Suppressing scattering-induced nanosecond pre-pulses in Ti:sapphire multi-pass amplifiers

Abstract

In this Letter, we experimentally investigate a new kind of nanosecond pre-pulse, which originates from the bidirectional scattering of crystals in traditional Ti:sapphire multi-pass amplifiers. The experimental results demonstrate that the intensity of scattering-induced pre-pulses is very sensitive to the scattering angle, and the delay time between the pre-pulse and the main pulse is an integer multiple of the light path in each pass of the amplifier. An optimized multi-pass amplifier configuration is proposed, for what is believed to be the first time, to suppress the scattering-induced pre-pulses. The contrast ratio between pre-pulses and the main pulse is enhanced by more than two orders of magnitude, reaching a level of 10−10. This novel multi-pass amplifier configuration is very simple and economical, and provides an effective solution for the temporal contrast enhancement in the nanosecond range.

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

“…[21], the ns prepulses generated in the multipass amplifiers mainly include two types: BS, the ns prepulses from reflection or backward scattering; and FS, the ns prepulses from forward scattering. The intensity distributions of backward scattering and forward scattering are angle-dependent with the directions of the reflected and transmitted laser beams [22] .…”

“…In this way, the directions of reflected laser beams can be changed to prevent the backward scatterings from entering the optical paths to form ns prepulses. To suppress the forward-scattered prepulses, a novel four-pass amplifier configuration has been demonstrated, which has larger angles between the odd passes or even passes (e.g., the first pass and the third pass) compared with the traditional multipass amplifier configuration [22] . However, amplifiers with more than four-pass configurations would suffer more scattered noise, which makes it more difficult to totally eliminate the ns prepulse induced by the scattering.…”

“…The ns prepulse generated from the four-grating compressor can be suppressed by blocking the zeroth-order diffraction of the gratings. The ns prepulses from the multipass amplifier can be effectively suppressed by adopting a novel amplifier configuration [22] . However, this novel amplifier configuration has only been demonstrated in a four-pass amplifier.…”

A Promising Route to Compact and Economic Sub-15 fs, PW-Level Ti:Sapphire Lasers

“…The moderate amplified energy indicates that fewer amplification stages and pump energy are required, which can significantly reduce the size and cost of the laser facility. To suppress the scatteringinduced nanosecond prepulses, an optimized four-pass configuration is applied in both PA and FA [40]. Moreover, benefitting from the broadband seed source, the dual-crystal OPCPA front-end, and the PEF, the final amplified output spectrum can still support sub-15 fs pulses.…”