Enhancement of mechanical Q-factors by optical trapping

TL;DR

This paper demonstrates a method to significantly enhance the mechanical Q-factor of a resonator using optical trapping, surpassing material limits and improving sensitivity and quantum observation potential.

Contribution

The authors introduce an optical trapping technique that increases the Q-factor of a micro-mechanical resonator beyond traditional material and fabrication constraints.

Findings

Q-factor increased 50-fold to approximately 5.8×10^5

Resonance frequency increased from 6.2 kHz to 145 kHz

Technique enables surpassing conventional material dissipation limits

Abstract

The quality factor of a mechanical resonator is an important figure of merit for various sensing applications and for observing quantum behavior. Here, we demonstrate a technique to push the quality factor of a micro-mechanical resonator beyond conventional material and fabrication limits by using an optical field to stiffen or "trap" a particular motional mode. Optical forces increase the oscillation frequency by storing most of the mechanical energy in a lossless optical potential, thereby strongly diluting the effect of material dissipation. By using a 130 nm thick SiO$_2$ disk as a suspended pendulum, we achieve an increase in the pendulum center-of-mass frequency from 6.2 kHz to 145 kHz. The corresponding quality factor increases 50-fold from its intrinsic value to a final value of $Q=5.8(1.1)\times 10^5$, representing more than an order of magnitude improvement over the conventional limits of SiO$_2$ for this geometry. Our technique may enable new opportunities for mechanical sensing and facilitate observations of quantum behavior in this class of mechanical systems.