Spatiotemporal characterization of laser pulse amplification in double-pass active mirror geometry

Tinghao Liu,Qiang Liu,Mali Gong,Xing Fu,Zhan Sui

doi:10.1017/hpl.2020.28

Abstract

Abstract We present a spatiotemporal model of pulse amplification in the double-pass active mirror (AM) geometry. Three types of overlap condition are studied, and the spatiotemporal scaling under the four-pulse overlapping (4PO) condition is fully characterized for the first time, by mapping the temporal and spatial segments of beam to the instantaneous gain windows. Furthermore, the influence of spatiotemporal overlaps on the amplified energy, pulse distortion and intensity profile is unraveled for both AM and zigzag configurations. The model, verified by excellent agreement between the predicted and measured results, can be a powerful tool for designing and optimizing high energy multi-pass solid-state laser amplifiers with AM, zigzag and other geometries.

Highlights

Diode-pumped nanosecond lasers with high energy, good beam quality and high conversion efficiency have a wide range of applications such as inertial confinement fusion, material processing and hard X-ray generation
The active mirror (AM) geometry[1,2,3,4,5,6], in which the gain medium acts as a mirror to allow round-trip energy extraction in a single pass, has drawn much attention for its potential for highenergy lasers with superior performance
For a double-pass AM configuration, laser pulses that propagate forward and backward along the same route within the gain medium may lead to a collinear overlap, that is, both the leading and trailing edges of the pulse share an inverted population at the location they arrive at, at the same time

Summary

Introduction

Diode-pumped nanosecond lasers with high energy, good beam quality and high conversion efficiency have a wide range of applications such as inertial confinement fusion, material processing and hard X-ray generation. The active mirror (AM) geometry[1,2,3,4,5,6], in which the gain medium acts as a mirror to allow round-trip energy extraction in a single pass, has drawn much attention for its potential for highenergy lasers with superior performance. The pulse overlap in the double-pass amplification process was firstly investigated by Hirano et al in 1999[7], presenting a numerical solution by using the iterative procedure method. In 2017, Li et al.[9] presented an intuitive numerical method by meshing the pulse and gain medium into spatial grids, in which the pulse distortion caused by double-pass scaling is discussed.

Methods

Results

Conclusion