Asymmetric split ring resonators for optical sensing of organic materials

Area of Science:

• Plasmonics and Nanophotonics
• Spectroscopy
• Materials Science

Background:

• Asymmetric Split Ring Resonators (ASRs) exhibit resonant modes with enhanced optical electric fields at arm ends.
• This characteristic increases sensitivity in spectral techniques, including Surface-Enhanced Raman Scattering (SERS).

Purpose of the Study:

• To investigate the plasmonic resonances of circular ASRs with varying gap and section lengths in the mid-infrared spectrum.
• To demonstrate the application of these ASRs for highly sensitive detection of organic compounds, specifically PMMA.

Main Methods:

• Experimental fabrication and characterization of ASRs with varied dimensions.
• Electromagnetic simulations to support experimental observations of plasmonic resonances.
• Utilizing thin films of PMMA with different thicknesses to study spectral shifts.

Main Results:

• Asymmetry in ASRs leads to distinct plasmonic resonances influenced by arm lengths and inter-arm coupling.
• A steepening of the reflection spectrum slope between resonances was observed, enhancing sensitivity.
• Characteristic spectral shifts were detected with varying PMMA film thicknesses.
• Successful matching of ASRs to a molecular resonance of PMMA was demonstrated.

Conclusions:

• ASRs offer a pathway to enhanced sensitivity in mid-infrared spectral detection.
• The design of ASRs, including asymmetry and dimensional tuning, is crucial for optimizing plasmonic responses.
• These resonators show significant potential for highly sensitive molecular sensing applications.