Femtosecond deep-infrared optical parametric oscillator pumped directly by a Ti:sapphire laser

摘要

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, characterised using intensity autocorrelation, have durations of ~260-320 fs, with corresponding time-bandwidth product of △v△τ~1. The idler and signal output exhibit a TEM_(00) 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 table-top alternative to synchrotron and supercontinuum sources for deep-IR applications in spectroscopy, metrology and medical diagnostics.