Polychromatic laser guide star using a single laser at 330 nm

J.P. Pique (1) , Ioana C. Moldovan (1) , Vincent Fesquet (1) , Hugues Guillet de Chatellus (1) , Fabien Marc (1)

1 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]

The differential atmospheric tip-tilt can be measured using a Polychromatic Laser Guide Star. A two photon excitation has been proposed. It consists in exciting the 4D 5/2 level of mesospheric sodium atoms with two identical lasers operating at 589 nm and 569 nm. With two modeless lasers of 2×15W at the mesosphere level, this scheme will produce a returned flux at 330 nm of about 4×10 4 photons/s/m2. Thanks to our modeless laser, we propose a new method which consists in exciting directly the 4P 3/2 sodium level with one photon excitation, using a single laser operating at 330 nm. This solution was previously rejected probably because of strong saturation problems using single longitudinal mode lasers. We show that 1 W modeless laser at 330 nm can produce the same returned flux at 330 nm. This solution will save at least 400 k€ of equipment. Moreover, our new method is very promising in terms of simplicity but also in terms of flux because the returned flux above will probably be not sufficient for getting a good Strehl ratio. We propose very efficient solid state laser systems for the production of tens of watts at 330 nm.

Domaines: Optique [physics.optics]; Physique [physics]; Physique Atomique [physics.atom-ph]; Instrumentations et Détecteurs [physics.ins-det]; Agrégats Moléculaires et Atomiques [physics.atm-clus]

J.P. Pique, Ioana C. Moldovan, Vincent Fesquet, Hugues Guillet de Chatellus, Fabien Marc. Polychromatic laser guide star using a single laser at 330 nm. Proceedings of SPIE, the International Society for Optical Engineering, 2006, Advances in Adaptive Optics II. Edited by Ellerbroek, Brent L.; Bonaccini Calia, Domenico., 6272, pp.62723D. ⟨10.1117/12.692350⟩. ⟨hal-01118420⟩