Efficient modeless laser for a mesospheric sodium laser guide star
Résumé
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 D2 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 D2-line profile. By comparison with a single-mode laser excitation, we show that our modeless-laser sodium D2 star becomes six times brighter.
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