Spectrometer-Free Graphene Plasmonics Based Refractive Index Sensor

Synthesis of chiral graphene structures and their comprehensive applications: a critical review

From a molecular viewpoint, chirality is a crucial factor in biological processes. Enantiomers of a molecule have identical chemical and physical properties, but chiral molecules found in species exist in one enantiomer form throughout life, growth, and evolution. Chiral graphene materials have considerable potential for application in various domains because of their unique structural framework, properties, and controlled synthesis, including chiral creation, segregation, and transmission. This review article provides an in-depth analysis of the synthesis of chiral graphene materials reported over the past decade, including chiral nanoribbons, chiral tunneling, chiral dichroism, chiral recognition, and chiral transfer. The second segment focuses on the diverse applications of chiral graphene in biological engineering, electrochemical sensors, and photodetectors. Finally, we discuss research challenges and potential future uses, along with probable outcomes.

Efficient and high-quality absorption enhancement using epsilon-near-zero cylindrical nano-shells constructed by graphene

This paper presents a detailed scattering analysis of a hollow-core plasmonic-shell cylindrical wire to design an efficient, compact, narrowband, and reconfigurable optical absorber. The shell is formed by a thin graphene material, investigated in its epsilon-near-zero (ENZ) plasmonic region. Compared to the graphene plasmonic resonances in the terahertz(THz)/far-infrared (FIR) frequencies, the ENZ plasmonic resonances offer a blue shift in the operating frequency of the second-order plasmonic resonances by increasing the geometrical dimensions. This feature is successfully used to design efficient optical wave absorbers with absorption cross-sections much larger than geometrical and scattering cross-sections. The observed blue shift in the resonance spectrum, which is the key point of the design, is further verified by defining each particle with its polarizability and fulfilling the resonant scattering condition in the framework of Mie's theory. Furthermore, graphene relaxation time and chemical potential can be used to manipulate the absorption rate. Observed resonances have narrow widths, achieved with simple geometry. To consider more practical scenarios, the one-dimensional arrangement of the cylindrical elements as a dense and sparse array is also considered and the design key point regarding graphene quality is revealed. The quality factor of the sparse array resonance is 2272.8 and it demands high-quality graphene material in design. It is also observed that due to the use of small particles in the design, the near-field and cooperative effects are not visible in the absorption cross-section of the array and a clear single peak is attained. This polarization-insensitive absorber can tolerate a wide range of incident angles with an absorption rate above 90%.

Polarization-sensitive multi-frequency switches and high-performance slow light based on quadruple plasmon-induced transparency in a patterned graphene-based terahertz metamaterial

A periodic patterned graphene-based terahertz metamaterial comprising three transverse graphene strips and one longitudinal continuous graphene ribbon is proposed to achieve a dynamically tunable quadruple plasmon-induced transparency (PIT) effect. Further analysis of the magnetic field distribution along the x-direction shows that the quadruple-PIT window can be produced by the strong destructive interference between the bright mode and the dark mode. The spectral response characteristics of the quadruple-PIT effect are numerically and theoretically investigated, and the results obtained by the finite-difference time-domain (FDTD) simulation fit well with that by the coupled mode theory (CMT) calculation. In addition, two hepta-frequency asynchronous switches are achieved by tuning the Fermi energy of the graphene, and their maximum modulation depths are 98.9% and 99.7%, corresponding to the insertion losses of 0.173 dB and 0.334 dB, respectively. Further studies show that polarization light has a significant impact on the quadruple-PIT, resulting in a polarization-sensitive switch being realized with a maximum modulation depth of 99.7% and a minimum insertion loss of 0.048 dB. In addition, when the Fermi energy is equal to 1.2 eV, the maximum time delay and group refractive index of the quadruple-PIT can be respectively as high as 1.065 ps and 3194, and the maximum delay-bandwidth product reaches 1.098, which means that excellent optical storage is achieved. Thus, our proposed quadruple-PIT system can be used to design a terahertz multi-channel switch and optical storage.