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Thomas Feurer: Giant Electric Field Enhancement in Split Ring Resonators Featuring Nanometer-Sized Gaps

January 27, 2015

Resonant electric field enhancement structures show an electric field enhancement as high as ~14,000 at 50 GHz 

Over the past 20 years, continuous progress in Terahertz (THz) technologies has facilitated numerous breakthroughs in scientific and industrial research. Mostly through linear time-domain THz spectroscopy we have witnessed a marked increase in THz research on molecules, biomolecules, liquids, semiconductors, superconductors, crystals or complex materials.
Moreover, THz spectroscopy forms the basis for stand-off detection of hidden chemicals; in comparison to visible or infrared radiation, THz frequencies can penetrate into organic materials such as skin, plastics, cloths, or paper products and have thus become indispensable in security applications.Here, we report on a novel antenna design, i.e. a split ring resonator featuring a nanometer sized gap, which extends into the inner part of the split ring resonator. Such structures, as outlined below, show promise for extremely high THz electric field enhancement at their resonance frequencies. These frequencies can be easily tuned throughout the entire THz spectrum by changing the structure’s dimensions.

Bagiante, S., Enderli, F., Fabiańska, J., Sigg, H., and Feurer, T. (2015) Giant Electric Field Enhancement in Split Ring Resonators Featuring Nanometer-Sized Gaps. Sci Rep 5, 8051 (10.1038/srep08051)

Figure 1. (a) SEM image of the split ring resonator and a close-up view, which shows part of the 100 nm wide gap region. (b) Schematic
illustration of the split ring resonator with all relevant dimensions, the (E, H, k) triad of the incident THz field, k refers to the wave vector, and the coordinate system (x,y,z).

Figure 2. (a) Absolute value of the electric field enhancement in the gap as a function of frequency for the three gap widths 100 nm, 500 nm, and 970 nm, respectively. Absolute electric field amplitude of the incident THz spectrum in gray. (b) Electric field enhancement distribution in a 500 nm gap SRR at 56 GHz.

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