Influence of axial temperature distribution to optical parametric gain in CW-OPO

We use the fiber-pumped MgO:PPLN crystal to realize the MIR CW-OPO operation, and observe the nonuniform temperature distribution on the central axis of the crystal. Then we use the heat transfer model in COMSOL software to simulate the temperature distribution in the crystal and find the near linear temperature gradient on the central axis of the crystal. Input the axial temperature distribution to our SRO model based on MATLAB and the simulation results show that the linear axial temperature gradient distribution will not only cause the center wavelength shift of the signal light, but also reduce the parametric gain of the signal light, the uniform temperature along the crystal axis will get the maximum gain. This feature limits the prospect of the single OPO in high-power narrow linewidth laser.