Analysis of a third-order optical parametric oscillator in TiO 2

Abstract

A novel third-order optical parametric oscillator (OPO) based on four-wave mixing process in bulk TiO 2 crystal is theoretically characterized. The OPO is assumed to be synchronously pumped by pulses of either 100 fs duration at 800 nm or 100 ps at 1.06 mm. For the former case, its signal is tunable from 0.45 to 0.8 mm by changing the crystal orientation; for the latter case, the OPO is tunable from approximately 0.6 to 1.06 mm. The threshold conditions are also calculated considering the effect of group velocity mismatch (GVM) between the pump pulse and the signal (or idler) pulse. The threshold is dependent on signal wavelength since GVM increases as signal wavelength decreases. Using a 2 mm-length crystal and assuming optimum focusing, the threshold for the singly resonant condition is 710 mW at 700 nm for the former case and 93.6 W for all the signal wavelengths for the latter case. The threshold condition is also calculated assuming different pumping pulse widths. The result shows the ideal pulse width is around 2 ps, for which the threshold power is 1.42 W for all the signal wavelengths.