Actively pulse-shaped 2 mJ, 200 W fiber MOPA at 2048 nm for mid-IR generation in OPOs

We report on a high-power, nanosecond-pulsed, linearly polarized fiber MOPA system operating at 2048 nm, based on a flexible Tm^3+-doped photonic crystal fiber (PCF), developed for pumping an optical parametric oscillator (OPO) for mid-infrared (mid-IR) generation. The system delivers pulses with 2.07 mJ pulse energy, 49 ns pulse duration, and 52 kW peak power at 100 kHz, resulting in 207W average output power. Active temporal shaping yields nearly rectangular pulses with a narrow 10-dB linewidth of 390 pm. We apply the developed laser to pump a linear, doubly resonant OPO targeting mid-IR generation across 3 μm to 5 μm via type-I phase matching in ZnGeP₂ (ZGP) and CdSiP₂ (CSP). For a 2 cm long ZGP crystal, we obtain 25.8W at 37.6W pump power, hence a 69% conversion efficiency and a mid-IR pulse energy of 1.03 mJ at a beam quality of M_s²=4.1 (signal) and M_i²=4.8 (idler). For a 1 cm long CSP crystal, we achieve 13.3W at 27.9W pump power and a 48% conversion efficiency with 0.53 mJ mid-IR pulse energy at a beam quality of M_s²=2.5 (signal) and M_i²=2.4 (idler).