SBIR-STTR Award

The objective of the proposed research is to demonstrate high-power, scalable, and stable laser sources at specific wavelengths with narrow linewidth matched to the single velocity class of mesospheric atomic sodium for guide star application. The operation at tailored wavelengths, 1141 nm and 1178 nm (for 589 nm via frequency doubling) is addressed by the use of bandgap-engineered optically pumped semiconductor lasers, which are capable of producing multiple watts to multiple tens of watts per single device in diffraction-limited transverse mode. The scalable architecture is realized by employing multiple VECSEL devices in one resonator, thus allowing high saturated output power of the laser device. With multiple resonant periodic gain (RPG) structures in one laser resonator, an issue arises concerning the stability of the standing wave pattern. We will solve this issue by using the twisted-mode configuration so that the antinode of the standing wave pattern always matches the location of the quantum wells, which provide optical gain.

The objective of the proposed effort is to demonstrate robustly-engineered stable vertical-external-cavity surface-emitting laser (VECSEL) sources of 20 W at 589Â nm and 10 W at 1141Â nm with narrow linewidth matched to a single velocity class of mesospheric atomic sodium for guide star application. A scalable architecture is realized by employing multiple VECSEL devices in one resonator, thus allowing high saturated output power. A critical output of Phase I was the demonstration of the "twisted-mode"? cavity configuration which stabilizes the standing wave pattern in a resonator with multiple resonant periodic gain structures. In this arrangement, the antinode of the standing wave pattern always matches the location of the quantum wells which provide optical gain and ensures single-frequency operation. In Phase II, the prototype 1178 nm device will be optimized for power, with the addition of further VECSEL devices, an external doubling cavity will be added to convert the output to 589 nm, and the 1141 nm device will be constructed using VECSEL devices already in hand. Both lasers will be engineered for deployment to a telescope. The 589 nm laser will be demonstrated on sky at a 1.5 m telescope.