Over-coupled resonator for broadband surface enhanced infrared absorption (SEIRA)

This repository contains all datasets and MATLAB codes used in the paper "Over-coupled resonator for broadband surface enhanced infrared absorption (SEIRA)"

3 folders can be found

BMM contains a main python script that reproduces the electromagnetic computations of the article

CMT : contains 3 scripts

Absorption2D.m computes a 2D map of the absorption from the resonator from eq.1 of the main text as a function of f and  (ω − ωr )/γnr .

DeltaRm.m plots the analytical expression of Delta Rm computed in the SI as a function of f.

DRanalytics.m plots the reflexion with the absorber  as a function of omega. The expression is derived from the coupled mode formalism as described in the supplemental information.

Data_exp: contains raw experimental datasets of the figures.

over_coupling_package : contains scripts to reproduce the electromagnetic simulations presented in the paper

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PAPER ABSTRACT:

Detection of molecules is a key issue for many applications. Surface enhanced infrared absorption (SEIRA) uses arrays of resonant nanoantennas with good quality factors which can be used to locally enhance the illumination of molecules. The technique has proved to be an effective tool to detect small amount of material. However nanoresonators can detect molecules on a narrow bandwidth so that a set of resonators is necessary to identify a molecule fingerprint. Here, we introduce an alternative paradigm and use low quality factor resonators with large radiative losses (over-coupled resonators). The bandwidth enables to detect all absorption lines between 5 and 10 µm, reproducing the molecular absorption spectrum. Counterintuitively, despite a lower quality factor, the system sensitivity is improved and we report a reflectivity variation as large as one percent per nanometer of molecular layer of PMMA. This paves the way to specific identification of molecules. We illustrate the potential of the technique with the detection of the explosive precursor 2,4-dinitrotoluene (DNT). There is a fair agreement with electromagnetic simulations and we also introduce an analytic model of the SEIRA signal obtained in the over-coupling regime.