Abstract
We report a low threshold, efficient picosecond fiber optical parametric oscillator (FOPO) at 643 nm, synchronously pumped via free-space coupling in the normal-dispersion regime by a Nd-doped MOPA laser source at 914 nm. The large downshift of 271 nm is achieved by using a short photonic crystal fiber (PCF) with a zero-dispersion wavelength (ZDW) near 960 nm. The ring cavity is numerically designed to maximize the conversion efficiency at the anti-Stokes wavelength by managing the cavity dispersion and the temporal walk-off. An average output power of 100 mW is achieved experimentally, representing an in-fiber conversion efficiency of 27%, in agreement with predictions from numerical simulation.