Toroidal moment is an electromagnetic excitation that lies outside the familiar picture of electric and magnetic multipoles. It has recently been a topic intense research in fields nanophotonics metamaterials due to its weakly radiating nature ability confine energy. Among extensive studies on toroidal moments their applications, high quality factor (Q) resonances have experimentally realized only very limited set geometries wavelengths. In this study, we demonstrate metasurface consisting...

Nanoconfined waters exhibit low static permittivity mainly due to interfacial effects that span about one nanometer. The characteristic length scale may be much longer in the terahertz (THz) regime where long-range collective dynamics occur; however, THz have been largely unexplored because of lack a robust platform. Here, we use metallic loop nanogaps sharply enhance light-matter interactions and precisely measure real imaginary refractive indices nanoconfined water at gap widths ranging...

Terahertz (THz) nanogap structures have emerged as versatile platforms for THz science and applications by virtue of their strong in-gap field enhancements accompanying high levels sensitivity to gap environments. However, despite potential, reliable fabrication methods which create with sub-10 nm gaps remain limited. In this work, we fabricated split-ring resonator (SRR) arrays featuring a split gap. Our method, involving photolithography, argon ion milling, atomic layer deposition, is...

Abstract The ideals of reconfigurable metasurfaces would be operation in a broad frequency range with high extinction ratio and fatigue resistivity. In this paper, all the above is achieved microwave regime by transforming bare metallic film into well‐controlled nanometer sized gaps fully reversible manner. It shown that adjacent patterns deposited at different times can form “zero‐nanometer gaps,” or “zerogaps,” while maintaining optical electrical connectivity. zerogaps readily open...

Recent advances in emerging atomically thin transition metal dichalcogenide semiconductors with strong light-matter interactions and tunable optical properties provide novel approaches for realizing new material functionalities. Coupling two-dimensional all-dielectric resonant nanostructures represents an especially attractive opportunity manipulating both the near-field far-field regimes. Here, by integrating single-layer WSe2 titanium oxide (TiO2) dielectric metasurfaces toroidal...

Strong demand for plasmonic devices with an enormously enhanced electric field and desired resonance frequencies has led to extensive investigations of metallic slot structures. While strong enhancement can be achieved by reducing the width slot, effect gap surface plasmon limits maximum achievable at higher frequencies. Specifically, becomes stronger as decreases strongly suppresses transmission while causing a red-shift resonance. Here, we overcome these issues realize enhancements...

A well-designed narrow gap between noble metal nanostructures plays a prominent role in surface-enhanced Raman scattering (SERS) to concentrate electromagnetic fields at the local point, called "hot spot". However, SERS-active substrate fabrication remains substantial hurdle due high process cost and difficulty of engineering efficient plasmonic hot spots target area. In this study, we demonstrate simple photolithographic method for generating ultrasensitive SERS desired positions. The...

Abstract Slot-type nanogaps have been widely utilized in transmission geometry because of their advantages exclusive light funneling and exact quantification near-field enhancement at the gap. For further application electromagnetic interactions with various target materials, complementary studies on both reflection properties are necessary. Here, we observe an anomalous extinction terahertz waves interacting rectangular ring-shaped sub-30 nm wide gaps. Substrate works as index matching...

Abstract The convergence of nano‐optics with an aqueous environment is promising for future chemical or biological applications. While the rapid development in nanofabrication has led to realization sub‐10 nm nanogaps various structures, coupling water into high aspect ratio metallic a well‐defined area not yet demonstrated. Here, arrays 10 wide trenches are reported filled dielectric, air, liquid water, and molecules optical hotspots. Due height‐to‐width 20:1 strong gap plasmon width, show...

Ohmic absorption of light is an indication a light-matter interaction within metals, where many interesting phenomena and application potentials can be found. To realize the ohmic at long wavelengths, metals are highly reflective, one use metamaterial absorber design to concentrate electromagnetic field thin metal film. This concept has enabled thinning perfect absorbers from quarter-wave thickness several tens nanometers, greatly improving utility efficiency light-metal interactions....

We demonstrate microwave funneling through metallic gaps of nanometer-scale width, corresponding to λ/10 000 000. For achieving both resonant transmission and strong confinement microwaves, we fabricate two types samples with an extreme aspect ratio: 300 nm wide, 3.5 mm long slots sub-10 wide rectangular rings a perimeter 6.5 mm. Considering the peak transmittance value 45% small coverage ratio transparent area in nanogap surface, can infer giant intensity enhancement factor up 25 million...

We present a new and versatile technique of self-assembly lithography to fabricate large scale Cadmium selenide quantum dots-silver nanogap metamaterials. After optical electron microscopic characterizations the metamaterials, we performed spatially resolved photoluminescence transmission measurements. obtained highly quenched spectra compared those from bare dots film. then quantified quenching in terms an average enhancement factor. A finite difference time domain simulation was understand...

Abstract Metallic nanogaps are being widely used for sensing applications, owing to their ability confine and enhance electromagnetic field within the hot spots. Since enhanced does not itself perfectly gap, however, fringe fields well away from gap of potential use as in real systems. Here, we extend concept near absorption enhancement by quantitatively analyzing terahertz behavior water molecules outside spots sub-20 nm-wide, ∼100 μm-long nanotrenches. Contrary point-gaps which show...

Abstract Electromagnetic absorbers based on ultra-thin metallic film are desirable for many applications such as plasmonics, metamaterials, and long-wavelength detectors. A will achieve a maximum 50% of electromagnetic wave absorption, frequency independent, at thickness defined by its conductivity, typically in the sub-Angstrom range good metals if bulk conductivity is maintained throughout. This makes it extremely difficult to obtain substantial absorption from thin metal films, contrast...

Abstract Metallic nanostructures are combined with various active materials for electrical, optical, and thermal modulations of their optical properties. In particular, the modulation, deformation metallic at high temperatures limits applications to relatively low temperatures, where expansion metals is negligible. Here, a unique regime reported terahertz (THz) waves transmitting through 5 nm wide slot antennas can be significantly modulated via controlled without materials. The normalized...

Split-ring resonator (SRR) based metamaterials have been studied for the development of highly sensitive, small-sized, low-power chemical and biomolecular sensors. However, anisotropic behavior arising from their two-dimensional (2D) structure presents substantial challenges leading to ambiguity in transmission spectra. In this paper, we present design a three-dimensional (3D) isotropic octagram split-ring (OSRR) demonstrating three-dimensionally coupled resonance that overcomes response...

Atomic layer deposition is an efficient method for coating a few nanometer-thick alumina over wafer scale. This combined with the standard photolithography process was presented to fabricate metallic nanometer gaps that optically act in terahertz regimes. However, cross-sectional view of gap shape metal–insulator–metal nanogap structure varies depending on conditions from stepwise procedure. In specific, selecting photoresist materials, adding ion milling and chemical etching processes,...

Abstract Various material properties change considerably when is thinned down to nanometer thicknesses. Accordingly, researchers have been trying obtain homogeneous thin films with thickness but depositing few nanometers thick gold film challenging as it tends form islands rather than homogenous film. Recently, studies revealed that treating the substrate an organic buffer, (3-mercaptopropyl) trimethoxysilane (MPTMS) enables deposition of ultra-thin having low 5 nm. Different aspects MPTMS...

A metallic nano-trench is a unique optical structure capable of ultrasensitive detection molecules, active modulation as well potential electrochemical applications. Recently, wet-etching the dielectrics metal-insulator-metal structures has emerged reliable method creating optically nano-trenches with gap width 10 nm or less, opening new venue for studying dynamics nanoconfined molecules. Yet, high surface tension water in process drying leaves vulnerable to collapsing, limiting achievable...

Slot antennas have been exploited as important building blocks of optical magnetism because their radiations are invoked by the magnetic fields along axes, vectorial Babinet principle predicts. However, a few-nanometer-width slit, for which fascinating applications found due to colossal field enhancement but fails nonnegligible thickness, has not investigated. In this paper, we demonstrated that plays dominant role in light transmission through 5-nm slit on 150-nm-thick gold film. The was...

Plasmon-mediated polymerization has been intensively studied for various applications including nanolithography, near-field mapping, and selective functionalization. However, these studies have limited from the near-infrared to ultraviolet regime. Here, we report a resist using intense terahertz pulses nanoantennas. The is polymerized near nanoantennas, where giant field enhancement occurs. We experimentally show that physical origin of cross-linking electron emission nanoantenna, rather...

Metallic nanogaps have emerged as a versatile platform for realizing ultrastrong coupling in terahertz frequencies. Increasing the strength generally involved reducing gap width to minimize mode volume, which presents challenges fabrication and efficient material coupling. Here, we propose employing nanoslots, can efficiently squeeze volume an extra dimension alongside width. Our experiments using 500 nm wide nanoslots integrated with organic-inorganic hybrid perovskite demonstrate...

Critical factors for terahertz polarizers include broadband operation, high transmittance, and a good extinction ratio. In this paper, using 5 nm-wide metallic slit array with 200 nm periodicity as wire grid polarizer, we achieved over 95% transmittance an average ratio of 40 dB, the entire spectrum defined by time-domain spectroscopy (0.4 ∼ 2 THz). Theoretical calculations revealed that can show 100% transmission up to THz, wider bandwidths higher cutoff frequency be reducing periodicity....