In this paper, a metal-insulator-metal plasmonic biosensor based on two adjacent disk resonators and the unidirectional reflectionless propagation effect is proposed and investigated. The numerical results obtained from the finite difference time domain simulations are verified analytically by means of the coupled-mode theory. The resonant properties of the proposed structure including the full-width at half-maximum and quality factor are optimized by determining the suitable geometrical parameters. The presented biosensor is then utilized to detect some biomaterials such as ether, ethyleneglycol, chlorobenzene, and quinoline. It is shown that the proposed structure shows high sensitivity of ~1500nm/RIU, large figure of merit of 242.66RIU-1 and large quality factor of 242.8, compared to the previously reported optical biosensors. Moreover, the effect of the dielectric used in the waveguides is also inspected.

The concept and analysis of a nano‐scale multifunctional logic gate based on graphene/hexagonal boron nitride ( h ‐BN) plasmonic waveguides at a wavelength of 7.5µm are presented. By using graphene as a metamaterial with outstanding electro‐optical properties, various logical operations including AND, OR, and XOR are implemented. The proposed multifunctional structure supports surface plasmons (SPs) whose dispersion properties can be controlled by applying an electrical field to graphene. The effects of the incident polarisation and the substrate of graphene on the transmission of SPs are investigated. Simulations by finite difference time domain method show that the extinction ratios for the presented logical operations are higher than 15dB. Also, the structure has a compact footprint of 1.12µm ² which is suitable for using in integrated photonic circuits. This provides a path for the development of novel nano‐scale practical on‐chip applications such as plasmonic memory devices.

In this paper, a novel broadband solar absorber based on $\mathrm{TiN}/{\mathrm{TiO}}_2$ is presented. The unit cell is composed of a multi-layer disk that is surrounded by a TiN ring. By using the finite-difference time-domain method, the effects of the number of disk layers as well as the height of the ring on the absorption are comprehensively investigated. It is shown that the light with shorter wavelengths is trapped by the disks, while the longer wavelengths are absorbed by the ring. Also, the variation of the absorption due to the period changes is studied. According to the simulation results, the average absorption of the proposed absorber is 93% in the wavelength range of 200–4000 nm. In addition, the absorption is higher than 90% in a wide wavelength range of 200–3000 nm under normal incidence, which covers the whole spectrum of solar radiation. It is shown that the proposed absorber can absorb more than 80% of light for angles less than 50° for both the TE and TM modes. Owing to the use of TiN and ${\mathrm{TiO}}_2$, this solar absorber has high thermal and chemical stability. This structure can act as a blackbody emitter in thermal emitter devices. Due to its high absorption and subwavelength structure, the proposed solar absorber is a suitable candidate for use in many solar-based applications.

In this paper, a novel broadband plasmonic absorber based on cross-shaped titanium nitride (TiN) resonators in the ultraviolet, visible, and near-infrared regions is presented. The proposed perfect solar absorber consists of periodic arrays of cross-shaped TiN resonators located on a stack of S i O 2 / T i N layers. By using the finite-difference time-domain method, the effects of variations of the thickness and radius of the elliptical metasurface resonators on the absorption are comprehensively investigated. The cross-shaped metamaterial absorber exhibits an averaged absorption of 90%, ranging from 200 to 3000 nm, and shows over 90% absorption from 200 to 2500 nm. Furthermore, the proposed absorber indicates absorption efficiency over 80% for an oblique incidence up to 50 deg for both TE- and TM-polarized light. These features make the proposed solar absorber usable in many solar-based applications, imaging, and thermal emitting.