A micro-electrical mechanical oscillator has a resonant frequency of oscillation that is varied by application of heat. The resonant frequency is varied at a frequency different from the resonant frequency of the oscillator to amplify oscillations. In one embodiment, the oscillator is disc of material supported by a pillar of much smaller diameter than the disc. The periphery of the disc is heated by a laser to provide a time varying shift of the resonant frequency (or equivalently the stiffness) of the disc. Feedback from movement of the disc is used to modulate the intensity of the laser, and thus the stiffness of the disc to provide parametric amplification of sensed vibrations, using heating as a pump. Various other shapes of micro-electrical mechanical oscillators are used in other embodiment, including an array of such oscillators on a substrate, each having different resonant frequencies.