Metamaterial (MM) is artificial material in which an unit cell, having a size much smaller than the wavelength of external electromagnetic (EM) wave, is periodically arranged. This MM offers a new tool that can significantly improve the effectiveness of absorber and the sensitivity of sensor through its powerful localization and field enhancement. This review presents recent the potential applications of electromagnetically-induced transparency (EIT) and absorption (EIA) phenomena in MM-based absorber and MM-based sensors, and summarizes the sensitivity differences from the existing sensors. These phenomena provide a high-performance platform for a variety of sensors with easy adjustment of the EM response, and can produce effective narrow- or multi-band absorption.
Metamaterial (MM) is artificial material in which an unit cell, having a size much smaller than the wavelength of external electromagnetic (EM) wave, is periodically arranged. This MM offers a new tool that can significantly improve the effectiveness of absorber and the sensitivity of sensor through its powerful localization and field enhancement. This review presents recent the potential applications of electromagnetically-induced transparency (EIT) and absorption (EIA) phenomena in MM-based absorber and MM-based sensors, and summarizes the sensitivity differences from the existing sensors. These phenomena provide a high-performance platform for a variety of sensors with easy adjustment of the EM response, and can produce effective narrow- or multi-band absorption.
We theoretically investigate the classical analog of electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) in a planar metamaterial at optical frequency, which originates from destructive and constructive interference between dark and radiative elements.The metamaterial consists of two coupled resonators with different geometries.An EIT-like transparent window with low absorption is observed and found to be strongly affected by resonant states of the resonators.The transition between the EIT and EIA is achieved by changing the split width and coupling distance.The absorption is enhanced up to 2.5 times compared with the dipolar case.The excitation of the dark mode is very important for EIT-and EIA-like responses of the proposed metamaterial.The EIT and EIA phenomena offer a potential method for manipulating electromagnetic response in metamaterial-based devices.
The vigorous research on low-loss photonic devices has brought significance to a new kind of electromagnetic excitation, known as toroidal resonances. Toroidal excitation, possessing high-quality factor and narrow linewidth of the resonances, has found profound applications in metamaterial (MM) devices. By the coupling of toroidal dipolar resonance to traditional electric/magnetic resonances, a metamaterial analogue of electromagnetically induced transparency effect (EIT) has been developed. Toroidal induced EIT has demonstrated intriguing properties including steep linear dispersion in transparency windows, often leading to elevated group refractive index in the material. This review summarizes the brief history and properties of the toroidal resonance, its identification in metamaterials, and their applications. Further, numerous theoretical and experimental demonstrations of single and multiband EIT effects in toroidal-dipole-based metamaterials and its applications are discussed. The study of toroidal-based EIT has numerous potential applications in the development of biomolecular sensing, slow light systems, switches, and refractive index sensing.
In this work, using finite-difference time-domain method, we propose and numerically demonstrate a novel way to achieve electromagnetically induced transparency (EIT) phenomenon in the reflection spectrum by stacking two different types of coupling effect among different elements of the designed metamaterial. Compared with the conventional EIT-like analogues coming from only one type of coupling effect between bright and dark meta-atoms on the same plane, to our knowledge the novel approach is the first to realize the optically active and precise control of the wavelength position of EIT-like phenomenon using optical metamaterials. An on-to-off dynamic control of the EIT-like phenomenon also can be achieved by changing the refractive index of the dielectric substrate via adjusting an optical pump pulse. Furthermore, in near infrared region, the metamaterial structure can be operated as an ultra-high resolution refractive index sensor with an ultra-high figure of merit (FOM) reaching 3200, which remarkably improve the FOM value of plasmonic refractive index sensors. The novel approach realizing EIT-like spectral shape with easy adjustment to the working wavelengths will open up new avenues for future research and practical application of active plasmonic switch, ultra-high resolution sensors and active slow-light devices.
Abstract Electromagnetically induced transparency (EIT) stems from a quantum system, where an opaque atomic medium appears the narrow transparent state within a wide absorption area. This phenomenon can be achieved by quantum interference of pumping light and detecting light at different energy levels of transitions. In the generation process of EIT effect, in addition to transparent state, the atomic medium is usually accompanied with a strong dispersion effect, which will bright about a significant reduction of light velocity, thus realizing many important applications, such as slow light propagations. Although the EIT effect has many important applications, its application scenarios are greatly limited due to the fact that EIT realization usually requires specific and complicated conditions, such as refrigeration temperature, high intensity laser, etc. Recently, the analogue of EIT effect in metamaterial has attracted increasing attentions due to its advantages such as controllable room temperature and large operating bandwidth. Metamaterial analogue of EIT effect has become a new research focus. In this article, we review current research progresses on EIT metamaterials. Firstly, we describe the theoretical models for analyzing EIT metamaterials, including the mechanical oscillator model and the equivalent circuit model. Then, we describe the simulations, designs and experiments of passive EIT metamaterials with fixed structures and active EIT metamaterials with tunable elements. Furthermore, the applications of EIT metamaterials in the areas of slow lights, sensings, absorptions and other fields are also reviewed. Finally, the possible directions and key issues of future EIT metamaterial researches are prospected.
Metamaterials, or artificial materials with optical properties not known for natural materials, have recently been used to demonstrate unusual optical phenomena, such as negative refraction, perfect lenses, subwavelength components, and electromagnetic invisibility cloaks. Most of the metamaterials designed to date are periodic structures containing a single resonating element in each unit cell, such as a split-ring resonator (SRR), a cutwire, or a slab-wire pair [1]. In this contribution, we demonstrate that a metamaterial with two coupled SRRs can exhibit an effect reminiscent of electromagnetically induced transparency (EIT), a coherent process normally observed in three-level atomic media [2]. Due to this process, a small transparency window with low absorption appears in the spectral response of the metamaterial. Simultaneously, extremely steep normal dispersion is observed in the transparency window, which is useful for slow-light applications.
Abstract Metamaterials are a class of non-natural materials with special properties, the microstructure of which does not exist in nature. By artificially designing the structure of such materials, they can acquire electromagnetic properties that conventional materials in nature do not have. Electromagnetically induced transparency refers to the process of quantum interference effect between atomic energy levels in microscopic systems, which makes an energy-transmitting window appear in the original energy-absorbing region, simply put, a medium strongly absorbs a certain frequency of the light beam, and when another light beam is applied, the absorption of the first light beam by the medium will be greatly reduced or no longer absorbed. This phenomenon is called electromagnetically induced transparency, or EIT for short. In this paper, we combine the graphene material with the EIT structure to improve the manipulability of the EIT structure and obtain a controllable EIT structure based on the multi-mode coupled EIT extension.