Sodium UV modeless laser excitation for PLGS

In the framework of Laser Guide Star projects and more particularly of VASAO project of the Canada France Hawaii Telescope, we have developed a modeless laser at 330 nm and we have carried out photometry experiments in laboratory, in order to evaluate the feasibility of the sodium atom excitation at 330 nm. Our modeless laser is a DCM dye laser frequency doubled by a BBO crystal. A high efficiency acousto-optical crystal assures the modeless property. We present the experimental results of sodium atom excitation of 3S 1/2 → 4P 3/2 transition at 330.24 nm and 3S 1/2 → 3P 3/2 transition at 589 nm. The rate equation model gives a good interpretation of the experimental results.