A surface plasmon resonance (SPR) based graphene biosensor is presented. It consists of a graphene sheet coated above a gold thin film, which has been proposed and experimentally fabricated recently [ChemPhysChem 11, 585 (2010)]. The biosensor uses attenuated total reflection (ATR) method to detect the refractive index change near the sensor surface, which is due to the adsorption of biomolecules. Our calculations show that the proposed graphene-on-gold SPR biosensor (with L graphene layers) is (1 + 0.025 L) × γ (where γ > 1) times more sensitive than the conventional gold thin film SPR biosensor. The improved sensitivity is due to increased adsorption of biomolecules on graphene (represented by the factor γ) and the optical property of graphene.

Doped graphene emerges as a strong contender for active plasmonic material in mid-infrared wavelengths due to the versatile external control of its permittivity function and also its highly compressed graphene surface plasmon (GSP) wavelength. In this paper, we design active plasmonic waveguide devices based on electrical modulation of doped graphene nanoribbons (GNRs) on a voltage-gated inhomogeneous dielectric layer. We first develop figure-of-merit (FoM) formulae to characterize the performance of passive and active graphene nanoribbon waveguides. Based on the FoMs, we choose optimal GNRs to build a plasmonic shutter, which consists of a GNR placed on top of an inhomogeneous ${\mathrm{SiO}}_2$ substrate supported by a Si nanopillar. Simulation studies show that for a simple, 50 nm long plasmonic shutter, the modulation contrast can exceed 30 dB. The plasmonic shutter is further extended to build a four-port active power splitter and an eight-port active network, both based on GNR cross-junction waveguides. For the active power splitter, the GSP power transmission at each waveguide arm can be independently controlled by an applied gate voltage with high-modulation contrast and nearly equal power-splitting proportions. From the construct of the eight-port active network, we see that it is possible to scale up the GNR cross-junction waveguides into large and complex active waveguide networks, showing great potential in an exciting new area of mid-infrared graphene plasmonic integrated nanocircuits.

An all-silicon photodetector integrated in a silicon-on-insulator waveguide for the telecom regime is proposed. The device is based on internal photoemission from electrically floating metal silicide nanoparticles (NPs) embedded in the space charge region of a Si p-n junction. Numerical simulation indicates that the light absorption could be enhanced if localized surface plasmon resonances are excited on the metal silicide nanoparticles, thus enabling to shrink the detector’s footprint to a submicron scale. A proof-of-concept detector fabricated using standard silicon complementary metal-oxide-semiconductor technology exhibits a peak responsivity of ∼30 mA/W at 5-V reverse bias and a 3-dB bandwidth of ∼6 GHz. It is expected that the overall performance would be significantly improved by optimization of both the detector’s configuration and the fabrication parameters.

Surface plasmon polaritons (SPPs) are viable candidates for integration into on‐chip nano‐circuitry that allow access to high data bandwidths and low energy consumption. Metal–insulator–metal tunneling junctions (MIM‐TJs) have recently been shown to excite and detect SPPs electrically; however, experimentally measured efficiencies and outcoupling mechanisms are not fully understood. It is shown that the MIM‐TJ cavity SPP mode (MIM‐SPP) can outcouple via three pathways to i) photons via scattering of MIM‐SPP at the MIM–TJ interfaces, ii) SPPs at the metal–dielectric interfaces (bound‐SPPs) by mode coupling through the electrodes, and iii) photons and bound‐SPP modes by mode coupling at the MIM‐TJ edges. It is also shown that, for Al‐AlO_x‐Cr‐Au MIM‐TJs on glass, the MIM‐SPP mode outcouples efficiently to bound‐SPPs through either electrode (pathway 2); this outcoupling pathway can be selectively turned on and off by changing the respective electrode thickness. Outcoupling at the MIM‐TJ edges (pathway 3) is efficient and sensitive to the edge topography, whereas most light emission originates from roughness‐induced scattering of the MIM‐SPP mode (pathway 1). Using an arbitrary roughness profile, it is demonstrated that various roughness facets can raise MIM‐SPP outcoupling efficiencies to 0.62%. These results pave the way for understanding the topographical parameters needed to develop CMOS‐compatible plasmonic circuitry elements.

Variational quantum algorithms (VQAs) are one of the most promising methods that can be implemented on noisy intermediate-scale quantum (NISQ) machines to achieve a quantum advantage over classical computers. This article describes the use of a VQA in conjunction with the finite difference method for the calculation of propagation modes of an electromagnetic wave in a hollow metallic waveguide. The two-dimensional (2-D) waveguide problem, described by the Helmholtz equation, is approximated by a system of linear equations, whose solutions are expressed in terms of simple quantum expectation values that can be evaluated efficiently on quantum hardware. Numerical examples are presented to validate the proposed method for solving 2-D waveguide problems.