Repetition rate dependence of gray-tracking in KTiOPO4 during second-harmonic generation at 532 nm

The aim of this work is to study gray tracking during type II second-harmonic-generation 1064→532 nm in halide flux grown KTiOPO4 crystals. The repetition rate of the laser varies from 1 to 20 kHz. We experimentally demonstrate that the gray-tracking threshold, expressed by the harmonic peak power density, is a decreasing exponential function of the Q-switch frequency. The corresponding 532 nm average power density, however, remains constant.