title: Surface-reflection-initiated pulse-contrast degradation in an optical parametric chirped-pulse amplifier.
abstract: We study a novel mechanism of pre-pulse generation in an optical parametric chirped-pulse amplification (OPCPA) system through an analytical approach together with numerical simulations. The acquired pre-pulses are initiated from the surface-reflection-induced modulation of the seed spectrum and occur as a consequence of high-order distortion of such modulated spectrum due to the instantaneous gain saturation effect. We demonstrate that the intensities of pre-pulses increase quadratically with the initial temporal modulation-depth of the stretched signal pulse as well as the conversion efficiency prior to substantial pump-depletion. Explicit formulas for estimating the contrast limit due to surface reflections are present. We also discuss the impact of group-velocity mismatch on the pre-pulse generation. The results of this work may deepen our cognition on the complexity of the pulse-contrast problem in OPCPA systems.
authors.affiliation: Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Peng
authors.initials: P
authors.lastname: Yuan
authors.forename: Jingui
authors.initials: J
authors.lastname: Ma
authors.forename: Yongzhi
authors.initials: Y
authors.lastname: Wang
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Xie
authors.forename: Liejia
authors.initials: L
authors.lastname: Qian