Nonlinear mechanisms in encapsulated micromechanical resonators
- Resonant Micro-electromechanical systems (MEMS) are an important technology that underlies many of the resonant sensors and oscillators used in scientific research and commercial products. Studying core properties of the resonators that make up these systems allows for future improvements in the performance of existing systems and enables new applications of resonators. Capacitively coupled readout is a common method to measure the motion of a MEMS resonator; in this work, I consider the system of an encapsulated mechanical resonator capacitively coupled to a lossy readout. I demonstrate that losses induced due to coupling are highly dependent on the parasitic capacitance in the readout and the properties of the readout amplifier, and can reduce the quality factor of the mechanical system by a factor of 15. Nonlinear properties of resonant systems affect their applications as resonant sensors and oscillators in the linear regime, and in novel nonlinear modes. I explore a case of measurements of a doubly clamped beam resonator that features negative nonlinear dissipation. By performing both directly-driven and parametrically-pumped characterizations of the system, I measure nonlinear dissipation that makes the effective linewidth of the device decrease with amplitude. The dissipation appears to be drive-induced, as it does not appear in the free response of system. I then study the impacts of nonlinear phenomena on the phase noise of resonant systems, which is relevant for improving the performance of MEMS clocks. Using parametric pumping tuned to achieve maximum parametric suppression, which reduces the phase to frequency noise conversion in our amplifier-noise dominated measurement setup, I decrease the measured resonator phase noise by almost threefold. Nonlinearity also can be used as a means to readout a MEMS resonator. I demonstrate an implementation of dispersive readout in our epitaxially encapsulated resonators and characterize its performance by measuring a Lamé mode resonator at room temperature. This novel readout achieves a displacement resolution of 522 fm/rtHz, representing a state-of-the-art resolution for measurements of encapsulated bulk-mode resonators. I further demonstrate that the dispersive readout technique can be used to measure mechanical system properties from 12 K to below 1 K. At the lowest temperature of 500 mK, I measure the resonator quality factor as 7.8 million, and an f x Q product of 7.9 x 10^13 Hz, which is the highest known measured value for an encapsulated bulk-mode resonator.
|Type of resource
|electronic resource; remote; computer; online resource
|1 online resource.
|Bousse, Nicholas Eric
|Degree committee member
|Degree committee member
|Stanford University, School of Engineering
|Stanford University, Department of Mechanical Engineering
|Statement of responsibility
|Nicholas Eric Bousse.
|Submitted to the Department of Mechanical Engineering.
|Thesis Ph.D. Stanford University 2023.
- © 2023 by Nicholas Eric Bousse
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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