This Small Business Innovation Research Phase I project is directed to the improvement of the optical transmission of ZnGeP2 crystals. ZnGeP2 single crystals have the highest figure of merit for use in optical parametric oscillators (OPOs) to generate 3 to 11 micron tunable radiation. However, ZnGeP2 shows an anomalous absorption between 1 and 3 microns, which is the desired spectral region for pumping OPOs. This absorption sharply limits the average power that can be handled by IR OPOs. Although we have found that thermal annealing of ZnGeP2 crystals will improve the optical transmission from 1 to 3 microns, the improvement is not great enough, and it requires an excessive annealing time. INRAD, Inc., proposes to utilize fast electron and gamma ray radiation to improve the optical transmission of ZnGeP2.
