We report on a new scheme for efficient continuous-wave (CW) mid-infrared generation using difference frequency generation (DFG) inside a PPLN-based optical parametric oscillator (OPO). The pump sources were two CW fiber lasers fixed at 1018 nm and 1080 nm. One worked as the assisted laser to build parametric oscillation and generate oscillating signal beam while the other worked at low power (≤3 W) for inducing DFG between it and the signal beam. The PPLN temperature was properly adjusted for enabling OPO and DFG synchronously meet phase-matching conditions. At last, both low-power 1018 nm and 1080 nm pump beams were successfully converted to 3.1 μm and 3.7 μm idler beams separately. The conversion efficiency of 1018 nm and 1080 nm pumped DFG reached 20% and 15% separately while their slope efficiency reached 19.6% and 15%. All these data were comparable with the OPOs pumped by themselves and never realized before in traditional CW DFG schemes. The results reveal that the high efficiency frequency down conversion can be achieved with low-power near-infrared pump source.
Cheng Xi, Peng Wang, Xiao Li, Liu Zejin. High Efficient continuous-wave mid-infrared generation based on intracavity difference frequency mixing[J]. High Power Laser Science and Engineering, , (): .
