Measuring spatio-temporal couplings using modal spatio-spectral wavefront retrieval

TL;DR

This paper introduces a fast, cost-effective method called FALCON for quantitatively measuring spatio-temporal couplings in high-power lasers using a novel wavefront retrieval algorithm and simple experimental setup.

Contribution

The paper presents a new algorithm based on Zernike-Taylor basis for retrieving spatio-temporal couplings and demonstrates its implementation with a simple, inexpensive setup.

Findings

Successfully measured spatio-temporal couplings at ATLAS-3000 laser.

FALCON method provides rapid, quantitative diagnostics.

Easy integration into existing laser facilities.

Abstract

Knowledge of spatio-temporal couplings such as pulse-front tilt or curvature is important to determine the focused intensity of high-power lasers. Common techniques to diagnose these couplings are either qualitative or require hundreds of measurements. Here we present both a new algorithm for retrieving spatio-temporal couplings, as well as novel experimental implementations. Our method is based on the expression of the spatio-spectral phase in terms of a Zernike-Taylor basis, allowing us to directly quantify the coefficients for common spatio-temporal couplings. We take advantage of this method to perform quantitative measurements using a simple experimental setup, consisting of different bandpass filters in front of a Shack-Hartmann wavefront sensor. This fast acquisition of laser couplings using narrowband filters, abbreviated FALCON, is easy and cheap to implement in existing facilities. To this end, we present a measurement of spatio-temporal couplings at the ATLAS-3000 petawatt laser using our technique.