Abstract-Asymmetric gap resonator based near-field coupling in terahertz metamaterials (Conference Presentation)

S. Jagan Mohan Rao, Yogesh Kumar Srivastava, Gagan Kumar,  Dibakar Roy Chowdhury

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10983/109830Z/Asymmetric-gap-resonator-based-near-field-coupling-in-terahertz-metamaterials/10.1117/12.2519820.short?SSO=1

The metamaterial is an arrangement of artificial structural elements designed to achieve advantageous and unusual electromagnetic properties. In the unit cell level, metamaterials are composed of an array of small structured elements called split ring resonators (SRRs). Recently, a lot of emphases has been given to the realization of terahertz metamaterials owing to its significance in the construction of terahertz photonic components. In this context, near-field coupling in terahertz metamaterials is extremely crucial. The short-range coupling in metamaterials occurs via the electric and magnetic fields due to the close proximity of the neighboring resonators. The electric field mainly couples through the gaps of SRRs, while the magnetic field couples through the circumference. In this work, we experimentally investigate near-field gap to gap capacitive coupling between a pair of single split gap ring resonators (SRRs) in a terahertz metamaterial. This has been achieved by manipulating the near field electric interactions via changing one resonator split gap with respect to the other resonator split gap for several inter resonator separations. Introducing asymmetry by changing the split gap in one resonator with respect to the other resonator, results in the split in the fundamental resonance mode when operated in the strong near-field coupled regime. The split occurs because of the strong near field capacitive/electric interactions between the resonators. We have further calculated Q factor for the lower and higher resonance modes for different inter resonator separations. The modulation of resonances in capacitive coupled planar terahertz metamaterial systems studied through this work has great potential in manipulating and controlling electromagnetic waves which can ultimately result in novel applications for terahertz frequency domain.

Abstract-Modulating Fundamental Resonance in Capacitive Coupled Asymmetric Terahertz Metamaterials

S. Jagan Mohan Rao, Yogesh Kumar Srivastava, Gagan Kumar & Dibakar Roy Chowdhury

https://www.nature.com/articles/s41598-018-34942-2

In this work, we experimentally investigate near-field capacitive coupling between a pair of single-gap split ring resonators (SRRs) in a terahertz metamaterial. The unit cell of our design comprises of two coupled SRRs with the split gaps facing each other. The coupling between two SRRs is examined by changing the gap of one resonator with respect to the other for several inter resonator separations. When split gap size of one resonator is increased for a fixed inter-resonator distance, we observe a split in the fundamental resonance mode. This split ultimately results in the excitation of narrow band low frequency resonance mode along with a higher frequency mode which gets blue shifted when the split gap increases. We attribute resonance split to the excitation of symmetric and asymmetric modes due to strong capacitive or electric interaction between the near-field coupled resonators, however blue shift of the higher frequency mode occurs mainly due to the reduced capacitance. The ability of near-field capacitive coupled terahertz metamaterials to excite split resonances could be significant in the construction of modulator and sensing devices beside other potential applications for terahertz domain.