Abstract
Metamaterials provide a good platform for biochemical sensing due to its strong field localization at nanoscale. In this work, we show that electric and magnetic resonant modes in split-ring-resonator (SRR) can be efficiently excited under unpolarized light illumination when the SRRs are arranged in fourfold rotationally symmetric lattice configuration. The fabrication and characterization of deep subwavelength (~λ/15) gold-based SRR structures with resonator size as small as ~ 60 nm are reported with magnetic resonances in Vis-NIR spectrum range. The feasibility for sensing is demonstrated with refractive index sensitivity as high as ~ 636 nm/RIU.
Highlights
Metamaterials provide a good platform for biochemical sensing due to its strong field localization at nanoscale
Having magnetic resonance in the visible spectrum range is highly desirable since most experiments on biochemical sensing and molecular spectroscopy employ coherent/broadband visible light source
The SRR lattices in this work were fabricated by a robust electron beam lithography (EBL) process we developed recently[15,16], which has very high contrast (c, 25) and is capable of sub-15-nm patterning at low exposure dose (,100 mC/cm2)
Summary
Metamaterials provide a good platform for biochemical sensing due to its strong field localization at nanoscale. We show that electric and magnetic resonant modes in split-ring-resonator (SRR) can be efficiently excited under unpolarized light illumination when the SRRs are arranged in fourfold rotationally symmetric lattice configuration. We demonstrate the fabrication and characterization of deep-subwavelength SRR lattices that have magnetic resonances within the visible spectrum, with the smallest SRR of , 60 nm size and , 20 nm feature width. The capability of such lattices for biochemical sensing is studied, and the refractive index sensitivity as high as , 636 nm/RIU is observed for fundamental magnetic resonance in the near infrared wavelength range
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