High Sensitivity Terahertz Biosensor Based on Mode Coupling of a Graphene/Bragg Reflector Hybrid Structure

In this work, a high-sensitivity terahertz (THz) biosensor is achieved by using a graphene/Bragg reflector hybrid structure. This high-sensitivity THz biosensor is developed from the sharp Fano resonance transmission peak created by coupling the graphene Tamm plasmons (GTPs) mode to a defect mode. It is found that the proposed THz biosensor is highly sensitive to the Fermi energy of graphene, as well as the thickness and refractive index of the sensing medium. Through specific parameter settings, the composite structure can achieve both a liquid biosensor and a gas biosensor. For the liquid biosensor, the maximum sensitivity of >1000°/RIU is obtained by selecting appropriate parameters. We believe the proposed layered hybrid structure has the potential to fabricate graphene-based high-sensitivity biosensors.

Resonance Transmission of Dual Plates with Narrow Small Slots due to Two Parallel Wires for Frequencies around 2 GHz

This paper presents the transmission cross-section (TCS) of a dual plate with narrow small slots when a plane wave is incident from the left half-space. Numerical results show that the TCS depends mainly on the plate spacing for a specified frequency. The TCS fluctuates with the plate spacing; the fluctuation period is approximately 0.5λ. When the plate spacing is larger than 0.5λ, the TCS reduces to 90% in the single plate case, and TCS enhancement is extremely difficult. However, when the plate spacing is less than 0.5λ, the TCS decreases gradually to approximately 36% in the single plate case, and TCS enhancement can be realized using two parallel wires. The analysis results show that resonance transmission is effectively obtained by the wires connected on the slots for a plate spacing within 0.5λ. Experimental measurements are presented to validate the theory.

Actively modulated propagation of electromagnetic wave in hybrid metasurfaces containing graphene

Here we present the actively modulated transportation of electromagnetic wave through hybrid metasurfaces containing graphene. The hybrid metasurfaces are composed of patterned metallic layers of extraordinary transmission and backed with graphene-sandwich layers. With the designed metallic layer with perforated structure, we demonstrated effective modulation on the on-resonance transmission amplitude by increasing the bias voltage from 0 to 4 V to electrically tune the Fermi level as well as the sheet resistance of the graphene-sandwich structure. We also found that the modulation depth can be further improved by properly designing the perforated metallic structure. By change the geometry from cut-wire structure to the “butterfly”-like pattern we preliminarily achieved 19.2% improvement on the on-resonance transmission modulation. The measured transmittances of the active metasurfaces show good agreement with the numerical simulations with fitted graphene sheet resistances. The hybrid metasurfaces presented in this work may be deployed in a wide range of applications based on active electromagnetic or optical modulations.

Neutron resonance transmission analysis of cylindrical samples used for reactivity worth measurements

A characterisation of cylindrical samples by Neutron Resonance Transmission Analysis (NRTA) at the GELINA facility of JRC Geel (Belgium) is presented. The samples were designed and produced for reactivity worth measurements in the MINERVE reactor of CEA Cadarache (France). NRTA was applied to determine the nuclide composition of UO2, Al2O3 and liquid samples that were doped with silver. The volume number densities of 238U, 107Ag and 109Ag obtained by NRTA are within 2 % fully consistent with the values that are quoted by the manufacturer. In addition, the NRTA data reveal a tungsten contamination which is not reported by the provider. It is shown that such a contamination contributes by up to 5.7 % to the reactivity worth.