Tunable and chirp free femtosecond signal pulses generated by a PPLN OPO pumped by Ytterbium fiber laser chirped pulses

Abstract

Chirp of the pulses generated in the 1.4 µm-1.8 µm spectral ranges and in a singly resonant OPO build around a 3 mm long PPLN crystal pumped at 108 MHz by 40 nJ, 1 ps chirped or 350 fs weakly chirped pump pulses centered at 1035 nm is analyzed. Whatever the chirp of the pump pulses, we achieved a pump to signal conversion efficiency > 30%. We demonstrate that by adjusting the cavity length around synchronism condition, chirped or almost chirped free (down to 80 fs) signal pulses are generated. A simple mechanism accounts for this phenomenon.