In this study, a structure to realize a switchover between two different responses of electromagnetically induced transparency (EIT) was designed and implemented by simulation. Taking advantage of the anisotropy in the structure and the coupling between the radiative and dark elements, a metasurface switch with modulation depth of over 85% between orthogonal polarization incident light illuminations was demonstrated. The key mode switchover between the "on" and "off" states was achieved by electrically changing the dressing light polarization with a liquid crystals layer pre-aligned with a mature technology, without changing the incident light and an expected and reversible transition from an EIT-like spectrum to a strong spectral dip was observed. The modulation in the EIT switch fabricated with the proposed straightforward approach is a promising tool to control the groping velocity delay.
In this study, a structure to realize a switchover between two different responses of electromagnetically induced transparency (EIT) was designed and implemented by simulation. Taking advantage of the anisotropy in the structure and the coupling between the radiative and dark elements, a metasurface switch with modulation depth of over 85% between orthogonal polarization incident light illuminations was demonstrated. The key mode switchover between the "on" and "off" states was achieved by electrically changing the dressing light polarization with a liquid crystals layer pre-aligned with a mature technology, without changing the incident light and an expected and reversible transition from an EIT-like spectrum to a strong spectral dip was observed. The modulation in the EIT switch fabricated with the proposed straightforward approach is a promising tool to control the groping velocity delay.
Electromagnetically induced transparency (EIT) is a promising technology for the enhancement of light-matter interactions, and recent demonstrations of the quantum EIT realized in artificial micro-structured medium have remarkably reduced the extreme requirement for experimental observation of EIT spectrum. In this paper, we propose to electrically control the EIT spectrum in a metamaterial for an electromagnetic modulator. A diode acting as a tunable resistor is loaded in the gap of two paired wires to inductively tune the magnetic resonance, which induces remarkable modulation on the EIT spectrum through the metamaterial sample. The experimental measurements confirmed that the prediction of electromagnetic modulation in three narrow bands on the EIT spectrum, and a modulation contrast of up to 31 dB was achieved on the transmission through the metamaterial. Our results may facilitate the study on active/dynamical technology in translational metamaterials, which connect extraordinary manipulations on the flow of light in metamaterials, e.g., the exotic EIT, and practical applications in industry.
Abstract Active control of electromagnetically induced transparency (EIT) in metamaterials promises tremendous potential applications. However, previously reported strategies most require sensitive materials as well as additional experimental apparatus, which are inconvenient for on-chip operation and restrain their implementations in fully integrated design. We propose a low-loss all-dielectric metamaterial with orthogonal double bright modes, which shows a narrowband transparency window at 950.05 nm with a high Q -factor of 2111. Just by varying the incident light polarization angle, an on-to-off in-situ EIT modulation without changing Q -factor is perfectly achieved, and the modulation depth can be up to 99.7%. Additionally, optical control of group delay with up to 36.22 ps is also demonstrated. This work provides a simple route to design chip-scale devices with optically dynamic controllability and finds fascinating applications in low-loss active slow light devices, optical switch and sensitive bio-sensing.
The realization of tunable metasurfaces is of fundamental importance for boosting the electromagnetic field control ability. Especially, it is important to put forward new modulation methods to further understand their underlying modulation mechanism and expand their application range. In this paper, tunable electromagnetically induced transparency (EIT) metasurfaces based on the phase change material Ge2Sb2Te5 (GST) are proposed and experimentally demonstrated. Different from previous modulation methods of directly introducing the GST film below the metasurfaces, here a two-step lithography method is introduced to combine independent GST strips with bright and dark meta-atoms in the EIT structures, respectively, achieving the independent modulation of the EIT-like spectra. In addition, by applying temporal coupled-mode theory (TCMT), the EIT-like spectra with different GST crystallization levels were analysed and the corresponding characteristic parameters were determined simultaneously. These fitting results reveal that GST strips can modulate the resonances of the bright and dark meta-atoms independently by shifting the resonant frequency and increasing the decay rate, which in turn result in the different modulation features of the EIT-like spectra. This method improves the degree of freedom of active modulation and provides a new route for tunable slow light devices.
We experimentally demonstrated a controllable electromagnetically induced transparency (EIT)-like spectral response at microwave frequencies in a planar metamaterial consisting of two identical split-ring resonators (SRRs) with side-by-side symmetry. In our scheme, phase coupling between the two SRRs (serving as the bright mode), which were excited strongly by the incident wave, was employed, and it was found that the EIT-like spectral response could be controlled by simply adjusting the incident angle. Thus, our scheme may be used for electromagnetic-wave switching. A high group index for slow-light application and a high quality factor could be obtained by simply controlling the incident angle.
In this work, using finite-difference time-domain method, we propose and numerically demonstrate a novel way to achieve electromagnetically induced transparency (EIT) phenomenon in the reflection spectrum by stacking two different types of coupling effect among different elements of the designed metamaterial. Compared with the conventional EIT-like analogues coming from only one type of coupling effect between bright and dark meta-atoms on the same plane, to our knowledge the novel approach is the first to realize the optically active and precise control of the wavelength position of EIT-like phenomenon using optical metamaterials. An on-to-off dynamic control of the EIT-like phenomenon also can be achieved by changing the refractive index of the dielectric substrate via adjusting an optical pump pulse. Furthermore, in near infrared region, the metamaterial structure can be operated as an ultra-high resolution refractive index sensor with an ultra-high figure of merit (FOM) reaching 3200, which remarkably improve the FOM value of plasmonic refractive index sensors. The novel approach realizing EIT-like spectral shape with easy adjustment to the working wavelengths will open up new avenues for future research and practical application of active plasmonic switch, ultra-high resolution sensors and active slow-light devices.
Abstract Based on graphene, an ultra-broadband electromagnetically induced transparency (EIT) window with dynamic tunability is realized in theory. Through altering the Fermi level of graphene that can be regulated by the external voltage, the EIT window and the EIT effect, especially the slow-wave effect, can be easily adjusted. Moreover, the bandwidth of the EIT window can be changed by the incidence angle, achieving the transformation from broadband to narrowband. At the same time, by discussing the polarization state and loss index, the characteristics of polarization insensitivity and low loss are proved. Additionally, the influences of other parameters are discussed, such as the relaxation time of graphene and coupling distance. These unique features enable the designed EIT metamaterial to be masterly applied to optical switches, optical modulators, and slow-light devices.