title: Ultrasensitive broadband probing of molecular vibrational modes with multifrequency optical antennas.
abstract: Optical antennas represent an enabling technology for enhancing the detection of molecular vibrational signatures at low concentrations and probing the chemical composition of a sample in order to identify target molecules. However, efficiently detecting different vibrational modes to determine the presence (or the absence) of a molecular species requires a multispectral interrogation in a window of several micrometers, as many molecules present informative fingerprint spectra in the mid-infrared between 2.5 and 10 μm. As most nanoantennas exhibit a narrow-band response because of their dipolar nature, they are not suitable for such applications. Here, we propose the use of multifrequency optical antennas designed for operating with a bandwidth of several octaves. We demonstrate that surface-enhanced infrared absorption gains in the order of 10(5) can be easily obtained in a spectral window of 3 μm with attomolar concentrations of molecules, providing new opportunities for ultrasensitive broadband detection of molecular species via vibrational spectroscopy techniques.
authors.affiliation: The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom. h.aouani@imperial.ac.uk
authors.forename: Heykel
authors.initials: H
authors.lastname: Aouani
authors.forename: Hana
authors.initials: H
authors.lastname: Šípová
authors.forename: Mohsen
authors.initials: M
authors.lastname: Rahmani
authors.forename: Miguel
authors.initials: M
authors.lastname: Navarro-Cia
authors.forename: Kateřina
authors.initials: K
authors.lastname: Hegnerová
authors.forename: Jiří
authors.initials: J
authors.lastname: Homola
authors.forename: Minghui
authors.initials: M
authors.lastname: Hong
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Maier
mesh_terms: D008422:Materials Testing; D015336:Molecular Probe Techniques; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D020349:Surface Plasmon Resonance / Q000379:methods*; D014732:Vibration