Abstract

High power, continuous-wave (cw), singly resonant optical parametric oscillators (SROs), tunable in the near-and mid-IR are of great importance for applications in spectroscopy, biomedicine, and atmospheric propagation. Such cw SROs using the most widely used nonlinear material, periodically poled lithium niobate (PPLN), has been extensively demonstrated previously. However, attainment of high optical powers in the near- and mid-IR is an experimentally challenging proposition, essentially due to heavy thermal loading of the nonlinear crystal resulting from the high intracavity signal power at increased pump powers. This can lead to saturation and subsequently a substantial drop in efficiency, thus limiting the available output power. To date, a maximum of 10 W at 50 W of pump at 20% efficiency has been reported in a cw SRO [1]. A substantial reduction in the thermal loading by out-coupling the resonating signal has enabled considerable increase in the overall extraction efficiency up to 59% resulting in a total power of 8.6 W (5.1 W signal, 3.5 W idler) for 15 W of pump power [2]. Recently, we also demonstrated that the use of output coupling can result in substantial enhancement in the overall performance of cw SROs without degrading output power and stability [3]. Using the out-coupling approach, we have now generated up to 16.6 W (8.3 W of signal and 8.3 W of idler) of output power from a cw SRO for 26.8 W of pump power at an extraction efficiency to 62%. Moreover, the device is based on an Yb fiber laser pump, resulting in a highly compact, practical, and portable design.

© 2009 IEEE