Point absorbers in Advanced LIGO
Authors: Brooks Aidan F. , Vajente Gabriele , Yamamoto Hiro , Abbott Rich , Adams Carl , Adhikari Rana X. , Ananyeva Alena , Appert Stephen , Arai Koji , Areeda Joseph S. , Asali Yasmeen , Aston Stuart M. , Austin Corey , Baer Anne M. , Ball Matthew , Ballmer Stefan W. , Banagiri Sharan , Barker David , Barsotti Lisa , Bartlett Jeffrey , Berger Beverly K. , Betzwieser Joseph , Bhattacharjee Dripta , Billingsley Garilynn , Biscans Sebastien , Blair Carl D. , Blair Ryan M. , Bode Nina , Booker Phillip , Bork Rolf , Bramley Alyssa , Brown Daniel D. , Buikema Aaron , Cahillane Craig , Cannon Kipp C. , Cao Huy Tuong , Chen Xu , Ciobanu Alexei A. , Clara Filiberto , Compton Camilla , Cooper Sam J. , Corley Kenneth R. , Countryman Stefan T. , Covas Pep B. , Coyne Dennis C. , Datrier Laurence E. , Davis Derek , Difronzo Chiara D. , Dooley Katherine L. , Driggers Jenne C. , Dupej Peter , Dwyer Sheila E. , Effler Anamaria , Etzel Todd , Evans Matthew , Evans Tom M. , Feicht Jon , Fernandez-Galiana Alvaro , Fritschel Peter , Frolov Valery V. , Fulda Paul , Fyffe Michael , Giaime Joe A. , Giardina Dwayne D. , Godwin Patrick , Goetz Evan , Gras Slawomir , Gray Corey , Gray Rachel , Green Anna C. , Gupta Anchal , Gustafson Eric K. , Gustafson Dick , Hall Evan , Hanks Jonathan , Hanson Joe , Hardwick Terra , Hasskew Raine K. , Heintze Matthew C. , Helmling-Cornell Adrian F. , Holland Nathan A. , Izmui Kiamu , Jia Wenxuan , Jones Jeff D. , Kandhasamy Shivaraj , Karki Sudarshan , Kasprzack Marie , Kawabe Keita , Kijbunchoo Nutsinee , King Peter J. , Kissel Jeffrey S. , Kumar Rahul , Landry Michael , Lane Benjamin B. , Lantz Brian , Laxen Michael , Lecoeuche Yannick K. , Leviton Jessica , Jian Liu , Lormand Marc , Lundgren Andrew P. , Macas Ronaldas , Macinnis Myron , Macleod Duncan M. , Mansell Georgia L. , Marka Szabolcs , Marka Zsuzsanna , Martynov Denis V. , Mason Ken , Massinger Thomas J. , Matichard Fabrice , Mavalvala Nergis , McCarthy Richard , McClelland David E. , McCormick Scott , McCuller Lee , McIver Jessica , McRae Terry , Mendell Gregory , Merfeld Kara , Merilh Edmond L. , Meylahn Fabian , Mistry Timesh , Mittleman Richard , Moreno Gerardo , Mow-Lowry Conor M. , Mozzon Simone , Mullavey Adam , Nelson Timothy J. , Nguyen Philippe , Nuttall Laura K. , Oberling Jason , Oram Richard J. , Osthelder Charles , Ottaway David J. , Overmier Harry , Palamos Jordan R. , Parker William , Payne Ethan , Pele Arnaud , Penhorwood Reilly , Perez Carlos J. , Pirello Marc , Radkins Hugh , Ramirez Karla E. , Richardson Jonathan W. , Riles Keith , Robertson Norna A. , Rollins Jameson G. , Romel Chandra L. , Romie Janeen H. , Ross Michael P. , Ryan Kyle , Sadecki Travis , Sanchez Eduardo J. , Sanchez Luis E. , Tiruppatturrajamanikkam Saravanan R. , Savage Richard L. , Schaetzl Dean , Schnabel Roman , Schofield Robert M. , Schwartz Eyal , Sellers Danny , Shaffer Thomas , Sigg Daniel , Slagmolen Bram J. , Smith Joshua R. , Soni Siddharth , Sorazu Borja , Spencer Andrew P. , Strain Ken A. , Sun Ling , Szczepanczyk Marek J. , Thomas Michael , Thomas Patrick , Thorne Keith A. , Toland Karl , Torrie Calum I. , Traylor Gary , Tse Maggie , Urban Alexander L. , Valdes Guillermo , Vander-Hyde Daniel C. , Veitch Peter J. , Venkateswara Krishna , Venugopalan Gautam , Viets Aaron D. , Vo Thomas , Vorvick Cheryl , Wade Madeline , Ward Robert L. , Warner Jim , Weaver Betsy , Weiss Rainer , Whittle Chris , Willke Benno , Wipf Christopher C. , Xiao Liting , Yu Hang , Yu Haocun , Zhang Liyuan , Zucker Michael E. , Zweizig John 
Published: April 2021

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.