Can amplified spontaneous emission produce intense laser guide stars for adaptive optics?

Abstract

Adaptive optics (AO) is a key technology for ground-based optical and infrared astronomy, providing high angular resolution and sensitivity. AO systems employing laser guide stars (LGS) can achieve high sky coverage, but their performance is limited by LGS return flux. We examine the potential of two new approaches that might produce high-intensity atmospheric laser beacons. Amplified spontaneous emission could potentially boost the intensity of beacons produced by conventional resonant excitation of atomic or molecular species in the upper atmosphere. This requires the production of a population inversion in an electronic transition that is optically-thick to stimulated emission. Potential excitation mechanisms include continuous wave pumping, pulsed excitation and plasma generation. Alternatively, a high-power femtosecond pulsed laser could produce a white-light supercontinuum high in the atmosphere. The broad-band emission from such a source could also facilitate the sensing of the tilt component of atmospheric turbulence.

Stand-off magnetometry with directional emission from sodium vapors

“…This is, indeed, possible using the technique of mirrorless lasing, a method to generate backward directional emission with the help of so called backward amplified spontaneous emission (ASE) [7,8], which was demonstrated with atomic vapors confined to vapor cells. The question of the possibility to "scale" the laboratory results to onsky experiments remains open and is a subject of ongoing investigation [8,9].…”