Tunable Plasmon-induced Transparency Research Articles

Tunable plasmon-induced transparency in anisotropic graphene-black phosphorus photonic device for high-performance sensors and switchers

A novel photonic device composed of graphene and black phosphorus (G-BP) has been proposed, which achieves high-performance plasmon-induced transparency (PIT) effect within the THz range and maintains substantial tunability and anisotropy. The anisotropy of the PIT effect arises from the near-field coupling between two bright modes characterized by distinct effective electron masses of BP, resulting transparency window at 33.35 THz for TE polarization and at 26.92 THz for TM polarization. Through the modulation of Fermi energy in graphene, doping levels of BP and geometric parameters separately, a tunable transparency window is achieved. Notably, the convergence or divergence of the anisotropic transparency windows can be well manipulated with different BP doping levels. Furthermore, the proposed G-BP photonic device exhibits a high sensitivity to changes in the surrounding refractive index and substrates, with a maximum sensitivity of 12.04 THz/RI, rendering it suitable for sensor applications. Overall, the proposed photonic device exhibits notable PIT effects characterized by high anisotropic performance, substantial tunability, great sensitivity, and stability, making it a promising candidate for applications in sensors, polarizers, and switchers.

All-optical multichannel switch and slow light based on dynamically tunable plasmoninduced transparency

All-optical multichannel switch and slow light based on dynamically tunable plasmoninduced transparency

Actively Tunable Plasmon-Induced Transparency via Alternately Coupled Resonators Based on Bulk Dirac Semimetal Metamaterials

Actively Tunable Plasmon-Induced Transparency via Alternately Coupled Resonators Based on Bulk Dirac Semimetal Metamaterials

Actively tunable plasmon-induced transparency in terahertz based on Dirac semimetal metamaterials.

We numerically investigate a tunable plasmon-induced transparency based on bulk Dirac semimetal (BDS) metamaterial in the terahertz band. In the unit cell, the prominent transparent peak appears to be due to the interference between the cut wires (CWs) and split-ring resonators (SRRs). An active modulation via near-field coupling is obtained by varying the Fermi level of the BDS. Introducing photoactive silicon, it will be found that once the intensity of the pump light is adjusted, a tunable transparent peak will appear. Furthermore, by shifting the coupling distance between CWs and SRRs, the depth of the transparent peak will change accordingly. Finally, we place the structure in environments with different refractive indices, which will exhibit excellent sensitivity and facilitate the application of biochemical sensors. This simple and easy-to-fabricate metamaterial structure will have excellent potential applications in modulation, filters, and detection.

Dynamically Adjusting Borophene-Based Plasmon-Induced Transparency in a Polymer-Separated Hybrid System for Broadband-Tunable Sensing.

Borophene, an emerging two-dimensional (2D) material platform, is capable of supporting highly confined plasmonic modes in the visible and near-infrared wavebands. This provides a novel building block for light manipulation at the deep subwavelength scale, thus making it well-suited for designing ultracompact optical devices. Here, we theoretically explore a borophene-based plasmonic hybrid system comprising a continuous borophene monolayer (CBM) and sodium nanostrip gratings (SNGs), separated by a polymer spacer layer. In such a structure, a dynamically tunable plasmon-induced transparency (PIT) effect can be achieved by strongly coupling dark and bright plasmonic modes, while actively controlling borophene. Here, the bright mode is generated through the localized plasmon resonance of SNGs when directly excited by TM-polarized incident light. Meanwhile, the dark mode corresponds to a propagating borophene surface plasmon (BSP) mode in the CBM waveguide, which cannot be directly excited, but requires phase matching with the assistance of SNGs. The thickness of the polymer layer has a significant impact on the coupling strength of the two modes. Owing to the BSP mode, highly sensitive to variations in the ambient refractive index (RI), this borophene-based hybrid system exhibits a good RI-sensing performance (643.8 nm/RIU) associated with a wide range of dynamically adjustable wavebands (1420-2150 nm) by tuning the electron density of borophene. This work offers a novel concept for designing active plasmonic sensors dependent on electrically gating borophene, which has promising applications in next-generation point-of-care (PoC) biomedical diagnostic techniques.

Tunable terahertz slow light with hybrid coupling of a magnetic toroidal and electric dipole metasurface

We present a hybrid coupling scheme of a magnetic toroidal and electric dipole metasurface with suppressed radiation loss, which can produce the tunable plasmon-induced transparency (PIT) with an enhanced slow-light effect in the terahertz regime. The terahertz metasurface is constructed by nesting a dual-split ring resonator (DSRR) inside a ring resonator (RR) to exploit the destructive coherence of hybrid electromagnetic mode coupling at the PIT resonance. The polarization-dependence excitation performs the active tunability of a PIT-induced group slowing down by rotating the polarization angle, experimentally achieving a maximum group delay of 3.5 ps. Furthermore, the modified terahertz metasurface with a four-split ring resonator (FSRR) nested in an RR is prepared on photoconductive silicon, demonstrating the pump-controllable group delay effect at the PIT resonance. The large group delay from 2.2 to 0.9 ps is dynamically tunable by adjusting the pump power. The experimental results are in good accord with the theoretical simulations.

Multiple plasmon-induced transparency based on black phosphorus and graphene for high-sensitivity refractive index sensing.

A hybrid bilayer black phosphorus (BP) and graphene structure with high sensitivity is proposed for obtaining plasmon-induced transparency (PIT). By means of surface plasmon resonance in the rectangular-ring BP structure and ribbon graphene structure, a PIT effect with high refractive index sensitivity is achieved, and the surface plasmon hybridization between graphene and anisotropic BP is analyzed theoretically. Meanwhile, the PIT effect is quantitatively described using the coupled oscillator model and the strong coherent coupling phenomena are analyzed by adjusting the coupling distance between BP and graphene, the Fermi level of graphene, and the crystal orientation of BP, respectively. The simulation results show that the refractive index sensitivity S = 7.343 THz/RIU has been achieved. More importantly, this is the first report of tunable PIT effects that can produce up to quintuple PIT windows by using the BP and graphene hybrid structure. The high refractive index sensitivity of the quintuple PIT system for each peak is 3.467 THz/RIU, 3.467 THz/RIU, 3.600 THz/RIU, 4.267 THz/RIU, 4.733 THz/RIU and 6.133 THz/RIU, respectively, which can be used for multiple refractive index sensing function.

Tunable plasmon induced transparency in one-dimensional gold nano-grating as a new kind of neuro-transmitter sensor

The plasmon induce-transparency (PIT) is a promising research area for slow light, nonlinearity, metamaterial, and sensing applications. This physical phenomenon originated in plasmonic nanostructures with the interference between wideband (superradiant) and narrowband (subradiant) states (modes). We report tunable plasmon-induced transparency in one-dimensional gold nano-grating electro-plasmonic consisting of a straight nanorod of gold grating embedded in the polycarbonate layer, which combines the plasmonic properties of gold nanostructure and the external applying voltage. Tunable PIT is achieved under the excitation of power supply from 1 v to 3 v, with spectroscopy employed to monitor the changes of transmission spectrum with different voltages applied on the plasmonic periodically with the surface plasmon resonance. Also, we use this plasmonic sensor to sense and monitor dopamine concentration as a neurotransmitter. The results revealed that we obtain a clear sharp window for tunable PIT and a good sensor to sense the dopamine concentration.

Versatile terahertz graphene metasurface based on plasmon-induced transparency

A monolayer terahertz graphene metasurface is designed to achieve tunable plasmon-induced transparency (PIT) effect in two perpendicular polarization directions based on surface plasmon polariton resonance. The penta-frequency and dual-frequency switch can be easily implemented by adjusting the Fermi levels of graphene, and the switch has excellent performances including modulation degree of amplitude (81.4 % < MDA < 97.1 %) and insertion loss (0.01 dB < IL < 0.04 dB). Moreover, the metasurface has high sensitivity, which can be up to 30500 nm/RIU. Also, the designed PIT metasurface has a good slow light effect, and group indexes are respectively 1100 and 2396 corresponding to x-polarized and y-polarized light. This work demonstrates that graphene metasurface has potential applications in switch, sensor and slow-light devices.

Controlled and tunable plasmon-induced transparency based on graphene metasurfaces in atmospheric windows

Considering the development of plasmon-induced transparency functional devices and the research value of the atmospheric windows in many civilian and military applications, we propose a mid-infrared metasurface composed of a multilayer elliptical graphene and two graphene strips that can generate PIT, and the PIT can be dynamically tuned in the range of 3.67 μm–9.53 μm beyond monolayer graphene. The numerical results from Finite-Difference Time-Domain (FDTD) method are consistent with the analytical results from Lorentz oscillator theory. In addition, we can control the generation and vanishment of the PIT by changing the polarization of the source, achieving a triple-frequency asynchronous switch, and the performance index indicates that the modulation depth is maintained at about 90% at a relatively high Fermi energy level. Our work achieves a dynamically tunable and controllable PIT for applications including filters and optical switches in atmospheric windows.

Graphene and metal hybridized terahertz metasurfaces toward tunable plasmon-induced transparency effects

Tunable metasurfaces have attracted much attention recently, owing to their capability of actively controlling electromagnetic waves. Here, we propose tunable graphene-metal hybridized terahertz (THz) metasurfaces exhibiting plasmon induced transparency (PIT) effects, driven alternately by metal and graphene resonators. The proposed meta-molecule comprises a central metal (graphene) strip placed orthogonally to two side graphene (metal) strips. Then, near-field coupling between the strips is probed by translating the central strip along the length of the side strips and the evolution of the PIT effect is investigated for orthogonal polarizations of probing THz. The coupled oscillator-based analytical model explains the coupling mechanism in these metasystems. We observe the strongest coupling and the most prominent PIT effect for edge-to-edge coupling (threshold position) between the central and side strips. Further, active PIT response is achieved by altering graphene's Fermi energy. These metasurfaces can contribute in designing compact and active metasurface-based hybrid devices for THz domain.

Tunable plasmon-induced transparency in graphene-based plasmonic waveguide for terahertz band-stop filters

Terahertz (THz) tunable filters have great advantages in miniaturizing integrated and multiband communication systems. Here, THz band-stop filter with switchable single/double plasmon-induced transparency (PIT) based on metal-dielectric-metal waveguide consisting of a ring-stub cavity and two graphene ribbons (GRs) on stub sidewalls is proposed. The switchable characteristics of single and dual-PIT are investigated numerically and theoretically by the finite-difference time-domain and the radiating multi-oscillator theory, displaying good correspondence. The single-PIT is excited by the destructive interference between bright mode and dark mode, which possesses significant tunability of resonant frequency and transmission amplitude due to the existence of GRs. When independently regulating chemical potentials of GRs on the left and right sidewalls, the dual-PIT emerges. And the filter based on dual-PIT switches from single stopband to dual-stopband or even multi-stopband filtering. Besides, the band-stop filtering performance of the tunable PIT can be further optimized by increasing the number of ring-stub cavities. The tunable PIT in graphene-based plasmonic waveguide holds potential for THz multiband communications and subwavelength plasmonic devices, such as filters, switches, modulators.

Tunable plasmon-induced transparency with coupled L-shape graphene metamaterial

A graphene-based metamaterial structure, consisting of a graphene strip (GS) and a L-shaped graphene-rectangular block (GRB), is proposed to generate the plasmon-induced transparency (PIT) effect. The potential physical properties of the PIT effect are analyzed by using the coupled mode theory (CMT). The PIT has the unique characteristics of controlling light propagation through the static and dynamic regulations, resulting in a prospective switching application. The performance of the optical switch is evaluated through different parameters, including the geometric size, Fermi level and polarization angle. The modulation depth of the amplitude can reach 74.9% with a specific Fermi level, while the maximum polarization extinction ratio can reach 11.34 dB. Furthermore, dual and triple PIT effects are achieved by the designing and optimizing the structure. The maximum multiple switching effect is obtained with a modulation depth of 97.3%, which has a promising prospect in terahertz optical switches.

Tunable terahertz group slowing effect with plasmon-induced transparency metamaterial.

We present a tunable plasmon-induced transparency (PIT) metamaterial for manipulating the group velocity of terahertz (THz) waves. The metamaterial is composed of metal split rings and photoconductive silicon strips. The strong PIT effect with slowing down THz waves is generated by the bright-bright mode coupling between the high-order plasmon mode and the lattice surface mode via electromagnetic destructive interference. By varying the conductivity of silicon strips, the group slowing performance is dynamically tunable. The group delay can achieve beyond 20 ps with the group index as high as 592, showing the promising application for THz signal manipulation.

Dynamically Tunable Plasmon-Induced Transparency in Parallel Black Phosphorus Nanoribbons

In this paper, we investigate the dynamically tunable plasmon-induced transparency (PIT) effects in parallel black phosphorus nanoribbons (BPNRs). The proposed structures consist of several parallel BPNRs having different lengths in one transverse period. The periods of all proposed structures are set as \(P = 500 \, nm\). To our best knowledge, these proposed structures have not been reported in published papers. It is the first time that simulates PIT effects by this way. The results show that the BPNRs can be regarded as bright modes. Single-band, double-band, triple-band, and multi-band PIT effects based on the bright-bright mode coupling between parallel BPNRs are achieved. The physical mechanism of the single-band model can be explained theoretically by the radiating two-oscillator (RTO) model. Due to the heavier effective mass in the zigzag (ZZ) direction of the BP, the frequencies of the transparent peaks are shifted to lower frequencies when the placement directions of BPNRs are changed from the X-direction to the Y-direction. Furthermore, the resonant frequencies of the transparent windows in each model can be tuned by changing the relaxation rates of the BPNRs. The frequencies of the transparent windows are blue-shifted as the relaxation rates are increased. Finally, the corresponding sensors based on single-band PIT effect show high sensitivities of 7.35 THz/RIU. Our study has potential applications for improving the design of multiple-band filters, sensors, and on–off switcher.

Graphene-based tunable plasmon-induced transparency utilizing circular and two rectangular gold rings in the near-infrared spectrum

A plasmonic induced transparency utilizing one circular and two rectangular gold rings in silicon substrate covered by a monolayer graphene sheet is investigated numerically and theoretically in the near infra-red spectrum. Three-dimensional finite difference time domain (3D-FDTD) simulations are employed to extract the set of geometrical parameters to achieve a 1200–2200 nm transparency window. By sweeping the Fermi level of the graphene, we study transmissions, phase shifts, and group delays of the proposed structure. The group delay was about 0.02 ps (ps) for 0.6 electron-volt(eV) Fermi level, and it showed the capability of slow light applications. Moreover, a linear modulation index of 11% was achieved at λ = 1550 nm for 4-layer graphene. The results offered that the plasmonic induced transparency (PIT) effect may be used in the slow-light devices and active plasmonic modulation in the communication wavelength.

Tunable and switchable bifunctional meta-surface for plasmon-induced transparency and perfect absorption

Tunable multi-function metasurfaces have become the latest research frontiers in planar optics. In this study, a dynamically tunable plasmon-induced transparency (PIT) structure based on a graphene split-ring resonator and graphene ribbon is proposed. The influences of the structural parameters and graphene Fermi energy on the PIT response were investigated both analytically and numerically simulations. The inclusion of an additional vanadium dioxide (VO2) substrate layer enables the metasurface to achieve dynamic switching between PIT and perfect absorption using the phase change property of VO2. The new metasurface device exhibits the PIT effect when the VO2 layer is in an insulating state and acts as a perfect absorber when it is in a metallic state. Moreover, the response of the two functions can be easily adjusted dynamically by changing the Fermi energy of graphene. In addition, both functions were highly sensitive to changes in the ambient refractive index. The results of this work have potential applications in slow-light devices, optical switches, modulators, perfect absorbers, highly sensitive sensors, and multifunctional devices.

Multiple and Tunable Plasmon Induced Transparency with L-Shape Graphene Strips Structure at Terahertz Frequency

Multiple and Tunable Plasmon Induced Transparency with L-Shape Graphene Strips Structure at Terahertz Frequency

Dynamically tunable plasmon-induced transparency effect based on graphene metasurfaces

Plasmon-induced transparency (PIT) is theoretically explored for a graphene metamaterial using finite-difference time-domain numerical simulations and coupled-mode-theory theoretical analysis. In this work, the proposed structure consists of one rectangular cavity and three strips to generate the PIT phenomenon. The PIT window can be regulated dynamically by adjusting the Fermi level of the graphene. Importantly, the modulation depth of the amplitude can reach 90.4%. The refractive index sensitivity of the PIT window is also investigated, and the simulation results show that a sensitivity of 1.335 THz RIU−1 is achieved. Additionally, when the polarization angle of the incident light is changed gradually from 0° to 90°, the performance of the structure is greatly affected. Finally, the proposed structure is particularly enlightening for the design of dynamically tuned terahertz devices.

Dynamical manipulation of a dual-polarization plasmon-induced transparency employing an anisotropic graphene-black phosphorus heterostructure.

Dynamical tunable plasmon-induced transparency (PIT) possesses the unique characteristics of controlling light propagation states, which promises numerous potential applications in efficient optical signal processing chips and nonlinear optical devices. However, previously reported configurations are sensitive to polarization and can merely operate under specific single polarization. In this work we propose an anisotropic PIT metamaterial device based on a graphene-black phosphorus (G-BP) heterostructure to realize a dual-polarization tunable PIT effect. The destructive interference coupling between the bright mode and dark modes under the orthogonal polarization state pronounced anisotropic PIT phenomenon. The coupling strength of the PIT system can be modulated by dynamically manipulating the Fermi energy of the graphene via the external electric field voltage. Moreover, the three-level plasmonic system and the coupled oscillator model are employed to explain the underlying mechanism of the PIT effect, and the analytical results show good consistency with the numerical calculations. Compared to the single-polarization PIT devices, the proposed device offers additional degrees of freedom in realizing universal tunable functionalities, which could significantly promote the development of next-generation integrated optical processing chips, optical modulation and slow light devices.