Abstract

High-average-power high-repetition-rate picosecond sources at wavelengths >5 µm in the deep-infrared (deep-IR) are interesting for variety of applications in spectroscopy and medicine [1]. In the absence of conventional ultrafast lasers, synchronously-pumped optical parametric oscillators (OPOs) offer a viable approach to the generation of ultrashort pulses in the deep-IR [2]. In the high-repetition-rate picosecond regime involving low pulse energies and peak powers, the increasingly stringent and simultaneous demands on nonlinear materials including wide transparency, large nonlinearity, high optical quality and low transmission loss, and long interaction length under noncritical phase-matching (NCPM) has proved a major barrier to the realisation of picosecond OPOs in the deep-IR using widely available mode-locked lasers near 1 µm. The new nonlinear crystal, CdSiP₂ (CSP), is an excellent material possessing high nonlinearity (d_eff∼84.5 pm⁄V), broad transparency and NCPM capability [3], enabling access to deep-IR using well-established solid-state and Yb-fiber pump lasers at ~1 µm. However, the development of picosecond OPOs based on CSP synchronously pumped by low-energy pulses at high repetition rate has so far remained illusive. Here we report what we believe to be the first high-repetition-rate picosecond OPO based on CSP and tunable across 6205-6724 nm in the deep-IR.

© 2017 IEEE