Large-aperture adaptive optical system for correcting wavefront distortions of a petawatt Ti : sapphire laser beam

This paper reports a large-aperture adaptive optical system with a bimorph deformable mirror and Shack - Hartmann wavefront sensor for aberration correction and beam focusing improvement in state-of-the-art petawatt Ti : sapphire lasers. We consider methods for providing feedback to the wavefront sensor and obtaining an objective wavefront that optimises beam focusing onto a target. The use of an adaptive system with a controlled 127-channel 320-mm-aperture mirror in a Ti : sapphire laser with an output power of 4.2 PW has made it possible to obtain a record high laser beam intensity: 1.1 x 10(23) W cm(-2).