Response of interferometric detectors to scalar gravitational waves

We rigorously analyze the frequency response functions and antenna sensitivity patterns of three types of interferometric detectors to the scalar mode of gravitational waves which is predicted to exist in the scalar-tensor theory of gravity. By a straightforward treatment, we show that the antenna sensitivity pattern of the simple Michelson interferometric detector depends strongly on the wavelength λ_SGW of the scalar mode of the gravitational waves if λ_SGW is comparable to an arms length of the interferometric detector. For the Delay-Line and Fabry-Perot interferometric detectors with an arms length much shorter than λ_SGW, however, the antenna sensitivity patterns depend weakly on λ_SGW even though λ_SGW is comparable to the effective path length of those interferometers. This agrees with the result obtained by Maggiore and Nicolis.