Electromagnetically induced transparency is an optical phenomenon that is characterized by the elimination of the effect of a medium on a propagating beam of electromagnetic radiation in a specific frequency band. In this study, EIT was investigated at a proposed metamaterial with the dimensions milimeter and in the area of frequency of GHz. The computation results indicated that EIT with high transmission rate and high Q factor occurs in certain frequencies by breaking the symmetry in this structure. The sensitivity studies showed that the use of silver in the structure increases the quality factor so significantly that this quantity reaches 338 for gold and copper, while it reaches 677 for silver. In addition, By reducing the temperature, the transmission rate in the structure increases and reaches acceptable degree 98%. This structure can be an appropriate option for slow light usages, and it can be utilized for light amplification in microwave structures.
Electromagnetically induced transparency is an optical phenomenon that is characterized by the elimination of the effect of a medium on a propagating beam of electromagnetic radiation in a specific frequency band. In this study, EIT was investigated at a proposed metamaterial with the dimensions milimeter and in the area of frequency of GHz. The computation results indicated that EIT with high transmission rate and high Q factor occurs in certain frequencies by breaking the symmetry in this structure. The sensitivity studies showed that the use of silver in the structure increases the quality factor so significantly that this quantity reaches 338 for gold and copper, while it reaches 677 for silver. In addition, By reducing the temperature, the transmission rate in the structure increases and reaches acceptable degree 98%. This structure can be an appropriate option for slow light usages, and it can be utilized for light amplification in microwave structures.
The electromagnetically induced transparency (EIT), which is a result of destructive interference between different excitation paths in a three-energy-level atomic medium, makes opaque probe light transparent over a range of frequencies. As this EIT effect is usually accompanied with strong dispersion, it has potential applications such as slow light propagation, optical buffering, nonlinear optics, optical sensing, etc. However, for conventional quantum EIT effect which requires stable gas lasers and low temperature environment, the implementation of EIT in chip-scale applications is severely hampered by the scathing experimental requirements. Recently, the EIT-like effect in metamaterials, which are constructed by designing the artificial subwavelength functional elements and arranging the spatial sequences, attracts tremendous attention because of its advantages, such as room temperature manipulability, large bandwidth, and small sizes. In addition, the high-quality factor(Q) value obtained by EIT-like effect has great significance in designing the metamaterial-based devices. In this paper, we design an EIT-like metamaterial with such a structure. The unit cell of the proposed metamaterial is constructed by two asymmetric silicon blocks embedded on a silicon dioxide substrate. Meanwhile, we analyze its optical properties and EIT-like effects by using three-dimension (3D) FDTD method. Based on the coupled Lorentz model, the EIT-like effect of the designed metamaterial is investigated. Then, by employing the electric field distribution on the surface of the metamaterial, and combining with the three-level atomic system, the mechanism of the EIT-like effect is analyzed in detail. We find that the EIT-like effect in the proposed metamaterial has high Q value (Q ≈ 8616) and the high transmission (T = 96%). By changing the length of the silicon block to destroy the asymmetry of the metamaterial structure, an active tuning EIT-like effect is realized. Furthermore, the metamaterial structure has the advantages of low loss, easy preparation, and active-controllability. This study represents an innovative approach to designing the EIT-like metamaterial, which is expected to be useful for designing active tunable slow-light devices and highly sensitive optical sensors.
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.
We report on our numerical work concerning a planar metamaterial exhibiting classical electromagnetically induced transparency (EIT). Using a structure with two asymmetric short strips, we demonstrate that an EIT-like resonance with a high quality factor can be achieved and this high quality factor leads to a large group index of the order of 700. The operation of metamaterial at low temperatures is anticipated to be a promising path towards low-loss metamaterials since nonradiative losses are strongly suppressed. By decreasing temperature from 300 K to 100 K, a controlled behavior with a 26% increase in the quality factor of the resonance and an 85% increase in the group index was observed.
Polarization-insensitive electromagnetically induced transparency (EIT) based on ultra-thin coupling planar metamaterials has been numerically demonstrated. The height (h) of ultra-thin coupling planar metamaterials can reach to 1/94 λ, which is the thinnest height so far. Such ultra-thin EIT metamaterials can reduce the cost of production. When the angles of the incident electromagnetic wave are changed, the EIT metamaterials show polarization-insensitive characteristics. When the height of the EIT metamaterials gradually increases, the group index gradually decreases and the transmission peak value and h/λ gradually increase. All of above characteristics make the ultra-thin coupling EIT have potential application in slow light devices. In addition, using the coupling of the top and below layer has proposed a way to obtain ultra-thin metamaterials in the microwave region.
Based on solid-state plasma (SSP), an electromagnetically induced transparent (EIT) metamaterial is proposed. Simulations illustrate that the given metamaterial has the characteristics of adjustment, polarization insensitivity, and low dissipation. Because SSP can be coordinated in state I, the ideal transmittance frequency band can cover 8.0335–9.02531 GHz (a narrow band). If the regulatory status is switched to state II, that frequency region will alter to 9.7982–12.9275 GHz (a broad band). As SSP can be switched back and forth between states I and II under actual demand, the tailored EIT metamaterial can be achieved. The maximum group delays of state I and state II are 0.9437 ns and 0.5546 ns, respectively, and the maximum group refractive indices are 526.60 and 300.45, respectively, which conforms to its slow light characteristic. Regardless of how the polarization angle changes, the two transmission valleys of state I are at 7.9172 GHz and 10.4446 GHz, and the transmission peak is situated at 8.2091 GHz, and those values of state II are 9.3777 GHz, 13.9600 GHz, and 10.1920 GHz, respectively, which proves that the obtained EIT is polarization independent and also has a low dissipation factor. Such an EIT metamaterial has excellent properties in sensing, communication, slow light, and other fields.
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.