Z-scan confocal method for indirect focusing location

TL;DR

The paper introduces the z-scan confocal method, a technique for accurately locating and sizing the focal spot of ultrashort laser pulses, enabling fast target positioning in laser plasma experiments.

Contribution

It presents a novel, rapid method for determining the absolute focal position and size, improving automation in laser plasma target alignment.

Findings

Accurately locates the focal spot in ultrashort laser pulses.

Enables fast positioning of targets in laser experiments.

Demonstrates measurement of defocusing in a rotating disc.

Abstract

We present a new technique that we have defined as the z-scan confocal method to determine the absolute location and size of the focal spot in a tight focused ultrashort laser pulse. The method permits to accurately position a target in the focal spot with a fast response. The technique is designed to help to automatize the location of an overdense target in focus in a laser plasma experiment. The method allows for a fast localization of the focal position and the relative motion of the target with respect to it. As an example of the capacities we measure the defocusing of a fast rotating disc in several radius to reconstruct the motion of the disc at focus.