Two generations of laser-guide-star adaptive-optics experiments at the Starfire Optical Range

We report results that were obtained with two generations (Generation I and Generation II) of a laser-guide-star adaptive-optics system that is capable of continuous compensation at 65-Hz (Generation I) and 130-Hz (Generation II) closed-loop bandwidths on a 1.5-m telescope. We used a copper-vapor laser that was focused at a 10-km range as the laser guide star and a range-gated Shack–Hartmann sensor to operate a continuous-facesheet deformable mirror that controlled either 149 or 241 actuators. We used a separate full-aperture sensor and a steering mirror to remove overall tilt. System performance was measured by imaging stars with a high-resolution CCD camera in a narrow spectral band that was centered at 0.88 μm, from which we computed point-spread functions, optical transfer functions, and Strehl ratios. Using the laser guide star, we achieved a FWHM image resolution of 0.13 arcsec and a Strehl ratio of 0.48. Using a natural guide star, we achieved a Strehl ratio of 0.64 at 0.13 arcsec FWHM resolution. We also obtained compensated images of the Trapezium region in Orion in H-α light, using only the laser guide star.