28 June 2006 Polychromatic laser guide star using a single laser at 330 nm
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Abstract
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 4D5/2 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 4×104 photons/s/m2. Thanks to our modeless laser, we propose a new method which consists in exciting directly the 4P3/2 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.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jean-Paul Pique, Ioana C. Moldovan, Vincent Fesquet, Hugues Guillet de Chatellus, Fabien Marc, "Polychromatic laser guide star using a single laser at 330 nm", Proc. SPIE 6272, Advances in Adaptive Optics II, 62723D (28 June 2006); doi: 10.1117/12.692350; https://doi.org/10.1117/12.692350
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