Use of scanning Hartmann sensor for measurement of thermal lensing in TGG crystal

Abstract

Investigations of thermal effects caused by absorption of laser radiation in Faraday isolators and Faraday mirrors are becoming more important. A most promising medium for Faraday devices in the wavelength range of 600-1200 nm is the terbium gallium garnet (TGG) crystal. In order to measure its thermo-optic constants (which are unknown) we used a scanning Hartmann sensor technique. This technique can easily and inexpensively measure wavefront distortions induced by optical elements to within 2nm.