Mid-infrared narrow-linewidth wavelength tuning in MgO:PPLN optical parametric oscillation

A narrow-linewidth wavelength tuning MgO:PPLN intracavity optical parametric oscillator is reported in this paper. 1064 nm fundamental light generated by a Q-switched Nd:YVO4 laser is used to excite an MgO:PPLN crystal, with two Fabry-Perot (F-P) etalons inserted into the composite cavity. By narrowing the spectral linewidths of the fundamental and signal lights with two etalons, the spectral linewidth of the idler light can be indirectly reduced. When MgO:PPLN's temperature is set to 40 degrees C with a repetition rate of 40 Hz and an injected power of 39.45 W, 3.797 mu m mid-infrared laser achieves maximum output power of 1.06 W and narrowest linewidth of 0.863 nm, corresponding to an conversion efficiency of 2.68 % from 808 nm to 3.797 mu m, and beam quality factors M-2 of 1.97 and 2.03 in the orthogonal direction. By ajusting the MgO:PPLN crystal temperature from 30 to 70 degrees C, a mid-infrared laser is generated spanning 3.762 similar to 3.804 mu m, accompanied by a tuning bandwidth of 42 nm and spectral linewidth variations of 0.863 similar to 1.093 nm. This method successfully combines narrow linewidth and broad tunability in mid-infrared laser generation, addressing limitations of excessive linewidth broadening in optical parametric oscillator.