Three-dimensional FDTD analysis of a nanostructured plasmonic sensor in the near-infrared range

Abstract

Finding new ways to access the nanoscale and high-Q-factor plasmonics resonance remains a major challenge in the field of plasmonic metasurfaces. In the present paper, we aim to report a nanoscale gold metasurface containing structure to realize high-quality plasmon-induced transparency (PIT) responses. The properties of the proposed model are numerically investigated with different physical parameters by the three-dimensional finite difference time domain (3D-FDTD) method. For this purpose, the effects of the geometrical parameters, metasurface materials, dielectric constant, and incident angle in the visible to near-infrared regions are studied. To obtain of dynamical tunability of the proposed model, graphene metasurfaces are then utilized. Numerical results show that the proposed devices are able to operate as high-quality PIT sensors with a maximum figure-of-merit of 1090, and sensitivity of 700 nm/refractive index unit for slight change of Δn=0.15, in the refractive index of the dielectric layer, which originates from its ultra-narrow transparency window and strong coupling between dark–bright modes. Moreover, the structure has a nanoscale footprint of 40  nm×60  nm×31  nm. We believe that the proposed sensor can be used as a promising platform for future nanosensing applications, such as nanostructure plasmonic sensors.