Theoretical study of diode pumped intracavity backward optical parametric oscillator based on periodically poled lithium niobate

In this paper, a diode pumped mid-IR laser based on a singly resonant intracavity backwards optical parametric oscillator (SR IC-BOPO) is proposed and a simulation model is established. The model takes into account light emission from a laser crystal (e.g., Nd:YVO4), a SR IC-BOPO from a periodically poled nonlinear crystal (e.g., periodically poled lithium niobate (PPLN)), linear loss resulting from optical components, nonlinear loss due to the pump depletion in the BOPO process, thermal lens effect in the laser crystal, and optical mode overlapping between pump, signal and idler beam in PPLN nonlinear crystal. It is shown that the proposed mid-IR laser is capable of generating continuous wave (CW), narrow linewidth, mid-IR light, ranging from 2.1 to 4.5 μm, by employing PPLN with the fifth-order quasi-phase matching (QPM). It is found that a mid-IR laser with an output power as high as 0.47 W can be achieved using a 10 W 808 nm pump laser diode and PPLN crystal with the fifth-order QPM. To the best of our knowledge, this is the first time that a manufacturable SR IC-BOPO is modeled using PPLN, while also taking into account the nonlinear depletion losses in the cavity.