Cavity enhanced Raman microscopy of individual carbon nanotubes
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.
Nature communications