Optically pumped parametric amplification for micromechanical oscillators

Micromechanical oscillators in the rf range were fabricated in the form of silicon discs supported by a SiO2 pillar at the disk center. A low-power laser beam, (P-laser similar to 100 muW), focused at the periphery of the disk, causes a significant change of the effective spring constant producing a frequency shift, Deltaf(Deltaf/f similar to 10(-4)). The high quality factor, Q, of the disk oscillator (Q similar to 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. (C) 2001 American Institute of Physics.