Figure 1. An OPG: simply focus a pump laser through a crystal. If the crystal nonlinearity is high enough, and for high peak-power pump pulses, the efficiency can be high (~20%).
Figure 2. The signal output of an OPG both seeded and unseeded. Note that the seeded axis is the left axis and the unseeded is the right axis. The seeded peak intensity is approximately 30 times the unseeded peak intensity.
The tunability of the device is determined by the phasematching properties of the OPG crystal. In the case of periodically poled crystals such as PPLN, any frequency within the transparency range of lithium niobate is accessible. We have demonstrated tunabilty from 1.4 to 4.7 microns, see Figure 3.
Figure 3. Tuning range for the OPG system.