Performance studies on group-velocity-matched femtosecond optical parametric generation

We present a comparative study and detailed characterization of high-power femtosecond optical parametric generation (OPG) at 10 MHz repetition rate in the near and mid-infrared by exploiting near-zero group-velocity-mismatch (GVM) in the nonlinear crystals of PPLN and MgO:PPLN. Using a microchip-started amplified Mamyshev fiber oscillator delivering 198 fs pulses at 1064 nm as the pump source and deploying 19-mm-long PPLN and 42-mm-long MgO:PPLN as gain media, we study in detail the influence of crystal length and pump pulse duration on femtosecond group-velocity-matched interaction in the OPG process. The OPG source is tunable across 1445–1577 nm in the signal and 3318–4412 nm in the idler, and can provide average output powers of up to 439 mW in the signal at 1530 nm and 197 mW in the idler at 3550 nm, at slope efficiencies of ∼50% and ∼20% , respectively. Signal pulses as short as 275 fs are obtained using the shorter crystal, while longer signal pulses with similar output powers are generated with the longer crystal. Experimental results are supported by theoretical simulations, providing good agreement. The OPG source exhibits excellent power stability with high spatial quality of 𝑀2<1.5 in the signal and idler beams.