Resonance properties of THz plasmonic dipole-bowtie antenna array: The critical role of the substrate

Subwavelength arrays of dipole-bowtie antennas are designed and characterized using terahertz time-domain spectroscopy (THz-TDS) and finite element method (FEM) simulations. Two different substrates, silicon and mylar with an order of magnitude difference between their thickness values are used to study the resonance properties of the antennas. The 640-μm thick silicon substrate supports a sharper fundamental mode resonance. We discover that higher-order Fabry–Perot resonances can be excited only in 24-μm thin mylar substrates and show much higher sensitivity to dielectric changes in the environment and the geometrical parameters of the antennas than the fundamental dipole resonance.