Double-Layered Metal Nano-Strip Antennas for Sensing Applications

A coupled plasmonic system based on double-layered metal nano-strips for sensing applications is investigated by means of mode analysis and two-dimensional finite-difference time-domain simulations. The nano-strips act as optical antennas through constructive interference of short-range surface plasmon polaritons, thus increasing their scattering cross-section and optical field enhancement. Near-field modulation by optical trapped metal nanoparticles (NPs) is also demonstrated. Our results reveal that the device exhibits a refractive index sensitivity of ～200 nm/RIU, and a maximum surface-enhanced Raman scattering (SERS) factor of 10⁹–10¹⁰ from metal NPs trapped in the near-field region. The proposed device shows reasonable figure-of-merit and is ready for integration with common optofluidic biosensors.