Rayleigh Laser Guide Star Systems: UnISIS Bow‐Tie Shutter and CCD39 Wavefront Camera

Laser guide star systems based on Rayleigh scattering require some means todeal with the flash of low altitude laser light that follows immediately aftereach laser pulse. These systems also need a fast shutter to isolate the highaltitude portion of the focused laser beam to make it appear star-like to thewavefront sensor. We describe how these tasks are accomplished with UnISIS, theRayleigh laser guided adaptive optics system at the Mt. Wilson Observatory2.5-m telescope. We use several methods: a 10,000 RPM rotating disk, dichroics,a fast sweep and clear mode of the CCD readout electronics on a 10 $\mu$stimescale, and a Pockel's cell shutter system. The Pockel's cell shutter wouldbe conventional in design if the laser light were naturally polarized, but theUnISIS 351 nm laser is unpolarized. So we have designed and put into operationa dual Pockel's cell shutter in a unique bow tie arrangement.Comment: 19 pages, 5 figures, accepted for publication in October 2002 issue of PAS