1.06-µm absorption caused by stable color centers in flash-lamp-pumped Nd:YAG laser rods

The absorption losses for 1.06-µm laser radiation in Nd:YAG laser rods that are due to stable color centers are investigated. Stable color centers are created by a two-photon absorption process caused by theultraviolet part of the Xe flash-lamp spectrum. The reverse process of color center annihilation that is due to a one-photon bleaching process is observed. A model explaining these processes is proposed, and rate equations describing the creation and the annihilation of color centers are developed.