Plasmonic Rainbow Trapping Structures for Light Localization and Spectrum Splitting

“Rainbow trapping” has been proposed as a scheme for localized storage of broadband electromagnetic radiation in metamaterials and plasmonic heterostructures. Here, we articulate the dispersion and power flow characteristics of rainbow trapping structures, and show that tapered waveguide structures composed of dielectric core and metal cladding are best suited for light trapping. A metal-insulator-metal taper acts as a cascade of optical cavities with different resonant frequencies, exhibiting a large quality factor and small effective volume comparable to conventional plasmonic resonators

Time dependent behavior of a localized electron at a heterojunction boundary of graphene

We develop a finite-difference time-domain (FDTD) method for simulating the dynamics of graphene electrons, denoted GraFDTD. We then use GraFDTD to study the temporal behavior of a single localized electron wave packet, showing that it exhibits optical-like dynamics including the Goos–Hänchen effect [ F. Goos and H. Hänchen, Ann. Phys. 436, 333 (1947)] at a heterojunction, but the behavior is quantitatively different than for electromagnetic waves. This suggests issues that must be addressed in designing graphene-based electronic devices analogous to optical devices. GraFDTD should be useful for studying such complex time-dependent behavior of a quasiparticle in graphene

Electrostatic Steering of Thermal Emission with Active Metasurface Control of Delocalized Modes

We theoretically describe and experimentally demonstrate a graphene-integrated metasurface structure that enables electrically-tunable directional control of thermal emission. This device consists of a dielectric slab that acts as a Fabry-Perot (F-P) resonator supporting long-range delocalized modes bounded on one side by an electrostatically tunable metal-graphene metasurface. By varying the Fermi level of the graphene, the accumulated phase of the F-P mode is shifted, which changes the direction of absorption and emission at a fixed frequency. We directly measure the frequency- and angle-dependent emissivity of the thermal emission from a fabricated device heated to 250$^{\circ}$. Our results show that electrostatic control allows the thermal emission at 6.61 $\mu$m to be continuously steered over 16$^{\circ}$, with a peak emissivity maintained above 0.9. We analyze the dynamic behavior of the thermal emission steerer theoretically using a Fano interference model, and use the model to design optimized thermal steerer structures.Comment: 8 pages, 4 figure

A Standalone Vision Sensing System for Pseudodynamic Testing of Tuned Liquid Column Dampers

Experimental investigation of the tuned liquid column damper (TLCD) is a primal factory task prior to its installation at a site and is mainly undertaken by a pseudodynamic test. In this study, a noncontact standalone vision sensing system is developed to replace a series of the conventional sensors installed at the TLCD tested. The fast vision sensing system is based on binary pixel counting of the portion of images steamed in a pseudodynamic test and achieves near real-time measurements of wave height, lateral motion, and control force of the TLCD. The versatile measurements of the system are theoretically and experimentally evaluated through a wide range of lab scale dynamic tests

Electronic modulation of infrared emissivity in graphene plasmonic resonators

Electronic control of blackbody emission from graphene plasmonic resonators on a silicon nitride substrate is demonstrated at temperatures up to 250 C. It is shown that the graphene resonators produce antenna-coupled blackbody radiation, manifest as narrow spectral emission peaks in the mid-IR. By continuously varying the nanoresonators carrier density, the frequency and intensity of these spectral features can be modulated via an electrostatic gate. We describe these phenomena as plasmonically enhanced radiative emission originating both from loss channels associated with plasmon decay in the graphene sheet and from vibrational modes in the SiNx.Comment: 17 pages, 6 figure

An Electrical Wave Height Measurement at Spatial Multipoint Locations in Liquid Dampers for Structural Vibration Mitigation

Liquid dampers such as tuned liquid column dampers and tuned liquid dampers have been adopted to ensure serviceability of a vibratory building subjected to wind. In order to maximize efficiency of the vibration suppression, tuning frequency of the liquid dampers is supposed to be set to the first natural frequency of the building. Therefore, experimental evaluation of the natural frequency of liquid dampers is a primal factory task prior to their installation at the building. In this study, a novel liquid height measurement system based on variable resistance in an electric field is developed for observation of vertical motion of the liquid dampers. The proposed system can simultaneously measure the liquid height of multipoint locations in the electric field. In the experimental phase, natural frequency of the liquid dampers is experimentally evaluated utilizing the developed system. The performance of the proposed system is verified by comparison with the capacitive type wavemeter

Survey of viral hemorrhagic septicemia virus (VHSV) in olive flounder, Paralichthys olivaceus hatchery in Korea

Viral hemorrhagic septicemia (VHS) generally occurs after juvenile olive flounders (Paralichthys olivaceus) are moved from the hatchery to on-growing system in Korea during spring. However, it remains unclear whether fish are infected by VHS virus (VHSV) in the hatchery or the on-growing system. In the present study, a survey was conducted to investigate VHSV infection in 39 olive flounder hatcheries from 2014 to 2017. Fish were tested for the presence of VHSV by inoculating sample to fathead minnow (FHM) and chinook salmon embryo (CHSE-214) cells to observe cytopathic effect, reverse transcription-polymerase chain reaction (RT-PCR), and antibody detection enzyme-linked immunosorbent assay (ELISA). VHSV was not detected in any of the 2,430 fish (from 461 pooled and 156 unpooled samples), although 34 (20.3%) of 167 samples was found to be positive for marine birnavirus (MABV) by cell culture and RT-PCR. Antibody detection ELISA results showed that all 212 fish sera have optical density (OD) values below of 0.1, suggesting that these fish had no VHSV-specific antibodies. Moreover, VHSV was not detected in any of 40 pooled samples (172 fish) collected after shifting rearing water temperature from 17-21°C to 10-15°C. In conclusion, the 39 olive flounder hatcheries surveyed in Korea was not infected by VHSV

Highly Confined Tunable Mid-Infrared Plasmonics in Graphene Nanoresonators

Single-layer graphene has been shown to have intriguing prospects as a plasmonic material, as modes having plasmon wavelengths 20 times smaller than free space (λ_p ~ λ_0/20) have been observed in the 2–6 THz range, and active graphene plasmonic devices operating in that regime have been explored. However there is great interest in understanding the properties of graphene plasmons across the infrared spectrum, especially at energies exceeding the graphene optical phonon energy. We use infrared microscopy to observe the modes of tunable plasmonic graphene nanoresonator arrays as small as 15 nm. We map the wavevector-dependent dispersion relations for graphene plasmons at mid-infrared energies from measurements of resonant frequency changes with nanoresonator width. By tuning resonator width and charge density, we probe graphene plasmons with λ_p ≤ λ_0/100 and plasmon resonances as high as 310 meV (2500 cm^–1) for 15 nm nanoresonators. Electromagnetic calculations suggest that the confined plasmonic modes have a local density of optical states more than 10^6 larger than free space and thus could strongly increase light–matter interactions at infrared energies