Resonant-Opto-Thermomechanical Oscillator (ROTMO): A Low-Power, Large Displacement, High-Frequency Optically Driven Microactuator.

Abstract

A light-driven micromechanical oscillator is presented, which can be operated by a low optical power (in the mW, or even the µW range), can produce large mechanical displacements (>5-100µm), and can be designed to operate at frequencies from sub-kHz up to more than 200kHz. The actuation of the oscillator is achieved by an asymmetrically metal-coated optical microwire configured into a silica micromechanical oscillator. The metalized optical microwire confines and absorbs the light strongly over a short distance, which results in a controlled optical power conversion into heat, and, consequently, into mechanical actuation through the temperature rise and the difference in thermal expansions of the silica microwire and the asymmetrically applied metal layer. Mechanical displacements are amplified further by the resonance operation of the oscillator, which is driven by a low-power, harmonic optical excitation signal generated by a current-modulated laser diode. Proper selection of the micromechanical oscillator's geometrical configuration and materials allows for a high-frequency operation at large mechanical displacements of the oscillator, while relying on low excitation optical power. The presented concept of a fully optically driven micromechanical oscillator may, thus, present a basis for realization of new classes of actuated micro-opto-mechanical Systems and similar photonics microdevices.