New Adaptive Optics Approaches Leading to Visible Wavelength Adaptive Optics with Laser Guidestars on Large Telescopes Donald Gavel, Director of the Laboratory for Adaptive Optics, Lick Observatory, University of California Santa Cruz We discuss new non-traditional methods of wavefront sensing and control that could enable the next generation of wide-field, high sky coverage visible light adaptive optics systems. Imaging and spectroscopy at the diffraction limit becomes increasingly difficult as the science wavelength gets shorter because of the increased accuracy and higher temporal bandwidths needed for the AO correction. Brighter guide stars are demanded which, for any reasonable sky coverage, must be artificial stars provided by lasers. Unless we make breakthroughs in the sensing efficiency, the required laser power quickly becomes very expensive or simply unobtainable. At the LAO we have been investigating diffractive wavefront sensing and other novel techniques to provide the greatest accuracy per guidestar photon in the wavefront sensor. In addition, we are advocating the use of uplink correction, whereby the laser beam is corrected for turbulence on the up-propagation path in order to concentrate the guide star energy into a smaller spot, again, for greater wavefront sensing accuracy per laser photon. These techniques designed for astronomy could be directly extended to biological imaging applications, such as AO retinal imaging, where it would provide the benefit of increased sensing accuracy with decreased probe light intensity. In this presentation we give the conceptual framework leading to visible wavelength AO systems of the future. We will also present some results from the laboratory and on-sky experiments designed to demonstrate these concepts.