光谱扫描滤波法提升超强飞秒激光相干信噪比分析

光谱调制所形成的预脉冲和后沿脉冲的时频谱图将等间距、 平行地分布于啁啾主脉冲时频谱图的两侧, 基于光谱调制啁啾光脉冲的这种时频谱特点, 采用扫描滤波方式来提升其对比度. 数值模拟分析了扫描滤波过程中时间抖动、 扫描率差异和通带宽度等因素对扫描滤波效果的影响, 结论表明, 在扫描轨迹与信号光频率相同的情况下, 控制通带宽度, 相干信噪比提升率接近0.41F²倍, 而啁啾信号光以超过90%的透光率通过光谱扫描滤波器. 关键词： 超快激光技术 相干信噪比 光谱扫描滤波 短时傅里叶变换法

Theoretical analysis of scanning spectral filter method for coherent intensity contrast enhancement in femtosecond laser system

A scanning spectral filter method is proposed for improving the intensity contrast originating from the phase ripple in the femtosecond chains, which is made using the character that the instantaneous frequency varies with the time approximately linearly for the chirped pulse in the time-frequency domain. The scanning spectral filtering for reducing the pre-pulse and post-pulse intensity is analyzed in the time-frequency domain by using the short-time Fourier transformation method. Results show that the coherent intensity pulse contrast can be improved by 0.41F² for the chirped pulse or the compressed pulse, and the transmission efficiency of the chirped pulse can exceed 90% when the synchronizing time of the jitter ranges from -2 ps to 2 ps and the chirp rate p from 0.9C/T² to 1.1C/T².
Keywords： ultrafast optics coherent pulse contrast spectral scanning filtering short time Fourier transformation