Decrease Spectral Phase Modulation with Spectral Scanning Filter for Coherent pulse Contrast Improvement in Femtosecond Laser system

A spectral scanning filter method for decreasing the spectral phase modulation to improve the coherent intensity contrast in the chirped pulse amplification system is proposed and studied theoretically, which is made use of the frequency offset between the chirped signal pulse and the prepulse (or the postpulse). The spectral scanning filter based on the rapid Fabry–Pérot (F–P) interference for reducing the pre-pulse and post-pulse originated from the spectral phase modulation is analyzed theoretically and simulated numerically. The numerical simulation results show that the coherent pulse contrast can be improved by 0.41F2 for the chirped pulse and the compressed pulse, and the transmission efficiency of the chirped signal pulse can exceed 90% when the synchronizing time jitter ranges from −2ps to 2ps and the chirp rate parametric from −0.1C/T2 to 0.1C/T2.