Multi-pass amplifiers with self-compensation of the thermal lens

TL;DR

This paper introduces a new multi-pass amplifier architecture that uses optical Fourier transforms to achieve superior stability against thermal lens variations, maintaining high beam quality without extra losses.

Contribution

The proposed architecture demonstrates improved thermal lens compensation in multi-pass amplifiers using Fourier transforms, outperforming traditional 4f-based designs.

Findings

Enhanced stability against thermal lens variations.

Maintains high beam quality (TEM00) without additional losses.

Robustness to changes in the number of passes and aperture effects.

Abstract

We present a novel architecture for a multi-pass amplifier based on a succession of optical Fourier transforms and short propagations that shows a superior stability for variations of the thermal lens compared to state-of-the-art 4f-based amplifiers. We found that the proposed multi-pass amplifier is robust to variations of the active medium dioptric power. The superiority of the proposed architecture is demonstrated by analyzing the variations of the size and divergence of the output beam in form of a Taylor expansion around the design value for variations of the thermal lens in the active medium. The dependence of the output beam divergence and size is investigated also for variations of the number of passes, for aperture effects in the active medium and as a function of the size of the beam on the active medium. This architecture makes efficient use of the transverse beam filtering inherent in the active medium to deliver a beam with excellent quality (TEM00) without additional losses.