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The filter is one of the most important key elements of electronic circuit. With the rapid development of information, traditional electrical filters can no longer meet the requirements of fast information processing speed and low loss. All optical information processing is considered as one of the solutions to solve this problem. Therefore, there is great significance for studying the all-optical filter. Here, we put forward a kind of broadband band-stop filter which based on surface plasmon polaritons (SPPs) metal - insulator - metal (MIM) modulating by electromagnetically induced transparency (EIT) resonance. We use the finite element method for numerical simulation, and further research on the factors influencing the transmission characteristics of this structure by adjusting the geometric structure. Compared with similar SPPs-based filters, the proposed structure realizes broad stopband, and we can change the EIT resonance to modulate the band-stop filter wavelength range. The proposed broadband band-stop filter based on EIT effect modulation may have great potential in the next generation of all-optical information processing and communication.

In this paper, we had designed a microwave band permittivity sensor based on analog electromagnetic-induced transparency (A-EIT). By comparing the S-parameter changes of the tested sample before and after measurement, we can calculate the permittivity of the tested sample then distinguish material types with similar appearances. The transmission line had used impedance transformation structure, and the open circuit branch is vertically connected to the transmission line. The open circuit branch will have a coupling effect with the spiral cross structure and can also simulate the A-EIT phenomenon. The above design has potential applications in the miniaturization of sensors.

Metamaterial photonic integrated circuits with arrays of hybrid graphene–superconductor coupled split-ring resonators (SRR) capable of modulating and slowing down terahertz (THz) light are introduced and proposed. The hybrid device’s optical responses, such as electromagnetic-induced transparency (EIT) and group delay, can be modulated in several ways. First, it is modulated electrically by changing the conductivity and carrier concentrations in graphene. Alternatively, the optical response can be modified by acting on the device temperature sensitivity by switching Nb from a lossy normal phase to a low-loss quantum mechanical phase below the transition temperature (Tc) of Nb. Maximum modulation depths of 57.3% and 97.61% are achieved for EIT and group delay at the THz transmission window, respectively. A comparison is carried out between the Nb-graphene-Nb coupled SRR-based devices with those of Au-graphene-Au SRRs, and significant enhancements of the THz transmission, group delay, and EIT responses are observed when Nb is in the quantum mechanical phase. Such hybrid devices with their reasonably large and tunable slow light bandwidth pave the way for the realization of active optoelectronic modulators, filters, phase shifters, and slow light devices for applications in chip-scale future communication and computation systems.

In this work, the characterization and analysis of the physics of a GaAs quantum well with AlGaAs barriers were carried out, according to an interior doped layer. An analysis of the probability density, the energy spectrum, and the electronic density was performed using the self-consistent method to solve the Schrödinger, Poisson, and charge-neutrality equations. Based on the characterizations, the system response to geometric changes in the well width and to non-geometric changes, such as the position and with of the doped layer as well as the donor density, were reviewed. All second-order differential equations were solved using the finite difference method. Finally, with the obtained wave functions and energies, the optical absorption coefficient and the electromagnetically induced transparency between the first three confined states were calculated. The results showed the possibility of tuning the optical absorption coefficient and the electromagnetically induced transparency via changes to the system geometry and the doped-layer characteristics.

In this study, we use a phase-changing material vanadium dioxide (VO2) to design a multilayer metasurface structure to achieve the transition from an electromagnetically induced transparency(EIT) device to an absorber. The structure consists of a gold layer, a polyimide spacer layer, a VO2 layer, and a sapphire substrate. The top layer consists of one cut wire and two split-ring resonators with the same parameters. When the VO2 layer is in its insulating phase at room temperature, the peak of the EIT device will appear near 1.138 THz. When the VO2 layer is in the metallic state, two absorption peaks above 99.5% appear separately at 1.19 and 1.378 THz, respectively. To the best of our knowledge, this is the first time that a coupled mode equation is used to perform theoretical calculations for EIT devices and perfect absorbers simultaneously, and this is also the first time that coupled mode equations are used for the theoretical calculations of two absorption peaks in an absorber. The proposed metasurface combines the advantages of terahertz absorption, EIT and active device control, which will provide more ideas for the design of future terahertz devices and is also significant for the design and development of radomes for future stealth aircraft.

In this study, we investigate tunable broadband optical cavity via a medium with four-level atoms interacting with two strong pump fields and a weak probe field in an N-type configuration. The results indicate the amplitude of the Stokes field causes an additional control mechanism of the dispersion behavior. Moreover, the four-wave mixing condition induces higher linear gain for the probe field. Therefore, it allows the compensation of unavoidable optical losses through the optical cavity. By adjusting the control fields in the four-wave mixing condition, the negative dispersion of the atomic medium is able to balance the normal dispersion of cavity in the zero-absorption area, consequently a white-light cavity with tunable wideband is achievable. The present scheme is interesting for development of white-light-cavity applications such as gravitational wave detection.

The electromagnetic induced transparency (EIT) effect originates from the destructive interference in an atomic system, which contributes to the transparency window in its response spectrum. The implementation of EIT requires highly demanding laboratory conditions, which greatly limits its acceptance and application. In this paper, an improved harmonic spring oscillation (HSO) model with four oscillators is proposed as a classical analog for the tunable triple-band EIT effect. A more general HSO model including more oscillators is also given, and the analyses of the power absorption in the HSO model conclude a formula, which is more innovative and useful for the study of the multiple-band EIT effect. To further inspect the analogizing ability of the HSO model, a hybrid unit cell containing an electric dipole and toroidal dipoles in the metamaterials is proposed. The highly comparable transmission spectra based on the HSO model and metamaterials indicate the validity of the classical analog in illustrating the formation process of the multiple-band EIT effect in metamaterials. Hence, the HSO model, as a classical analog, is a valid and powerful theoretical tool that can mimic the multiple-band EIT effect in metamaterials.

The metasurfaces based on nanostructure film play an important role in many fields. Usually, the properties and functions of metasurfaces are limited by their structure. Once the metasurface samples are processed, their functions have already been restricted. The dual-function device designed in this work utilizes the phase transition characteristic of vanadium dioxide (VO2). The entire layer of VO2 film is inserted between the double metal micro-nano structure. When VO2 film is in the metallic state after phase change, an isotropic narrow absorber is obtained in the terahertz (THz) region, which consists of a top Z-shaped meta-atom, a middle dielectric layer, and a bottom VO2 film. By adjusting structure parameters of VO2 film, perfect absorption is realized at the frequency of 0.525 THz with the overall absorption beyond 91%. When VO2 is in insulating state, the top Z-shaped meta-atom will interact with the bottom Z-shaped structure, and the resonance coupling leads to the appearance of electromagnetically induced transparency (EIT). The designed metal-VO2 hybrid metamaterial opens possible avenues for switchable functionalities in a single device.

Two-dimensional (2D) materials and their vertically stacked heterostructures have attracted much attention due to their novel optical properties and strong light-matter interactions in the infrared. Here, we present a theoretical study of the near-field thermal radiation of 2D vdW heterostructures vertically stacked of graphene and monolayer polar material (2D hBN as an example). An asymmetric Fano line shape is observed in its near-field thermal radiation spectrum, which is attributed to the interference between the narrowband discrete state (the phonon polaritons in 2D hBN) and a broadband continuum state (the plasmons in graphene), as verified by the coupled oscillator model. In addition, we show that 2D van der Waals heterostructures can achieve nearly the same high radiative heat flux as graphene but with markedly different spectral distributions, especially at high chemical potentials. By tuning the chemical potential of graphene, we can actively control the radiative heat flux of 2D van der Waals heterostructures and manipulate the radiative spectrum, such as the transition from Fano resonance to electromagnetic-induced transparency (EIT). Our results reveal the rich physics and demonstrate the potential of 2D vdW heterostructures for applications in nanoscale thermal management and energy conversion.

A perfectly absorbing metamaterial (PAMM) coupled with vibrational modes has varied applications ranging from surface-enhanced vibrational spectroscopy to biological sensing. This endeavor considers a subwavelength PAMM sensor design and analysis using a commercially available finite element method (FEM) solver and analytically with temporal coupled mode theory (TCMT). A carbon double oxygen bond (C=O) at 52 THz or 1733 cm-1 that resides in poly(methyl methacrylate), PMMA, will be used as a stand-in analyte. Normal mode splitting that results from the resonant coupling between the PAMM and analyte’s molecular resonance is investigated and analyzed.