Abstract

Adaptive optics were originally developed for military applications, where they have improved the imaging of space objects up to 25 times that of conventional uncompensated imagery. The deployment of these systems in the civilian sector has revolutionized optical astronomy over the last few years. Adaptive optics remove distortions caused by atmospheric turbulence by making corrections to the incoming wave front using one or more bright points of light in the area being observed as references. The use of multi-conjugate adaptive optics with multiple reference points can provide three-dimensional imaging of the regional turbulence. The required reference points can be artificial light sources created by shooting multiple lasers at the sky to excite mesospheric sodium atoms located 90 kilometers above the ground. Laser systems for adaptive optics need to be precisely tuned to the sodium D, transition (589 nm) and are unusually powerful (7–24 W) for lasers at this wavelength. The current state-of-the-art laser guide star (LGS) systems consist of either complex sum-frequency generation lasers¹ or multiple-laser-pumped dye lasers based on the technology developed for the AVLIS Program at LLNL.^2,3 Both laser types are complicated and highly manpower intensive. For LGS systems to be usable for routine astronomical application, they must be reliable, robust and operate in a turnkey mode. Longer term, astronomers need robust, compact, energy- and cost- effective sodium lasers in the 10–50 W class for the next generation of extremely large aperture telescopes (30–100 m) proposed for construction by 2020.

© 2002 Optical Society of America