Abstract

We obtained optical parametric oscillation at 3.0 µm with resonator mirrors designed for this wavelength. The experiment was done with varying input pump power, minor reflectivity, and cavity distance, as well as different beam focusing of the pump beam. Some angle variations from the noncritical phase matching angle and the corresponding frequency shift were also investigated. An antireflection coating on the KTP crystal was important for improving threshold pump power requirements, and yielding efficient OPO. In the first case, the pump source was a pulsed Nd:YAG laser with 1-MW peak power, 14-ns pulse width, for external cavity OPO. For an internal cavity OPO, we used a Nd:YAG laser with a 40-kW peak power, a 200-ns pulse width, and a repetition rate in the range 1–4 kHz. The internal cavity OPO has a lower efficiency, but the pump threshold is not as high as in the external cavity OPO. At relatively high repetition rates, the efficiency was highly dependent on the stability of the pump beam. The dependence of the OPO output on the pump beam modes other than the TEM₀₀ mode was examined.

© 1991 Optical Society of America