Classical Analog and Hybrid Metamaterials of Tunable Multiple-Band Electromagnetic Induced Transparency

Abstract

The electromagnetic induced transparency (EIT) effect originates from the destructive interference in an atomic system, which contributes to the transparency window in its response spectrum. The implementation of EIT requires highly demanding laboratory conditions, which greatly limits its acceptance and application. In this paper, an improved harmonic spring oscillation (HSO) model with four oscillators is proposed as a classical analog for the tunable triple-band EIT effect. A more general HSO model including more oscillators is also given, and the analyses of the power absorption in the HSO model conclude a formula, which is more innovative and useful for the study of the multiple-band EIT effect. To further inspect the analogizing ability of the HSO model, a hybrid unit cell containing an electric dipole and toroidal dipoles in the metamaterials is proposed. The highly comparable transmission spectra based on the HSO model and metamaterials indicate the validity of the classical analog in illustrating the formation process of the multiple-band EIT effect in metamaterials. Hence, the HSO model, as a classical analog, is a valid and powerful theoretical tool that can mimic the multiple-band EIT effect in metamaterials.

Design and experimental realization of triple-band electromagnetically induced transparency terahertz metamaterials employing two big-bright modes for sensing applications

“…The surface patterned aluminum array of the triple-band transparency effect is merely formed by two sub-resonators, namely a fork-shaped resonator (FSR) and a U-shaped split-ring resonator (USRR), which correspond to two different “big-bright” resonance modes. Unlike the traditional bright mode in the EIT effects, 24–44 the “big-bright” resonance mode obtained here possesses two independent resonance dips having different frequencies, and the combination (or coupling) of these two sets of “big-bright” modes gives rise to a triple-band transparency response, resulting in three transparent windows at frequencies of 0.56 THz, 1.10 THz, and 1.33 THz. This of course also reduces the complexity of designing metamaterial basic cells and introduces different physical mechanisms to achieve a triple-band EIT response.…”

“…40 In addition to the widely reported dual-band transparency effect, the development of triple-band EIT resonance devices is also in full swing. [41][42][43][44] For instance, multiple patterned graphene sub-resonators distributed in four alternating stacked layers were theoretically reported. 41 A coplanar structure formed by five different-sized metallic elements, including a cross, a pair of square frames, and a pair of square SRRs, was theoretically proposed to obtain a triple-band EIT response.…”

“…The triple-band EIT functional devices typically require more sub-resonators in their basic cells. [41][42][43][44] This seems to have entered a strange cycle: the more the transparent peaks are, the more complex the basic cell designs are, and the more the sub-resonators are. [38][39][40][41][42][43][44] The fundamental reason for this phenomenon is that these papers use brightbright coupling, where each sub-resonator corresponds to a single resonance mode, and the result is that only the presence of a large number of sub-resonators in their basic cells, usually exceeding the number of transparent peaks, could achieve multi-band transparency effects.…”

“…[41][42][43][44] This seems to have entered a strange cycle: the more the transparent peaks are, the more complex the basic cell designs are, and the more the sub-resonators are. [38][39][40][41][42][43][44] The fundamental reason for this phenomenon is that these papers use brightbright coupling, where each sub-resonator corresponds to a single resonance mode, and the result is that only the presence of a large number of sub-resonators in their basic cells, usually exceeding the number of transparent peaks, could achieve multi-band transparency effects. 14,[38][39][40][41][42][43][44] This kind of design is unfavorable for the compact structural dimension and could bring certain difficulties to device preparation, resulting in one of the current situations being that there are few experimental reports on the triple-band EIT effect, and most of them are presented through theoretical simulation and theoretical code results.…”

“…[38][39][40][41][42][43][44] The fundamental reason for this phenomenon is that these papers use brightbright coupling, where each sub-resonator corresponds to a single resonance mode, and the result is that only the presence of a large number of sub-resonators in their basic cells, usually exceeding the number of transparent peaks, could achieve multi-band transparency effects. 14,[38][39][40][41][42][43][44] This kind of design is unfavorable for the compact structural dimension and could bring certain difficulties to device preparation, resulting in one of the current situations being that there are few experimental reports on the triple-band EIT effect, and most of them are presented through theoretical simulation and theoretical code results. [41][42][43][44] Second, the discussion on the applications of the triple-band EIT effect, such as sensing and group delay, remains at the stage of conceptual design and lacks necessary experimental verification.…”