Optical parametric oscillator for lidar system

A lidar system comprising:

• a pump laser configured to produce pulses of light at a pump wavelength;
• an optical parametric oscillator (OPO) comprising an OPO medium configured to:
• receive the pump pulses from the pump laser;
• convert at least part of the received pump pulses into pulses of light at a signal wavelength and pulses of light at an idler wavelength;
• and
• emit at least a portion of the signal pulses;
• a scanner configured to scan the emitted signal pulses of light across a field of regard;
• a receiver configured to detect at least a portion of the scanned pulses of light scattered by a target located a distance from the lidar system, wherein:
• an output beam of the lidar system comprises the emitted signal pulses of light which are scanned across the field of regard;
• an input beam of the lidar system comprises the portion of the scanned pulses of light detected by the receiver;
• and
• the input and output beams are substantially coaxial;
• an overlap mirror configured to overlap the input and output beams so that they are substantially coaxial, wherein the overlap mirror comprises:
• a hole, slot, or aperture which the output beam passes through;
• and
• a reflecting surface that reflects at least a portion of the input beam toward the receiver;
• and
• a processor configured to determine the distance from the lidar system to the target based at least in part on a round-trip time of flight for an emitted pulse of light to travel from the lidar system to the target and back to the lidar system.