Increasing the efficiency of a fixed-wavelength cascaded Raman resonator for a non-resonant pump by using a reflector

A narrow-band, fixed-wavelength cascaded Raman resonator can be effectively used only for a given input wavelength. The efficiency of wavelength conversion of a cascaded Raman resonator decreases sharply when a non-resonant pump is used. Designing and fabricating new grating sets for the resonator for different pump sources isn’t a feasible option as it compromises the simplicity and cost-effectiveness of this approach. We identified that by seeding the cascaded Raman conversion suitably, a substantial improvement in efficiency can be achieved. This is demonstrated using a coupler-based broadband reflector to significantly improve the performance of CRR for a non-resonant pump source. Remarkable improvement in efficiency is obtained with $\sim 70$% of the output power at 1480nm Stokes wavelength when the CRR is pumped by a 16W Ytterbium doped fiber laser at 1057nm.