Power and tuning characteristics of a broadly tunable femtosecond optical parametric oscillator based on periodically poled stoichiometric lithium tantalate

Abstract

We report on power, tuning, and temporal characteristics of an optical parametric oscillator (OPO) based on a periodically poled stoichiometric lithium tantalate (PPSLT) crystal and pumped by a high-power mode-locked Ti:sapphire laser. Focus is given to the OPO operating range spanning from 900 to 1350 nm, which is important in nonlinear optical microscopy and spectroscopy. Generation of peak powers beyond the 10 kW level is strongly affected by the onset of intracavity power-dependent loss, which is due to the high ultrafast Kerr nonlinearity of the gain material. The crystal withstands combined power densities higher than 60 GW/cm2 for ∼100 fs optical pulses before breakdown occurs. A resonator design that mitigates self- and cross-beam focusing effects delivers ∼40 kW peak power for 85–160 fs pulses. The high parametric gain of the PPSLT allows OPO operation at the twelfth harmonic of the pump laser repetition rate (∼0.91 GHz). Stable operation with the possibility of broad wavelength tuning is demonstrated without active cavity length stabilization at a repetition rate of ∼530 MHz and average powers above 150 mW. In addition, up to 50 mW of power at ∼530 nm is output as a result of SHG of the 1060 nm signal beam resulting from third-order quasi phase matching.