No abstract

A self-referenced terahertz (THz) refractive index sensor is proposed. The structure consists of two opposite-facing, graphene-covered distributed Bragg reflectors (DBRs), with a cavity formed in between. The cavity is filled with the ambient medium, and its resonance frequency is sensitive to the changes of the ambient refractive index. On the other hand, Tamm-plasmonic modes, which are excited at the DBR-graphene boundaries, are insensitive to the ambient refractive index and thus provide a frequency reference. The proposed structure is studied using a semi-analytical transfer matrix method (TMM). The sensor, studied for gas sensing, achieves a sensitivity of 0.982 THz per refractive index unit (THz/RIU), and a figure of merit (FoM) of 142 R I U − 1 at the cavity resonance frequency of 1.1 THz. The effects of different parameters on the sensor’s performance are also investigated. Compared to the previous high-performance THz refractive index sensing approaches, the proposed structure is simpler because it requires no phase- or polarization-matching devices, such as polarizers, prisms, and gratings. Moreover, it provides a self-referenced operation, which was rarely achievable using previous methods.

No abstract

No abstract

In this paper, a nano-metamaterial with the structure of Ag-SiO2-PbTe is proposed that has a random arrangement in the host medium of expanded polystyrene (foam) for the realization of a broadband negative refractive index at the visible spectrum. The negative refractive index for the purposed meta-material was obtained from the plasmonic resonance in the core and outer layer for both electric and magnetic components of light. Here, we use different radii for the outer layer of nanoparticles to create the broadband negative permeability. In this way, the doped semiconductor nanoparticles are included in the host medium to create the broadband negative permittivity. The overlap between the spectrum of the negative permittivity and permeability introduces the broadband negative refractive index at the visible band. The novel introduced structure creates the broadband negative refractive index and it is simple and practical for fabrication. For the realization of the proposed material, synthesis and characterization of the designed nanocomposite structure are investigated. To this end, the absorption and the transmission coefficients of the synthesized material are measured and compared with theoretical results. The obtained results indicate that the numerical simulations using Mie theory have good agreement with the experimental results.