Optical strength of YAG and LiNbO3crystals irradiated with giant pulses from a YAG:Er3+laser (λ= 2.94μ)

Abstract

Measurements were made of the bulk damage threshold Id of yttrium aluminum garnet (YAG) crystals, either free of deliberately introduced impurities or activated with Er3+ ions in different concentrations (up to 80 wt.%), and also of LiNbO3 crystals. This threshold was determined using giant pulses from a YAG:Er3+ laser emitting at λ = 2.94μ; the energy per pulse was 70 mj and the pulse duration was 120nsec. In the case of YAG crystals it was found that Id varied considerably from sample to sample in the range Id = (1.5–18) × 1010 W/cm2, which was not associated with the presence of Er3+ but was clearly due to the presence of some accidental impurities. A considerable increase in Id was observed for YAG:Er3+ samples characterized by low damage thresholds when these samples were annealed in air. In the case of LiNbO3, a typical value of the damage threshold was Id ≈ 1011 W/cm2. The results obtained indicated a sufficiently high optical strength of YAG:Er3+ and LiNbO3 crystals, used respectively as the active and modulating elements in YAG:Er3+ lasers.