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排序方式: 共有229条查询结果,搜索用时 62 毫秒
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A 1 064-nm pulsed coherent Doppler lidar (CDL) prototype is developed to measure short range wind speed in the lower altitude troposphere layer. The CDL system adopts an injection-seeded Nd:YAG laser with the pulse duration of 80 ns, single pulse energy of 0.5 mJ, and pulse repetition rate of 200 Hz. Speed calibration experiments are implemented to obtain a speed accuracy of 0.3 m/s using a hard target. Data analysis results show that the CDL system can obtain a line-of-sight wind velocity at a range of 30 to 500 m with the range resolution of 40 m and 38 pulses accumulation. 相似文献
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A three-wavelength lidar system is set up. The backscatter signals of 355, 532, and 1 064 nm are mea- sured simultaneously to derive the optical depth, lidar ratio, and backscatter color ratio of cirrus clouds, respectively. The lidar configuration and the data processing are described. The case study shows that the optical depths of cirrus clouds are not dependent on wavelength while the backscatter color ratios are. 相似文献
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UV–visible spectral characterization and density functional theory simulation analysis on laser-induced crystallization of amorphous silicon thin films 下载免费PDF全文
The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon (a-Si:H) thin films was studied both theoretically and experimentally. The thin films were irritated by a frequency-doubled (λ= 532 nm) Nd:YAG pulsed nanosecond laser. An effective density functional theory model was built to reveal the variation of bandgap energy influenced by thermal stress after laser irradiation. Experimental results establish correlation between the thermal stress and the shift of transverse optical peak in Raman spectroscopy and suggest that the relatively greater shift of the transverse optical (TO) peak can produce higher stress. The highest crystalline fraction (84.5%) is obtained in the optimized laser energy density (1000 mJ/cm2) with a considerable stress release. The absorption edge energy measured by the UV- visible spectra is in fairly good agreement with the bandgap energy in the density functional theory (DFT) simulation. 相似文献
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<正>A new method to obtain linear polarization operation by Brewster's angle-polished fiber end is demonstrated. By using the special polarization operation technique together with introducing a narrow-linewidth fiber grating into the laser cavity,a cladding-pumped linear polarization and single-transverse-mode (M~21.1) Yb-doped fiber laser with narrow linewidth whose full-width at half-maximm(FWHM) is less than 0.2 nm,is obtained in a simple configuration.The output power is up to 10 W which is continuouswave output at 1085 nm,and the slope efficiency is 63%with respect to the coupled pump power and 75%with respect to the absorbed pump power,respectively.The measured 21-dB polarization extinction ratio does not degrade with the output power.The simplicity of such an approach is highly beneficial for a number of applications,including the use of a fiber laser for the nonlinear wavelength conversion (especially for the intracavity frequency doubling) and for the coherent and spectral beam combination. 相似文献
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报道了半导体激光器端面抽运不同结构的声光调Q的双包层光纤激光器的脉冲输出特性. 对前向、后向不同抽运方式的掺镱调Q双包层光纤激光器在输出平均功率,调Q脉冲宽度及脉冲稳定性进行了对比及讨论;其中后向抽运的光纤激光器,在10kHz重复频率调制下,获得了斜效率为60%的平均功率输出,其脉冲宽度为52ns,单脉冲能量为03mJ. 最后利用不同抽运方式下的速率方程,理论分析调Q脉冲的特性,分析结果与实验相符.
关键词:
双包层光纤激光器
声光开关
前向抽运
后向抽运 相似文献
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偏振-米散射激光雷达的研制 总被引:1,自引:0,他引:1
研制的偏振-米散射激光雷达(PML),可用于探测卷云和沙尘气溶胶的后向散射光退偏振比以及研究流层大气气溶胶的消光特性。采用窄带滤光片和光阑,将接收到的激光大气回波信号谱线(米散射和瑞利散射光谱)从天空太阳背景噪声中分离出来,以提高系统的白天探测能力。介绍了偏振-米散射激光雷达的结构、技术参数、测量方法和数据处理方法。对偏振-米散射激光雷达的性能参数进行了测定,并对测定结果进行了分析与讨论,给出了偏振-米散射激光雷达对合肥市地区(117.16°E, 31.90°N)上空大气气溶胶的消光特性和卷云的结构、退偏振比垂直廓线以及光学厚度的典型探测结果,对这些结果进行了分析和讨论。结果表明:研制的偏振-米散射激光雷达性能可靠,能对大气气溶胶和卷云的物理和光学特性进行有效的探测。 相似文献