Compact mid-infrared self-optical parametric oscillator directly-pumped by diode laser based on a single Nd:MgO:PPLN crystal

•Self-optical parametric oscillator simplifies and miniaturizes mid-infrared lasers.•Laser oscillation and nonlinear down conversion are realized in a single crystal.•Unique thermal problem of this multi-functional crystal is studied comprehensively.•Watt-level and tunable infrared lasers are achieved in a compact cavity. We present a diode-pumped self-optical parametric oscillator (SOPO) in which the laser oscillation and frequency down conversion were simultaneously realized in a single Nd:MgO:PPLN crystal. The special thermal problem in this multi-functional crystal was studied by integrative optimization of the diode laser wavelength, pump beam size, and compact cavity design. At an absorbed pump power of 15.4 W, the SOPO output power was 1.2 W for both the 3.85 μm idler and 1.51 μm signal lasers. Wavelength tuning of the idler laser at different cooling temperature in the mid-infrared region was also demonstrated.