Cavity-enhanced Raman Microscopy of Individual Carbon Nanotubes

TL;DR

This paper demonstrates cavity-enhanced Raman microscopy using a tunable microcavity to significantly boost signals from individual carbon nanotubes, enabling detailed molecular diagnostics and potential quantum control applications.

Contribution

The study introduces a novel cavity-enhanced Raman technique with high enhancement factors for single nanotubes, combining Raman and absorption imaging for detailed molecular analysis.

Findings

320-fold increase in Raman spectral density

Effective Purcell factor of 6.2 achieved

Collection efficiency of 60% demonstrated

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.