  We consider an oscillating micromirror replacing one of the two fixed mirrors
of a Mach-Zehnder interferometer. In this ideal optical set-up the quantum
oscillator is subjected to the radiation pressure interaction of travelling
light waves, no cavity is involved. This configuration shows that squeezed
light can be generated by pure scattering on a quantum system, without
involving a cavity. The squeezing can be detected at the output ports of the
interferometer either by direct detection or by measuring the spectrum of the
difference current. We use the Hudson-Parthasarathy equation to model the
global evolution. It can describe the scattering of photons and the resulting
radiation pressure interaction on the quantum oscillator. It allows to consider
also the interaction with a thermal bath. In this way we have a unitary
dynamics giving the evolution of oscillator and fields. The Bose fields of
quantum stochastic calculus and the related generalized Weyl operators allow to
describe the whole optical circuit. By working in the Heisenberg picture, the
quantum Langevin equations for position and momentum and the output fields
arise, which are used to describe the monitoring in continuous time of the
light at the output ports. In the case of strong laser and weak radiation
pressure interaction highly non-classical light is produced, and this can be
revealed either by direct detection (a negative Mandel Q-parameter is found),
either by the intensity spectrum of the difference current of two
photodetector; in the second case a nearly complete cancellation of the shot
noise can be reached. In this last case it appears that the Mach-Zehnder
configuration together with the detection of the difference current corresponds
to an homodyne detection scheme, so that we can say that the apparatus is
measuring the spectrum of squeezing.
