  Gravitational waves are perturbations of the metric of space-time. Six
polarizations are possible, although general relativity predicts that only two
such polarizations, tensor plus and tensor cross are present for gravitational
waves. We give the analytical formulas for the antenna response functions for
the six polarizations which are valid for any equal-arm interferometric
gravitational-wave detectors without optical cavities in the arms.The response
function averaged over the source direction and polarization angle decreases at
high frequencies which deteriorates the signal-to-noise ratio registered in the
detector. At high frequencies, the averaged response functions for the tensor
and breathing modes fall of as $1/f^2$, the averaged response function for the
longitudinal mode falls off as $1/f$ and the averaged response function for the
vector mode falls off as $\ln(f)/f^2$.
