Plasmon induced transparency (PIT) effect in a terahertz graphene metamaterial is numerically and theoretically analyzed. The proposed metamaterial comprises of a pair of graphene split ring resonators placed alternately on both sides of a graphene strip of nanometer scale. The PIT effect in the graphene metamaterial is studied for different vertical and horizontal configurations. Our results reveal that there is no PIT effect in the graphene metamaterial when the centers of both the split ring resonators and the graphene strip are collinear to each other. This is a noteworthy feature, as the PIT effect does not vanish for similar configuration in a metal-based metamaterial structure. We have further shown that the PIT effect can be tuned by varying the Fermi energy of graphene layer. A theoretical model using the three level plasmonic system is established in order to validate the numerical results. Our studies could be significant in designing graphene based frequency agile ultra-thin devices for terahertz applications.
Tuesday, November 21, 2017
Abstract-A non-destructive method for quality control of the pellet distribution within a MUPS tablet by terahertz pulsed imaging
Anna Novikova, Daniel Markl, J. Axel Zeitler, Thomas Rades, Claudia S.Leopold
μm below the tablet surface. An increasing amount of pellets within the MUPS tablets appears to slightly decrease the detectability of the pellets within the tablets by TPI. TPI was shown to be a non-destructive method for the detection of pellets within the tablets and could resolve structures thicker than 30 μm. In conclusion, a proof-of-concept was provided for TPI as a method of quality control for MUPS tablets.
Takashi Arikawa, Shohei Morimoto, and Koichiro Tanaka
Monday, November 20, 2017
Abstract-A split-ring-resonator-based polarization-insensitive ultra broadband filter in terahertz range
Split-ring-resonators (SRRs) are one of the most common unit cell designs for metamaterials. Though extensively studied and well understood, such devices are often used as narrow-band filters due to SRRs' sharp resonance to electromagnetic wave. In this work, based on the idea of patterning metal SRRs on both sides of a dielectric substrate while rotating patterns on one side 90 to the other, we show that simple circular SRR can be a building block for broadband filters in terahertz (THz) range. The design principle is detailed with simulation results, showing that such fabricated devices essentially equates to two narrow-band filters on both sides of the substrate connected in series. By changing the unit cell from single SRR to double SRR, we effectively expanded the stop band width of the broadband filter. Devices were created on two types of substrates, 1 mm thick quartz and 100 µm thick polyethylene terephthalate (PET), demonstrating the ease and wide applicability of the fabrication process, while a bandwidth of as large as 1.40 THz has been achieved.
We present a theoretical study of the spontaneous emission of a line dipole source embedded in a graphene–coated subwavelength wire of arbitrary shape. The modification of the emission and the radiation efficiencies are calculated by means of a rigorous electromagnetic method based on Green’s second identity. Enhancement of these efficiencies is observed when the emission frequency coincides with one of the plasmonic resonance frequencies of the wire. The relevance of the dipole emitter position and the dipole moment orientation are evaluated. We present calculations of the near–field distribution for different frequencies which reveal the multipolar order of the plasmonic resonances.