PYROELECTRICALLY INDUCED OPTICAL-EMISSION FROM POTASSIUM TITANYL PHOSPHATE CRYSTALS

We have observed optical scintillations and corresponding electric cur rent pulses when uniformly heating potassium titanyl phosphate (KTP) c rystals at 0.1-0.4 Ws over the temperature range 8-300 K. The scintill ations correspond to molecular nitrogen emission occurring during the electrical breakdown of air near the crystal surface, and imply the ex istence of pyroelectrically induced peak electric fields at the crysta l surface exceeding 30 kV/cm, which is ten times larger than de electr ic fields reported to induce electrochromic (EC) damage in this materi al. Recent optical damage studies on KTP under high repetition rate, h igh average-power laser irradiation reveal an EC-like damage, implying the existence of an internal electric field arising during laser irra diation. Our observation of a sizable total pyroelectric response sugg ests one possible mechanism for the origin of these internal fields in KTP and other nonlinear optical materials. (C) 1997 American Institut e of Physics.