Infrared Metamaterial-Based Molecular Ruler

We report a metamaterial-based molecular ruler resonant at infrared (IR) frequency for molecular structure analysis with ultrahigh sensitivity. The molecular ruler is composed of a series of metamaterials with resonances at the infrared regime. A set of split ring resonators (SRRs) with specific resonant frequencies are designed and fabricated. The nanoscale restriction of the plasmonic field provided by the gap of SRRs enhances the local interaction between light and matter, which offer a leverage for trace analysis with high accuracy and sensitivity. To demonstrate proof-of-concept, a series of SRRs with absorption bands between 1600cm
^-1
and 1700cm
^-1
, which can serve as IR molecular ruler with capabilities to identify molecular structure with trace amount are fabricated. The spectroscopic signatures information of the protein molecule can be amplified by the SRR and acquired by a Scanning near-field optical microscopy (SNOM). The demonstration of molecular ruler devices provides opportunities for trace detection and molecular structure analysis applications.