| Continuous wave doubly resonant optical parametric oscillators (DRO's) were invented more than 25 years ago. Continuous wave DRO's, however, have not found wide-spread use because of its narrow continuous tuning range and extreme sensitivity to cavity length and pump frequency fluctuations. It is well known that the OPO's tolerance to external perturbations as well as its tuning range can be substantially improved by resonating only the signal or the idler wave. Such a singly resonant OPO's or SRO's, unfortunately, have a very high threshold. The SRO's high threshold has impeded its development and prevented its realization in the continuous wave domain in the past. In this thesis, we report the first experimental demonstration of a continuous wave singly resonant OPO.; The pump source for the cw SRO consists of an injection-locked Nd:YAG laser that is resonantly doubled in an external enhancement cavity. With 19 W fundamental power incident on the external cavity, a maximum of 11.2 W of second harmonic power at 532 nm was generated using a 8 mm long LiB{dollar}sb3{dollar}O{dollar}sb5{dollar} crystal.; Using this 532 nm pump source, we investigated power and spectral stability of doubly resonant OPO's with fixed low signal loss and arbitrary idler loss. We find that as the idler loss is increased, the OPO power and spectral stability improves when pumped at a few times above threshold. A theory is developed which accounts for the increased stability as the OPO progresses toward the SRO limit. In addition, measurements of DRO threshold with increasing idler loss allowed us to extrapolate to the 100% idler loss limit and thus obtain a realistic estimate of cw SRO threshold.; Based on this threshold estimate, we designed three different types of cw singly resonant OPO's that use type II non-critical phase-matched interaction in KTP crystal. Two of the SRO's were operated with high efficiency. In particular, with 6.7 W pump power incident on the ring cavity SRO, 1.9 W of non-resonant idler was generated. All three types of SRO's ran stably in a single axial mode. |
