An efficient modeless laser for a mesospheric sodium laser guide star

We will describe the characteristics of our pulsed modeless laser system which is composed of a cw oscillator with an intra-cavity pre-amplifier. The modeless laser has remarkable properties. The laser system we are developing is of a great facility of use. Its simplicity allows the design of a very compact and reliable chain. This is also an important point in the context of an astronomical site. The use of natural reference-stars for adaptive optics provides poor sky-coverage for near-diffraction-limited observation at visible and near-infrared wavelengths. It is internationally admitted now, that the future of adaptive optics in astronomy, passes by the use of sodium laser guide star .The modeless laser that we have developed would allow to gain almost 2 magnitudes compared to an artificial D/sub 2/-star obtained with a single-longitudinal-mode laser. This result makes both polychromatic and monochromatic laser guide star projects much more credible.