Laser-induced wavefront distortion in optical materials: a general model

Abstract

Wavefront distortion in optical components induced by thermal lensing may affect performance and stability of optical systems, such as high-power lasers, and is also the base of several photothermal techniques. This distortion is a result of complex photoelastic effects that characterize the degradation and the propagation of the beam. A simple analytical solution is obtained only for low absorbing materials, with the assumption that the stresses obey either thin-disk or long-rod type distributions. In a previous work, part of this limitation was overcome, in which a unified model was proposed for the optical path change for weakly absorbing materials, regardless of its thickness. In this work, we developed a generalized theoretical model for the optical path change that is related to the temperature profile in a relatively simple manner for all classes of absorbing optical materials. The modeling is based on the solution of the thermoelastic equation and provides time-dependent expressions for the temperature, surface displacement, and stresses. This generalized model could have a significant impact on designing laser systems and has direct application in photothermal techniques, which correlate optical path change to thermal, optical, and mechanical properties of solid materials.