A continuous wave dye laser for use in astronomical adaptive optics

Abstract

Powerful lasers are needed to generate artificial guide stars for astronomical adaptive optics. Continuous wave (CW) lasers yield the most efficient excitation of the D2 line in the mesopheric sodium layer. Data is presented from early systems which used commercially available CW dye lasers. Building on these results, a dye laser was designed and constructed which incorporates a sodium Faraday filter (SFF) to select and lock the laser frequency to the peak of the D2 sodium resonance. This laser was the first ring dye laser made using an intra-cavity SFF, and also the first incorporating a SFF to produce a significant amount of power in a single longitudinal mode. A major part of this thesis concerns the design and construction of the SFF. The theory of operation is developed and then used to design a SFF with a high throughput at the D2 line of sodium. The two main elements of a SFF are a sodium cell and a magnet. The design and construction of these two elements is discussed in detail. The design and construction of a wavefront sensor for the Multiple Mirror Telescope's unique geometry is presented. This wavefront sensor and a CW dye laser were used to generate the first astronomical images sharpened by an adaptive optics system incorporating a sodium laser guide star.