Optical cavities with small mode volume are well-suited to detect the vibration of sub-wavelength sized objects. Here we employ a fiber-based, high-finesse optical microcavity to detect the Brownian motion of a freely suspended carbon nanotube at room temperature under vacuum. The optical detection resolves deflections of the oscillating tube down to 50pm/Hz^1/2. A full vibrational spectrum of the carbon nanotube is obtained and confirmed by characterization of the same device in a scanning electron microscope. Our work successfully extends the principles of high-sensitivity optomechanical detection to molecular scale nanomechanical systems.
@article{arxiv.1211.1608,
title = {Cavity-enhanced optical detection of carbon nanotube Brownian motion},
author = {S. Stapfner and L. Ost and D. Hunger and E. M. Weig and J. Reichel and I. Favero},
journal= {arXiv preprint arXiv:1211.1608},
year = {2013}
}