不同抽运波形条件下参量荧光对信噪比的影响

Impact of Optical Parametric Fluorescence on Temporal Contrast for Various Pump Profiles

光参量啁啾脉冲放大器(OPCPA)是现阶段最常用的超短超强脉冲放大器之一。参量荧光是OPCPA的本征量子噪声,其形成的脉冲底座会大大降低输出信号脉冲的信噪比。采用数值模拟的方法,研究了不同脉宽比和抽运波形条件下参量荧光的演化规律及其对信噪比的影响。计算结果表明,在增益一定的情况下,随着脉宽比的增大,信噪比与效率-带宽积都呈先增大后减小的趋势。存在一个最佳脉宽比,使得两者同时达到最大。脉宽比小于此最佳值时,随着超高斯抽运光波形阶数的增大,信噪比减小而效率-带宽积增大;脉宽比大于此最佳值时,随着超高斯抽运光波形阶数的增大,信噪比增大而效率-带宽积减小。

The optical parametric chirped-pulse amplifier （OPCPA） is one of the widely utilized amplifiers to boost ultra-short and ultra-intense pulses. The optical parametric [luorescence is the intrinsic quantum noise of OPCPA and the formed pedestal can degrade the temporal contrast of the output signal pulses greatly. Numerical simulation is adopted to study the evolution of the parametric fluorescence and its impact on the temporal contrast under various signal-to-pump duration ratios and various pump profiles. The results indicate that when the gain is fixed, the temporal contrast and the product of conversion efficiency and bandwidth increase firstly and then decrease with the increasing duration ratio. There is an optimal ratio to maximize the temporal contrast and the product simultaneously. When the ratio is lower than the optimal value, the temporal contrast decreases and the product increases with the increasing order of super-Gaussian pump profiles. The temporal contrast increases and the product decreases with the increasing order when the duration ratio is higher than the optimum.