Partial Gap Transduced MEMS Optoacoustic Oscillator Beyond Gigahertz

PROJECT TITLE :

Partial Gap Transduced MEMS Optoacoustic Oscillator Beyond Gigahertz

ABSTRACT:

Electrostatically actuated microelectromechanical system (MEMS) oscillators are restricted to few megahertz-gigahertz range on account of transduction inefficiency at higher frequencies. Piezoelectric transduction affords lower motional impedances at high frequencies, however mass-loading on account of metal electrodes imposes sensible limits on the mechanical quality issue of piezoelectric resonators in the gigahertz frequency regime. During this paper, we present a silicon optoacoustic oscillator operating at a pair of.05 GHz with signal power eighteen dBm and section noise -eighty dBc/Hz at 10-kHz offset from carrier. We have a tendency to employ displacement amplification and partial air gap capacitive transduction to reinforce the transduction potency. An unconventional photolithography step is performed on a released MEMS structure, which greatly simplifies the fabrication method and permits electrical contact with the electrodes. Engineered-in nonlinear optomechanical modulation provides noiseless up-conversion of the oscillation signal all the means up to sixteen.four GHz with -45-dBm signal power. We tend to develop a section noise model for the oscillator and identify the photodetector shot noise to be the dominant noise supply. Using a high gain and low noise avalanche photodetector permits reduction of the far-from-carrier section noise floor by 15dB. The section noise model provides insights into understanding the influence of laser detuning on the oscillator noise performance, that has not been studied thus far.

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