Nonresonant 104 Terahertz Field Enhancement with 5-nm Slits

Abstract

Transmission of Terahertz (THz) electromagnetic wave through a substrate is encumbered because of scattering, multiple reflections, absorption, and Fabry–Perot effects when the wave interacts with the substrate. We present the experimental realization of nonresonant electromagnetic field enhancement by a factor of almost 104 in substrate-free 5-nm gold nanoslits. Our nanoslits yielded greater than 90% normalized electric field transmission in the low-frequency THz region; the slit width was 5 nm, and the gap coverage ratio was 10−4 of the entire membrane, 0.42 mm2. This large field enhancement was attributed to gap plasmons generated by the THz wave, which squeezes the charge cross-section, thus enabling very highly dense oscillating charges and strong THz field transmission from the nanoslits.

Sensing viruses using terahertz nano-gap metamaterials

“…4(c) which shows a plot of Δf as a function of the surface density and gap width; the frequency shift is larger and more rapidly saturated as the gap width decreases. This result can be understood by the enhancement of the electric field in the gap region as the gap width decreases [11,[28][29][30].…”

Terahertz characterization of two-dimensional low-conductive layers enabled by metal gratings

“…Electromagnetic (EM) wave transmission through sub-wavelength slits (or gaps) fabricated in metal films have been extensively studied [26][27][28][29][30][31][32][33] . In order to understand the working principle of enhanced transmission through an array (metallic grating), we refer to the terahertz transmission and large E-field enhancement through a single slit shown in Ref.…”

Terahertz wave interaction with metallic nanostructures

“…19 This simplified FE can be broadly applied to the range of micron gaps to nanogaps. Enhanced electromagnetic field through subwavelength gaps have been intensively explored both theoretically and experimentally over ultra-broadband wavelength regime covering microwave [191,192], THz [98,[193][194][195], IR [196,197], and visible regime [198,199]. Especially subwavelength photonics has been focused on THz frequencies (0.1-10 THz, 0.03-3 mm), having taken advantage of their relatively large aspect ratio between the wavelengths and structure scales, in turn providing a colossal FE effect.…”

“…To realize such large-area sample with high-resolution patterning, various recipes have been introduced, e.g. fs-laser machining for microscale punctured structures [64,241,242], focused ion beam [243,244], e-beam lithography [245,246], and photolithography techniques [125,247,248] for metamaterial structures and, finally, atomic layer deposition (ALD) for atomic-scale gap structures [75,193,249,250]. For nanoscale gap structures, photolithography can be considered as a promising fabrication method for mass production at the same time, as shown in Figure 16.…”