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Abstract
Plasmonic Bragg reflectors based on graphene with multiple channeled phenomena are proposed and investigated numerically. As a mid-infrared waveguide, the monolayer graphene exhibits locally variable optical properties through the modulation of electric fields. The periodical change of the effective refractive index (ERI) on graphene can be determined by applying external gate voltage. When we introduce an unmatched configuration or gate voltage, periodicity is disrupted, and a defect resonance mode is generated. At this point, the structure can be regard as a Fabry-Perot cavity. Accordingly, multiple-channel effects can be achieved by introducing cascaded multiple defects or including double symmetrical Fabry-Perot structures. This design shows applications potential in the graphene-based optoelectronic devices, particularly in the development of low-cost hyperspectral imaging sensors in mid-infrared region.
Highlights
Surface plasmons polaritons (SPPs) are considered as energy and information carriers because of their excellent properties of overcoming the classical diffraction limit as well as confining and propagating electromagnetic energy at a sub-wavelength scale with the development of nanotechnology,[1,2] which allows miniaturization of optical devices.[3,4,5] Among the structures based on SPPs, the metal-insulator-metal (MIM) structure has been investigated extensively in design of plasmonic Bragg reflectors (PBRs)
We propose a PBR structure composing a graphene layer and silicon grating that are separated by a silica layer, and we numerically study its performance
External gate voltages can be applied to tune the surface conductivity of graphene, and the periodical change of the effective refractive index (ERI) can be obtained to form Bragg structures
Summary
Surface plasmons polaritons (SPPs) are considered as energy and information carriers because of their excellent properties of overcoming the classical diffraction limit as well as confining and propagating electromagnetic energy at a sub-wavelength scale with the development of nanotechnology,[1,2] which allows miniaturization of optical devices.[3,4,5] Among the structures based on SPPs, the metal-insulator-metal (MIM) structure has been investigated extensively in design of plasmonic Bragg reflectors (PBRs). Periodic changes in the dielectric materials of the MIM waveguides have been proposed to design effective filtering around the Bragg frequency,[6] Thick-modulated and index-modulated Bragg reflectors for widening the stopband have been reported;[7] metalembedded MIM structures have been studied to improve the performance of conventional step profile MIM PBRs.[8] difficult tunability, significant Ohmic losses, high costs, and low transmission efficiency restrict the extensive practical application of these devices. We propose a PBR structure composing a graphene layer and silicon grating that are separated by a silica layer, and we numerically study its performance. External gate voltages can be applied to tune the surface conductivity of graphene, and the periodical change of the effective refractive index (ERI) can be obtained to form Bragg structures. We believe that our proposal can pave the way for new avenues in actively designing tunable modulators
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