Synchronously pumped OPO-OPO and OPO-DFM devices

The efficient conversion of near infrared radiation into the 2-5 μm waveband is of considerable interest to applications that exploit the mid-infrared atmospheric transmission windows. This work describes an experimental investigation of synchronously pumped optical parametric oscillator (OPO) devices that use two different conversion steps. The tandem OPO (TOPO) described uses two separate periodically poled lithium niobate (PPLN) crystals. The first crystal is pumped at 1.064 μm and generates signal and idler beams at 1.48 and 3.80 μm respectively. The signal beam at 1.48 μm then pumps the second crystal to generate signal and idler beams tunable between 2.16-2.36 μm and 3.98-4.74 μm respectively. In the OPO-DFM (difference frequency mixing) device both conversion stages are located on a single PPLN crystal. In the first part of the crystal, signal and idler beams at 1.46 and 3.90 μm are generated. The second part of the crystal is phased matched for difference frequency mixing between the signal and idler. Both devices build upon our earlier results in which the tandem OPO was pumped by an amplified mode-locked laser