An online diagnosis technique for simultaneous measurement of the fundamental, second and third harmonics in one snapshot

Xue Dong,Cheng Liu,Xingchen Pan,Jianqiang Zhu

doi:10.1017/hpl.2019.26

Abstract

A three-wavelength coherent-modulation-imaging (CMI) technique is proposed to simultaneously measure the fundamental, second and third harmonics of a laser driver in one snapshot. Laser beams at three wavelengths (1053 nm, 526.5 nm and 351 nm) were simultaneously incident on a random phase plate to generate hybrid diffraction patterns, and a modified CMI algorithm was adopted to reconstruct the complex amplitude of each wavelength from one diffraction intensity frame. The validity of this proposed technique was verified using both numerical simulation and experimental analyses. Compared to commonly used measurement methods, this proposed method has several advantages, including a compact structure, convenient operation and high accuracy.

Highlights

High-power laser facilities have been established for research on inertial confinement fusion (ICF), high-energydensity (HED) physics, laboratory-scale astrophysics, etc. [1,2,3,4]
A frequency converter based on sumfrequency generation is composed of one doubler and one tripler, and the excitation laser beam always includes the fundamental frequency (1053 nm), and the second (526.5 nm) and third (351 nm) harmonic frequencies
The original CMI technique can only measure the complex amplitude of a single wavelength, we have previously demonstrated that a light field of two wavelengths can be accurately measured using this approach by utilizing a multi-mode algorithm to perform the reconstruction[25]

Summary

Introduction

High-power laser facilities have been established for research on inertial confinement fusion (ICF), high-energydensity (HED) physics, laboratory-scale astrophysics, etc. [1,2,3,4]. CDI can directly reconstruct the amplitude and phase of the radiation field from a diffraction intensity pattern via an iterative algorithm without the need for high-quality optics including lenses. The advantages of CMI, which include an extremely compact structure and single exposure measurement, make it an ideal tool for online high-power laser beam diagnosis In this regard, the results of several studies have demonstrated its practical merits[23, 24]. It is shown that by replacing the binary-value phase plate with a multi-value plate, a hybrid laser beam consisting of the wavelengths 1053 nm, 526.5 nm and 351 nm can be measured via the same approach This is an ideal technique to analyze high-power laser beams behind the FOAs of the laser drivers. It was shown that the spatial resolution and measurement accuracy can approach 125 μm and 0.2 wavelengths, respectively, for 1053 nm

Phase modulator design

Algorithm

Simulation

Experiments

Findings

Conclusion