Fiber Optical Parametric Oscillator for Large Frequency-Shift Wavelength Conversion

We investigate a fiber optical parametric oscillator (OPO) for sub-1-μm wavelength operation with threshold sufficiently low to allow for pumping by readily available all-fiber master-oscillator power-amplifier (MOPA) sources at 1.1 μm. The required low threshold is achieved in an all-fiber OPO ring-cavity which incorporates a photonic crystal fiber as gain medium, synchronously pumped by a wavelength-filtered Yb-doped fiber MOPA. Experimentally, we demonstrate an in-fiber conversion efficiency of 8.6% from the pump at 1079 nm to the anti-Stokes at 715 nm, corresponding to a frequency-shift of 142 THz. While the output power was restricted by a low output coupling, a reduction in feedback losses will allow for most of the generated anti-Stokes power to be out-coupled. Although we use free-space coupling of the pump MOPA to the OPO cavity, the low threshold and the increasing availability of advanced fiber components does allow for fully fiber-integrated solutions.