Optical damage of W-doped KTioPo4non linear single crystals

Abstract
A photochromic damage has been observed in W-doped KTP single crystals. The damage consists in the growth of a broad optical absorption in the visible and near infrared. It has been determined that the excitation spectrum of this damage is mainly confined in the ultraviolet region. A complete annealing of the damage may be obtained by heating at 250°C or above. The origin of the damage has been mostly related with the presence of W4+ ions behaving as electron donors. Ti4+ ions trap electrons and the Ti3+ ions formed are responsible of the optical absorption observed.