Graphene Sandwiches as a Platform for Broadband Molecular Spectroscopy

Sensing is to date one of the most successful applications of surface plasmons thanks to the exceptional field amplification and sensitivity of these modes in metallic nanostructures. Here we introduce a promising detection scheme based on the propagation of strongly confined antibonding plasmons supported by graphene sandwiches. Instead of measuring changes in the refractive index or enhancing a restricted number of molecular absorption lines, the proposed device can recover an extended portion of the infrared spectrum of a molecule. Moreover, the extreme compression of light in graphene means that a diluted 2 nm-thick analyte can cause up to 3 dB intensity changes. The broadband capability and sensitivity also imply that one can easily identify different chemicals in a mixture and extract their respective concentration. We conclude by presenting a simple experimental setup based on this mechanism for infrared spectroscopy that could become a cheap Fourier transform infrared accessory and an alternative to crystal-based attenuated total reflection spectroscopy.