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7 February 2003 Rayleigh laser guide stars for extremely large telescopes
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Rayleigh laser guide star technology is discussed here with particular attention paid to the effects of laser pulse length, a parameter that becomes more significant to the design when telescope apertures are greater than 10 meters. After reviewing the relative return signal for Rayleigh versus sodium laser guide stars, a brief review of the pulse length characteristics of sodium lasers is given. Only one of the proposed sodium laser systems is pulsed while the others are CW. To insure star-like sources at the wavefront sensor with FWHM < 1.0 arcsec, lasers that will be most useful for Extremely Large Telescopes must have a short pulse format whereas CW lasers will be of little to no use. A relatively simple Rayleigh laser guide star method is described for Ground Layer Adaptive Optics (GLAO). This method provides a way to average out the effects of high altitude turbulence with a single Rayleigh laser guide star leaves intact the wavefront sign needed to correct ground-layer wavefront perturbations.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Laird A. Thompson "Rayleigh laser guide stars for extremely large telescopes", Proc. SPIE 4839, Adaptive Optical System Technologies II, (7 February 2003);

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