Showing papers on "Electromagnetically induced transparency published in 2022"

Vector Spatiotemporal Solitons and Their Memory Features in Cold Rydberg Gases

Abstract: We propose a scheme to generate stable vector spatiotemporal solitons through a Rydberg electromagnetically induced transparency (Rydberg-EIT) system. Three-dimensional vector monopole and vortex solitons have been found under three nonlocal degrees. The numerical calculation and analytical solutions indicate that these solitons are generated with low energy and can stably propagate along the axes. The behavior of vector spatiotemporal solitons can be manipulated by the local and nonlocal nonlinearities. The results show a memory feature as these solitons can be stored and retrieved effectively by tuning the control field.

Analogue of electromagnetically induced transparency in square slotted silicon metasurfaces supporting bound states in the continuum

Abstract: In this work, a silicon metasurface designed to support electromagnetically induced transparency (EIT) based on quasi-bound states in the continuum (qBIC) is proposed and theoretically demonstrated in the near-infrared spectrum. The metasurface consists of a periodic array of square slot rings etched in a silicon layer. The interruption of the slot rings by a silicon bridge breaks the symmetry of the structure producing qBIC stemming from symmetry-protected states, as rigorously demonstrated by a group theory analysis. One of the qBIC is found to behave as a resonance-trapped mode in the perturbed metasurface, which obtains very high quality factor values at certain dimensions of the silicon bridge. Thanks to the interaction of the sharp qBIC resonances with a broadband bright background mode, sharp high-transmittance peaks are observed within a low-transmittance spectral window, thus producing a photonic analogue of EIT. Moreover, the resonator possesses a simple bulk geometry with channels that facilitate the use in biosensing. The sensitivity of the resonant qBIC on the refractive index of the surrounding material is calculated in the context of refractometric sensing. The sharp EIT-effect of the proposed metasurface, along with the associated strong energy confinement may find direct use in emerging applications based on strong light-matter interactions, such as non-linear devices, lasing, biological sensors, optical trapping, and optical communications.

Rydberg atom-based field sensing enhancement using a split-ring resonator

Abstract: We investigate the use of a split-ring resonator (SRR) incorporated with an atomic-vapor cell to improve the sensitivity and the minimal detectable electric (E) field of Rydberg atom-based sensors. In this approach, a sub-wavelength SRR is placed around an atomic vapor-cell filled with cesium atoms for E-field measurements at 1.3 GHz. The SRR provides a factor of 100 in the enhancement of the E-field measurement sensitivity. Using electromagnetically induced transparency (EIT) with Aulter–Townes splitting, E-field measurements down to 5 mV/m are demonstrated with the SRR, while in the absence of the SRR, the minimal detectable field is 500 mV/m. We demonstrate that by combining EIT with a heterodyne Rydberg atom-based mixer approach, the SRR allows for a sensitivity of 5.5 μV/m[Formula: see text], which is two-orders of magnitude improvement in sensitivity than when the SRR is not used.

Shortcut to Self-Consistent Light-Matter Interaction and Realistic Spectra from First Principles

Abstract: We introduce a simple approach to how an electromagnetic environment can be efficiently embedded into state-of-the-art electronic structure methods, taking the form of radiation-reaction forces. We demonstrate that this self-consistently provides access to radiative emission, natural linewidth, Lamb shifts, strong coupling, electromagnetically induced transparency, Purcell-enhanced and superradiant emission. As an example, we illustrate its seamless integration into time-dependent density-functional theory with virtually no additional cost, presenting a convenient shortcut to light-matter interactions.

Spatiotemporal Lineshape Tailoring in BIC‐Mediated Reconfigurable Metamaterials

Abstract: The bound state in the continuum (BIC) is a unique nonradiating eigenstate that possesses rich physics and has attracted intensive attention in the field of optics and photonics. Actively tailoring BICs in a designable fashion is highly desired for diversified photonic devices. However, to date, most BIC‐assisted works have been limited to showing passive control in a fixed structure configuration without tuning the spectral responses. Here, a new scheme to construct a coupled photon cavity for spatiotemporal lineshape tailoring, in which a nonradiating BIC is embedded in the electromagnetic induced transparency (EIT) window, is proposed. This approach uses the phase transition of VO2 inclusions to induce spatial symmetry breaking, leading to the formation of a quasi‐BIC coupled EIT state. As an extra dimension for dynamic tuning, a layer with a transient photoconductivity much shorter than the photon lifetime is introduced to ultrafast switch the leaky modes for both EIT‐ and quasi‐BIC‐coupled EIT cavities. As the symmetry‐protected BIC and coupling effect are quite common in optical metasurfaces, this proposal provides a general paradigm to active steer spatiotemporal spectrum across multiple dimensions, which is thus believed to promote active metadevices for potential applications in modulators, sensors, filters, and dynamic imaging.

Nonvolatile Reconfigurable Electromagnetically Induced Transparency with Terahertz Chalcogenide Metasurfaces

Abstract: Metasurface analog of electromagnetically induced transparency (EIT) provides a compact platform for generating a narrow‐band transmission window with very sharp spectral features. They hold promise for many appealing applications including ultrasensitive detectors, slow‐light devices, nonlinear optical devices etc. In particular, reconfigurable EIT metasurfaces are crucial for expanding the capability of light field control, which are promising for terahertz (THz) communications and optical networks. Yet, the investigation on reconfigurable EIT metasurfaces with nonvolatile operation remains scarce. Here, reversible switching of the metasurface‐induced transparency in the THz spectrum is experimentally realized. The reconfigurable response (reversible spectral shift) is obtained by integrating a nonvolatile chalcogenide phase change material, Ge2Sb2Te5 (GST225) into the meta‐atoms. A giant reversible switching of EIT takes place under an excitation of nanosecond laser pulses, showing a reconfigurable group delay of the THz waves. The proposed reconfigurable THz metadevices may provide a new route for the ultrafast laser induced switching and reconfigurable slow‐light devices.

Electromagnetically induced moiré optical lattices in a coherent atomic gas

Abstract: Electromagnetically induced optical (or photonic) lattices via atomic coherence in atomic ensembles have recently received great theoretical and experimental interest. We here conceive a way to generate electromagnetically induced moiré optical lattices — a twisted periodic pattern when two identical periodic patterns (lattices) are overlapped in a twisted angle (θ) — in a three-level coherent atomic gas working under electromagnetically induced transparency. We show that, changing the twisted angle and relative strength between the two constitutive sublattices, the moiré Bloch bands that are extremely flattened can always appear, resembling the typical flat-band and moiré physics found in other contexts. Dynamics of light propagation in the induced periodic structures demonstrating the unique linear localization and delocalization properties are also revealed. Our scheme can be implemented in a Rubidium atomic medium, where the predicted moiré optical lattices and flattened bands are naturally observable.

Exchange of orbital angular momentum of light via noise-induced coherence

Abstract: The noise-induced coherence created via the quantum interference of incoherent radiation in atomic three-level systems of V and \ensuremath{\Lambda} types driven by a pair of weak laser pulses is shown to result in exchange of optical vortices. In the three- level V-type atom-light coupling the system is populated in its ground level, while in the \ensuremath{\Lambda} model the system is initially prepared in an electromagnetically induced transparency state. By solving the quantum optical Maxwell-Bloch equations and with quantum interference of incoherent radiation present, we show that the orbital angular momentum (OAM) of the vortex probe beam can be transferred to a generated signal field. While the exchange efficiency in the V configuration is higher, the losses are less in the \ensuremath{\Lambda} scheme when we consider such a noise-induced coherence. We further discuss the effects of phase mismatching and inhomogeneous broadening on the energy conversion between light beams carrying OAM.

Photon-photon interactions in Rydberg-atom arrays

Abstract: We investigate the interaction of weak light fields with two-dimensional lattices of atoms, in which two-photon coupling establishes conditions of electromagnetically induced transparency and excites high lying atomic Rydberg states. This system features different interactions that act on disparate length scales, from zero-range defect scattering of atomic excitations and finite-range dipole exchange interactions to long-range Rydberg-state interactions that span the entire array. Analyzing their interplay, we identify conditions that yield a nonlinear quantum mirror which coherently splits incident fields into correlated photon-pairs in a single transverse mode, while transmitting single photons unaffected. Such strong photon-photon interactions in the absence of otherwise detrimental photon losses in Rydberg-EIT arrays opens up a promising approach for the generation and manipulation of quantum light, and the exploration of many-body phenomena with interacting photons.

Electromagnetically induced moiré optical lattices in a coherent atomic gas

Abstract: Electromagnetically induced optical (or photonic) lattices via atomic coherence in atomic ensembles have recently received great theoretical and experimental interest. We here conceive a way to generate electromagnetically induced moiré optical lattices — a twisted periodic pattern when two identical periodic patterns (lattices) are overlapped in a twisted angle (θ) — in a three-level coherent atomic gas working under electromagnetically induced transparency. We show that, changing the twisted angle and relative strength between the two constitutive sublattices, the moiré Bloch bands that are extremely flattened can always appear, resembling the typical flat-band and moiré physics found in other contexts. Dynamics of light propagation in the induced periodic structures demonstrating the unique linear localization and delocalization properties are also revealed. Our scheme can be implemented in a Rubidium atomic medium, where the predicted moiré optical lattices and flattened bands are naturally observable.

Electromagnetically induced transparency based Rydberg-atom sensor for traceable voltage measurements

Abstract: We investigate the Stark shift in Rydberg rubidium atoms through electromagnetically induced transparency for the measurement of direct current (dc) and 60 Hz alternating current (ac) voltages. This technique has direct application to the calibration of voltage measurement instrumentation. We present experimental results for different atomic states that allow for dc and ac voltage measurements ranging from 0 to 12 V. While the state-of-the-art method for realizing the volt, the Josephson voltage standard, is significantly more accurate, the Rydberg atom-based method presented here has the potential to be a calibration standard with more favorable size, weight, power, and cost. We discuss the steps necessary to develop the Rydberg atom-based voltage measurement as a complementary method for dissemination of the voltage scale directly to the end user and discuss sources of uncertainties for these types of experiments.

Achieving dual-band absorption and electromagnetically induced transparency in VO2 metamaterials

Abstract: A new type of terahertz switchable metamaterial is proposed with dual functions. By introducing vanadium dioxide possessing insulator-to-metal transition, the designed metamaterial can be switched from a dual-band absorber to an analog of electromagnetically induced transparency. When vanadium dioxide is in the conducting state, the designed structure works as a dual-band absorber with 100% absorptance at 1.02 THz and 1.71 THz. When vanadium dioxide is in the insulating state, the designed structure works as an analog of electromagnetically induced transparency. The performances of bifunctionality are omnidirectional and efficient in the incident angle range of 60° or 30° in two modes. The proposed design may enable advanced applications in the fields of modulator and filter.

Dynamically Tunable Electromagnetically Induced Transparency-Like Effect in Terahertz Metamaterial Based on Graphene Cross Structures

Abstract: A simple and multi-layer metamaterial made of graphene to realize excellent manipulation of EIT-like effect is proposed. The unit cell consists of four layers: Substrate 1, Cross 1, Substrate 2 and Cross 2, which can obtain tunable EIT-like effect by adjusting the Fermi level of graphene. The surface current distributions of four different views clearly explain the underlying physical mechanism. A three-level Λ-type system is employed to describe the coupling process between Cross 1 and 2. The calculated transmission spectra based on two-particle model have great agreement with the simulated transmission spectra. In addition, the effects of geometrical parameters on EIT-like effect are discussed and wideband EIT-like effect with high transmission can be obtained by adjusting the lengths of Cross 1 and 2. Also, the polarization-insensitive character of EIT-like metamaterial is confirmed by the transmission spectra under different polarization angles. The maximum of group delay (25.48 ps) is far greater than the group delay of previously reported EIT-like metamaterials. Our study provides a novel way for the development of slow-light devices and modulators.

Continuously tunable radio frequency electrometry with Rydberg atoms

Abstract: We demonstrate a continuously tunable electric field measurement based on the far off-resonant AC stark effect in a Rydberg atomic vapor cell. In this configuration, a strong far off-resonant field, denoted as a local oscillator (LO) field, acts as a gain to shift the Rydberg level to a high sensitivity region. An incident weak signal field with a few hundreds of kHz difference from the LO field is mixed with the LO field in the Rydberg system to generate an intermediate frequency signal, which is read out by Rydberg electromagnetically induced transparency (Rydberg-EIT) spectroscopy. Not like resonant EIT-Autler–Townes spectra, we realize the electric field measurement of the signal frequency from 2 to 5 GHz using a single Rydberg state. The detectable field strength is down to 2.25 μV/cm with sensitivity of the electrometry 712 nV cm−1 Hz−1/2, and a linear dynamic range is over 65 dB. The detectable field strength is comparable with a resonant microwave-dressed Rydberg heterodyne receiver using the same system, which is 0.96 μV/cm with sensitivity of 304 nV cm–1 Hz−1/2. We also show the system has an inherent polarization selectivity feature. Our method can provide high sensitivity of electric field measurement and be extended to arbitrary frequency measurements.

Imaging lattice switching with Talbot effect in reconfigurable non-Hermitian photonic graphene

Abstract: By taking advantage of the optical induction method, a non-Hermitian photonic graphene lattice is efficiently established inside an atomic vapor cell under the condition of electromagnetically induced transparency. This non-Hermitian structure is accomplished by simultaneously modulating both the real and imaginary components of the refractive index into honeycomb profiles. The transmitted probe field can either exhibit a hexagonal or honeycomb intensity profile when the degree of non-Hermiticity is effectively controlled by the ratio between imaginary and real indices. The experimental realization of such an instantaneously tunable complex honeycomb potential sets a new platform for future experimental exploration of non-Hermitian topological photonics. Also, we demonstrate the Talbot effect of the transmitted probe patterns. Such a self-imaging effect based on a –

Quadruple plasmon-induced transparency and tunable multi-frequency switch in monolayer graphene terahertz metamaterial

Abstract: A monolayer graphene metamaterial composed of a graphene block and four graphene strips, which has the metal-like properties in terahertz frequency range, is proposed to generate an outstanding quadruple plasmon-induced transparency (PIT). Additional analyses show that the forming physical mechanism of the PIT with four transparency windows can be explained by strong destructive interference between the bright mode and the dark mode, and the distributions of electric field intensity and electric field vectors under the irradiation of the incident light. Coupled mode theory and finite-difference time-domain method are employed to study the spectral response characteristics of the proposed structure, and the theoretical and simulated results are in good agreement. It is found that a tunable multi-frequency switch and excellent optical storage can be achieved in the wide PIT window. The maximum modulation depth is up to 99.7%, which corresponds to the maximum extinction ratio of 25.04 dB and the minimum insertion loss of 0.19 dB. In addition, the time delay is as high as 0.919 ps, the corresponding group refractive index is up to 2755. Thus, the proposed structure provides a new method for the design of terahertz multi-frequency switches and slow light devices.

Achieving dual-band absorption and electromagnetically induced transparency in VO2 metamaterials

Abstract: A new type of terahertz switchable metamaterial is proposed with dual functions. By introducing vanadium dioxide possessing insulator-to-metal transition, the designed metamaterial can be switched from a dual-band absorber to an analog of electromagnetically induced transparency. When vanadium dioxide is in the conducting state, the designed structure works as a dual-band absorber with 100% absorptance at 1.02 THz and 1.71 THz. When vanadium dioxide is in the insulating state, the designed structure works as an analog of electromagnetically induced transparency. The performances of bifunctionality are omnidirectional and efficient in the incident angle range of 60° or 30° in two modes. The proposed design may enable advanced applications in the fields of modulator and filter.

Electromagnetically induced transparency metamaterials: theories, designs and applications

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.

Optical nonreciprocity and nonreciprocal photonic devices with directional four-wave mixing effect.

Abstract: A scheme for magnetic-free optical nonreciprocity in an ensemble of four-level cold atoms is proposed by exploiting the directional four-wave mixing effect. Using experimentally achievable parameters, the nonreciprocal optical responses of the system can be observed and the conversion on nonreciprocal transmission and nonreciprocal phase shift can be implemented. These nonreciprocal phenomena originate from the directional phase matching, which breaks the time-reversal symmetry and dynamic reciprocity of the cold atomic system. Moreover, by embedding the cold atoms into a Mach-Zehnder interferometer and choosing proper parameters, a two-port optical isolator with an isolation ratio of 79.70 dB and an insertion loss of 0.35 dB and a four-port optical circulator with a fidelity of 0.9985 and a photon survival probability of 0.9278 can be realized, which shows the high performance of isolation and circulation. The proposal may enable a new class of optically controllable cavity-free nonreciprocal devices in optical signal processing at the low light level.

Tunable dual-band linear-to-circular polarization conversion based on the electromagnetically induced transparency utilizing the graphene metamaterial

Abstract: A tunable dual-band linear-to-circular polarization conversion (LTCPC) related to electromagnetically induced transparency (EIT) is theoretically proposed by employing the graphene metamaterial in the terahertz (THz) regime. Since the electric resonance (bright mode) and the magnetic resonance (quasi-dark mode) for the x- and y-polarized (TM and TE) waves are mutually coupled, the EIT behavior is realized due to the destructive interference. Two transparent EIT windows have emerged in 1.452–1.661 THz and 1.348–1.683 THz when the TM and TE waves are incidents. The corresponding values of the maximum group delay and group index respectively are 225 ps, 162 ps, 1636, and 1177. The LTCPC is achieved at 1.432 THz and 1.676 THz when the graphene does not exist. While the graphene is introduced, the LTCPC is dynamically adjustable by controlling the Fermi energy (Ef) of the graphene. The optimal ARs can dynamically change between 1.438 (1.689) THz and 1.452 (1.696) THz while the Ef changes from 0.1 eV to 0.9 eV. A theoretical investigation of two-oscillator model further confirms the effectiveness and consistency of the simulation results. The presented metamaterial with a thickness of subwavelength and high transparency for the electromagnetic waves opens a new path to the applications in beam steering and polarization controls.

Simultaneously Achieving Circular‐To‐Linear Polarization Conversion and Electromagnetically Induced Transparency by Utilizing a Metasurface

Abstract: In this work, the simultaneous realization of circular‐to‐linear polarization conversion (PC) and electromagnetically induced transparency (EIT) is theoretically reported in terahertz (THz) range by utilizing a metasurface when left‐handed circularly polarized (LCP) waves are incident. The metasurface is composed of two kinds of via‐coupled modules (VCMs). Each module can realize the same EIT phenomenon by the destructive interference during the bright and dark modes due to the symmetry‐broken rotation operation of the structure instead of the near‐field coupling. The VCMs can simultaneously respond to the incident LCP waves and are identically converted into LCP and right‐handed circularly polarized (RCP) waves, which own the same amplitudes and phase shifts. Therefore, the LCP and RCP waves can generate a resultant linearly polarized (LP) wave. The EIT transparent windows have emerged in 0.729–1.051 THz during the transmission of the LCP waves and the conversion of LCP to RCP. The values of maximum group delays both are 358 ps. The operating frequency band of the PC is located in 0.65–1.10 THz, and relative bandwidth reaches 51.4%. Optimal relative conversion efficiency reaches 93.2% at 0.921 THz. The EIT behavior has been investigated by the two‐oscillator model to further confirm the consistency of the simulation results.

Continuous-frequency weak electric field measurement with Rydberg atoms

Abstract: We demonstrate a continuous frequency electric field measurement based on the far off-resonant AC stark effect in a Rydberg atomic vapor cell. In this configuration, a strong far off-resonant field, denoted as a local oscillator (LO) field, acts as a gain shifting the Rydberg level to a high sensitivity region. An incident weak signal field with a few hundreds of kHz difference from the LO field is mixed with the LO field in Rydberg system to generate an intermediate frequency (IF) signal, which is read out by the Rydberg electromagnetically induced transparency (Rydberg-EIT) spectroscopy. Not like resonant EIT-AT spectra, we realize the electric field measurement of the signal frequency from 2 GHz to 5 GHz using a single Rydberg state. A minimum detectable filed strength is down to 2.31 µ V/cm and a linear dynamic range is over 65 dB. The minimum detectable filed is comparable with a resonant microwave-dressed Rydberg heterodyne receiver using the same system, which is 1.45 µ V/cm. We also show the system has an inherent polarization selectivity feature. Our method can provide a high sensitivity of electric field measurement and be extended to arbitrary frequency measurements.

A practical guide to electromagnetically induced transparency in atomic vapor

Abstract: This tutorial introduces the theoretical and experimental basics of electromagnetically induced transparency (EIT) in thermal alkali vapors. We first give a brief phenomenological description of EIT in simple three-level systems of stationary atoms and derive analytical expressions for optical absorption and dispersion under EIT conditions. Then we focus on how the thermal motion of atoms affects various parameters of the EIT system. Specifically, we analyze the Doppler broadening of optical transitions, ballistic versus diffusive atomic motion in a limited-volume interaction region, and collisional depopulation and decoherence. Finally, we discuss the common trade-offs important for optimizing an EIT experiment and give a brief ‘walk-through’ of a typical EIT experimental setup. We conclude with a brief overview of current and potential EIT applications.

Few-photon storage on a second timescale by electromagnetically induced transparency in a doped solid

Abstract: We present the experimental demonstration of light storage towards the single photon level at a long storage time by electromagnetically induced transparency in a rare-earth ion-doped Pr3+:Y2SiO5 crystal. We apply decoherence control by static magnetic fields and appropriately designed radio-frequency composite pulse sequences to prolong the storage time in the memory. A rare-earth ion-doped filter crystal prepared by optical pumping serves to efficiently separate the signal at the single photon level from optical noise. Multipass setups around the memory and the filter crystal improve the storage efficiency and filter selectivity. Already without decoherence control, the setup permits storage of single photons in the microsecond regime at a storage efficiency of 42%. With decoherence control we demonstrate storage of weak coherent pulses containing some 10 photons for up to 10 s at a storage efficiency of several percent. The experimental data clearly demonstrate the applicability of EIT light storage to implement a true quantum memory in Pr3+:Y2SiO5 at long storage times. The scientific findings and technical developments are of relevance also to other protocols and media for quantum information storage.

Effects of neighboring transitions on the mechanisms of electromagnetically induced absorption and transparency in an open degenerate multilevel system

Abstract: In this study, optical Bloch equations with and without neighboring hyperfine states near the degenerate two-level system (DTLS) in the challenging case of [Formula: see text]Rb D2 transition, which involves the Doppler broadening effect, are solved. The calculated spectra agree well with the experimental results obtained based on the coupling-probe scheme with orthogonal linear polarizations of the coupling and probe fields. The mechanisms of electromagnetically induced absorption (electromagnetically induced transparency) for the open [Formula: see text] and 3 transitions (open [Formula: see text] and 3 transitions) are determined to be the effect of the strong closed [Formula: see text] transition line (strong closed [Formula: see text] transition line); this finding is based on a comparison between the calculated absorption profiles of the DTLS without neighboring states and those of all levels with neighboring states, depending on the coupling and probe power ratios. Furthermore, based on the aforementioned comparison, the crucial factors that enhance or reduce the coherence effects and lead to the transformation between electromagnetically induced absorption and electromagnetically induced transparency, are (1) the power ratios between the coupling and probe beams, (2) the openness of the excited state, and (3) effects of the neighboring states due to Doppler broadening in a real atomic system.

Polarization and incidence insensitive analogue of electromagnetically induced reflection metamaterial with high group delay.

Abstract: In this work, we demonstrate an analogue of electromagnetically induced reflection (EIR) effect with hybrid structure consisting of a silica (SiO2) square array layer embedded in graphene-dielectric-Au film constructed F-P cavity. It is shown that the SiO2 square array and F-P cavity create transverse waveguide with high quality factor (Q-factor) and longitudinal F-P modes, and their destructive interference effectively forms the EIR-like effect, which benefits for obtaining high group delay. In addition, the C4 symmetric structure ensures the polarization-independent for this EIR-like effect. With high Q-factor at the reflection window, the ultra-high group delay as high as 245 ps can be obtained. This structure will be useful to develop the EIT-like devices with excellent performance such as high group delay, polarization and incident insensitivity, and environmental stability.

Three-stimulus control ultrasensitive Dirac point modulator using an electromagnetically induced transparency-like terahertz metasurface with graphene.

Abstract: This letter presents a fabricated Dirac point modulator of a graphene-based terahertz electromagnetically induced transparency (EIT)-like metasurface (GrE & MS). Dynamic modulation is realized by applying three stimulus modes of optical pump, bias voltage, and optical pump-bias voltage combination. With increasing luminous flux or bias voltage, the transmission amplitude undergoes two stages: increasing and decreasing, because the graphene Fermi level shifts between the valence band, Dirac point, and conduction band. Thus, an approximate position of the Dirac point can be evaluated by the transmission spectrum fluctuation. The maximum modulation depth is measured to be 182% under 1 V. These findings provide a method for designing ultrasensitive terahertz modulation devices.