Evaluating the effect of transmissive optic thermal lensing on laser beam quality with a Shack-Hartmann wave-front sensor

We examine wave-front distortion caused by high-power lasers on transmissiv e optics using a Shack-Hartmann wave-front sensor. The coupling coefficient for a thermally aberrated Gaussian beam to the TEM00 mode of a cavity was determined as a function of magnitude of the thermally induced aberration. One wave of thermally induced phase aberration between the Gaussian intensi ty peak and the 1/e(2) radius of the intensity profile reduces the power-co upling coefficient to the TEM,, mode of the cavity to 4.5% with no compensa tion. With optimal focus compensation the power coupling is increased to 79 %. The theoretical shape of the thermally induced optical phase aberration is compared with measurements made in a neutral-density filter glass, Farad ay glass, and lithium niobate. The agreement between the theoretical and th e measured thermal aberration profiles is within the rms wave-front measure ment sensitivity of the Shack-Hartmann wave-front sensor, which is a few na nometers. (C) 2001 Optical Society of America OCIS codes: 120.5050, 120.393 0, 140.3460, 140.6810.