Asymmetric split ring resonators for optical sensing of organic materials

Abstract

Asymmetric Split Ring Resonators are known to exhibit resonant modes where the optical electric field is strongest near the ends of the arms, thereby increasing the sensitivity of spectral techniques such as surface enhanced Raman scattering (SERS). By producing asymmetry in the structures, the two arms of the ring produce distinct plasmonic resonances related to their lengths - but are also affected by the presence of the other arm. This combination leads to a steepening of the slope of the reflection spectrum between the resonances that increases the sensitivity of the resonant behavior to the addition of different molecular species. We describe experimental results, supported by simulation, on the resonances of a series of circular split ring resonators with different gap and section lengths--at wavelengths in the mid-infra red regions of the spectrum--and their utilization for highly sensitive detection of organic compounds. We have used thin films of PMMA with different thicknesses, resulting in characteristic shifts from the original resonance. We also demonstrate matching of asymmetric split ring resonators to a molecular resonance of PMMA.

Enriching the Symmetry of Maxwell Equations through Unprecedented Magnetic Responses of Artificial Metamaterials and Their Revolutionary Applications

“…Another approach is to fabricate anisotropic SRR structures that are reconfigurable in response to an external stimulus such as a thermal effect [52]. Label-free, coupler-free, and refractive-index SRR-based biosensors have undergone significant development due to the capacitance of SRR structures' high sensitivity relative to external environments [53][54][55]. We expect that, in the near future, the findings of such successful demonstrations, by using a given SRR structure, can be readily extended to applications in our lives.…”

Artificial Magnetic Materials Synthesis With Generic Metallic Broken Loops

“…The electromagnetic properties of metamaterials have generated new applications. These growing applications are using metamaterial slabs as a probe for the near-field sensing [5], as a substrate or a superstrate for enhancing low-profile antenna performance [6], as a perfect lens for microwave imaging [7], as microwave shields or absorbers [8] and even as bio-sensors for medical applications [9].…”

Mapping the sensitivity of split ring resonators using a localized analyte

“…[7][8][9] It is also possible to match the plasmonic resonance of the SRRs with the molecular vibrational resonances of a selected bond in a target analyte, for enhanced detection and identification. [10][11][12] In this paper we compare the accuracy and sensitivity of SRRs in probing thin films ($110 nm thick) of poly-methyl methacrylate (PMMA) that are localized as square blocks (150 nm  150 nm) in various positions in their vicinity.…”

“…In previous work, we have used asymmetric SRRs (A-SRRs) for optical detection of minute quantities of PMMA, localizing square blocks of PMMA near the electromagnetic hot-spots of the A-SRRs to determine their sensitivity. 12 SRR arrays were fabricated on a fused silica substrate using EBL. Patterns were written using a PMMA resist bi-layer and subsequent temperature controlled development in isopropyl alcohol and ultrapure water (UPW).…”