Demonstrating Enhanced Return from Sodium Laser Guide Stars

The work in Phase I of this STTR has advanced a new technology to generate a sodium beacon. The membrane external-cavity surface-emitting laser (MECSEL) has been demonstrated at 589 nm from intra-cavity doubling of a fundamental at 1178 nm. Importantly, the laser frequency can be easily modulated. This will be exploited in Phase II to test frequency chirping and other modulation schemes which a parallel modeling effort has shown should improve the efficiency of the beacon. In Phase II HartSCI plans to further advance the laser itself, supported by additional modeling of expected on-sky performance. After an acceptance test of the laser by the government in the laboratory, the laser will be the integrated at a government telescope followed by on-sky tests and data analysis. Our expectation, based on communication with the government in Phase I, is that the test facility will be the 1 m Auxiliary Beam Director (ABD) at the Starfire Optical Range (SOR) which is designed for laser beam propagation. HartSCI will work with the government to plan the laser deployment and field tests. Such tests will support detailed analysis of the performance of the LGS enhancement methods on sky and inform the optimal design of laser systems for deployment to AO-equipped SDA sensors.