Point absorbers in Advanced LIGO
A. F. Brooks, G. Vajente, Hiro Yamamoto, Rich Abbott, Carl Adams, R. X. Adhikari, A. Ananyeva, Stephen Appert, K. Arai, J. S. Areeda, Y. Asali, Stuart Aston, Corey Austin, A. M. Baer, M. Ball, S. Ballmer, S. Banagiri, David Barker, L. Barsotti, Jeffrey Bartlett, B. K. Berger, J. Betzwieser, D. Bhattacharjee, G. Billingsley, Sébastien Biscans, C. D. Blair, Ryan Blair, N. Bode, P. Booker, Rolf Bork, Alyssa Bramley, Daniel D. Brown, A. Buikema, C. Cahillane, K. C. Cannon, H. Cao, Chen Xu, A. A. Ciobanu, F. Clara, C. M. Compton, S. J. Cooper, K. R. Corley, S. T. Countryman, P. B. Covas, D. C. Coyne, L. E. H. Datrier, D. Davis, C. DiFronzo, K. L. Dooley, Jenne C. Driggers, P. Dupej, S. E. Dwyer, A. Effler, T. Etzel, M. Evans, T. M. Evans, J. Feicht, A. Fernandez-Galiana, P. Fritschel, Valery Frolov, P. Fulda, M. Fyffe, Joe Giaime, Dwayne Giardina, P. Godwin, E. Goetz, Slawomir Gras, Corey Gray, R. Gray, A. C. Green, Anchal Gupta, E. K. Gustafson, Dick Gustafson, E. D. Hall, Jonathan Hanks, J. Hanson, Terra Hardwick, R. K. Hasskew, M. C. Heintze, A. F. Helmling-Cornell, N. A. Holland, Kiamu Izmui, Wenxuan Jia, Jeff Jones, S. Kandhasamy, Sudarshan Karki, M. Kasprzack, K. Kawabe, N. Kijbunchoo, Peter King, J. S. Kissel, Rahul Kumar, M. Landry, B. B. Lane, B. Lantz, M. Laxen, Y. K. Lecoeuche, Jessica Leviton, Liu Jian, Marc Lormand
Abstract
Small, highly absorbing points are randomly present on the surfaces of the main interferometer optics in Advanced LIGO. The resulting nanometer scale thermo-elastic deformations and substrate lenses from these micron-scale absorbers significantly reduce the sensitivity of the interferometer directly though a reduction in the power-recycling gain and indirect interactions with the feedback control system. We review the expected surface deformation from point absorbers and provide a pedagogical description of the impact on power buildup in second generation gravitational wave detectors (dual-recycled Fabry-Perot Michelson interferometers). This analysis predicts that the power-dependent reduction in interferometer performance will significantly degrade maximum stored power by up to 50% and, hence, limit GW sensitivity, but it suggests system wide corrections that can be implemented in current and future GW detectors. This is particularly pressing given that future GW detectors call for an order of magnitude more stored power than currently used in Advanced LIGO in Observing Run 3. We briefly review strategies to mitigate the effects of point absorbers in current and future GW wave detectors to maximize the success of these enterprises.