A thermoelastic limit on the focal intensity in Fabry-P\'erot cavities

TL;DR

This paper presents an analytical model predicting a thermoelastic limit on the maximum focal intensity in Fabry-Pérot cavities, supported by experimental measurements of mirror properties.

Contribution

The authors develop a new analytical model for thermoelastic effects in Fabry-Pérot cavities and experimentally validate the predicted intensity limit.

Findings

Thermoelastic deformation limits the mode's focal intensity to about 2.9 TW/cm^2.

Experimental results show at least 70% of the predicted limit can be achieved.

Higher mirror absorption increases thermoelastic effects, reducing maximum achievable intensity.

Abstract

Light in the mode of a Fabry-P\'erot cavity heats the mirror surfaces via optical absorption, causing thermoelastic deformation of the mirror substrates, which in turn dictates the shape of the mode. We develop an analytical model which predicts that this effect limits the maximum focal intensity of the mode. Using two near-concentric Fabry-P\'erot cavities -- one with 4.5-fold higher mirror absorption than the other -- we measure the thermoelastic properties of the cavity mirrors and demonstrate that it is possible to achieve at least 70% of this predicted limit (in the high-absorption cavity), and that the predicted limit is 2.9 TW/cm^2 (in the low-absorption cavity).