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EECS500 Fall 2017 Department Colloquium

Presenter: 
Guillermo Villanueva
Title: 
Nonlinear Effects in NEMS - Improving Frequency Stability
Affiliation: 
École Polytechnique Fédérale de Lausanne
Location: 
White 411
Time: 
11:30 AM - 12:30 PM
Date: 
September 5, 2017

Resonant Nanoelectromechanical Systems (NEMS) have generated an enormous interest over the last 15 years, driven by a combination of fundamental questions and practical needs. The combination of relatively high frequencies, high quality factors and small masses make them ideal for a plethora of sensing applications. As an example, it has been possible to detect from a single atom landing on a carbon nanotube until single nuclear spin rotations.

However, NEMS have failed to made an impact in the field of oscillators or frequency sources. The main reason is that noise is larger for these small devices, since nonlinearity becomes readily accessible at small vibration amplitudes. Over the past few years we have focused our efforts in bypassing this limitation that comes from nonlinearity.

In this talk, we will analyze all the contributions to the phase noise in an oscillator based on a nonlinear resonator. We will show the existence of a special region in the parameter space, above the nonlinear threshold, where the dominant contributions to the phase noise are suppressed. This theory has been combined with experimental work and we will show a nonlinear NEMS-based oscillator, using a nanomechanical doubly-clamped beam resonator, for which we characterized its phase noise. The agreement of experimental data with our theoretical model is good, and unequivocally confirm experimentally the existence of the special region described above, where the phase noise performance is improved beyond the limitations of the linear regime. Our findings contravene conventional phenomenological wisdom, which assumes that operation beyond the threshold of nonlinearity necessarily degrades phase noise. Indeed, by operating the oscillator in this region, the signal level can be increased to large values without the conventionally expected performance degradation. It is therefore possible to overcome fundamental limitations of oscillator performance due to thermodynamic noise.

Biography: 

Guillermo Villanueva is a Tenure Track Assistant Professor at EPFL in Lausanne. He obtained his Ms. Sc. in Physics in 2002 from the University of Zaragoza (Spain) and his Ph.D. in Microelectronic Engineering from the Autonomous University of Barcelona in 2006 for his work on NEMS/MEMS for biodetection and scanning probes. He then worked as a post-doctoral researcher at EPFL, Caltech and DTU in the fields of nanofabrication, coupled and non-linear phenomena and dissipation in NEMS respectively. In 2013 he joined EPFL as a SNSF Assistant Professor to continue his research in fundamentals of nanomechanical systems for sensing and communications. In 2005 he was awarded the MNE Young Investigator Award for his PhD work, in 2008 he was awarded a Marie Curie Fellowship and in 2014 he was awarded the MEE Young Investigator Award.