Confining near-infrared (NIR) and mid-infrared (MIR) radiation (1–10 μm) at the nanoscale is one of the main challenges in photonics. Thanks to the transparency of silicon in the NIR-MIR range, opt...

https://pubs.acs.org/doi/pdf/10.1021/acsanm.0c02690

Near- And Mid-Infrared Graphene-Based Photonic Architectures for Ultrafast and Low-Power Electro-Optical Switching and Ultra-High Resolution Imaging

High-contrast gratings (HCGs) can be designed as a resonator with high-quality factor and surface-normal emission, which are excellent characters for designing optical devices. In this work, we combine HCGs with plasmonic graphene structure to achieve an ultrathin five-band coherent perfect absorber (CPA). The presented CPA can achieve multi- and narrow-band absorption with high intensity under a relatively large incident angle. The good agreement between theoretical analysis and numerical simulated results demonstrates that our proposed HCGs-based structure is feasible to realize CPA. Besides, by dynamically adjusting the Fermi energy of graphene, we realize the active tunability of resonance frequency and absorption intensity simultaneously. Benefitting from the combination of HCGs and the one-atom thickness of graphene, the proposed device possesses an extremely thin feature. Our work proposes a novel method to manipulate coherent perfect absorption and is helpful to design tunable multi-band and ultrathin absorbers.

Ultrathin multi-band coherent perfect absorber in graphene with high-contrast gratings.

Effect of CdSeS/ZnS quantum dot concentration on the electro-optical and dielectric properties of polymer stabilized liquid crystal

In this paper, a design method for tunable liquid crystal (LC)-based metamaterial absorber (MMA) with the compact unit cell and the wideband absorption is proposed. A compact LC-based MMA unit cell...

A Tunable Metamaterial Absorber Based on Liquid Crystal with the Compact Unit cell and the Wideband Absorption

Graphene-based hyperbolic metamaterials provide a unique scaffold for designing nanophotonic devices with active functionalities. In this work, we have theoretically demonstrated that the characteristics of a polarization-dependent tunable hyperbolic microcavity in the mid-infrared frequencies could be realized by modulating the thickness of the dielectric layers, and thus breaking periodicity in a graphene-based hyperbolic metamaterial stack. Transmission of the tunable microcavity shows a Fabry–Perot resonant mode with a Q-factor > 20, and a sixfold local enhancement of electric field intensity. It was found that by varying the gating voltage of graphene from 2 to 8 V, the device could be self-regulated with respect to both the intensity (up to 30%) and spectrum (up to 2.1 µm). In addition, the switching of the device was considered over a wide range of incident angles for both the transverse electric and transverse magnetic modes. Finally, numerical analysis indicated that a topological transition between elliptic and type II hyperbolic dispersion could be actively switched. The proposed scheme represents a remarkably versatile platform for the mid-infrared wave manipulation and may find applications in many multi-functional architectures, including ultra-sensitive filters, low-threshold lasers, and photonic chips.

/pdf/graphene-based-tunable-hyperbolic-microcavity-fy5cx4b4be.pdf

Graphene-based tunable hyperbolic microcavity

A tunable graphene-based hyperbolic metamaterial is designed and numerically investigated in the mid-infrared frequencies. Theoretical analysis proves that by adjusting the chemical potential of graphene from 0.2 eV to 0.8 eV, the reflectance can be blue-shifted up to 2.3 µm. Furthermore, by modifying the number of graphene monolayers in the hyperbolic metamaterial stack, we are able to shift the plasmonic resonance up to 3.6 µm. Elliptic and type II hyperbolic dispersions are shown for three considered structures. Importantly, a blue/red-shift and switching of the reflectance are reported at different incident angles in TE/TM modes. The obtained results clearly show that graphene-based hyperbolic metamaterials with reversibly controlled tunability may be used in the next generation of nonlinear tunable and reversibly switchable devices operating in the mid-IR range.

Graphene-based hyperbolic metamaterial as a switchable reflection modulator.

In this work, we studied and analysed a particular variety of liquid crystals, the so-called dual-frequency nematic liquid crystals (DFNLCs). The interest was to perform dielectric spectroscopy and...

Investigations of dual-frequency nematic liquid crystals doped with dichroic dye

In this work, the terahertz (THz) adsorption spectra in the range between 0.3 THz and 10.0 THz of chosen liquid crystal (LC) molecules were studied by using the density functional theory (D...

0.3–10.0 THz spectra for chosen liquid crystal molecules – simulation and physical properties

In this work, the terahertz (THz) absorption of homologous series of isothiocyanobiphenyls (nBT) and 4-(trans-4ʹ-n-alkylcyclohexyl)isothiocyanato-benzene (nCHBT) are simulated by using the ...

Simulations of some physical parameters of homologous series of nBT and nCHBT at 0.3–20.0 THz

In this work we, propose a tunable 2D-hydrid epsilon-near-zero (ENZ) platform in telecom windows. Taking advantage to the intrinsically ENZ of the Indium-thin-oxide (ITO) and exploiting the graphene capability to dynamically tune the plasmon polaritons we were able to adjust the cross-over frequency, where the epsilon vanishes, in four telecom bandwidth windows. Additionally, tunabilty can be achieved via electrical gating of the ITO leading to an interplay modulation of the surface plasmon polaritons at the graphene-ITO interface. Furthermore, a giant Purcell factor (PF) was observed at ENZ regimes. These results show how 2D-hybrid ENZ materials potentially find applications in multifunctional nonlinear nanophotonic systems such as ultrafast modulators, data processing and photonic quantum computers (QPCs).

2D hybrid epsilon near-zero platform for nanophotonics

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