismuth Alloy Films
Jiang Laixin, Lu Xinmiao, Wang Yang, and Wu Yiqun
Antimony-Bismuth alloy is a new functional material for optical super-resolution. It is very important to understand its fundamental optical properties for its applications in optical memory and other photonic devices. Antimony-bismuth alloy films: Sb1-XBiX (X=0, 0.1, 0.2, 0.3, 0.88, 1) are prepared by magnetron sputteAntimony-Bismuth alloy is a new functional material for optical super-resolution. It is very important to understand its fundamental optical properties for its applications in optical memory and other photonic devices. Antimony-bismuth alloy films: Sb1-XBiX (X=0, 0.1, 0.2, 0.3, 0.88, 1) are prepared by magnetron sputtering method. Optical constants (refractive index nand extinction coefficient k) of these films are measured by spectroscopic ellipsometer. Results indicate that both refractive index n and extinction coefficient k of the SbBialloy films decrease with rising concentration of bismuth in the visible wavelength range. The refractive index n of SbBi alloy films increase with increasing wavelength, showing the films possessed anomalous dispersion characteristics. The effects of bismuth composition on the surface morphology and microstructure of the films are studied by atomic force microscope and X-ray diffraction analysis respectively. The SbBi alloy films are at polycrystalline states and its crystallization extent increases with rising concentration of bismuth. This may be the major factor influencing its optical constants..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 907001 (2012)
Measurement and Metrology
Transmission-Virtual Grating Method and Its Applications in Measuring Deformed Liquid Surface
Zhao Yuchen, Huang Xianfu, Liu Zhanwei, Xie Huimin, and He Guang
A novel method based upon deformed transmission-virtual grating is proposed for determination of deformed liquid surface. Mathematic relations between out-of-plane displacement of deformed liquid surface and in-plane displacement of transmission-virtual grating for the method are derived. By addressing an orthogonal grA novel method based upon deformed transmission-virtual grating is proposed for determination of deformed liquid surface. Mathematic relations between out-of-plane displacement of deformed liquid surface and in-plane displacement of transmission-virtual grating for the method are derived. By addressing an orthogonal grating (1~5 line/mm) under the transparent water groove and then capturing images from upset of the deformed water surface, a displacement vector of full-field which directly associates the three-dimensional (3D) deformed liquid surface then can be evaluated by processing the recorded deformed fringe pattern by using special algorithm. By substituting the displacement field to the obtained equations then the out-of-plane displacement of 3D deformed liquid surface can be calculated. Validation test to measure the deformed water surface caused by a Chinese one-cent coin has been conducted. The result agrees with the previous literature, with except a slight difference of 2%, which demonstrates the feasibility of the developed method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 908001 (2012)
Optimizational Design Method for Receiver Filter Bandwidth of Satellite Laser Altimeter
Zhou Hui, Li Song, Zheng Guoxing, Tu Lanfen, and Zhang Qiang
Receiver filter bandwidth (RFB) of satellite laser altimeter (SLA) resolves the key performances of SLA. According to the operational principle of SLA, the theoretical models of received signal and receiver signal-to-noise ratio (SNR) are established, and the mathematical expressions about range error, probability of dReceiver filter bandwidth (RFB) of satellite laser altimeter (SLA) resolves the key performances of SLA. According to the operational principle of SLA, the theoretical models of received signal and receiver signal-to-noise ratio (SNR) are established, and the mathematical expressions about range error, probability of detection and false alarm are deduced. Under the condition that probability of detection and false alarm can satisfy the threshold, an optimizational design method for RFB on the basis of minimizing the range error is put forward. As an example of MOLA-2, the distributions of RFB and range error related with different target slope angles are simulated. The results show that the optimizational design values of RFB are larger than values given by conventional method within 40° target slope angle, whose difference limits the scope from 0.7 MHz to 58.7 MHz. However, corresponding range errors are less than them obtained by conventional method, the extent of their difference is 0.2~16.2 m. With the restrictions of target variety and complexity, it is difficult to make every target correspond with a receiver filter during its manufacture, so multiple receiver filter channels are set up to piecewise fit the distribution curve of range errors, the RFB and corresponding scope of target slope angle for each channel are achieved. The optimizational method of designing the RFB provide a superior and practicable scheme for manufacturing receiver filter..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 908002 (2012)
Design of Launch Orbits Spatial Geometry Coordinate Coherence Calibration System Based on Positive Sensitive Detector
Rong Sihai, Shen Hua, Zhu Rihong, Huang Ya, Wang Xiaofeng, and Bian Yinxu
In the research of bullet flight attitude in modern launch orbits space, the transient attitude of the bullet is captured by several groups of shadow cameras. By image processing and calculation, the whole flight data can be known. In order to acquire accurate measured data, it is critical to calibrate spatial geometriIn the research of bullet flight attitude in modern launch orbits space, the transient attitude of the bullet is captured by several groups of shadow cameras. By image processing and calculation, the whole flight data can be known. In order to acquire accurate measured data, it is critical to calibrate spatial geometrical coordinates. Considering the low precision and poor calibration coherence of traditional grid calibration system, a new type of shadow camera calibration system based on positive sensitive detector and optical lever is researched. The principle background, components and adjusting means are illustrated, and the experimental consequence is analyzed. The results indicate that the calibration accuracy of angle is better than 10″, and the measurement error is less than 0.06 mm. The multi-group cameras′ calibration coherence error is less than 0.1 mm in use with this new system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 908003 (2012)
Study on Beam Stabilization Technique in Lithography Illumination System
Bao Jianfei, Huang Lihua, Zeng Aijun, Ren Bingqiang, Yang Baoxi, Peng Xuefeng, Hu Xiaobang, and Huang Huijie
Beam stabilization technique is one of the most important techniques in modern lithography illumination system. It provides a stable light intensity distribution for the illumination system by stabilizing the pointing and position of laser beam transmitting a long distance. Beam stabilization system is composed of a beBeam stabilization technique is one of the most important techniques in modern lithography illumination system. It provides a stable light intensity distribution for the illumination system by stabilizing the pointing and position of laser beam transmitting a long distance. Beam stabilization system is composed of a beam measurement functional module and a beam steering functional module. The beam transfer matrix between two modules is deduced and an optoelectronic closed-loop control experimental system is built based on LabView. Performances of the system are tested by importing given beam drifting. The system pointing steady-state error is obtained to be better than ±3 μrad, the position steady-state error is better than ±0.04 mm, and the adjustment time is less than 80 ms. These results prove that the system can accurately stabilize the beam to specified pointing and position..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 908004 (2012)
Temperature Variable Time-of-Flight Measurement Technique Applied on Carrier Mobility in Conducting Polymer
Zhang Yating, Xu Zhangcheng, and Yao Jianquan
Carrier mobility is an important factor in conjugated polymer opto-electronic devices. Its value is much smaller than that of semiconductor material, so time-of-flight (TOF) is often used to measure it. By setting up a temperature variable TOF detection system, the carrier mobility in polymer can be accurately measuredCarrier mobility is an important factor in conjugated polymer opto-electronic devices. Its value is much smaller than that of semiconductor material, so time-of-flight (TOF) is often used to measure it. By setting up a temperature variable TOF detection system, the carrier mobility in polymer can be accurately measured. In principle and practice, some of the key factors affecting the accuracy of test are discussed, including the limit in the number of optical generated carrier, film thickness, pulse width, the external circuit response time, carrier relaxation period in a dielectric, as well as frequency of amplifier and detector. The accurate and reliable results can be achieved only when experimental parameters are selected appropriately..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 908005 (2012)
Elimination of the Nonlinearity of Heterodyne Displacement Interferometers
Hou Wenmei, Zhang Yunbo, Le Yanfen, and Ju Aisong
The heterodyne laser interferometer can achieve a sub-nanometer resolution on the basis of a stable subdivision of the light wavelength using phase measurement. However, due to inevitable imperfectness in optical system, a phase error occurs in the measurement signal and results in a nonlinear relation between the measThe heterodyne laser interferometer can achieve a sub-nanometer resolution on the basis of a stable subdivision of the light wavelength using phase measurement. However, due to inevitable imperfectness in optical system, a phase error occurs in the measurement signal and results in a nonlinear relation between the measured phase difference and the respective displacement. Based on the optical phase compensation theory, a significant approach is found to eliminate the nonlinearity of laser interferometer. This method can be used in most science researches and the industry precision nanometer measurement, and it is valid for nonlinearity errors whether it is a one-order or a two-order error..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 908006 (2012)
Optical Communication
Optical Characteristic Parameters of Gradient-Index Fiber Probe
Wang Chi, Bi Shubo, Ding Wei, Yu Yingjie, and Ouyang Hangkong
In order to investigate miniaturized probes for optical coherence tomography (OCT) imaging, the optical characteristic parameters of the gradient-index (GRIN) fiber probe are analyzed. The model of GRIN fiber probe is overviewed that consists of a single-mode fiber, a coreless fiber and a GRIN fiber len. The optical chIn order to investigate miniaturized probes for optical coherence tomography (OCT) imaging, the optical characteristic parameters of the gradient-index (GRIN) fiber probe are analyzed. The model of GRIN fiber probe is overviewed that consists of a single-mode fiber, a coreless fiber and a GRIN fiber len. The optical characteristic parameters (working distance, and focal spot size) of the probe are defined and solved by the complex beam parameter matrix transformation method. A method is proposed to validate the characteristic parameters experimentally. The results show that, setting the length of the coreless-fiber 0.48 mm and the length of the GRIN fiber len 0.17 mm respectively, the theoretical working distance and focal spot size are 1.05 mm and 28.2 μm accordingly. Given the same conditions, the experimental measured working distance and focal spot size are 1.0 mm and 28 μm respectively. Therefore, the theoretical values are in good agreement with the measured data, which validate the proposed optical characteristic parameters of GRIN fiber probe..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 905001 (2012)
Analysis of Repeater for Time and Frequency Dissemination via Optical Fiber
Hua Yun, Gui Youzhen, Yang Fei, and Cai Haiwen
Based on the theoretical analysis of cascaded optical fiber time and frequency dissemination system, the general formula of total time jitter is calculated. A two-stages optical fiber link for ultra-stable frequency dissemination with a total fiber length of 2×50 km is demonstrated. Then the phase error voltage anBased on the theoretical analysis of cascaded optical fiber time and frequency dissemination system, the general formula of total time jitter is calculated. A two-stages optical fiber link for ultra-stable frequency dissemination with a total fiber length of 2×50 km is demonstrated. Then the phase error voltage and time jitter of single-stage and two-stage systems in closed-loop is measured. After comparing experimental results and theoretical calculation, the main sources of experimental error is analyzed. Analyze the impact of phase noise on signal to noise ratio (SNR), which the phase noise is caused by the amplified spontaneous emission (ASE) of the erbium-doped fiber amplifier (EDFA). The stability of transfer system is gotten due to the decline of signal to noise ratio (SNR)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 905002 (2012)
Simultaneous Measurement of Temperature and Refraction Index Based on Multimode Interference and Long-Period Fiber Grating
Wang Jieyu, Tong Zhengrong, Yang Xiufeng, and Cao Ye
Based on the multimode interference theory and the sensing characteristics of long-period fiber grating (LPFG), a fiber-optic sensor composed of a single mode fiber (SMF)-multimode fiber (MMF)-SMF (SMS) structure and a LPFG is proposed for simultaneous measurement of temperature and refractive index. The experimental rBased on the multimode interference theory and the sensing characteristics of long-period fiber grating (LPFG), a fiber-optic sensor composed of a single mode fiber (SMF)-multimode fiber (MMF)-SMF (SMS) structure and a LPFG is proposed for simultaneous measurement of temperature and refractive index. The experimental results show that the interference spectrum of SMS structure and LPFG have different response sensitivities to temperature and refraction index, and the temperature sensitivity coefficients are 0.017 nm/℃ and 0.060 nm/℃, respectively. The SMS structure is insensitive to refractive index while the refractive index sensitivity coefficient of LPFG is -35.60 nm/RIU. Using the sensitivity matrix, simultaneous measurement of temperature and refractive index is realized. The maximum measurement errors of temperature and refraction index are ±0.59 ℃ and ±0.0013, respectively. With the advantages of high sensitivity, simple structure, immunity to electromagnetic interferences and good linearity, the structure has a excellent application prospect in biochemistry field..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 905003 (2012)
Application in Secret Communication of Chaos Driving Synchronization of Vertical Cavity Surface Emitting Lasers with Optical Feedback
Liu Yujin, Zhang Shenghai, Yang Hua, and Tan Jianfeng
Based on the chaos driving synchronization of vertical cavity surface emitting lasers (VCSELs) with optical feedback, the chaotic secure communication system of VCSELs with optical feedback is designed. Through the realizations of simulation signal and digital signal in the chaotic secure communication system, the feasBased on the chaos driving synchronization of vertical cavity surface emitting lasers (VCSELs) with optical feedback, the chaotic secure communication system of VCSELs with optical feedback is designed. Through the realizations of simulation signal and digital signal in the chaotic secure communication system, the feasibility of this system is verified. Besides, the secret communications of text and digital image can be well achieved by this scheme. Furthermore, the difference of image grey value between their histograms of encryption image and decryption image is calculated. Numerical simulation results show that the secret communication system has a good decryption effect..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 905004 (2012)
Least Mean Square Adaptive Algorithm for Direct-Detection Optical Orthogonal Frequency Division Multiplexing Transmission System
Liu Binhui, Chen Lin, and Xiao Jiangnan
In order to overcome the defects of least squares (LS) estimator used to defend chromatic dispersion in the direct-detection (DD) optical orthogonal frequency division multiplexing (OOFDM) transmission system, an adaptive least mean square (LMS) estimator is presented owing to its brief calculation and easy signal blocIn order to overcome the defects of least squares (LS) estimator used to defend chromatic dispersion in the direct-detection (DD) optical orthogonal frequency division multiplexing (OOFDM) transmission system, an adaptive least mean square (LMS) estimator is presented owing to its brief calculation and easy signal block processing. The performance of the proposed estimator is evaluated in an experimental system with 2.5 Gb/s DD-OOFDM signal at back-to-back (BTB) and transmitting over 100 km standard single mode fiber (SSMF). The experimental results show that the power penalty of system using LMS equalizer is 2 dB less at 10×10-2.5 bit error rate (BER) and 2.5 dB less at 10×10-2.0 BER than using LS equalizer when the OFDM signals transmitted by BTB and 100 km SSMF. It is proved that the system using LMS equalizer has a better performance to restore signals than using LS equalizer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 905005 (2012)
Magnetic Sensitivity Studies of Fiber Optic Gyroscope in Direct Current and Alternating Current Magnetic Fields
Tan Xi, Liu Jun, Yin Jianling, and Yu Weitao
The mechanism of the magnetic sensitivity of fiber optic gyroscope (FOG) is introduced and experimental study is done. The Helmholtz coils equipment and FOG test platform is utilized, the magnetic sensitivity of FOG in direct current (DC) magnetic field is studied, and the linear relation of FOG data output and the magThe mechanism of the magnetic sensitivity of fiber optic gyroscope (FOG) is introduced and experimental study is done. The Helmholtz coils equipment and FOG test platform is utilized, the magnetic sensitivity of FOG in direct current (DC) magnetic field is studied, and the linear relation of FOG data output and the magnetic flux density is found. Axial magnetic field and radial magnetic field influence coefficients and the orientation of the magnetic sensitivity axis of FOG are also found. Then the influence on FOG bias and bias stability and the alternating current (AC) magnetic field sensitivity in 50 Hz AC magnetic field are mainly analyzed, finding that the influence of AC magnetic field on the bias can be neglected, but the magnetic flux density and the size of FOG bias stability are almost linear relation. Finally the influence of different frequency AC magnetic fields on the FOG data output is studied, indicating that the data output of FOG is mainly proportional to the transient magnetic flux density, different frequency AC magnetic fields have different influences on the bias of FOG. There is a frequency (or frequency range) with much stronger influence on the bias of FOG, which is related to FOG output bandwidth..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 905006 (2012)
Multi-Area Perimeter Sensing System Based on Optical Fiber Wavelength Division Multiplexing Technology
Dong Xiaopeng, and Zheng Junda
A new multi-area perimeter sensing system based on optical fiber wavelength division multiplexing (WDM) technology is proposed and demonstrated. The traditional single channel system with broadband mirror is improved by introducing fiber Bragg grating (FBG) as the mirror, and the number of the monitoring areas is expanA new multi-area perimeter sensing system based on optical fiber wavelength division multiplexing (WDM) technology is proposed and demonstrated. The traditional single channel system with broadband mirror is improved by introducing fiber Bragg grating (FBG) as the mirror, and the number of the monitoring areas is expanded by using the FBG with different reflecting wavelengths matching the demodulation channels of a WDM apparatus. The WDM and FBG technology employed in the system makes the measurement in each channel independent, simultaneous, no mutual-interfering between channels sharing the same interference device. The experimental results show that the proposed perimeter sensing system is able to detect and recognize the perturbation localization simultaneously in each area or channel. The response time of the system is less than 1 ms, and crosstalk between channels is less than -20 dB..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 905007 (2012)
Return-to-Zero/Nonreturn-to-Zero Signal Data Format Conversion Based on Microwave Photonic Filter
Xu Jing, Jiang Yang, Zhou Zhuya, Li Hengwen, and Wang Shunyan
From the view of signal processing in the frequency domain, a scheme for the return-to-zero (RZ) to nonreturn-to-zero (NRZ) signal data format conversion based on a tunable microwave photonic filter is analyzed and demonstrated. Theoretically, the spectral characteristics of RZ and NRZ baseband signals and microwave phFrom the view of signal processing in the frequency domain, a scheme for the return-to-zero (RZ) to nonreturn-to-zero (NRZ) signal data format conversion based on a tunable microwave photonic filter is analyzed and demonstrated. Theoretically, the spectral characteristics of RZ and NRZ baseband signals and microwave photonic filter characteristics are analyzed. It is found that RZ to NRZ data format conversion can be successfully realized by a low-pass filter on the RZ signal with strong suppressing the clock component of the RZ data. In the experimental demonstration, a 10 Gbit/s NRZ signal is successfully converted from a RZ signal by utilizing an two-tap microwave photonic filter with two different light sources and intensity modulation. Both waveform and spectrum show the signal has good quality. In addition, signals with various repetition rate can be well processed by simply adjusting some parameters of the filter. It is shown that this scheme is very simple and flexible..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 905008 (2012)
Optical Design and Fabrication
Design of Waveguide Head-Up Display with Embedded Gratings
Meng You, Zhanhua Huang, and and Huaiyu
The embedded grating is applied in the waveguide head-up display. As an incident and exit coupling grating, it can satisfy the highly efficient and uniform display for large field of view (FOV) based on rigorous coupled wave analysis (RCWA). Compared with holograms in previous designs, it can be easily duplicated with The embedded grating is applied in the waveguide head-up display. As an incident and exit coupling grating, it can satisfy the highly efficient and uniform display for large field of view (FOV) based on rigorous coupled wave analysis (RCWA). Compared with holograms in previous designs, it can be easily duplicated with high reliability and low costs. The total internal reflection condition is discussed in the plate, and the revolving problems are discussed in the rod. The system is simulated in software with good optical performance: 50-mm exit pupil, a 30° × 20° FOV, distortion of less than 0.5%, and low aberration. The results are useful for transparent display in vehicles or wearable helmets..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 916001 (2012)
[in Chinese]
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 9, 916002 (2012)
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