Graphene nano-ribbon waveguides of record-small mode area and ultra-high effective refractive indices for future VLSI

Abstract

Electronics circuits keep shrinking in dimensions, as requested by Moore's law. In contrast, photonic waveguides and circuit elements still have lateral dimensions on the order of the wavelength. A key to make photonics have a microelectronics-like development is a drastic reduction of size. To achieve this, we need a low-loss nanoscale waveguide with a drastically reduced mode area and an ultra-high effective refractive index. For this purpose, we propose here several low-loss waveguide structures based on graphene nano-ribbons. An extremely small mode area (~10(-7)λ(0)(2), one order smaller than the smallest mode area of any waveguide that has ever been reported in the literature; here λ(0) is the operating wavelength in vacuum) and an extremely large effective refractive index (several hundreds) are achieved. As a device example, a nano-ring cavity of ultra-small size (with a diameter of ~10(-2)λ(0)) is designed. Our study paves the way for future VLSI (very-large-scale integration) optoelectronics.

Tunable Plasmonic Induced Transparency in Graphene Nanoribbon Resonators

“…The effective index of graphene SPPs can attain to ∼ 100 in the mid-infrared region, comparing to a typical value of ∼ 1.03 for SPPs on metals [17]. Meanwhile, when the width of graphene ribbon decreases to tens of nanometers, only edge mode leaves, which is more suitable for the electromagnetic coupling between the adjacent elements [18][19][20]. Due to the above advantages, more attentions have been focused on investigating tunable EIT-like structures based on graphene, which is usually achieved by two kinds of means: the bright-dark mode coupling [21][22][23][24] and the bright-bright mode coupling [25].…”

“…The width of graphene is set as w = 20 nm, which can only support graphene SPPs edge mode. Compared to waveguide modes, edge modes have a relatively higher effective index [18], which can make the plasmonic device more compact than that with the waveguide modes. Figure 2(a) illustrates the schematic of the proposed PIT structure investigated in this paper.…”

Attenuation, dispersion and nonlinearity effects in graphene-based waveguides

“…We considered a graphene nanoribbon located between similar dielectric layers, as will be described further. Previous reports illustrated several details regarding these waveguides [1][2][3][4][5][6][7]; however, the attenuation, dispersion and nonlinear effects were not focused on in detail.…”

Actively controlled plasmonic Bragg reflector based on a graphene parallel-plate waveguide

“…14 Comparing to the metal case, SPPs on the graphene show stronger mode confinement and lower propagation loss in the infrared region due to its large carrier mobility at room temperature. 15 More importantly, the propagation properties of graphene SPPs can be tuned by external gate voltages. It is because the surface conductivity of graphene depends on the chemical potential, which can be tuned by applying bias voltage.…”