Absorption measurements of laser optical materials by interferometric calorimetry

Abstract

The widespread use of high-power lasers requires further studies of the very low loss materials. The development of such materials has led to the progress in the measurement technique of small absorption coefficients. We propose a new technique of measuring bulk and surface absorption coefficients using an interferometric calorimetry. It is important to separate surface absorption from bulk absorption, for recent studies have revealed that surface damage occurs earlier than bulk damage. The sample exposed to a laser beam absorbs the light proportional to its absorption coefficient. Change in optical path arises because the index of refraction and the sample thickness depends on temperature. We can obtain the bulk and the surface absorption coefficients by measuring this change of optical path length by using the Michelson interferometer or the holographic interferometer.