Single-Stage Ti:sapphire-Pumped Deep-Infrared Femtosecond Optical Parametric Oscillator based on CdSiP2

Abstract

We report a high-repetition-rate femtosecond optical parametric oscillator (OPO) for the deep-infrared (deep-IR) based on the nonlinear optical crystal, CdSiP 2 (CSP), pumped directly by a Ti:sapphire laser, for the first time. By pumping CSP at <;1 μm, we have achieved practical output powers at the longest wavelengths generated by any Ti:sapphire-pumped OPO. Using a combination of pump wavelength tuning, type-I critical phase matching, and cavity delay tuning, we have generated continuously tunable radiation across 6654-8373 nm (1194-1503 cm -1 ) at 80.5-MHz repetition rate, providing up to 20 mW of average power at 7314 nm and >7 mW beyond 8000 nm, with idler spectra exhibiting bandwidths of 140-180 nm across the tuning range. Moreover, the near-IR signal is tunable across 1127-1192 nm, providing up to 37 mW of average power at 1150 nm. Signal pulses, characterized using intensity autocorrelation, have durations of ~260-320 fs, with corresponding time-bandwidth product of ΔυΔτ ~ 1. The idler and signal output exhibit a TEM00 spatial profile with single-peak Gaussian distribution. With an equivalent spectral brightness of ~6.68 × 10 20 photons s -1 mm -2 sr -1 0.1% BW -1 , this OPO represents a viable alternative to synchrotron and supercontinuum sources for deep-IR applications in spectroscopy, metrology, and medical diagnostics.