Transient defects in potassium dihydrogen phosphate were characterized by using acoustic signals generated in the crystal when it was bombarded with pulsed laser radiation. The defects were produced by the simultaneous absorption of two 266nm photons, and exhibited linear absorption in the visible and UV spectral region. The decay kinetics of the defects were studied by using a method that was based upon analysis of the acoustic signal generated by visible pulses. The acoustic measurement of the decay time exhibited a non-exponential decay, and was free from thermal lensing or beam deformation. It was proposed that the origin of the photo-acoustic signal was the heat released by de-excitation of the energy levels of the defects when they were excited by visible pulses.

Photo-Acoustic Characterization of Transient Defects in Potassium Dihydrogen Phosphate Crystals. O.M.Matos, G.A.Torchia, G.M.Bilmes, J.O.Tocho: Physical Review B, 2004, 69[22], 224102 (6pp)