Yb-fiber-pumped mid-infrared picosecond optical parametric oscillator tunable across 6.2–6.7 µm

We report a high-average-power picosecond optical parametric oscillator (OPO) tunable in the mid-infrared (mid-IR) based on CdSiP₂ synchronously pumped by an Yb-fiber laser at ~ 80 MHz repetition rate. Successful operation of this high-repetition-rate singly-resonant picosecond OPO has been enabled by the improved CSP crystal quality over a long interaction length. The OPO can be tuned across 1264–1284 nm in the near-IR signal and 6205–6724 nm in the mid-IR idler by temperature tuning the CSP crystal over 39–134 °C. By deploying a 5% output coupler for the resonant signal, we have extracted up to 44 mW of average power in the near-IR and up to 95 mW of non-resonant idler power at 6205 nm at 6.3% total conversion efficiency, with > 50 mW over > 55% of the mid-IR tuning range. We have investigated temperature-tuning characteristics of the OPO and compared the data with the theoretical calculations using the recent Sellmeier and thermo-optic coefficients for CdSiP₂. The signal pulses from the OPO exhibit a Gaussian pulse duration of 19 ps centered at 1284 nm. We have also studied the output power stability of the OPO, resulting in a passive stability better than 1.9% rms for the near-IR signal and 2.4% rms for the mid-IR idler, measured over > 17 h, with both beams in high spatial quality.