"Generating non-classical states of light by opto-mechanical coupling depends critically on the mechanical. and optical properties of micro-oscillators and on the minimization of thermal noise. We present an. oscillating micro-mirror with a mechanical quality factor Q = 2.6 × 10^6 at cryogenic temperature and a. Finesse of 65000, obtained thanks to an innovative approach to the design and the control of mechanical. dissipation. We predict that, already at 4 K with an input laser power of 2 mW, the radiation-pressure. quantum fluctuations become the main noise source, overcoming thermal noise. This feature makes our. devices particularly suitable for the production of pondero-motive squeezing." (ENG)