Study on 2.7 μm and 4.0 μm dual-wavelength optical parametric oscillator based on periodic cascade MgO:PPLN

A mid-infrared dual-wavelength optical parametric oscillator using a double-ended Yb-doped fiber-pumped double-period cascaded MgO:PPLN is reported. By optimizing the crystal’s effective gain length and adjusting the dual-end pump power, dual-wavelength mid-infrared laser outputs of 2.12 W at 2.7 μm and 1.87 W at 4.0 μm were obtained with pump powers of 14.21 W and 15.87 W from the 1064 nm fiber laser. The effects of gain competition in multi-parameter oscillation were effectively mitigated, enabling dual-wavelength mid-infrared synchronous resonance and reducing the power difference from 0.635 W to 0.25 W. The corresponding conversion efficiencies were 14.9 % and 11.7 %, with pulse widths of 55.39 ns and 40.24 ns, and output power stabilities of 3.16 % and 3.58 %, respectively. By adjusting the temperature of the cascaded crystal between 25 °C and 105 °C, tunable mid-infrared laser outputs with wavelengths ranging from 2477.6 to 2705.6 nm and from 3918.4 to 4006.3 nm were achieved, with corresponding tuning bandwidths of 228 nm and 87.9 nm, respectively.