  We consider the linear density response of a two-component (superfluid) Fermi
gas of atoms when the perturbation is caused by laser light. We show that
various types of laser excitation schemes can be transformed into linear
density perturbations, however, a Bragg spectroscopy scheme is needed for
transferring energy and momentum into a collective mode. This makes other types
of laser probing schemes insensitive for collective excitations and therefore
well suited for the detection of the superfluid order parameter. We show that
for the special case when laser light is coupled between the two components of
the Fermi gas, density response is always absent in a homogeneous system.
