Detecting free-mass common-mode motion induced by incident gravitational waves - art. no. 102002

In this paper we show that information on both the differential and common mode free-mass response to a gravitational wave can provide important infor mation on discriminating the direction of the gravitational wave source and between different theories of gravitation. The conventional Michelson inte rferometer scheme only measures the differential free-mass response. By cha nging the orientation of the beam splitter, it is possible to configure the detector so it is sensitive to the common-mode of the free-mass motion. Th e proposed interferometer is an adaptation of the Fox-Smith interferometer. A major limitation to the new scheme is its enhanced sensitivity to laser frequency fluctuations over the conventional, and we propose a method of ca ncelling these fluctuations. The configuration could be used in parallel to the conventional differential detection scheme with a significant sensitiv ity and bandwidth. [S0556-2821(99)03308-1].