Transparency Resonance Research Articles

Phase-change-mediated coupling between phononic and photonic mode in the mid-infrared region

By coupling the surface phonon polaritons (SPhPs) of the aluminum nitride (AIN) layer with the germanium antimony tellurium alloy (Ge2Sb2Te5, GST) planar waveguide (PWG) modes, phonon-induced transparency (PhIT) and Fano resonance (FR) can be achieved. The Kretschmann configuration consists of a high-index prism, AIN layer, dielectric spacing layer and phase change materials (PCMs). During the phase change of Ge2Sb2Te5, the interactions between SPhP and PWG modes can be dramatically tuned, resulting in hybrid phonon-photon coupling and consequently splitting the resonance. FR can be excited and its characteristics strongly depend on the thickness of the spacing and WG layer. Moreover, the model of classical harmonic oscillator (CHO) is used to explain FR, and the mechanical calculations agree well with numerical electromagnetic (EM) numerical results.

Electromagnetic-Induced Transparency and Slow Light in Plasmonic Metasurfaces

We report numerically electromagnetic-induced transparency (EIT) and Fano resonances in simple plasmonic metasurfaces consisting of gold nanobars arranged in pi, H, and four-shaped fashion. The bright and dark elements in the metasurfaces are responsible for the emergence of EIT and Fano effects in the transmission spectrum. The concept of symmetry breaking is also introduced by incorporating multiple cavities in the metasurface, which relaxes the dipole coupling selection rules resulting in a mixture of dipole and higher order modes that interact and engenders EIT and Fano modes simultaneously in a nanostructure. Furthermore, the EIT and Fano resonances experience a significant red shift by increasing the refractive index of the background medium due to which high sensitivity of around 574 nmRIU−1, figure of merit of 32, and contrast ratio of 41% are realized. Moreover, the effective group index of the proposed metasurface is retrieved and is observed to be very high around the steep asymmetric Fano line shape and within the EIT window, signifying its potential use in slow light applications.

Dielectric resonator antenna with Y3Al5O12 transparent dielectric ceramics for 5G millimeter‐wave applications

AbstractMicrowave dielectric ceramics are considered to be one of the key materials for dielectric resonators (DR) and have very broad application prospects in the fifth generation (5G) mobile communication system. Here we have prepared high‐quality factor Y3Al5O12 (YAG) transparent dielectric ceramics using high‐purity α‐Al2O3 and Y2O3 powders by cold isostatic pressing of the vacuum sintered with tungsten meshes as the heating elements. Optimum relative permittivity () ~10.53, quality factor Q × f (Q = 1/dielectric loss, f = resonant frequency) ~95, 270 GHz (at =7.37 GHz), and temperature coefficient of resonant frequency (TCF) ~ −51.7 ppm °C−1 were obtained at a sintering temperature of 1780°C for 12 h. For the first time, YAG transparent ceramic dielectric resonator antenna (DRA) is designed as a dominant mode and a higher‐order mode using the aperture coupling feeding configuration excitation. The proposed transparent dielectric ceramic DRA can provide a broad impedance bandwidth of 4.193 GHz (ranging from 21.90 to 26.09 GHz) for S11 < −10 dB, radiation efficiency of 92.1%, and compact DR unit. The proposed DRA can be used potentially as a 5G millimeter (mm)‐wave multiple‐input‐multiple‐output (MIMO) antenna unit.

Sensing Enhancement of Electromagnetically Induced Transparency Effect in Terahertz Metamaterial by Substrate Etching

A broad range of terahertz (THz) metamaterials have been developed for refractive index sensing. However, most of these metamaterials barely make sufficient use of the excited electric field which is crucial to achieve high sensitivity. Here, we proposed a metamaterial sensor possessing electromagnetically induced transparency (EIT) resonance that is formed by the interference of dipole and quadrupole resonance. In particular, the strengthening of light-matter interaction is realized through substrate etching, leading to a remarkable improvement in sensitivity. Hence, three kinds of etching mode were presented to maximize the utilization of the electric field, and the corresponding highest sensitivity is enhanced by up to ~2.2-fold, from 0.260 to 0.826 THz/RIU. The proposed idea to etch substrate with a strong light-matter interaction can be extended to other metamaterial sensors and possesses potential applications in integrating metamaterial and microfluid for biosensing.

Two-color optical nonlinearity in an ultracold Rydberg atom gas mixture

We report the experimental observation of strong two-color optical nonlinearity in an ultracold gas of $^{85}\mathrm{Rb}$-$^{87}\mathrm{Rb}$ atom mixture. By simultaneously coupling two probe transitions of $^{85}$Rb and $^{87}$Rb atoms to Rydberg states in electromagnetically induced transparency (EIT) configurations, we observe significant suppression of the transparency resonance for one probe field when the second probe field is detuned at $\sim1~\mathrm{GHz}$ and hitting the EIT resonance of the other isotope. Such a cross-absorption modulation to the beam propagation dynamics can be described by two coupled nonlinear wave equations we develope. We further demonstrate that the two-color optical nonlinearity can be tuned by varying the density ratio of different atomic isotopes, which highlights its potential for exploring strongly interacting multi-component fluids of light.

Optomechanically induced transparency, amplification, and Fano resonance in a multimode optomechanical system with quadratic coupling

We explore the optical response of a multimode optomechanical system with quadratic coupling to a weak probe field, where the cavity is driven by a strong control field and the two movable membranes are, respectively, excited by weak coherent mechanical driving fields. We study the two cases that the two movable membranes are degenerate and nondegenerate. For the degenerate case, it is shown that only one transparency window occurs and the transition between optomechanically induced transparency and Fano resonance can be realized by tuning the cavity-control field detuning. For the nondegenerate case, two transparency windows are observed and the absorption spectrum can switch between a single Fano resonance and double Fano resonances. Furthermore, we show that the output probe field can be greatly amplified or completely suppressed due to the complex interference effect by tuning the amplitude and phase of the mechanical driving fields. Our results can be extended to the optomechanical system with multiple membranes, which enables us to control the light propagation more flexibly.

Surface plasmon polaritons broadband band-stop filter based on EIT effect modulation

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.

Electromagnetic-Induced Transparency Resonance with Ultrahigh Figure of Merit Using Terahertz Metasurfaces

In this paper, a terahertz metasurface supercell consists of two ring resonators with slightly different radii is proposed. Electromagnetic-induced transparency (EIT)–like resonance is excited with an ultrahigh figure of merit. Furthermore, the impact of the coupling between the two rings is investigated on the transmission amplitude response, the quality factor, and the EIT peak amplitude by varying the radius of the top resonator. The achieved figure of merit of the EIT peak reaches 88.65 and almost 20,000 when gold and a perfect electric conductor are used for the metallic layer, respectively. The simplicity and unique properties of the proposed design could render it to be a desirable candidate for filtering, slow light applications, and sensing.

Spatiotemporal Terahertz Metasurfaces for Ultrafast All‐Optical Switching with Electric‐Triggered Bistability

AbstractOptoelectronic terahertz switching achieved by dynamically tuning metamaterials is viewed as a major breakthrough in promoting the advancement of terahertz technology. However, the main thrust toward the development of ultrafast switchable components and optical logic operations is still in a catch‐up stage for progressively increasing information and communication demands. Here, a novel spatiotemporal metadevice is proposed for terahertz wave steering in multidimensional domains with ultrahigh spatial and ultrafast temporal manipulations. By spatially changing the interconnect architecture via the embedded vanadium dioxide bridges, the state of electromagnetically induced transparency resonance is switched between “1” and “0” states under electrical stimuli, exhibiting a typical 1 bit coding bistability with a long retention time. Furthermore, with the characteristic of writable/erasable logic operation, ultrafast photoswitching of each memorized state is manifested by delivering optical excitations. The high‐speed temporal response of terahertz radiation exhibits an on–off–on switching cycle within 16 ps, owing to the defect‐rich germanium photoactive layer. By leveraging both degrees of freedom in space and time domains, this multifunctional spatiotemporal metaphotonic device can upgrade and improve the current capabilities of optical computing, data storage, and ultrahigh‐speed information processing, paving the way for a highly unexplored territory toward manipulations of light.

Erratum: Demonstration of resonant phenomena analogous to Autler-Townes splitting, electromagnetically induced transparency and Fano resonances in a deformed waveguide resonator

In this erratum to the original paper [1] we correct an error in the calculation of the reflection and transmission spectra of the bent waveguide-based Fabry-Perot resonator. The error resulted from the neglect of cladding modes in the straight input and output sections before and after the resonator under study (Fig. 2a in the original paper). Although these modes do not contribute directly to the calculated reflected and transmitted power carried by the fundamental modes in the input and output sections, they must be taken into account for the correct computation of the reflection and transmission spectra of the resonator as was found out after the original paper had been published. In this erratum we provide the amended results as well as some corrections to the conclusions of the original paper.

Robust tunable plasmon induced transparency in coupled-resonance finite array of metasurface nanostructure

Robust and dynamically polarization-controlled tunable plasmon induced transparency (PIT) resonance in designed finite-array nanostructures metasurface is demonstrated, where sharp resonance is guaranteed by design and protected against large geometrical imperfections even for micro-zone sub-array. By employing the explicit analysis of near-field characteristic in the reciprocal-space based on the momentum matching, and the far-field radiation features with point-scattering approach in real-space sparked from Huygens’s principles, the physics of interference resonance for plane-wave optical transmission and reflection of the metasurface is theoretically and thoroughly investigated. The distinctive polarization-selective and Q-tunable PIT shows robust features to performance degradations in traditional PIT system caused by inadvertent fabrication flaws or geometry asymmetry-variations, which paves way for the development of reconfigurable and flexible metasurface and, additionally, opens new avenues in robust and multifunctional controllable nanophotonics device design and applications.

Controlling single-photon scattering in a rectangular waveguide by a V-type three-level emitter.

The single-photon scattering by a V-type three-level emitter in a rectangular waveguide is studied. Here the frequency value of input photons can be large beyond the single-transverse-mode region. By using Green's function formalism, the necessary and sufficient conditions of complete transmission as well as complete reflection are derived analytically. In the region of single transverse mode, the physical mechanisms of complete transmission and complete reflection are electromagnetically induced transparency (EIT) and Fano resonance, respectively. In the region of multiple transverse modes, which are induced by the finite cross section, the quantum interference between multiple scattering pathways with different transverse modes can be used to manipulate the single-photon transport. We find that the emitter becomes transparent when the superposition of waveguide modes has zero amplitude at the position of emitter. And the perfect reflection is absent even under Fano resonance unless the input-state is in a coherent superposition state. These results may promote the development of single-photon devices with wide applicable frequency region.

Band-stop filter based on tunable Fano resonance and electromagnetically induced transparency in metal-dielectric-metal waveguide coupling systems

Metal-dielectric-metal (MIM) waveguide coupling systems based on surface plasmon polaritons (SPPs) are designed and studied. The finite element method is used to simulate the transmission spectra of structures in the whole simulation process. One waveguide coupling system consists of an inverted T-shaped cavity with defect (ITD) and a waveguide with a metal wall. The filter band appears in the transmission spectrum due to the opposite direction of two Fano resonances. The filter band width and the filtering range can be tuned effectively by changing the structure parameters. In this system, the center frequency and bandwidth of the filter band are 1330 nm and 114 nm, respectively. The insertion loss and reflection loss are −1.41 dB and −16.89 dB, respectively. The optimization is carried out on the basis of the first system in order to improve the filtering performance. Optimized waveguide coupling system contains an ITD and a waveguide with a slot cavity. Electromagnetically induced transparency (EIT) and Fano resonance exist simultaneously, and the filter band is induced in the transmission spectrum. In this system, the center frequency and bandwidth of the filter band are 1412 nm and 120 nm, respectively. The insertion loss and reflection loss are −0.50 dB and −37.32 dB, respectively. EIT and Fano resonance can not only be regulated independently, but also be regulated simultaneously by changing the structural parameters. And the intensity of EIT and the width of the filter band can be manipulated with changes of the structural parameters. The transmission response of SPPs propagating in the structure can be adjusted dynamically. Moreover, these novel SPPs optical waveguide structures have good filtering efficiency and can meet different filtering needs. These results show that the proposed systems are promising for filter, slow light device and photonic device integration applications.

Effect of Damping on Magnetic Induced Resonances in Cross Waveguide Structures

We consider, in the frame of long-wavelength Heisenberg model, a simple magnetic device consisting of two dangling side stubs grafted at the same site along a waveguide. This simple structure is designed to obtain bound in continuum (BIC) modes, magnonic induced transparency (MIT) and magnonic induced absorption (MIA), the analogues of electromagnetic induced transparency (EIT) and absorption (EIA) resonances respectively. By detuning the lengths of the two stubs, a resonance can be squeezed between two transmission zeros induced by the two resonators. We give detailed analytical expressions for the transmission and reflection coefficients as well as the absorption coefficient of the whole structure. A sharp peak with high Q factor is found as the consequence of the constructive interference of the waves in the two stubs. For some specific detuning values, the Q factor may reach infinity giving rise to the so-called bound in continuum state. Also, we give several explicit expressions for other physical characteristics, e.g., the transmission function close to the resonance, the position, the width and the Fano parameters of the resonances as a function of the difference between the lengths of the stubs. The reported analytical results are obtained by means of a Green’s function method. These results should have important consequences for designing a selecting or rejecting magnon filter.

All-dielectric magnetic metasurface for advanced light control in dual polarizations combined with high-Q resonances

Nanostructured magnetic materials provide an efficient tool for light manipulation on sub-nanosecond and sub-micron scales, and allow for the observation of the novel effects which are fundamentally impossible in smooth films. For many cases of practical importance, it is vital to observe the magneto-optical intensity modulation in a dual-polarization regime. However, the nanostructures reported on up to date usually utilize a transverse Kerr effect and thus provide light modulation only for p-polarized light. We present a concept of a transparent magnetic metasurface to solve this problem, and demonstrate a novel mechanism for magneto-optical modulation. A 2D array of bismuth-substituted iron-garnet nanopillars on an ultrathin iron-garnet slab forms a metasurface supporting quasi-waveguide mode excitation. In contrast to plasmonic structures, the all-dielectric magnetic metasurface is shown to exhibit much higher transparency and superior quality-factor resonances, followed by a multifold increase in light intensity modulation. The existence of a wide variety of excited mode types allows for advanced light control: transmittance of both p- and s-polarized illumination becomes sensitive to the medium magnetization, something that is fundamentally impossible in smooth magnetic films. The proposed metasurface is very promising for sensing, magnetometry and light modulation applications.

Mode Switching With Waveguide-Coupled Plasmonic Nanogratings

Active photonic elements enable a wide range of on-chip optical applications, including enhanced light emission, integrated optical sensing and spectroscopy, photonic signal routing, and optical computing. The ability to select between different optical channels forms the basis for many of these systems. Both spectral and spatial selectivity of optical modes are desirable and together offer flexibility in tailoring the optical response of the system. In this work, we experimentally demonstrate a platform for the active switching of hybrid plasmonic-photonic Fano resonances. Our structure consists of gold nanogratings sandwiched between two dielectric thin films. Diffractive coupling into each layer is modulated by varying the refractive index above the structure. By controlling the interaction of the substrate and superstrate modes through refractive index tuning, we experimentally demonstrate on/off switching of the narrow (FWHM = 30-40 nm) Fano resonance transparency windows with up to 85% resonance contrast, and tunability across a wide spectral range (600-850 nm). Full-wave electromagnetic simulations support these results and reveal that the tuning of these modes enables both spectral and spatial selectivity.

Bound in continuum states and induced transparency in mesoscopic demultiplexer with two outputs

We investigate the electronic transport in a simple mesoscopic cross structure made of two wires (stubs) grafted at the same point along a quantum waveguide. We show that the structure may exhibit important phenomena such as bound in continuum (BIC) states. These states are transformed into electromagnetically induced transparency (EIT) resonance by detuning slightly the lengths of the stubs. The last phenomenon is used to propose and study a mesoscopic demultiplexer device with an input waveguide and two output waveguides. We give closed-form expressions of the geometrical parameters that allow a selective transfer of a given state in the first waveguide without perturbing the second waveguide. The effect of temperature on the transmission resonances is also examined by using Landauer–Büttiker formula. The analytical results of the dispersion relation and transmission and reflection coefficient are obtained using the Green’s function method.

Double Fano Resonances in S-Shaped Plasmonic Metasurfaces in Terahertz Region

We numerically and experimentally demonstrated double Fano resonances in a simple S-shaped plasmonic metasurface in the terahertz frequency range. Apart from the LC resonance and electric dipole (ED) resonance, two trapped modes are excited in two different types of asymmetric S-shaped structures in the frequency range 0.2–1.4 THz, which are mainly attributed to a magnetic dipole (MD) and an electric quadrupole (EQ). Thereafter, double Fano resonances (one Fano and one electromagnetically induced transparency (EIT) resonance) are achieved via the coupling of the two dark trapped modes and a broad bright ED at normal incidence of the metasurfaces. Furthermore, under oblique incidence, strong Fano responses can be observed; they are considerably enhanced in asymmetric structures, and even in a symmetric structure. The proposed S-shaped plasmonic metasurfaces are easy to fabricate and have potential applications in multi-wavelength optical switches, filters‚ and sensors.

Controllable optical response in a quadratically coupled optomechanical system with mechanical driving

We study the response of the output field from a quadratically coupled optomechanical system, where the optical cavity is driven by a strong control field and a weak probe field. In addition, a weak coherent mechanical driving field is applied to excite the mechanical mode and modify the optical response of the system. Under different driving conditions, we show that the transmission spectrum of the probe field can exhibit the phenomena of optomechanically induced transparency, amplification, and Fano resonance. Within the narrow transparency and amplification windows, the four-wave mixing (FWM) intensity can be resonantly enhanced. Moreover, it is shown that the FWM intensity can be further enhanced or suppressed by tuning the amplitude and phase of the mechanical driving, and the physical origin is explained in terms of interference effect. Our results may find potential applications in optical switching and frequency conversion.

Coherent control of Fano resonances in a macroscopic four-mirror cavity

We demonstrate coherent control of optomechanically induced transparency and Fano resonances in a four mirror macroscopic optomechanical cavity, with two movable mirrors, each driven by an external mechanical pump. The variable control of the amplitude and phase of the coherent mechanical pumps provides a means of tuning the shape and nature of the Fano profiles. Further, our scheme shows the occurrence of tunable optomechanical features, even at very low mechanical driving field amplitudes, in macroscopic optomechanical cavities.