Diffraction enhanced transparency (DET) using frequency detuned and displaced resonant rods

In this contribution, we demonstrate that a periodic lattice of frequency-detuned and displaced resonant rods can suppress the THz extinction at the central resonant frequency, leading to an enhanced spectral window of near perfect transparency. The system consists of a periodic lattice of metallic rods of two different sizes. Each of the rods supports a strong half-wavelength (λ/2) resonance which are detuned with respect to each other. Furthermore, both the rods are spatially displaced within each unit cell of the lattice. The group-index obtained from far-field measurements shows that the THz field is strongly delayed by more than four orders of magnitude at the spectral transparency window. Using micro-spectroscopic measurements of the electric near fields, we show that this transparency window has its origin in the interference between two surface lattice resonances, arising from the diffractively enhanced radiative coupling of the two λ/2 resonances in the lattice. Thus, we term this phenomenon as Diffraction Enhanced Transparency (DET). Since DET does not involve near-field coupling between resonators, the fabrication tolerance to imperfections is expected to be very high. This remarkable response and ease of fabrication renders these systems as very interesting components for THz communication