Downselect of the signal extraction scheme for LCGT

Abstract

Large Cryogenic Gravitational wave Telescope (LCGT) is the future Japanese gravitational-wave detector. It will employ the broadband resonant sideband extraction (RSE) as its optical configuration. We compared four signal extraction schemes that have been proposed so as to downselect one of them as the scheme for LCGT. The selected scheme uses the phase and amplitude modulation sidebands: the phase modulation sidebands transmitting to the antisymmetric port (AP) and the amplitude modulation sidebands reffected to the symmetric port (SP) by the functions of the Michelson asymmetry. Using these sidebands, a new technique called ‘delocation’ is applicable. One advantage is that the control signals of the undesired signals do not appear at the AP, where the differential signals appear.