4.4 W, Continuous-Wave, Narrow Linewidth Optical Parametric Oscillator at $3.77~\mu$ m

A high-power, continuous-wave, narrow linewidth singly resonant optical parametric oscillator at 3.77 μm is demonstrated, which is pumped by a 1064 nm fiber laser featuring kilohertz linewidth. A moderate cavity finesse of the optical parametric oscillator at signal wavelength is applied, aiming at narrow linewidth signal and idler output. By optimizing the confocal parameter of the resonated signal wave, with a pump power of 34 W, mid-infrared idler wave with an output power of 4.4 W, and a minimum power fluctuation root mean square of 0.72 % is obtained. A linewidth of less than 25 MHz for the idler wave at 3.77 μm was confirmed by checking the signal wave's reflected interference pattern on an F-P cavity. At the maximum idler output, the M
²
factors on the X and Y axis were 1.36 and 1.40, respectively.