Electromagnetically Induced Transparency Phenomenon Research Articles

Dynamically Tunable Resonant Strength in Electromagnetically Induced Transparency (EIT) Analogue by Hybrid Metal-Graphene Metamaterials

In this paper, a novel method to realize a dynamically tunable analogue of EIT for the resonance strength rather than the resonance frequency is proposed in the terahertz spectrum. The introduced method is composed of a metal EIT-like structure, in which a distinct EIT phenomenon resulting from the near field coupling between bright and dark mode resonators can be obtained, as well as an integrated monolayer graphene ribbon under the dark mode resonator that can continuously adjust the resonance strength of transparency peak by changing the Fermi level of the graphene. Comparing structures that need to be modulated individually for each unit cell of the metamaterials, the proposed modulation mechanism was convenient for achieving synchronous operations for all unit cells. This work demonstrates a new platform of modulating the EIT analogue and paves the way to design terahertz functional devices which meet the needs of optical networks and terahertz communications.

Variation of probe absorption with intensity of radiation fields in three energy-level system

The variation of probe absorption with the intensity of coupling and probe field in a cascade three energy-level atomic systems is observed based on the density matrix equation. It shows that in the case of weak probe field, probe absorption presents electromagnetically induced transparency (EIT) near the resonant frequency. The depth of transparent window increases with the increase of the intensity of the coupling field until complete transparent. After that, the width of EIT window increases and changes to Aulter-Townes double peak finally. While with the increase of the probe intensity, the contrast of EIT declines rapidly, and EIT will disappear when Rabi frequency of the probe field exceeds the decay rate of the transverse relaxation. If the coupling field is off-resonance, the double peak of probe absorption is no longer symmetric to the resonant point and the intensity of two peaks is no equal also. With the increase of the probe field, the intensity of two peaks converts each other, and at last forms one wide peak by overlapping together. At room temperature, EIT phenomenon can still be observed if adopting Doppler-free configuration and weak probe field. But if the probe field is strong enough, besides the absorption curve is broadened, a small peak which comes from Doppler effects will appear at the bottom of the EIT window also. Thus if we engage in the research work related to EIT, we ought to adopt Doppler-free configuration and weak probe field.

Chirality-dependent electromagnetically induced transparency based on a double semi-periodic helix metastructure.

A chiral metastructure composed of spatially separated double semi-periodic helices is proposed and investigated theoretically and experimentally in this Letter. Chirality-dependent electromagnetically induced transparency (EIT) and a slow light effect in the microwave region are observed from a numerical parameter study, while experimental results from the 3D printing sample yield good agreement with the theoretical findings. The studied EIT phenomenon arises as a result of destructive interference by coupled resonances, and the proposed chiral metastructure can be applied in areas such as polarization communication, pump-probe characterization, and quantum computing areas.

Electromagnetically Induced Transparency in a Silicon Self-Coupled Optical Waveguide

We investigate the resonance property of a self-coupled optical waveguide (SCOW) with four coupling points. Under a special condition that the two outer couplers are in weak coupling and the two inner couplers are in strong coupling, an implicit standing-wave resonance mode is formed inside the SCOW structure. As the resonance is feedback coupled via an S-shape bus waveguide, electromagnetically induced transparency (EIT)-like resonance features are observed in the output transmission spectrum. The SCOW resonator is analyzed using the coupled mode theory and finite-difference time-domain simulation. The device is experimentally demonstrated on the silicon-on-insulator platform. The measurement results overall agree well with the theoretical calculation. The EIT-like peak can be tuned by a thermo-optic phase shifter made of a NIN-type silicon resistor integrated in the feedback waveguide. The results point to new ways of creating on-chip optical analog of the EIT phenomenon that can be utilized for various optical signal processing applications.

Polarization-induced interference within electromagnetically induced transparency for atoms of double- V linkage

People have been paying attention to the role of atoms' complex internal level structures in the research of electromagnetically induced transparency (EIT) for a long time, where the various degenerate Zeeman levels usually generate complex linkage patterns for the atomic transitions. It turns out, with special choices of the atomic states and the atomic transitions' linkage structure, clear signatures of quantum interference induced by the probe and coupling light's polarizations can emerge from a typical EIT phenomena. We propose to study a four state system with double-V linkage pattern for the transitions and analyze the polarization induced interference under the EIT condition. We show that such interference arises naturally under mild conditions on the optical field and atom manipulation. Its anticipated properties and its potential application of all optical switching in polarization degree of freedom are also discussed. Moreover, we construct a variation form of double-M linkage pattern where the polarization induced interference enables polarization-dependent cross-modulation between incident lights that can be effective even at the few-photon level. The theme is to gain more insight into the essential question: how can we build non-trivial optical medium where incident lights will induce polarization-dependent non-linear optical interactions, covering a wide range of the incidence intensity from the many-photon level to the few-photon level, respectively.

Measurement of dispersive profile of a multiwindow electromagnetically induced transparency spectrum in a Doppler-broadened atomic medium

We have measured the dispersive profile of a multiwindow electromagnetically induced transparency (EIT) spectrum in a medium consisting of Rb atoms in the presence of Doppler broadening. The atomic medium is excited by a strong coupling light and a weak probe laser light via the V-type transitions within the D2 manifold. Under the EIT effect, an anomalous dispersive region of the medium is basically modified into multinormal and anomalous dispersive regions. Furthermore, the slope and position of the dispersion can be controlled with the intensity and frequency of the coupling light. An analytic model is proposed to simulate the observed spectrum with a good agreement. Such controllable dispersive properties with their analytic description would be useful for finding applications related to multiwindow EIT phenomena.

A tunable terahertz metamaterial and its sensing performance

A novel electromagnetically induced transparency (EIT)-like metamaterial of terahertz domain is proposed. The metamaterial is composed of a single metal wire and a couple metal wires above it. Numerical simulations demonstrate that by rotating the single metal wire around its center, EIT phenomenon is created. The amplitude of the transparent peak increases as the rotation angle increases. When the rotation angle is 60°, the amplitude of the transparent peak reaches its maximum. However, as the rotation angle keeps increasing, the amplitude of the transparent peak gets lower and the peak finally vanishes as the rotation angle equals 90°. We also analyze the sensing performance of the metamaterial with the rotation angle of 60°. The proposed structure is simple and adjustable, with high Q-factor value and good sensing performance.

Electromagnetically induced transparency in terahertz metamaterial based on two-bright-mode resonator

An electromagnetically induced transparency (EIT) in metamaterial resonator with two bright modes and one dark mode at the terahertz (THz) band is numerically and experimentally demonstrated. Different from two kinds of the traditional passive modulations, our design can realize the passive modulation of EIT phenomenon by adding another bright mode resonator. Simulated and experimental results show that the transmission peak varies for incident THz waves with different polarization directions due to its asymmetric structure, which provides a novel way to realize high efficiency switch and modulation.

Controllable Tunneling of Light through a Quantum-Dot-Molecule Dielectric Film via Electromagnetically Induced Transparency

Since discrete multilevel transitions of quantum-dot molecules driven by external electromagnetic fields can exhibit quantum coherence effects, such an optical characteristic can be utilized to control propagation of electromagnetic wave through a quantum-dot molecule dielectric film. Since inner-dot tunneling in quantum-dot molecules can be controlled by a gate voltage, destructive quantum coherence among multilevel transitions in quantum-dot molecule would give rise to EIT (electromagnetically induced transparency). In this report, we shall investigate controllable on- and off-resonance tunneling effects of an incident electromagnetic wave through such a quan-tum-dot-molecule dielectric film, of which the optical response is tuned by the switchable gate voltage. We have found from the theoretical mechanism that a high gate voltage can cause the EIT phenomenon of quan-tum-dot-molecule systems, and under the condition of on-resonance light tunneling through the thin film, the probe field will propagation without loss if the probe frequency detuning is zero. By taking advantage of these effects sensitive to the tunable gate voltage, such quantum coherence would be inte-grated in certain photonic structures, and some devices such as photonic switching and transistors can be designed. Transient evolution of optical characteristics in the quantum-dot-molecule dielectric film (once the tunable gate voltage is turned on or off) is also considered in this report.

Electromagnetically Induced Transparency Based on Cascaded π-Shaped Graphene Nanostructure

We demonstrate a cascaded π-shaped graphene nanostructure and investigate its transmission properties which could realize electromagnetically induced transparency (EIT). We also explore the influence of the distance between two π structures and the position of the top dipole strip on the EIT phenomenon, while the results show that when the distance reduces, there exhibits a small change of the transparency window as well as the intensity of this phenomenon. However, the window emerges and becomes stronger as the top dipole antenna moves from left to right. Moreover, the first transmission dip becomes stronger with the shift of the top dipole antenna while the second dip gets weaker. In addition, we design a more compact nanostructure and this structure could also achieve EIT. What is more, a tunable transmission window could be obtained through changing the Fermi energy of graphene, as well as a large group delay. This work has applications in biosensing, photonics, and optical filters.

Comparison of three EIT-type resonances formed in Rb nanocell

The electromagnetically induced transparency (EIT) phenomenon is studied using a nanometric thin (L = 795 nm) Rb vapour layer. EIT-type resonances that are formed in three different energy-level systems are reported. It is demonstrated that the EIT resonance which is formed in a Λ-system where the ground levels are separated by the hyperfine splitting (EITH-resonance) has the smallest linewidth (~10 MHz). The EIT resonance which is realized in a Λ-system formed by the Zeeman sublevels of the Fg = 2 → Fe = 1 transition (EITZ-resonance) has a larger linewidth (~14 MHz). The EITV-resonance which is formed in the V-system has the largest linewidth (~40 MHz). The uniqueness of the EIT phenomena reported here is that they can be formed in different types of Λ-systems even for L < 1 μm. The splitting of the EITZ-resonance into two components in a transverse magnetic field is reported. The theoretical model well describes the experiment.

Controlled Electromagnetically Induced Transparency and Fano Resonances in Hybrid BEC-Optomechanics.

Cavity-optomechanics, a tool to manipulate mechanical effects of light to couple optical field with other physical objects, is the subject of increasing investigations, especially with regards to electromagnetically induced transparency (EIT). EIT, a result of Fano interference among different atomic transition levels, has acquired a significant importance in many areas of physics, such as atomic physics and quantum optics. However, controllability of such multi-dimensional systems has remained a crucial issue. In this report, we investigate the controllability of EIT and Fano resonances in hybrid optomechanical system composed of cigar-shaped Bose-Einstein condensate (BEC), trapped inside high-finesse Fabry-Pérot cavity with one vibrational mirror, driven by a single mode optical field and a transverse pump field. The transverse field is used to control the phenomenon of EIT. It is detected that the strength of transverse field is not only efficiently amplifying or attenuating out-going optical mode but also providing an opportunity to enhance the strength of Fano-interactions which leads to the amplification of EIT-window. To observe these phenomena in laboratory, we suggest a certain set of experimental parameters. The results provide a route for tunable manipulation of optical phenomena, like EIT, which could be a significant step in quantum engineering.

Tailoring electromagnetically induced transparency effect of terahertz metamaterials on ultrathin substrate

Electromagnetically induced transparency (EIT) is a fascinating phenomenon in optical physics and has been employed in slow light technology. In this work, we use terahertz (THz) metamaterials to mimic EIT phenomenon and study their spectral dependence on the coupling strength between bright and dark resonators. In these metamaterials, two kinds of resonators are located on two different layers separated by a 10-µm-thick polyimide (PI) film. The whole sample is supported by a 5-µm-thick flexible PI film, so the Fabry-Perot resonance at THz can be avoided. The coupling strength is tuned by the translational offset of symmetry axes between two different kinds of resonators, resulting in the change of EIT-like spectra.

Experimental study of the band-pass filter and slow-wave effect in a MDM channel based on a magnetic plasmonic analogue of EIT

In connection with an analogue of electromagnetically-induced transparency (EIT), this paper studied experimentally the tunable band-pass filter and tunable slow-wave effect of MDM (μ-negative materials/double positive materials/μ-negative materials) magnetic plasmonic channel. The results of simulations and experiments show that an evident electromagnetically-induced transparency phenomenon appears in this channel with double-side resonators, which can be used to realize simultaneous the band-pass filter and the slow-wave effect. The band-pass filter’s center frequency is founded to be determined by the size of the side resonator, the resonator direction and the effective permeability of μ-negative (MNG) metamaterials. The bandwidth can be adjusted by detuning of the two resonator frequencies, the band size of the band-pass filter depends on the number of the resonators, Thus, the band-pass filter characteristics of the MDM waveguide can be tuned by changing the resonator parameters, the resonator direction and the effective permeability of the MNG materials. Moreover, the MDM structure can also be utilized to obtain a tunable slow-wave effect (such as an adjustable frequency, a slow-down factor, and even a muti-band slow wave) based on EIT. The experimental results are in good agreement with the simulation results.

Discerning electromagnetically induced transparency from Autler-Townes splitting in plasmonic waveguide and coupled resonators system

Electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) are two phenomena that can affect the transmission of a probe field in the presence of a stronger field, both yielding transparency in the absorption profile. Being able to discriminate these two similar but distinct phenomena is of vital importance. Here we propose a scheme to describe the EIT and ATS phenomena in a plasmonic system. The proposed system consists of one radiative resonator and one subradiant resonator in metal-insulator-metal waveguide, and the transition is observed from the ATS model to the EIT model through three qualitative regions as the coupling strength decreases. In addition, we apply the method proposed by Anisimov to the induced transparency spectrum in our model, and numerically discerning EIT from ATS based on the Akaike's information criterion in a clear way.

Handedness Dependent Electromagnetically Induced Transparency in Hybrid Chiral Metamaterials.

We provide the first experimental demonstration of the handedness dependent electromagnetically induced transparency (EIT) in chiral metamaterials during the interaction with circularly polarized waves. The observed chiral-sensitive EIT phenomena arise from the coherent excitation of a non-radiative mode in the component split ring resonators (SRRs) produced by the corresponding Born−Kuhn type (radiative) resonators that are responsible for the pronounced chirality. The coherent coupling, which is dominated by the bonding and antibonding resonances of the Born−Kuhn type resonators, leads to an extremely steep dispersion for a circularly polarized wave of predefined handedness. Accordingly, retrieved effective medium parameters from simulated results further reveal a difference of 80 in the group indices for left- and right-handed circularly polarized waves at frequencies within the EIT window, which can potentially result in handedness-sensitive pulse delays. These chiral metamaterials which enable a handedness dependent EIT effect may provide more degrees of freedom for designing circular polarization based communication devices.

Ultrafast and low-power all-optical switch based on asymmetry electromagnetically induced transparency in MIM waveguide containing Kerr material

We have proposed the analog of electromagnetically induced transparency (EIT) in a metal–insulator–metal (MIM) plasmonic waveguide side coupled with two stub resonators containing Kerr material. The mechanism of the EIT-like transmission sp ectra in our structure is theoretically analyzed and numerically investigated by using the Finite-Difference Time-Domain (FDTD) method. It is found that the symmetry of the EIT-like spectra can be broken and the asymmetry degree of the EIT-like spectra can be enhanced by increasing the width of the double stub resonators. Taking advantage of the asymmetry EIT phenomenon in the proposed plasmonic system, an ultrafast and low-power all-optical switch with femtosecond-scale feedback time and a required bistable pump light intensity as low as 24.2MW/cm2 was proposed and numerically investigated. The proposed all-optical switch may find potential important applications in highly integrated optical circuits.

Tunable subwavelength terahertz plasmon-induced transparency in the InSb slot waveguide side-coupled with two stub resonators

We numerically investigated the realization of electromagnetically induced transparency (EIT) at the terahertz (THz) region in an InSb slot waveguide side-coupled with two stub resonators. The mechanism of the EIT phenomenon is theoretically analyzed and numerically studied by using coupled mode theory and the finite element method, respectively, and the theoretical results are in good agreement with the simulation results. The simulation results reveal that the EIT-like response is strongly dependent on the coupling separation between the two stub resonators, and we derived the best separation between the two stub resonators to get the most obvious EIT-like spectra. More importantly, the central wavelength of the EIT-like spectra can be actively controlled by tuning the temperature. This plasmonic waveguide system may have potential applications for ultracompact THz integrated circuits, such as thermo-tunable filters, THz switching, slow-light components, and THz sensitive sensors.

Double electromagnetically induced transparency with nuclei inside a cavity

We propose a double electromagnetically induced transparency (EIT) system of nuclei confined inside a low-finesse cavity excited by a soft X-ray radiation source. The quantitative difference in the density of photon states at the node and antinode of the cavity gives rise to subradiant and superradiant kind of states, respectively. When nuclei ensembles are kept at node, node and antinode in the cavity that sustains X-ray radiation field, the configuration behaves like a four-level system with three degenerate upper levels, of which two are metastable, and thus exhibits the nuclear analog of the optical double EIT phenomenon.

EIT phenomenon for the three-level hydrogen atoms and its application to the era of cosmological recombination

AbstractThe paper evaluates the contribution of the electromagnetically induced transparency (EIT) phenomenon to the processes of the microwave background (CMB) formation in early universe. We found the additional function f to the integrated line absorption coefficient. This makes it the necessity to upgrade the Sobolev escape probability: p ij (τ S) → p ij (τ S · (1 + f)). We calculated the magnitude of the function f for different schemes of the hydrogen atom in the three-level approximation in terms of the field parameters. The electric field amplitudes are defined using the CMB distribution. We found that the contribution of f can be significant in some cases.