Temperature Dependence of Fiber-Format Multiwavelength Generation Process in Bulk MgO-PPLN Crystal Via High-Power Photonic Crystal Fiber Laser

In this paper, we report on a compact frequency conversion scheme based on high-power photonic crystal fiber (PCF) laser at optical communication band using a multigrating MgO-PPLN crystal. Temperature dependence of wave-vector mismatch, group velocity, central wavelength, and conversion efficiency was theoretically analyzed. Temperature tuning characteristics were experimentally obtained by propagating 240-fs pulses with a 126-MHz repetition rate in a 10-mm-long MgO-PPLN crystal. We also observed and characterized second-harmonic generation (SHG), third-harmonic generation (THG), and fourth-harmonic generation processes in the same crystal. Maximum SHG and THG conversion efficiency values of 27.5% and 4.3% were achieved at 100 °C and 77 °C, respectively.