Hybridization of dark resonant states in terahertz metasurfaces

Abstract

Dark resonating states render an important role in curtailing the dominant radiative losses in various photonic structures like metamaterials (MMs), photonic crystals, waveguides, etc. Currently, radiative losses are the major degrading factors toward the strong confinement of electromagnetic radiation for MMs’ applications in sensing, imaging, filters, modulators, nonlinear studies, etc. Generally, the dark states cannot be excited through the direct interaction of electromagnetic radiations with the metastructures. However, indirect excitation at suitable structural asymmetries can trigger the evolution of dark resonating states or trapped modes. In this work, we have experimentally demonstrated mode hybridization of such dark (sub-radiant) resonating states without the direct involvement of interacting bright (super-radiant) states in a metasurface consisting of asymmetric split-ring resonators. Our study further reveals that the lattice mode plays a crucial role in determining the line shapes of the split (hybridized) modes. Such tuning of dark resonance modes can find potential applications in metasurfaces-based sensing, non-linear devices besides other potential applications desiring multi-channel strong field confinement.

External bias dependent dynamic terahertz propagation through BiFeO3 film

“…In order to normalize the transmissions, an exactly similar BFO/LNO/ LAO material system without top Ni coating was used as a reference. The time-dependent THz pulse thus transmitted through the sample (figures 2(b) and (c)) is then converted to the complex frequency spectra using fast Fourier transformation (FFT) [49].…”

Hybrid resonant cavities: A route towards phase engineered THz metasurfaces

“…Employing metamaterials/metasurfaces lead to several other fascinating phenomena like negative and anomalous refraction (Smith et al, 2004;Shelby et al, 2001), flat lensing (Pendry, 2000), cloaking (Valentine et al, 2009), subwavelength resolution imaging (Khorasaninejad et al, 2016;Pendry et al, 2012), holography (Larouche et al, 2012;Ni et al, 2013), sensing (Karmakar et al, 2020a;Kaur et al, 2021a) realization of several quantum phenomena (like Fano and toroidal resonance, dark resonating states, electromagnetically induced transparency, bound state in the continuum etc.) in classical domain (Karmakar et al, 2020b(Karmakar et al, , 2021Kaur et al, 2021b). All these applications are based on engineering the phase of the electromagnetic waves by either abrupt or graded manner in spectral and/or spatial domains.…”