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Local readout enhancement for detuned signal-recycling interferometers

Rehbein, Henning and Müller-Ebhardt, Helge and Somiya, Kentaro and Li, Chao and Schnabel, Roman and Danzmann, Karsten and Chen, Yanbei (2007) Local readout enhancement for detuned signal-recycling interferometers. Physical Review D, 76 (6). Art. No. 062002. ISSN 2470-0010. doi:10.1103/PhysRevD.76.062002.

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High power detuned signal-recycling interferometers currently planned for second-generation interferometric gravitational-wave detectors (for example Advanced LIGO) are characterized by two resonances in the detection band, an optical resonance and an optomechanical resonance which is upshifted from the suspension pendulum frequency due to the so-called optical-spring effect. The detector's sensitivity is enhanced around these two resonances. However, at frequencies below the optomechanical resonance frequency, the sensitivity of such interferometers is significantly lower than non-optical-spring configurations with comparable circulating power; such a drawback can also compromise high-frequency sensitivity, when an optimization is performed on the overall sensitivity of the interferometer to a class of sources. In this paper, we clarify the reason for such a low sensitivity, and propose a way to fix this problem. Motivated by the optical-bar scheme of Braginsky, Gorodetsky, and Khalili, we propose to add a local readout scheme which measures the motion of the arm-cavity front mirror, which at low frequencies moves together with the arm-cavity end mirror, under the influence of gravitational waves. This scheme improves the low-frequency quantum-noise-limited sensitivity of optical-spring interferometers significantly and can be considered as an incorporation of the optical-bar scheme into currently planned second-generation interferometers. On the other hand it can be regarded as an extension of the optical-bar scheme. Taking compact binary inspiral signals as an example, we illustrate how this scheme can be used to improve the sensitivity of the planned Advanced LIGO interferometer, in various scenarios, using a realistic classical-noise budget. We also discuss how this scheme can be implemented in Advanced LIGO with relative ease.

Item Type:Article
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Schnabel, Roman0000-0003-2896-4218
Chen, Yanbei0000-0002-9730-9463
Additional Information:©2007 The American Physical Society. (Received 21 May 2007; published 21 September 2007) We thank Stan Whitcomb for very useful discussions. Research of H.M.-E., K.S., and Y.C. is supported by the Alexander von Humboldt Foundation’s Sofja Kovalevskaja Programme. Research of H.R. and R.S. is supported by the Deutsche Forschungsgemeinschaft through the EGC program and the SFB No. 407, respectively. Research of C.L. is supported in part by NSF grants No. PHY-0099568 and No. PHY-0601459.
Subject Keywords:gravitational wave detectors; light interferometers; mirrors
Issue or Number:6
Record Number:CaltechAUTHORS:REHprd07
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8887
Deposited By: Archive Administrator
Deposited On:25 Sep 2007
Last Modified:08 Nov 2021 20:54

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