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Published October 15, 2008 | Published
Journal Article Open

Optimal light beams and mirror shapes for future LIGO interferometers

Abstract

We report the results of a recent search for the lowest value of thermal noise that can be achieved in LIGO by changing the shape of mirrors, while fixing the mirror radius and maintaining a low diffractional loss. The result of this minimization is a beam with thermal noise a factor of 2.32 (in power) lower than previously considered Mesa Beams and a factor of 5.45 (in power) lower than the Gaussian beams employed in the current baseline design. Mirrors that confine these beams have been found to be roughly conical in shape, with an average slope approximately equal to the mirror radius divided by arm length, and with mild corrections varying at the Fresnel scale. Such a mirror system, if built, would impact the sensitivity of LIGO, increasing the event rate of observing gravitational waves in the frequency range of maximum sensitivity roughly by a factor of 3 compared to an Advanced LIGO using Mesa beams (assuming all other noises remain unchanged). We discuss the resulting beam and mirror properties and study requirements on mirror tilt, displacement, and figure error, in order for this beam to be used in LIGO detectors.

Additional Information

©2008 The American Physical Society. (Received 24 June 2008; published 2 October 2008) We thank Kip Thorne for suggesting this problem to us. We thank GariLynn Billingsley for providing information about mirror manufacturing and Rana Adhikari for information about suspension systems of future LIGO detectors. We thank Jayashree Balakrishna, Gregory Daues, Ruxandra Bondarescu, Andrew Lundgren, and Dave Tsang for carefully proofreading the manuscript, checking our calculations, and valuable advice on the content and the format of this paper. We thank Kentaro Somiya for helping us with Fig. 11. M.B. and Y.C. were supported by the Alexander von Humboldt Foundation's Sofja Kovalevskaja Programme, NSF Grants No. PHY-0653653 and No. PHY-0601459, as well as the David and Barbara Groce startup fund at Caltech. M.B. is grateful for travel support generously offered by The Center for Computation and Technology at The Louisiana State University, Rochester Institute of Technology, The American Physical Society, The University of Tuebingen, Universita Degli Studi Del Sanio, and Jayashree Balakrishna. While preparing this paper, we enjoyed inspiring and stimulating conversations with Gabrielle Allen, David Blair, Manuela Campanelli, Erika D'Ambrosio, Vincenzo Galdi, Kazuaki Kuroda, Konstantinos Kokkotas, Carlos Lousto, Vincenzo Pierro, Innocento Pinto, Ed Seidel, Dumitru Vulcanov, and Hiro Yamanoto.

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Created:
August 22, 2023
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October 17, 2023