Compact fiber laser approach to generating 589 nm laser guide stars

We are developing an all-fiber laser system for generating 589 nm light for laser-guided adaptive optics. If only natural stars can be used to measure the turbulence in the Earth's atmosphere, at most a few percent of the sky is accessible to adaptive optics correction. Laser guide stars are therefore crucial to the broad use of adaptive optics, because they facilitate access to a large fraction of possible locations on the sky. In particular, lasers tuned to the 589 nm resonance line of atomic sodium are able to create an artificial beacon at altitudes of 95-105 km, thus coming as close as possible to reproducing the light path of starlight. The deployment of multiconjugate adaptive optics on large aperture telescopes world-wide will require the use of three to five sodium laser guide stars in order to achieve uniform correction over the aperture with a high Strehl value. Current estimates place the minimum required laser power at 10 W per laser for a continuous wave source. In addition, the lasers need to be compact, efficient, robust and turnkey.