Modulating Fundamental Resonance in Capacitive Coupled Asymmetric Terahertz Metamaterials

Abstract

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.

Flexible 3D Printed Conductive Metamaterial Units for Electromagnetic Applications in Microwaves

“…Consequently, the SRR behaves as an inductor-capacitor (LC) circuit with a characteristic resonance frequency ~ . At the resonance a large confinement of the fields in certain areas of the meta-atom takes place—in particular in the area between the gaps and around them [ 32 , 33 , 34 ]. Placing a dielectric material in the high field position tunes the resonance.…”

“…The structure consists of two SRRs oriented so that their gaps are next to each other, as shown in Figure 1 . Said SRR configuration exhibits increased electromagnetic field confinement, which results in the high tunability of the response with relatively small changes in its environment [ 32 , 33 , 34 ]. Structures of variable length L , width w , thickness t and size of gap d (see Figure 1 a,b) were produced.…”

Tunable terahertz band-stop filter using strongly coupled split ring resonators integrated with on-chip waveguide

“…The SRRs then resonate at the same frequency producing one resonance. 26 By situating two SRRs in close proximity they experience near-field capacitive coupling however, 19 which causes resonant splitting for relative distances of less of than 100 μm into two modes. A cantilever comprising the arms of the outer SRR was then introduced to actively control the coupling between the two SRRs.…”

“…18 Furthermore, when two or more THz resonators are in close proximity, they experience nearfield coupling, which modifies their response. 19 It has also been shown that the response of a THz SRR can be adjusted by making a microelectromechanical systems (MEMS) cantilever from one arm of the SRR, 20 whose position and resonant response can then be adjusted using voltage. Tuneability of the resonances of the SRR was demonstrated in the frequency range of 200 -450 GHz for LC resonance and 700 -1000 GHz for dipole resonance by changing the cantilever position.…”

Resonance phenomena in electromagnetic metamaterials for the terahertz domain: a review

“…To bypass cumbersome generation and detection techniques, new, simpler, cost-effective techniques, such as THz attenuated total reflection spectroscopy and THz time-domain spectroscopy, were implemented [35][36][37]. THz metamaterials have acted as great stepping stones in research for the generation [38], modulation [8,39,40], polarization conversion [41,42], absorption [43,44] and sensing [45][46][47] of THz radiation. THz metamaterials have emerged as a versatile platform for sensing especially, where only trace amounts or thin films of analytes are available for investigation [48,49].…”