Nanomechanical resonant structures as tunable passive modulators of light

We report on the optical parametric excitation of silicon nanomechanical resonant structures. The threshold laser power needed to set these structures into self-oscillation was estimated to be around 70 μW. We measured resonant frequencies of up to 38 MHz by optical excitation; this method should extend to much higher frequencies. Under optical amplification of motion, the spectral response at resonance narrowed to the equivalent of a mechanical quality factor >20000 at room temperature. These structures act as frequency tunable passive modulators of light, requiring no additional drive.