  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. The aim of this configuration is to show
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 quantum-stochastic Schroedinger equation
(Hudson-Parthasarathy equation) to model the global evolution. Indeed, it can
describe the scattering of photons and the resulting radiation pressure
interaction on the quantum oscillator. Moreover, it allows to consider also the
interaction with a thermal bath, so that it can describe also the damping of
the harmonic oscillator and non-Markovian thermal effects. 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 a pronounced squeezing is detected
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.
