Terahertz split-ring metamaterials as transducers for chemical sensors based on conducting polymers: a feasibility study with sensing of acidic and basic gases using polyaniline chemosensitive layer

On-Chip Reconfigurable Focusing through Low-Loss Phase Change Materials Based Metasurfaces

Metasurfaces are useful subwavelength structures that can be engineered to achieve useful functionality. While most metasurfaces are passive devices, Phase Change Materials can be utilized to make active metasurfaces that can have numerous applications. One such application is on-chip beam steering which is of vital utility for numerous applications that can potentially lead to analog computations and non-Von Neumann computational architectures. This paper presents through numerical simulations, a novel metasurface that can realize beam steering through active phase switching of in-planted arrays of phase change material, Sb2S3. For the purpose of numerical demonstration of the principle, beam focusing has been realized, on-chip, through active switching of the Sb2S3 unit cell between the amorphous and crystalline phases. The presented architecture can realize on-chip transformation optics, mathematical operations, and information processing, thus opening the gates for future technologies.

Can a terahertz metamaterial sensor be improved by ultra-strong coupling with a high-Q photonic resonator?

When a metamaterial (MM) is embedded in a one-dimensional photonic crystal (PC) cavity, the ultra-strong coupling between the MM plasmons and the photons in the PC cavity gives rise to two new polariton modes with high quality factor. Here, we investigate by simulations whether such a strongly coupled system working in the terahertz (THz) frequency range has the potential to be a better sensor than a MM (or a PC cavity) alone. Somewhat surprisingly, one finds that the shift of the resonance frequency induced by an analyte applied to the MM is smaller in the case of the dual resonator (MM and cavity) than that obtained with the MM alone. However, the phase sensitivity of the dual resonator can be larger than that of the MM alone. With the dielectric perturbation theory - well established in the microwave community - one can show that the size of the mode volume plays a decisive role for the obtainable frequency shift. The larger frequency shift of the MM alone is explained by its smaller mode volume as compared with the MM-loaded cavity. Two main conclusions can be drawn from our investigations. First, that the dielectric perturbation theory can be used to guide and optimize the designs of MM-based sensors. And second, that the enhanced phase sensitivity of the dual resonator may open a new route for the realization of improved THz sensors.

HR-Si prism coupled tightly confined spoof surface plasmon polaritons mode for terahertz sensing

We report a high-resistivity silicon (HR-Si) prism coupled terahertz (THz) spoof surface plasmon polaritons (SSPPs) on flat subwavelength metasurface. Using a high refractive index prism as an external coupler, a more tightly confined SSPPs mode can be excited in a smaller resonant cavity, leading to strong light-matter interaction. Besides, theoretical analysis and experimental results have both indicated that the SSPPs resonance response to the filling patterns of analyte in the resonant cavity are quite different. In particular, we have found that the interaction between analyte and SSPPs wave can be maximized when the analyte filled with the whole resonant cavity and a higher sensitivity for THz sensing can be obtained. A high sensitivity varied from 0.31 THz/RIU to 0.85 THz/RIU is predicted. Furthermore, these SSPPs modes exhibit high Q-factor, and characteristic spectra of water caused by surface plasmon resonance (SPR) are observed, which is significant in promoting the THz-SPR sensing of polar liquids or aqueous analytes with THz metasurfaces.

Cell viability and hydration assay based on metamaterial-enhanced terahertz spectroscopy

We analyze cell viability and hydration state of tumor cells in a label-free manner based on metamaterial-enhanced terahertz spectroscopy.

Metamaterial Absorber for Electromagnetic Waves in Periodic Water Droplets

Perfect metamaterial absorber (PMA) can intercept electromagnetic wave harmful for body in Wi-Fi, cell phones and home appliances that we are daily using and provide stealth function that military fighter, tank and warship can avoid radar detection. We reported new concept of water droplet-based PMA absorbing perfectly electromagnetic wave with water, an eco-friendly material which is very plentiful on the earth. If arranging water droplets with particular height and diameter on material surface through the wettability of material surface, meta-properties absorbing electromagnetic wave perfectly in GHz wide-band were shown. It was possible to control absorption ratio and absorption wavelength band of electromagnetic wave according to the shape of water droplet–height and diameter– and apply to various flexible and/or transparent substrates such as plastic, glass and paper. In addition, this research examined how electromagnetic wave can be well absorbed in water droplets with low electrical conductivity unlike metal-based metamaterials inquiring highly electrical conductivity. Those results are judged to lead broad applications to variously civilian and military products in the future by providing perfect absorber of broadband in all products including transparent and bendable materials.