Intra-Cavity Optical Parametric Oscillator Based On A Yb-Doped Fiber Laser

In this work,we studied Yb-fiber-laser-based intra-cavity optical parametric oscillators(ICOPOs).The threshold power of an OPO can be effectively reduced by placing the nonlinear crystal in the resonant cavity of its pump laser.Existing ICOPOs were based on solid-state lasers,and the conversion efficiency was relatively low.This is due to the thermal generation and thermal lensing effect in the gain medium of solid-state lasers,which induces degradation of laser beam quality and reduces the efficiency of the nonlinear-frequency-conversion process,thus limiting its potential of power-scaling.We propose a new configuration of ICOPO systems based on ytterbium-doped fiber lasers in this study.In comparison to an ICOPO based on a solid-state laser gain medium,the benefits of using a fiber-based scheme include a superior beam-quality of the generated mid-infrared idler light at high power-levels,a more efficient process of nonlinear frequency conversion,and the prospect of scaling to higher power.In the preliminary experiment,we obtained a slope-efficiency of the down-converted power of as high as66% with respect to the absorbed LD power.At a maximum absorbed LD power of 11 W,the total generated idler power was estimated to be 671 mW at 3704 nm,and the central wavelength of the output idler wave was tuned from 3465 nm to 3813 nm.