Demonstration and comparison of tuned and detuned signal recycling in a large-scale gravitational wave detector

S. Hild*, H. Grote, M. Hewtison, H. Luck, J.R. Smith, K.A. Strain, B. Willke, K. Danzmann

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


The British/German gravitational wave detector GEO 600 located near Hannover in Germany is the first large-scale gravitational-wave detector using the advanced technique of signal recycling. Currently the instrument operates in detuned signal recycling mode. Several problems arise due to the fact that the signal recycling cavity changes amplitude and phase of all light fields (carrier and sidebands) present at the dark-port. In addition, in the case of detuned signal recycling this leads to unbalanced sideband fields at the detector output. The large amplitude modulation caused by this asymmetry does not carry any gravitational wave information, but might be the cause of saturation and nonlinearities on the main photodiode. We developed and demonstrated a new control method to realize tuned signal recycling operation in a large-scale gravitational wave detector. A detailed comparison of tuned and detuned signal recycling operation is given. The response function of the system (optical gain) was measured and compared, as was the size of amplitude modulation on the main photodiode. Some important noise couplings were measured and partly found to be strongly reduced in the case of tuned signal recycling operation.
Original languageEnglish
Pages (from-to)1513-1523
Number of pages11
JournalClassical and Quantum Gravity
Issue number6
Publication statusPublished - 21 Mar 2007
Externally publishedYes


  • GEO-600

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