Investigation of Surface Plasmon Polaritons in THz Metagrids


Il giorno 10 luglio 2019, ore 14:30, aula 2G27

 il dott. Gianpaolo Papari, Dip. Fisica,

terrà il seminario dal titolo:


 "Investigation of Surface Plasmon Polaritons in THz Metagrids for Accurate Sensing"



Surface plasmon polaritons (SPPs) can be easily activated in the THz band by operating a periodic removal of patches from an homogeneous conducting film, reducing in such a way  the plasma frequency [1]. In this work we deal with metagrids (MGs), which show a plasma frequency dependent on the metal filling factor, and study the THz response of two different geometries realized by standard PCB processing over a FR4 layer 160 mm thick. The first MG is in shape of a typical grid realized intersecting horizontal and vertical wires 300 mm wide, whereas the second one consists of a chessboard arrangement of square metal patches 300 mm sized. With the aid of full-wave electromagnetic simulations we can trace out the dependence of the plasma frequency on the MG filling factor, showing that the system undergoes a transition from a fully homogeneous "metamaterial" (inductive) behavior to a diffractive "photonic crystal" (capacitive) regime [2]. In the plot, measurements (black dots) and numerical results (blue and red symbol continuous curves for the two different geometries)  are presented and compared with the analytical behavior (black dash-dotted line) expected using a simple lumped element model. The evanescent field of SPPs can then be employed to perform label free sensing of biological fluids. We present a preliminary investigation where MGs can be used as bio-sensors, measuring the changes in the SPP resonances induced by the presence of an analyte. Using a suitable algorithm to improve the figure of merit, one can theoretically reach sensitivities comparable with the best values available in literature.

[1]       J. B. Pendry, L. Martin-Moreno, and F. J. Garcia-Vidal, "Mimicking Surface Plasmons with Structured Surfaces," Science 305, no. 5685, pp. 847–848, 2004.

[2]       G. P. Papari, C. Koral, and A. Andreone, "Geometrical Dependence on the Onset of Surface Plasmon Polaritons in THz Grid Metasurfaces," Sci. Rep., vol. 9, no. 1, pp. 1–12, 2019.

Data: 10/07/2019