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Abstract
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Using bus waveguides coupled to the graphene-loaded Si-ring resonators(GSRRs) all on a Si-oninsulator substrate, we propose a compact bidirectional switchable beam splitter/filter controlled by
graphene-based electro-absorptive (refractive) mode modulation. The design is suitable for dense
wavelength division multiplexing (DWDM), according to International Telecommunication Union
(ITU)standard. The proposed device consists of a through waveguide coupled to two drop waveguides
via two GSRRs. Each GSRR consists of a stack of hBN/graphene/hBN nanolayers sandwiched
between two Si-ring resonators. Using a finite difference time domain method, we have tuned the
resonant wavelengths of GSRRs in the range of 1551.5 < λ < 1552.1 nm, linearly with the slope of
∼2.46 nm eV−1 via appropriately changing the graphene chemical potential, electrostatically. The
numerical results show that when both GSRRs are in an electro-refractive state and a transverse
electric (TE) polarized light beam of an appropriate wavelength is launched into one of the thoughports, ∼ 84.5% of the input intensity equally splits between the adjacent drop-ports. The transmission
out of the second through-port is less than 0.8%. The numerical results further show that when one
GSRR is in an electro-refractive mode, and the other one is in an electro-absorptive state,∼68.4% of
the input intensity transmits out of the drop-port adjacent to the former GSRR, and the other ports
experience insignificant outputs(<0.7%). The device’s structural symmetry makes it a bidirectional
tunable, suitable for long-haul optical telecommunication applications. Finally, we investigated the
fabrication tolerances in the designed parameters.
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