A pulsed guide star laser can be the brightest

We report on a numerical model and supporting experiments to show that a high peak power, pulse burst, Na guide-star waveform, suitable for use with adaptive optics systems requiring dynamic refocusing to avoid guide star elongation, is capable of producing a return comparable to conventional guide star laser of comparable output power. The predictions from our numerical model using coherent pumping by short, high peak power pulses, or so-called π-pulse pumping, indicate that very bright fluorescence returns can be achieved in this regime. This is supported by experimental results where fluorescence is observed in alkali atoms (cesium) using variable input power and pulse lengths. The model is used to predict very bright Na guide stars, using short pulses to excite most of the Na atoms available, followed by sufficient time to let them decay. © 2010 SPIE.Nikita Simakov, Murray Hamilton, Peter J. Veitch and Jesper Munc