Within the framework of a laser guide star and in order to solve the major problem of saturation of the sodium atom, we present an "all-optical" modeless laser that excites all sodium velocity classes. A theoretical and experimental study of the excitation of the sodium D-2 line is presented in three cases: a single-mode laser of linewidth 1 MHz and modeless lasers of linewidths 3 and 4.5 GHz. The best result is obtained when the linewidth matches the Doppler-hyperfine sodium D-2-line profile. By comparison with a single-mode laser excitation, we show that our modeless-laser sodium D-2 star becomes six times brighter. (C) 2003 Optical Society of America. [References: 34]
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