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As the first generation of laser interferometric gravitational wave detectorsnear operation, research and development has begun on increasing theinstrument's sensitivity while utilizing the existing infrastructure. In theLaser Interferometer Gravitational Wave Observatory (LIGO), significantimprovements are being planned for installation in ~2007, increasing strainsensitivity through improved suspensions and test mass substrates, activeseismic isolation, and higher input laser power. Even with the highest qualityoptics available today, however, finite absorption of laser power withintransmissive optics, coupled with the tremendous amount of optical powercirculating in various parts of the interferometer, result in criticalwavefront deformations which would cripple the performance of the instrument.Discussed is a method of active wavefront correction via direct thermalactuation on optical elements of the interferometer. A simple nichrome heatingelement suspended off the face of an affected optic will, through radiativeheating, remove the gross axisymmetric part of the original thermal distortion.A scanning heating laser will then be used to remove any remainingnon-axisymmetric wavefront distortion, generated by inhomogeneities in thesubstrate's absorption, thermal conductivity, etc. A proof-of-principleexperiment has been constructed at MIT, selected data of which are presented.Comment: 11 pages, 7 figures, submitted to Classical and Quantum Gravit

Adaptive thermal compensation of test masses in advanced LIGO