Journals >Chinese Journal of Lasers
Contents
2008
Volume: 35 Issue 9
27 Article(s)
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Research Article
Characteristics of Intracavity-Frequency-Doubled Nd3+∶GdVO4/LBO Deep Blue 456 nm Laser
Li Yimin, Tan Huiming, Fu Xihong, Tian Yubing, Wang Baoshan, and Meng Yuqing
In the experiment of laser diode (LD) pumped intracavity frequency doubled Nd∶GdVO4/LBO deep blue 456 nm laser, in order to examine the effect of different neodymium concentrations in laser crystal on output power of frequency-doubled laser, two Nd∶GdVO4 crystals with the same size of 3 mm×3 mm×2 mm and diffeIn the experiment of laser diode (LD) pumped intracavity frequency doubled Nd∶GdVO4/LBO deep blue 456 nm laser, in order to examine the effect of different neodymium concentrations in laser crystal on output power of frequency-doubled laser, two Nd∶GdVO4 crystals with the same size of 3 mm×3 mm×2 mm and different neodymium concentrations with Nd3+ ion atom fraction of 15% and 25% are compared. In the experiment , the same length of laser cavity of 20 mm and an Ⅰ-type phase-matched frequency-duobled medium of LBO for 914 nm with the length of 10 mm were used, a output power of 105 mW was obtained at incident pumped power of 2.85 W in the former crystal. In experiment, the laser crystal with higher dopant concentration obtained lower output power relative to that with lower dopant concentration. Through analyzing optimal crystal length in quasi-three-level laser system, the actual length of the 15% Nd3+ doped crystal is closer to the optimal length compared with the other crystal. Through analyzing the accurate cut-angle of frequency-doubled medium and temperature control of LBO, the difference of cut-angle for 912 nm and 914 nm may be compensated by controlling the temperature..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1308 (2008)
High Peak Power Lamp-Pumped Pulsed Nd∶YAG Solid-State Laser with One Cavity
Liu Xuesheng, Xia Jiaozhen, Yan Xing, Hu Yue, Yao Shun, Cao Yinhua, and Wang Zhiyong
The experiment results of high peak power lamp-pumped pulsed Nd∶YAG laser adopting symmetrical parallel plane cavity are reported. Base on the rate equation, the expression of single pulse energy of pulsed Nd∶YAG solid-state laser is derived with the simulated optimum transmissivity and maximum output energy. The optimThe experiment results of high peak power lamp-pumped pulsed Nd∶YAG laser adopting symmetrical parallel plane cavity are reported. Base on the rate equation, the expression of single pulse energy of pulsed Nd∶YAG solid-state laser is derived with the simulated optimum transmissivity and maximum output energy. The optimal parameters are obtained by the experiments, and a high peak power lamp-pumped pulsed Nd∶YAG laser is developed with the results of theory simulating and optimal experiments being consistent with each other. When the laser works under 800 V voltage, 2 ms pulse width, it outputs laser with energy of 60 J, high peak power of 30 kW with beam quality M2=5.9, and the total electro-optic efficiency of 3.3%. When it works under 800 V voltage, 1.5 ms pulse width, the maximum output average power is 405 W. The 6 mm mild steel and 4 mm stainless steel were cut by the laser with the 2 ms pulse width, 6 Hz frequency and 30 kW peak power. The cutting speed for 4 mm stainless and 6 mm mild steel is 1 mm/s and 1.5～2 mm/s, respectively..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1313 (2008)
Single Mode Operation of an Injection Locked Fabry-Perot Laser
Han Wei, Zhang Yali, Zhang Yan, Ren Min, Li Liang, Zhang Hongguang, Xie Liang, and Zhu Ninghua
A Fabry-Perot (F-P) semiconductor laser (FP-LD) was single mode injection locked by a distributed feedback semiconductor laser (DFB-LD). The characteristics of optical spectrum, output power and frequency response were investigated by adjusting the bias current of the FP-LD, the output of the DFB-LD and the wavelength A Fabry-Perot (F-P) semiconductor laser (FP-LD) was single mode injection locked by a distributed feedback semiconductor laser (DFB-LD). The characteristics of optical spectrum, output power and frequency response were investigated by adjusting the bias current of the FP-LD, the output of the DFB-LD and the wavelength detuning between the master and the slave laser. The factors that affect the stability of injection locked FP-LD were analyzed. The stable range of injection locking was given. By optimizing the injection conditions, the side mode suppress ratio (SMSR) of the injection locked FP-LD as high as 55 dB was demonstrated. Comparing with the free running FP-LD, the injection locking technique can suppress the spread of the spectrum under high speed modulation. The 3 dB tuning bandwidth of 14 GHz was achieved. The results indicate that with injection locking the characteristic of optical spectrum and frequency response can be improved, by which the FP-LD can apply to the high speed fiber communication system..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1318 (2008)
High Power Laser Diode Array with 60% Electro-Optical Efficiency
Wang Jun, Bai Yiming, Chong Feng, Liu Yuanyuan, Feng Xiaoming, Wang Yonggang, Zhang Guangze, Liu Suping, and Ma Xiaoyu
The epitaxy material and device for high quantum efficiency and small optical loss 980 nm laser diode (LD) were designed and fabricated. The maximal electro-optical conversion efficiency of the standard 1cm laser bar with micro-channel cooler is 60.0% under continuous-wave (CW) working condition, the corresponding slopThe epitaxy material and device for high quantum efficiency and small optical loss 980 nm laser diode (LD) were designed and fabricated. The maximal electro-optical conversion efficiency of the standard 1cm laser bar with micro-channel cooler is 60.0% under continuous-wave (CW) working condition, the corresponding slope efficiency and output power are 1.1 W/A and 38.2 W, respectively. The measured internal loss coefficient and internal quantum efficiency are 0.58 cm-1 and 91.6%, respectively. The result shows that the improvement of electro-optical conversion efficiency is due to new InGaAs/GaAsP strain-compensated quantum well and the large optical-cavity waveguide structure..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1323 (2008)
Calculation and Experiment of Spectral Sideband Offset in Ring Cavity Fiber Laser by Nonlinear Polarization Rotation
Feng Jie, Xu Wencheng, Ye Hui, Liu Weici, Luo Zhichao, Song Chuangxing, and Liu Songhao
The dynamic equations which describe the pulse nonlinear polarization rotation (NPR) of nonlinear birefringence in ring cavity fiber laser were given. The theoretical formulae of spectrum sideband offset which stems from the interference between the dispersion wave and the soliton wave are deduced in ring cavity fiber The dynamic equations which describe the pulse nonlinear polarization rotation (NPR) of nonlinear birefringence in ring cavity fiber laser were given. The theoretical formulae of spectrum sideband offset which stems from the interference between the dispersion wave and the soliton wave are deduced in ring cavity fiber laser passively mode-locked by the nonlinear polarization rotation technique. Theoretical spectral sideband offsets are consistent with experimental results very well in the paper. And the maximal error is less than 4.1%, which explains the sideband offset in ring cavity fiber laser under passive mode-locking by NPR..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1333 (2008)
Simplified X-Ray Diode and Its Performance Measurement
Cheng Yuanli, Zhu Qiushi, Huang Bin, Zhao Yongpeng, and Wang Qi
We designed a simplified X-ray diode (XRD) to detect soft X-ray emission, which has advantages of simplified structure, bigger response area, and lower requirements for bias voltage and vacuum level. The response time and saturation current were analyzed. Meanwhile, the formula to calculate the energy was established aWe designed a simplified X-ray diode (XRD) to detect soft X-ray emission, which has advantages of simplified structure, bigger response area, and lower requirements for bias voltage and vacuum level. The response time and saturation current were analyzed. Meanwhile, the formula to calculate the energy was established and the XRD was calibrated at synchrotron radiation source. The energy calibration result matches the theoretical calculation one. With this XRD, we measured the pulse width and energy of discharged-pumped Ne-like Ar soft X-ray laser of 46.9 nm..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1338 (2008)
Effect of Flow Field Characteristics in Liquid Laser System on Thermally Induced Distortion
Yuan Yongke, Xu Zheng, Li Mi, Yan Feng, Zhang Wei, and Su Yi
Circulation system of liquid laser medium provides an effective method of eliminating thermal effect and improving laser beam quality. Based on turbulent flow field characteristic of this laser medium and numerical simulation using software Fluent6.53, the relationship between flow velocity, turbulent intensity, boundaCirculation system of liquid laser medium provides an effective method of eliminating thermal effect and improving laser beam quality. Based on turbulent flow field characteristic of this laser medium and numerical simulation using software Fluent6.53, the relationship between flow velocity, turbulent intensity, boundary layer thickness and temperature gradient has been investigated, which affects on thermally induced distortion. Increasing velocity of laser medium in the cell would reduce thermally induced distortion and boundary layer thickness. Setting proper aperture under current conditions can also further reduce the distortion. The maximum optical path difference decreases from 10 wavelengths to 5 wavelengths at the flow velocity of 20 m/s by setting aperture..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1342 (2008)
Junction Voltage Saturation and Quality of High Power Semiconductor Lasers
Shi Jiawei, Liang Qingcheng, Cao Junsheng, Liu Kuixue, Guo Shuxu, Li Hongyan, and Hu Guijun
To distinguish the different reliability and quality of the high power laser diodes facilely, efficiently and nondestructively, some high power laser diode devices were measured and studied with electrical and optical derivative techniques. The results show that the value of junction voltage saturation is a valuable paTo distinguish the different reliability and quality of the high power laser diodes facilely, efficiently and nondestructively, some high power laser diode devices were measured and studied with electrical and optical derivative techniques. The results show that the value of junction voltage saturation is a valuable parameter. It closely relates with the quality and reliability of the high power semiconductor laser. The devices with poor junction voltage saturation have so certain defect. For a certain kind of devices, the values of junction voltage saturation are in a certain range. And the device with the values overstepping the range is an unqualified device. Thus, the h value of the dip at the threshold is a valuable parameter to judge the device quality. Furthermore, the laser diode array simulated with shunt-wound laser diodes was measured. The relation between cells which compose array laser and array laser itself was studied. The results show that the junction voltage saturation of the laser diode array is correlated closely with the uniformity of its cells. If the uniformity of the cells composing the laser diode array was bad, the laser diode array itself is sure to have poor junction voltage saturation..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1346 (2008)
Fabrication and Study on the Small-Core Index-Guiding Photonic Crystal Fiber
Meng Jia, Hou Lantian, Zhou Guiyao, Gao Fei, and Mi Yan
A way of fabricating a small-core index-guiding photonic crystal fiber (PCF) is introduced. The first ring of the air holes around the core is deformed, the shape of which is similar to the grapefruit, and the diameter of the core is 1.7 μm; the pitch and diameter of the air hole are 3.4 μm and 2.8 μm, respectively. BeA way of fabricating a small-core index-guiding photonic crystal fiber (PCF) is introduced. The first ring of the air holes around the core is deformed, the shape of which is similar to the grapefruit, and the diameter of the core is 1.7 μm; the pitch and diameter of the air hole are 3.4 μm and 2.8 μm, respectively. Because of the special structure of the fiber, the effective refractive indices, dispersion coefficients of the fundamental modes, effective areas and nonlinear coefficients of the fiber are calculated by finite element method from 200 nm to 1600 nm. The results show that, in this wavelength range, the nonlinear coefficients of this fiber are extremely high and dispersion coefficients are positive. These characteristics are of benefit to the supercontinuum generating. After measuring the dispersion and loss properties of the fiber, the laser operating wavelength in 800 nm is chosen to be the light source because the loss in this wavelength is lower and the central wavelength of the pulse is in the range of abnormal dispersion. The femtosecond pulses with different powers are coupled into this small-core index-guiding photonic crystal fiber. The supercontinuum generating in the fiber is detected and analyzed..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1350 (2008)
Analysis and Design of Refractive-Index and Dopant Distributions for Large-Mode-Area Fibers
Yuan Yanyang, and Gong Mali
Based on the mode field theory of passive fiber and rate equation of active fiber, the calculative method of effective mode area and extraction efficiency of fundamental mode for large mode area fibers with arbitrary refractive-index profile and dopant distribution of is presented. The performance of various designs foBased on the mode field theory of passive fiber and rate equation of active fiber, the calculative method of effective mode area and extraction efficiency of fundamental mode for large mode area fibers with arbitrary refractive-index profile and dopant distribution of is presented. The performance of various designs for the core refractive-index and dopant distributions of large-mode-area fibers are numerically simulated and compared. The analysis shows that the hybrid profile fiber exhibits better overall performance than other traditional fibers in the design of large-mode-area fibers with core diameter of hundreds of microns..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1355 (2008)
Biomedical Photonics and Laser Medicine
Ophthalmic Imaging by Optical Coherence Tomography
Shi Guohua, Ding Zhihua, Dai Yun, Rao Xuejun, and Zhang Yudong
Single-mode fiber-designed optical coherence tomography (OCT) system is developed and applied in ophthalmic imaging. Images with high signal-to-noise ratio, high resolution and large image depth, are achieved by the developed system. The calibrated axial resolution and transversal resolution are 9 μm and 10 μm, respectSingle-mode fiber-designed optical coherence tomography (OCT) system is developed and applied in ophthalmic imaging. Images with high signal-to-noise ratio, high resolution and large image depth, are achieved by the developed system. The calibrated axial resolution and transversal resolution are 9 μm and 10 μm, respectively, and the maximum depth range is 3.4 mm. Comparison between experimental results and Zeiss OCT Ⅲ are presented. The results show that the proposes OCT system can image not only the layers of retina , but also the layers and vas of choroid which cannot be obtained by Zeiss OCT Ⅲ..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1429 (2008)
Micro-Raman Spectroscopy of the Interaction between Sodium Nitrite and Oxyhemoglobin
Shen Gaoshan, Gu Huaimin, Yan Tianxiu, and Wei Huajiang
To explore a new method to dignose methemoglobin, micro-Raman spectroscopy was used to investigate the interaction of sodium nitrite and oxyhemoglobin in aqueous solution, with 514.5 nm exitation. Hemoglobin was obtained from the healthy adult. The results show that the inensity ratio of the oxyhemoglobin marker band 5To explore a new method to dignose methemoglobin, micro-Raman spectroscopy was used to investigate the interaction of sodium nitrite and oxyhemoglobin in aqueous solution, with 514.5 nm exitation. Hemoglobin was obtained from the healthy adult. The results show that the inensity ratio of the oxyhemoglobin marker band 570 cm-1 to the aquomethemoglobin marker band 495 cm-1, and that of low spin state marker band 1586 cm-1 to the high spin state marker band 1555 cm-1 decrease during the interaction. The bands sensitive to the oxidation state shift to higher frequency. This work indicates that micro-Raman spectroscopy could monitor the bioeffects of sodium nitrite on the oxyhemoglobin, and distinguish hemoglobin and aquomethemoglobin. As a new method to detect methemoglobin, micro-Raman spectroscopy may have great potential applications in the diagnosis of methemoglobinemia..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1432 (2008)
Speckle Reduction in Optical Coherence Tomography
Shen Tingmei, Gu Ying, Wang Tianshi, and Ma Guojiang
Speckle noise significantly limits the information content extraction provided by optical coherence tomography (OCT). Therefore speckle reduction is an important issue in OCT imaging. Using a method of regularization by minimizing Csiszar’s I-divergence, we derive a method of speckle minimization. This method can not oSpeckle noise significantly limits the information content extraction provided by optical coherence tomography (OCT). Therefore speckle reduction is an important issue in OCT imaging. Using a method of regularization by minimizing Csiszar’s I-divergence, we derive a method of speckle minimization. This method can not only produce an image data that is consistent with the known data but also extrapolate additional detail. This algorithm is used to process the OCT image of the human finger. The results show that this method of speckle minimization can significantly reduce speckle and increase the signal-to-noise ratio, while preserve edge sharpness..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1437 (2008)
Laser Manufacturing
Microstructure and Performance of Laser Remelting Ni-Based Alloy Sprayed-Welding Layers
Hong Yongchang
Ni-based alloy flame sprayed-welding layers refusioned under different laser processing parameters, microstructure and phase identity in different temperature drawing temper were investigated using optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The hardness test and wear resNi-based alloy flame sprayed-welding layers refusioned under different laser processing parameters, microstructure and phase identity in different temperature drawing temper were investigated using optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The hardness test and wear resistance were also performed. The experimental results show that the phases of the remelted flame sprayed-welding layers mainly consist of γ-(Ni,Fe), Cr23C6, Cr7C3, Cr2B, CrB, Cr5B3, Fe3B and Fe2B. Compared with the flame sprayed-welding layers, microstructure of the remelted sprayed-welding layers are further refined, hardness and wear resistance are obviously enhanced. Under the same technological conditions, microstructure would be more compacted and finer, hardness and wear resistance would be higher with the quicker laser scanning speed, but the penetration of the remelted sprayed-welding layers is relatively shallower. The hardness of the remelted sprayed-welding layers after different temperature drawing temper is increased furtherly and the hardness of the remelted sprayed-welding layers after drawing temper of 600 ℃×3 h with the scanning speed of 360 mm/min is the highest. It indicates that adopting appropriate laser refusioning treating technology and subsequently heat treatment, Ni-based alloy flame sprayed-welding layers would be further strengthened and service performance would be further improved..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1388 (2008)
Laser Alloying of Magnesium Alloy AZ91D with Al-Si Powder and Its Corrosion Performance
Li Da, Qian Ming, Jin Chang, and Li Hui
Laser alloying of magnesium alloy AZ91D with direct Al-Si power feeding for improvement of corrosion resistance was investigated. The relationship between laser alloying parameters and dimensions of alloyed layers was studied. The microstructural features of the alloyed layer were characterized by using scanning electrLaser alloying of magnesium alloy AZ91D with direct Al-Si power feeding for improvement of corrosion resistance was investigated. The relationship between laser alloying parameters and dimensions of alloyed layers was studied. The microstructural features of the alloyed layer were characterized by using scanning electronic microscope (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD). Anodic polarization test was applied to evaluate the corrosion performance of AZ91D alloyed layer, which yielded enhanced corrosion resistance. The contribution of the intermetallic compounds (IMCs) of Mg2Si, Al12Mg17, Al3Mg2 in alloyed layers to corrosion resistance was studied..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1395 (2008)
Theory Analysis and Experiment Verification on Crack Characters during Laser Processing Ceramics
Yan Yinzhou, Ji Lingfei, Bao Yong, and Jiang Yijian
A thermal-stress field of laser drilling ceramic is calculated by building a two-dimensional (2D) thermal field model. Two types of cracks during pulsed laser drilling are predicted. One is along radial direction, and the other is along tangent direction. Further more, spreading characteristics of two types of cracks, A thermal-stress field of laser drilling ceramic is calculated by building a two-dimensional (2D) thermal field model. Two types of cracks during pulsed laser drilling are predicted. One is along radial direction, and the other is along tangent direction. Further more, spreading characteristics of two types of cracks, emanative and regressive, during pulsed laser cutting are analyzed and predicted. It is concluded that the restraint of cracks can be achieved by reducing temperature of processing point, decreasing size of heat affected zone and increasing hole diameter (or kerf width). Based on analyzing parameters of the theoretical model, relationships between model parameters and processing parameters are discussed. It is proposed that optimizing laser processing parameters should depend on lower duty cycle, higher gas pressure and focal position outside the workpiece. The prediction results of crack formation and spread analyzed by the mathematic model are accordant with the experimental results of laser drilling and cutting of alumina ceramic and single-crystal silicon. Laser crack-free processing of ceramics is achieved by optimizing laser processing parameters based on the theoretical model..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1401 (2008)
Application of Laser Scanning Confocal Microscopy in Roughness Characterization of Worn Surface
Sun Dale, Wu Qiong, Liu Changsheng, Zhang Heng, and Yao Lisong
Wear is the most frequently surface failure of the materials, and roughness is the most commonly used parameter to describe the characteristics of the worn surface numerically. Laser scanning confocal microscopy (LSCM) was used to get the image of wron surface topography by adjusting the objective lens and measuring fiWear is the most frequently surface failure of the materials, and roughness is the most commonly used parameter to describe the characteristics of the worn surface numerically. Laser scanning confocal microscopy (LSCM) was used to get the image of wron surface topography by adjusting the objective lens and measuring field of view and filter parameters, the accurate numerical description of the three-dimensional (3D) worn surface was obtained at the same time. For commonly roughness value between 0.5 and 2.0 μm, the 20× lens is the best choice, while for the larger or smaller roughness value, 10× and 50× lens should be used, respectively. For regular worn surface, the accurate roughness value can be obtained within 1 to 3 combined optical field, while for the irregular one, the combined number of optical field should be 3 to 5 or more. Based on this method, the worn surface topography of a Cr5 cold roll was well analyzed in different wear patterns..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1409 (2008)
Analysis of Smog Total Obscure Power on Visible Light Based on Laser Transmission Model
Wang Yingli, Liu Xiaodong, and Dai Jingmin
Based on the smog full-screening detection system, the total obscure power of normal yellow phosphorus smog in 0.38～0.76 μm visual band was measured, and the variation of the smog grain size with time was also measured with granulometry. According to laser transmission model, a total obscure power (TOP) theoretical calBased on the smog full-screening detection system, the total obscure power of normal yellow phosphorus smog in 0.38～0.76 μm visual band was measured, and the variation of the smog grain size with time was also measured with granulometry. According to laser transmission model, a total obscure power (TOP) theoretical calculation mode was established under the condition of single-decentralization spherical particle. With the mode, the TOP values of various grain size yellow phosphorus smog with absorption index were deduced, and the theoretical calculation results were agreement with the experimental results. According to the experimental results, under a middle humidity and room temperature, the particle diameters were about 0.5～3 μm and gradually decreased after forming the smoke for 10～30 s, and the TOP values reduced with the diameter decrement..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1415 (2008)
Cramer-Rao Lower Bounds of Parameter Estimation from Laser Doppler Velocimetry
Wang Jiqiang, Zhang Chunxi, Ma Zongfeng, Ou Pan, and Zhang Xiaoqing
Aiming at the high-speed and high-acceleration features of solid moving targets, the parameter estimation of laser Doppler velocimetry echo signal under white Gaussian noise were investigated. By computing the Fisher information metrix of parameter vectors, Cramer-Rao low bounds (CRLBs) of the real echo signal Doppler Aiming at the high-speed and high-acceleration features of solid moving targets, the parameter estimation of laser Doppler velocimetry echo signal under white Gaussian noise were investigated. By computing the Fisher information metrix of parameter vectors, Cramer-Rao low bounds (CRLBs) of the real echo signal Doppler frequency and frequency rate were analyzed, formulas of the CRLBs were derived when the length of sample data was large, and the maximum likelihood estimator (MLE) was discussed. The CRLBs of the variance of estimated parameter of the real echo signal are affected by the length of sample data, signal to noise ratio (SNR), and the initial phase. When the length of sample data is large, the CRLBs of the variance of estimated parameter are twice of the corresponding complex signal. The simulations under conditions of different lengths of sample data and different SNR indicate that increasing the length of sample data and SNR can minish CRLBs of the variance of estimated parameter, and the results fit well with theoretical analysis..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1419 (2008)
Theoretical Analysis and Testing Research of Stress-Strain of Coating Scratched by Infrared Laser
Yin Sumin, Ye Yong, Feng Aixin, and Cheng Chang
To research the relationship among the thermal-stress , strain and interfacial adhesion strength of coating. Thermal-stress and strain of coating were theoretically analyzed, and theoretical model of coating’s thermal-stress and strain formulas were established. The infrared-laser scratch testing indicates that there iTo research the relationship among the thermal-stress , strain and interfacial adhesion strength of coating. Thermal-stress and strain of coating were theoretically analyzed, and theoretical model of coating’s thermal-stress and strain formulas were established. The infrared-laser scratch testing indicates that there is an evident break process along the thickness of coating after it was scratched by infrared laser and the position of break point is the critical location where the coating is broken off from substrate. The research results also show that the separate-stress of coating becomes stronger with the coating’s temperature increasing when the coating is scratched by infrared laser. And the separate-stress presentes two-phase process, which further illuminates that the turning point of two-phase process reflects the interfacial adhesion strength of coating..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1423 (2008)
Materials and Thin Films
Effect of Vacuum on Preparation and Optical and Electrical Properties of VO2(B) Film
Liu Zhonghua, He Jie, Meng Qingkai, Zhang Lei, Song Tingting, and Sun Peng
The structure, valence, electrical properties and optical properties of the VO2(B) thin films are analysed and measured to study the effect of annealing vacuum on the thin films. The VO2 thin films are deposited by vacuum-evaporation technology using the V2O5 powder (purity≥99.99%, in mass) as raw material. The V2O5 thThe structure, valence, electrical properties and optical properties of the VO2(B) thin films are analysed and measured to study the effect of annealing vacuum on the thin films. The VO2 thin films are deposited by vacuum-evaporation technology using the V2O5 powder (purity≥99.99%, in mass) as raw material. The V2O5 thin films are annealed at high and low vacuum in the vacuum coating machine, respectively. The space group of the obtained VO2(B) thin films is C2/m. The thin films are measured by X-ray diffraction (XRD), X-ray photo-electron spectrum (XPS), temperature coefficient resistance (TCR) instrument and ultraviolet-visible spectrophotometer. The results suggest that the temperature range of the VO2(B) thin films gained is different. The range is from 400 ℃ to 480 ℃ when the film is annealed in low vacuum, and it was only from 400 ℃ to 440 ℃ when the film is annealed in high vacuum. The crystal sizes change bigger and the transmission of the thin films annealed in the high vacuum is 7%～8% bigger than that annealed in low vacuum, but the vanadium’s valence of the thin films are lower and the TCR’s absolute value of the films are bigger which is up to -2.4%/K when annealed in low vacuum..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1370 (2008)
Design and Research of Facular-Shaping on the Angle-Tuned Filter
Yu Kan, Liu Wen, Huang Dexiu, Chang Jin, and Huang Huamao
In testing the 100 GHz dense wavelength division multiplexer (DWDM) angle-tuned filter with low polarization dependent loss, the insertion loss and bandwidth broadening of the transmission optical spectrum will become more and more serious as the increase of incident angle. It is not coincide with the theoretical desigIn testing the 100 GHz dense wavelength division multiplexer (DWDM) angle-tuned filter with low polarization dependent loss, the insertion loss and bandwidth broadening of the transmission optical spectrum will become more and more serious as the increase of incident angle. It is not coincide with the theoretical design. According to the theory of the multiple-beam interference, the theoretical analysis model is built up and simulated. The simulation results show that the transmission facular of the thin film filter will broaden obviously. It cause a serious spectrum distortion because the collimator at the incepting port cannot collect all the output beams. According to the analysis results, one kind of facular-shaping fitting used the upright angle prisms is designed and fabricated in the paper. It can empress the elliptical facular into a nearly circular shape in one dimension. The experimental results show that it can effectively reduce the insertion loss and the phenomenon of half bandwidth broadening. Using the spot-shaping fitting, the tunable range of the filter is about 20 nm which coincides with the theoretical design..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1375 (2008)
Producing Subfemtosecond Pulses by Using Chirped Multilayer Mirror in the Extreme Ultraviolet Region
Chen Rui, Wang Fengli, and Wang Zhanshan
A major effort in ultrashort and ultrafast optics is to obtain subfemtosecond pulses from high harmonics generated by interaction of an intense short-pulse laser and a jet of rare gases. The chirped multilayer mirror in the extreme ultraviolet region can be used to select some high harmonics and compensate the chirp. IA major effort in ultrashort and ultrafast optics is to obtain subfemtosecond pulses from high harmonics generated by interaction of an intense short-pulse laser and a jet of rare gases. The chirped multilayer mirror in the extreme ultraviolet region can be used to select some high harmonics and compensate the chirp. It is an effective element for the production of subfemtosecond pulses. The mechanism of obtaining subfemtosecond pulses from high harmonics by using the mirror was presented. The chirp of high harmonics in specified experiment condition was calculated. The chirped multilayer mirror was designed by using a genetic algorithm. Its capability of producing subfemtosecond pulses was shown by numerical simulation. Results indicate that the designed chirped multilayer mirror can be used for production of 132 as pulses..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1380 (2008)
Influence of Deposition Temperature on Growth Orientation of PZT/LSAT Thin Film
Zhu Jie, Xie Kang, Zhang Hui, Hu Juntao, and Zhang Pengxiang
Pb(Zr0.3Ti0.7)O3 (PZT) ferroelectric thin films are grown by pulsed laser deposition (PLD) on LaSrAlTaO3 (LSAT) single crystal substrates from sintered targets of Pb(Zr0.3Ti0.7)O3 and Pb1.1(Zr0.3Ti0.7)O3 (excessive 10%-Pb) with variable temperature of 550～750 ℃, respectively. The pattern observed by X-ray diffraction (Pb(Zr0.3Ti0.7)O3 (PZT) ferroelectric thin films are grown by pulsed laser deposition (PLD) on LaSrAlTaO3 (LSAT) single crystal substrates from sintered targets of Pb(Zr0.3Ti0.7)O3 and Pb1.1(Zr0.3Ti0.7)O3 (excessive 10%-Pb) with variable temperature of 550～750 ℃, respectively. The pattern observed by X-ray diffraction (XRD) indicates that the orientation of thin film growth transits from approximate c-axis at 550 ℃ to approximate a-axis at 750 ℃ gradually in the no-excessive situation. But in the lead excessive situation, the thin film growth has no obvious transition change. Surface morphology measured by atomic force microscopy (AFM) demonstrates that the root-mean-square (RMS) roughnesses are 16.9 nm and 13.7 nm respectively when the PZT films are grown of approximate c-axis and a-axis. But in the mixed growth orientation, the RMS roughness was about 68 nm due to the competition growth..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1384 (2008)
Measurement and Metrology
Phase Modulation of Liquid Crystal Spatial Light Modulator Measured by a Twyman-Green Interferometer
Zhang Hongxin, Zhang Jian, and Wu Liying
In order to evaluate the performance of a reflective 256 pixel×256 pixel phase-only liquid crystal spatial light modulator (LC SLM) from American BNS Company, interference measurements are proposed on the characteristics of phase modulation using a Twyman-Green interferometer. Experimental results indicate that thIn order to evaluate the performance of a reflective 256 pixel×256 pixel phase-only liquid crystal spatial light modulator (LC SLM) from American BNS Company, interference measurements are proposed on the characteristics of phase modulation using a Twyman-Green interferometer. Experimental results indicate that the relation between phase and gray level is nonlinear. A linear look up table is established by inverse interpolation to correct the nonlinearity for this device. The nonlinearity decreases to 2.85% from 17.23%. The phase difference between the centre and the edge is 0.22π on the equal gray level and the root-mean-square error of phase modulation for the centre is 4 times of that for the edge, which shows the phase modulation for this device is nonuniform and the phase error for the centre should be corrected in wave-front control application..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1360 (2008)
Ultrafast Pump-Probe Reflectivity Study of Carrier Dynamics in Silicon Surface
Liu Guodong, Wang Guibing, Fu Bo, Jiang Jijun, Wang Weiping, and Luo Fu
Time-resolved reflectivity changes of crystalline silicon surface on a 50-ps time scale have been measured using the femtosecond (λ=800 nm) pump-probe technique, and the ultrafast carrier dynamics are also investigated. Time-resolved reflectivity changes can be well described by the reflectivity model which is based onTime-resolved reflectivity changes of crystalline silicon surface on a 50-ps time scale have been measured using the femtosecond (λ=800 nm) pump-probe technique, and the ultrafast carrier dynamics are also investigated. Time-resolved reflectivity changes can be well described by the reflectivity model which is based on the time evolution of free carrier density. This implies that the ultrafast response of reflectivity is dominated by the excited free-carrier contribution. Then the surface recombination velocity (SRV) value S=1.2×106 cm/s is extracted. A self-consistent carrier transport model is established to simulate the time evolution of carrier density and temperature. The results show that surface recombination plays a critical role in the response of carrier dynamics in intrinsic crystalline silicon surface..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1365 (2008)
Reviews
Superresolution Far-Field Fluorescence Bio-Imaging: Breaking the Diffraction Barrier
Mao Zhengle, Wang Chen, and Cheng Ya
Far-field optical fluorescence microcopy has become an essential tool in life science for a long time largely owing to its unique capability to provide noninvasive, three-dimensional (3D) imaging inside cells. However, resolution of a traditional wide-field optical microscopy is limited to about 230 nm laterally and 10Far-field optical fluorescence microcopy has become an essential tool in life science for a long time largely owing to its unique capability to provide noninvasive, three-dimensional (3D) imaging inside cells. However, resolution of a traditional wide-field optical microscopy is limited to about 230 nm laterally and 1000 nm axially, due to the diffraction-limit of light. Resolution improvement is urgently demanded because molecule-scale dynamics and structures are to be revealed inside living cells in today’s life science. So far, many scientists have proposed a significant amount of novel methods in order to enhance resolution of far-field optical imaging. For example, lateral resolution of approximately 100 nm has been achieved by use of structured illumination, whereas the axial resolution has been enhanced 5～10-fold using a standing wave produced by two beams propagating in opposite directions. Nevertheless, diffraction barrier was not broken in these cases until nonlinear optical effects were introduced into optical fluorescence microscopy. As an example, the use of a nonlinear optical effect, namely, simulated emission depletion microscopy has resulted in a 3D resolution of 30～50 nm. Furthermore, the barrier of diffraction-limit can also be broken by novel technologies based on fluorescence resonance energy transfer and high-accuracy localization of fluorophores, by which molecules can be positioned with a resolution of several nanometers..
Chinese Journal of Lasers
- Publication Date: Apr. 01, 2020
- Vol. 35, Issue 9, 1283 (2008)
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