Alternative Methods for Creating a Sodium Guidestar

The development of compact and telescope-deployable laser sources emitting in the yellow portion of the visible spectrum is critical for the advancement of DoD-relevant adaptive optics capabilities. The objective of this project is to continue the development of novel laser architectures based on optically-pumped substrate-transferred epitaxial gain media capable of efficient thermal management and thus power scaling for laser guidestar applications. Unlike conventional semiconductor disk lasers where the integrated Bragg mirror leads to a significant thermal bottleneck, our mirror-free gain chips simplify the epitaxial growth process, show the potential for efficient power scaling, and are amenable to mass manufacturing. These structures may be readily employed in a resonant cavity for laser and pump feedback, with the potential for wide tunability, while exhibiting a narrow laser linewidth. In Phase I, the feasibility of Watt-level output power near room temperature was successfully demonstrated in these devices. In our proposed Phase II, we will develop a prototype laser system to be deployed at the Starfire Optical Range with a near-infrared output power >40 W (1178 nm) frequency doubled to ~30 W at 589 nm. Extensive optimization efforts relating to thermal management will be pursued and ultimately integrated into a breadboard-level laser guidestar testbed.