Experimental optomechanics with silicon micromirrors

We experimentally demonstrate the high-sensitivity optical monitoring of moving micromirrors, made of low-loss dielectric coatings upon silicon resonators of various shapes and sizes. The record optical finesses obtained (F ≃ 30 000) has allowed us to measure the thermal noise of the micromirrors at room temperature with a quantum-limited sensitivity at the 10−19 m / √ Hz level and to completely characterize their mechanical behaviour, in excellent agreement with the results of a finite-element computation. Applications of such optomechanical systems range from quantum optics experiments to the experimental demonstration of the quantum ground state of a macroscopic mechanical resonator. 2