Interferometric measurements of the position of a macroscopic body: Towards observation of quantum limits

An optomechanical sensor suitable for the study of quantum effects has been developed and characterized. The sensor reads out the vibrations of a micr ofabricated miniature silicon mechanical oscillator which forms one end mir ror of a high finesse Fabry-Perot cavity. The mechanical quality factor is up to Q = 300 000 at 300 K and rises up to Q = 4 x 10(6) at 4 K. The therma l noise of the oscillator has been measured in the time and frequency domai ns at room temperature and at 4.5 K. The prospects for observing the standa rd quantum limit are discussed. [S1050-2937(99)07002-X].