Reception frequency bandwidth of a gravitational resonant detector with optical readout

Abstract

A gravitational resonant bar detector with a large scale Fabry-Perot cavity as an optical read out and a mechanical displacement transformer is considered. We calculate, in a fully analytical way, the final receiver bandwidth in which the potential sensitivity, limited only by the bar thermal noise, is maintained despite the additional thermal noise of the transformer and the additive noise of the optical readout. We discuss also an application to the OGRAN project, where the bar is instrumented with a 2m long FP cavity.

A high frequency resonance gravity gradiometer

“…Corresponding estimation had shown that the cooling of the bar close to 10 mK would allow to achieve sensitivity 10 −23 1/ √ Hz to metric perturbation, 13 which is comparable with sensitivity of the advance generation of laser interferometrical detectors. However, on this way, it will be necessary to solve the problem of "cryogenic mirrors" how it was formulated for the third generation of gravity wave detectors, so called "Einstein Telescope."…”

“…A perspective of the next development is associated with a cryogenic version of the opto-acoustical bar considered in Ref. 13 having a final goal sensitivity ∼ 10 −23 Hz −1/2 .…”