Investigation of chromium doped yttrium garnet spectral properties by analysis of photoacoustic signal phase delay dependence on light modulation frequency

Abstract
Three samples of yttrium-aluminum garnet single crystal doped with Cr and Mg were investigated. One ofthem was directly "as grown" and two other after thermal treatment in oxygen or hydrogen atmosphere. Photoacoustic (PA) signal phase shift dependence on modulation frequency was experimentally determined for each sample under two excitation wavelengths corresponding to maximums of absorption bands. The results obtained for the two bands were compared and analyzed using a basic or extended theory of PA signal generation. It have been shown that the PA signal phase dependence on modulation frequency is a good indicator for modification of the Cr ion centers due to the crystal thermal processing.