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研究了用于提高激光脉冲对比度的全光纤结构脉冲清洁器(OPC)。对利用非线性偏振旋转效应(NPR)提高脉冲对比度进行了理论分析。计算了脉冲清洁器对主脉冲峰值透射率与入射角度和光纤长度的关系,模拟了输出脉冲波形和脉宽的变化,并对1053 nm波长的百皮秒入射脉冲进行了实验。主脉冲与连续背景噪声的对比度提高47.5 dB以上,主脉冲与预脉冲对比度提高16.94 dB以上,输出信号的连续背景功率和预脉冲强度均低于探测器的最小响应极限。主脉冲的峰值功率透射率达28.05%;脉冲宽度由92 ps压缩至64 ps,与理论预期相符。利用可变衰减加光电转化的方法测量了1 Hz重复频率的脉冲对比度及信号透射率,解决了利用自相关仪不易测量低重复频率信号的问题。采用灵敏度更高的测量方式将测得更高的对比度提升。
An all-fiber structured pulse cleaner (OPC) was developed for improving the contrast of laser pulses. The theoretical analysis of improving the pulse contrast by using non-linear polarization rotation effect (NPR) is made. The relationship between the peak pulse transmittance of the main pulse and the angle of incidence and the length of the optical fiber was calculated. The output pulse waveform and pulse width were simulated. The 100 picosecond incident pulse at 1053 nm was also tested. The contrast between the main pulse and the continuous background noise is increased by more than 47.5 dB. The contrast between the main pulse and the pre-pulse is increased by more than 16.94 dB. The continuous background power and the pre-pulse intensity of the output signal are both lower than the minimum response limit of the detector. The main power pulse peak power transmittance of 28.05%; pulse width from 92 ps to 64 ps, in line with the theoretical expectation. The pulse contrast ratio and signal transmittance of 1 Hz repetition rate were measured by the method of variable attenuation and photoelectric conversion, which solved the problem that it is not easy to measure low repetition rate signal by using autocorrelator. Higher sensitivity will be measured with a more sensitive measurement.