Continuous-wave 1.57 m/3.84 m intra-cavity multiple optical parametric oscillator based on MgO:APLN

Continuous-wave (CW) coherent sources emitting two wavelengths of 1.57 m and 3.84 m have aroused much interest of scientists due to their many applications such as military multiband composite guidance, remote monitoring of the special environment, etc. Quasi-phase matching (QPM) optical parametric oscillator (OPO) device with periodically inverted structure of nonlinear coefficient can implement an efficient and wavelength conversion at arbitrary wavelength in the transparent range of the QPM material. Nowadays, using MgO:PPLN for QPM, various MgO:PPLN-OPOs pumped by conventional 1.06 m laser source can produce 1.57 m and 3.84 m laser and also achieve good results. But as a result of the limitation of momentum conservation condition and periodically poled structure, 1.57 m and 3.84 m laser can only meet a single band. To obtain the two-wavelength laser output at the same time, the MgO:PPLN-OPO could not be applied. In this paper, a CW 1.57 m and 3.84 m intra-cavity multiple optical parametric oscillator based on MgO:APLN is reported. The cross period parameter light is obtained by using a folded type doubly cavity which consists of 1064 nm resonator and multiple optical parametric oscillator. Considering both its thermal stability under high power pump and the light spot mode matching of multiple optical parametric oscillation process, through numerical simulation and theoretical analysis of two sub cavities, the optimum parameters of the cavity structure are determined. On this basis, the influences of output coupler transmittance on oscillation threshold, the down-conversion efficiency, output power stability are investigated in experiment. With T=10% at 1.47 m and 3.3 m output coupler used, the maximum output powers of 3.13 W at 1.57 m and 0.85 W at 3.84 m are obtained, corresponding to slope efficiencies of 6.8% and 1.9%, respectively. The power stabilities are better than 1.8% and 3% at the maximum output power in half an hour. The experimental results show that the intra-cavity multiple optical parametric oscillator based on a single poled crystal MgO:APLN is an effective method of obtaining a 1.57 m and 3.84 m CW laser.