title: Cavity-enhanced Raman microscopy of individual carbon nanotubes.
abstract: Raman spectroscopy reveals chemically specific information and provides label-free insight into the molecular world. However, the signals are intrinsically weak and call for enhancement techniques. Here, we demonstrate Purcell enhancement of Raman scattering in a tunable high-finesse microcavity, and utilize it for molecular diagnostics by combined Raman and absorption imaging. Studying individual single-wall carbon nanotubes, we identify crucial structural parameters such as nanotube radius, electronic structure and extinction cross-section. We observe a 320-times enhanced Raman scattering spectral density and an effective Purcell factor of 6.2, together with a collection efficiency of 60%. Potential for significantly higher enhancement, quantitative signals, inherent spectral filtering and absence of intrinsic background in cavity-vacuum stimulated Raman scattering render the technique a promising tool for molecular imaging. Furthermore, cavity-enhanced Raman transitions involving localized excitons could potentially be used for gaining quantum control over nanomechanical motion and open a route for molecular cavity optomechanics.
authors.affiliation: Fakultät für Physik, Ludwig-Maximilians-Universität, Schellingstraβe 4, München 80799, Germany.|Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, Garching 85748, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hümmer
authors.affiliation: Fakultät für Physik, Ludwig-Maximilians-Universität, Schellingstraβe 4, München 80799, Germany.|Center for NanoScience (CeNS), Ludwig-Maximilians-Universität, Schellingstraβe 4, München 80799, Germany.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Noe
authors.affiliation: Fakultät für Physik, Ludwig-Maximilians-Universität, Schellingstraβe 4, München 80799, Germany.|Center for NanoScience (CeNS), Ludwig-Maximilians-Universität, Schellingstraβe 4, München 80799, Germany.
authors.forename: Matthias S
authors.initials: MS
authors.lastname: Hofmann
authors.affiliation: Fakultät für Physik, Ludwig-Maximilians-Universität, Schellingstraβe 4, München 80799, Germany.|Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, Garching 85748, Germany.
authors.forename: Theodor W
authors.initials: TW
authors.lastname: Hänsch
authors.affiliation: Fakultät für Physik, Ludwig-Maximilians-Universität, Schellingstraβe 4, München 80799, Germany.|Center for NanoScience (CeNS), Ludwig-Maximilians-Universität, Schellingstraβe 4, München 80799, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Högele
authors.affiliation: Fakultät für Physik, Ludwig-Maximilians-Universität, Schellingstraβe 4, München 80799, Germany.|Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, Garching 85748, Germany.
authors.forename: David
authors.identifier: 0000-0001-6156-6145
authors.initials: D
authors.lastname: Hunger