Optically pumped parametric amplification for micromechanical oscillators

Micromechanical oscillators in the rf range were fabricated in the form of silicon discs supported by a ${\mathrm{SiO}}_{\mathrm{2}}$ pillar at the disk center. A low-power laser beam, ${\mathrm{(P}}_{\mathrm{laser}}\text{∼100\hspace{0.5em}μ}\mathrm{W}\mathrm{),}$ focused at the periphery of the disk, causes a significant change of the effective spring constant producing a frequency shift, ${\text{Δf(Δf/f∼10}}^{\text{−4}}\mathrm{).}$ The high quality factor, $\mathrm{Q,}$ of the disk oscillator ${\text{(Q∼10}}^4)$ allows us to realize parametric amplification of the disk’s vibrations through a double frequency modulation of the laser power. An amplitude gain of up to 30 was demonstrated, with further increase limited by nonlinear behavior and self-generation. Phase dependence, inherent in degenerate parametric amplification, was also observed. Using this technique, the sensitivity of detection of a small force is greatly enhanced.