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Published October 15, 2006 | public
Journal Article Open

New family of light beams and mirror shapes for future LIGO interferometers


Advanced LIGO's present baseline design uses arm cavities with Gaussian light beams supported by spherical mirrors. Because Gaussian beams have large intensity gradients in regions of high intensity, they average somewhat poorly over fluctuating bumps and valleys on the mirror surfaces (thermal noise). Flat-topped light beams (mesa beams) are being considered as an alternative because they average over thermal noise more effectively. However, the proposed mesa beams are supported by nearly-flat mirrors, which experience a very serious tilt instability. In this paper we propose an alternative configuration in which mesa-shaped beams are supported by nearly-concentric spheres, which experience only a weak tilt instability. The tilt instability is analyzed for these mirrors in a companion paper by Savov and Vyatchanin. We also propose a one-parameter family of light beams and mirrors in which, as the parameter alpha varies continuously from 0 to pi, the beams and supporting mirrors get deformed continuously from the nearly-flat-mirrored mesa configuration (FM) at alpha=0, to the nearly-concentric-mirrored mesa configuration (CM) at alpha=pi. The FM and CM configurations at the endpoints are close to optically unstable, and as alpha moves away from 0 or pi, the optical stability improves.

Additional Information

©2006 The American Physical Society (Received 21 September 2004; revised 16 August 2006; published 9 October 2006) We thank Pavlin Savov, Juri Agresti, Erika D'Ambrosio, Yanbei Chen, Geoffery Lovelace, and Poghos Kazarian for useful discussions and advice. M. B. thanks Manuela Campanelli and the University of Texas at Brownsville, and Ed Seidel, Gabrielle Allen and the Center for Computation and Technology at Louisiana State University for helpful discussions and travel support during this research. This research was supported in part by NSF Grants No. PHY-0099568 and PHY-0601459.


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