Delay-shift and asymmetric broadening of pre-pulses by post-pulses in a petawatt laser facility

Abstract

The temporal contrast of high-peak-power lasers is usually limited by pre-pulses, which are generally produced by post-pulses due to the nonlinearity of the active medium. The reason for the conversion between pre-pulse and post-pulse is now well known, but the mechanisms for the delay-shift and asymmetric broadening of the newly generated pre-pulse are not yet clear. In this work, a novel, to the best of our knowledge, numerical model combining the nonlinear Schrödinger equation and the Frantz–Nodvik equation is proposed to investigate the underlying mechanisms for the “distortion” of the pre-pulse. Numerical results show that the gain characteristics of Ti:sapphire amplifiers can only make a minor change on the temporal profile of the pre-pulse, but the high-order dispersion is the main cause for the delay-shift and asymmetric broadening of the pre-pulse, and the effects are more significant for the initial post-pulse with a relatively larger delay.

Suppression of nanosecond prepulses from regenerative amplifier and multipass amplifiers in the SULF-1PW laser

“…So far, the highest peak power has reached 10 PW, and the largest focused peak intensity has exceeded 10 23 W=cm 2 [7][8][9] . For such high-intensity laser facilities, the temporal contrast has become a crucial parameter for laser-matter interactions [10][11][12] . Since the prepulses or pedestals with intensity over 10 11 W=cm 2 would inevitably generate preplasma prior to the main pulse in the laser-matter interaction process [13] , the methods and techniques to suppress the unwanted prepulses or pedestals while maintaining the focused peak intensity of the main pulse deserve to be taken into consideration.…”