Asymmetric carbon nanotube dimers embedded in a dielectric slab: new plasmonic resonance behavior

Abstract

All prior work on modeling the full-wave electromagnetic response of carbon nanotubes (CNTs) have focused on CNTs in free-space, whereas in most practical applications, CNTs are embedded in a dielectric substrate. In this work, we use full-wave simulations to study the plasmonic resonances of CNT dimers embedded in a lossy dielectric slab with a finite thickness. The numerical results show that the finite thickness dielectric slab leads to the emergence of new CNT resonance behavior that is not present in a homogeneous environment. As a single CNT approaches the dielectric slab interfaces, the resonance frequency of the CNT increases due to reduced dielectric loading. The resonance behavior changes completely when two CNTs in proximity form a dimer near the slab interface. The bonding and antibonding resonances of CNT dimers and the absorbed power vary significantly with the distance between the slab interface and the CNT dimer. Using this phenomenon, we show that symmetric CNT dimers can behave like asymmetric CNT dimers. Also, the antibonding resonance of an asymmetric CNT dimer can be suppressed by adjusting the length and depth of the CNT dimer inside the slab. This work can guide future sensing modalities based on CNT dimer as well as can provide an accurate assessment of the proximity of a CNT network to the interface of the embedding substrate.