Recently reported metamaterial (MM) analogs of electromagnetically induced reflectance (EIR) enable a unique route to endow classical optical structures with aspects of quantum optical systems. This method opens up many fascinating prospects on novel optical components, such as slow light units, highly sensitive sensors, and nonlinear devices. Here we designed and simulated a microwave MM made from aluminum thin film to mimic the EIR system. High reflectance of about 99 percent and also a large group index at the reflectance window of about 243 are demonstrated, which mainly arise from the enhanced coupling between radiative and nonradiative elements. The interaction between the elements of the unit cell, induced directly or indirectly by the incident electromagnetic wave, leads to a reflectance window, resembling the classical analog of EIR. This reflectance window, caused by the coupling of radiative-nonradiative modes, can be continuously tuned in a broad frequency regime. The strong normal phase dispersion in the vicinity of this reflectance window results in the slow light effect. This scheme provides an alternative way to achieve tunable slow light in a broad frequency band and can find important applications in active and reversibly tunable slow light devices.
Recently reported metamaterial (MM) analogs of electromagnetically induced reflectance (EIR) enable a unique route to endow classical optical structures with aspects of quantum optical systems. This method opens up many fascinating prospects on novel optical components, such as slow light units, highly sensitive sensors, and nonlinear devices. Here we designed and simulated a microwave MM made from aluminum thin film to mimic the EIR system. High reflectance of about 99 percent and also a large group index at the reflectance window of about 243 are demonstrated, which mainly arise from the enhanced coupling between radiative and nonradiative elements. The interaction between the elements of the unit cell, induced directly or indirectly by the incident electromagnetic wave, leads to a reflectance window, resembling the classical analog of EIR. This reflectance window, caused by the coupling of radiative-nonradiative modes, can be continuously tuned in a broad frequency regime. The strong normal phase dispersion in the vicinity of this reflectance window results in the slow light effect. This scheme provides an alternative way to achieve tunable slow light in a broad frequency band and can find important applications in active and reversibly tunable slow light devices.
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.
Recently, metamaterials with unique electromagnetic (EM) properties have attracted people’s great interest. In metamaterials, the eclectic and magnetic response to incident light can be conveniently tuned. For example, the enhancement of electric and magnetic response can bring about effective negative permittivity (epsilon) and negative permeability (mu), respectively [1,2]. Since the interactions of metamaterials and light can be manipulated by varying the structural and geometric parameters of metamaterials, metamaterials provide us a convenient platform to mimic a variety of quantum-optic phenomena such as electromagnetically induced transparency (EIT) [3] and vacuum Rabi splitting [4]. EIT in quantum optics occurs when atoms can transit via two pathways and make a destructive interference to inhibit absorption, which brings about slow-wave effect and strong group velocity dispersion [5]. However, the building process of atomic EIT is still unclear due to the very quick time evolution in the transition. EIT analog in metamaterials realized by the interference in two classical pathways can observe the dynamic process during the establishment of EIT in the time scale much larger than the atomic counterpart. Based on a waveguide structure, we study the dynamic evolution of EIT in metamaterials and reveal experimentally the parameters controlling excitation transfer during the building process of EIT [6]. The dynamic properties of classical EIT not only mimic the population transfer between energy levels in the atomic EIT, but also present a physical picture of rapid optical response that plays an important role in fast manipulating light by EIT. Moreover, we study another important problem in classical EIT, i.e., the influence of intrinsic losses on EIT. We provide systematic experimental demonstration of EIT in metamaterials with tunable intrinsic loss. It is found under the EIT condition the maximum transmittance as well as the corresponding group delay in the transmission window is nearly unchanged and only the delay bandwidth is affected by the intrinsic loss. Vacuum Rabi splitting, which appears when atoms or atom-like systems are put inside a cavity, is another important quantum phenomenon that may be applied for the quantum entanglement and computations [7]. In a cavity with high quality factor and small volume, vacuum Rabi splitting can occur for a single atom in the strong coupling regime. In general, the cavity modes are all in the form of standing waves and the cavity fields are inhomogeneous. To ensure strong coupling of an atom (or a quantum dot) and photons, we need to place the atom right at the peak(s) of the fields, which is very challenging in atomic or solid-state experiments. Moreover, in atomic experiments, a cold atom is needed. This is because a hot atom can move around the position-variant fields under thermal fluctuation, making the coupling of the atom and the cavity unstable. To overcome the position uncertainty, we propose another type of cavity filled with zero-index metamaterials (ZIMs) in which epsilon=0 and/or mu=0 . In an impedance-matched ZIM ( epsilon=mu=0), both phases and amplitudes of the EM fields are homogeneous [8]. However, in a epsilon-near-zero (ENZ) medium (epsilon=0,mu=1), although the phases of EM waves are uniform, in most cases the amplitudes of electric fields will vary in space. In practice, a highly doped semiconductor such as InGaAs can be utilized as an ENZ medium [9] and self-assembled or colloidal quantum dots could be embedded in this ENZ medium. So how to realize uniform electric fields in an ENZ medium is an important practical problem. We discover that, when an ENZ medium is inserted in the center of a two-dimensional photonic crystal with a gap that plays a role of magnetic wall, the electric fields in the ENZ medium are forced to be nearly uniform, as required by Maxwell equations and boundary conditions. Then, we embed a quantum dot in the ENZ medium confined by the magnetic-wall-like photonic barrier and obtain a nearly position-independent Rabi-like splitting. This is because the enhanced electric fields are almost same at any place of the ENZ medium. Finally, by loading lumped capacitors and inductors in a microwave transmission line, we realize a cavity with effective ZIM in which the enhanced fields are nearly homogeneous [10]. When an atom-like split ring resonator is coupled to this effective ZIM at various locations, we observe the nearly position-independent Rabi-like splitting. A ZIM-filled cavity in the strong coupling regime will provide us a new platform to study the interactions of atoms and photons in the future.
Abstract The realization of electromagnetically induced transparency (EIT) on metamaterials has special properties, such as strong slow-light, frequency-selection and so on, which have allowed EIT to be widely used in the fields of slow-light, optical storages and filters. In this paper, a metamaterial with two pairs of split ring resonators and one cut-wire is designed to achieve dual-band EIT effect at 0.5–2.14 GHz and 0.4–2.10 GHz with independently tunable bandwidths of 1.64 GHz and 2.7 GHz, respectively. The coupled Lorentz model is adopted to principally study the coupling characteristics between dark and bright modes. It is shown that the coupling strength between the dark and bright modes could be modulated by the coupling distance, which make the dual-band transparent window could be independently modulated by only changing the coupling distance between the bright and dark mode. The group delay and energy storage are also simulated by setting the Gaussian pulse signal passing through the EIT structure. The results show that the group delay of the designed EIT structure is 16.9 times that of the same thickness of dielectric material. The manufactured metamaterial is tested in a microwave anechoic chamber. The experimental and theoretical results are well consistent. These results could be beneficial for the development of EIT research toward some up-and-coming novel slow-light, optical storage, sensor and optical filter applications.
Analogs of Electromagnetically Induced Transparency (EIT) in metamaterial have undoubtedly become a research hotspot in recent years. In this paper, we summarized some of the literature on EIT published to date and compared their performance. Then, we designed two kinds of metamaterials using aluminum and silicon. Both have the similar glasses-shaped structure of a periodic lattice with one bar resonator and two split ring resonators. We analyzed and compared the EIT performance in the near infrared waveband of these two metamaterials. The metallic EIT metamaterials with large radiation loss and ohmic heat loss have a smaller Q-factor than the dielectric counterpart with less energy loss, while having a higher sensitivity toward the ambient refractive index. The Q-factor of our designed aluminum metamaterial and silicon metamaterial are 10.06 and 412.6, respectively. Their sensitivities are 1642.97 nm/RIU and 433.05 nm/RIU, respectively, which are higher than most of their counterparts in the same waveband in the other literature. For the application of slow light, the dielectric metamaterials with higher Q-factor are far superior to the metallic metamaterials in the same waveband and comparable propagation distance. The group index of the aluminum metamaterial is 42.9, and the group delay is 0.01 ps in the near infrared waveband. For the silicon metamaterial, the group index is approximately 1907.1, and the group delay is 0.89 ps within the transmission window in the near infrared waveband; these values are both higher than most counterparts in the same waveband in other literature. The EIT metamaterials that we designed have excellent performance, and to the best of our knowledge, this paper presents the first detailed comparison of EIT metamaterials made of dielectric and metal with similar structure; this paper may have certain instructive meaning for further research on metamaterial analogues of EIT in the future.
Metamaterials are engineered materials composed of small electrical circuits producing novel interactions with electromagnetic waves. Recently, a new class of metamaterials has been created to mimic the behavior of media displaying electromagnetically induced transparency (EIT). Here we introduce a planar EIT metamaterial that creates a very large loss contrast between the dark and radiative resonators by employing a superconducting Nb film in the dark element and a normal-metal Au film in the radiative element. Below the critical temperature of Nb, the resistance contrast opens up a transparency window along with a large enhancement in group delay, enabling a significant slowdown of waves. We further demonstrate precise control of the EIT response through changes in the superfluid density. Such tunable metamaterials may be useful for telecommunication because of their large delay-bandwidth products.
An analogy of electromagnetically induced transparency (EIT) based on all-dielectric metamaterial is theoretically demonstrated in this paper. The U-shaped Silicon-based metamaterial unit cell comprises a dipole antenna supported by one horizontal nanoscale bar and a quadrupolar antenna supported by two vertical nanoscale bars. The near-field coupling between the two antennas and the reduction of absorption loss lead to a narrow EIT-like transmission window with a high quality-factor of 130, which exhibits a refractive index sensitivity with a figure-of-merit of 29. The group delay of 0.75 ps and the group index of 2035 are obtained in the transmission window. Due to these unique optical properties, the proposed metamaterial structure can find many applications including slow-light devices, optical sensors, enhancement of non-linear processes, and storage of quantum information.