Highly efficient graphene-on-gap modulator by employing the hybrid plasmonic effect

Abstract

We propose a highly efficient graphene-on-gap modulator (GOGM) by employing the hybrid plasmonic effect, whose modulation efficiency (up to 1.23 dB/μm after optimization) is ∼12-fold larger than that of the present graphene-on-silicon modulator (∼0.1 dB/μm). The proposed modulator has the advantage of a short modulation length of ∼3.6 μm, a relatively low insertion loss of ∼0.32 dB, and a larger modulation bandwidth of ∼0.48 THz. The physical insight is investigated, showing that both the slow light effect and the overlap between graphene and the mode field contribute. Moreover, an efficient taper coupler has been designed to convert the quasi-transverse electric mode of conventional silicon waveguide to the hybrid plasmonic mode of GOGM, with a high coupling efficiency of 91%. This Letter may promote the design of high-performance on-chip electro-optical modulators.

Significantly High Modulation Efficiency of Compact Graphene Modulator Based on Silicon Waveguide

“…Graphene-based devices hold great potential for enhancing the modulation efficiency with their advantages of compact footprint, low operation voltage, and ultrafast modulation speeds across broadband wavelengths. These properties of graphene have been exploited in electronic and photonic devices such as the electro-absorptive optical graphene modulator based on doped silicon waveguides 9 , 15 – 26 . An optical modulator with a graphene monolayer on a single silicon waveguide was first demonstrated in 2011 19 , and subsequently, a graphen,e modulator based on a micro-ring silicon waveguide was also exhibited, thereby demonstrating the potential of graphene integration with silicon waveguides 25 .…”

“…An optical modulator with a graphene monolayer on a single silicon waveguide was first demonstrated in 2011 19 , and subsequently, a graphen,e modulator based on a micro-ring silicon waveguide was also exhibited, thereby demonstrating the potential of graphene integration with silicon waveguides 25 . Moreover, graphene modulator employing hybrid plasmonic effect was proposed for higher efficiency and more compact size 26 . However, the abovementioned graphene modulators are only based on the electro-absorption effect of graphene; these modulators may suffer a severe degradation in the signal-to-noise ratio when applied in long-haul communications.…”

Large modulation capacity in graphene-based slot modulators by enhanced hybrid plasmonic effects

“…There are plenty of designs on the topic of graphene-based modulators including single-layer graphene 3 , 14 , bi-layer graphene 4 , 15 , four-layer graphene 7 and even eight-layer graphene 16 . All these studies reported improved ME, but the degree of improvement is quite different.…”

“…Graphene is an anisotropic material, its permittivity in the out-of-plane direction is a fixed at 2.5, while its in-plane permittivity can be expressed as: where Δ = 0.34 nm is the thickness of graphene 7 , and is the complex conductivity of graphene: where is the Fermi function, e , T, represent the electric charge, temperature and Plank constant respectively. ω is the angular frequency, Γ is the scattering rate, and μ is the chemical potential of graphene.…”

“… 3 . One possible solution we proposed before is to use the hybrid plasmonic effect in the slot waveguide to squeeze the optical field and enhance its integration with graphene 7 . However, in such design, the large portion of the mode leaks in the background.…”