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.

The exceptional tunable waveguiding characteristics of graphene surface plasmons have remained unrivaled since it has inspired many electro-optical (EO) devices in terahertz (THz) and mid-infrared (MIR) photonic circuits. We propose and numerically investigate a low-loss, highly extinctive resonant EO modulator based on a suspended graphene plasmonic waveguide. Unlike other resonance-based modulators, the input power has negligible interaction with lossy resonance cavity in on-state, remarkably reducing the losses. Achieving the insertion loss (IL) of 1.3 dB and the extinction ratio (ER) of 22 dB within a footprint less than 3 µm² substantiates the superiority of the proposed structure. The charge transport simulations are first conducted to calculate the steady-state charge distribution. The three-dimensional finite-difference time-domain (3D-FDTD) method is utilized to monitor the guided wave propagation and modulation properties. We show that the transmission spectrum is highly dependent upon geometric parameters of the structure, and the modulator can be effectively tuned to operate at the desired wavelength by applying a suitable gate voltage. Simulation results show the modulation bandwidth of 71 GHz corresponding to the total capacitance of 4.8 fF within the active area. The novel EO modulator structure has shown great potentiality and flexibility to find other applications in MIR and THz integrated circuits like controllable notch filters and switches.

In this paper, we present a new concept of electro-optical plasmonic Set-Reset flip-flops at mid-infrared frequencies. We use the 3D finite-difference time-domain (FDTD) method to simulate and evaluate our designed flip-flop. In the proposed structure, the propagation of surface plasmon polaritons is controlled by applying an electrostatic field and the switching actions occur in the electrical domain while the output signal is in the form of light. The energy consumed by each switch is 2.5 fJ/bit. In this flip-flop, the no-change state of the flip-flop is realized by using a Bias port. The time response diagram indicates that the minimum extinction ratio of the flip-flop is 14.61 dB. The probability of various errors in the flip-flop state occurring due to the lack of synchronization between the switches is also considered by the FDTD simulations and it is shown that the device has a great performance against errors. Furthermore, the structure has an ultra-compact footprint of 1.62 µm². Our surveys show that no plasmonic flip-flop has been reported to date.