Abstract
This paper presents an ultracompact tunable device for power splitting and switching by tuning the Fermi energy level of monolayer patternless graphene underneath a slotted multimode interference (MMI) coupler operating in the mid-infrared, λ = 9–11 μm. By introducing a high-index silicon slot in the central region of the MMI structure, which can significantly shorten the beat length, the proposed device has an approximately 4.5-fold reduction in device length and a two-fold improvement in power transmission compared with conventional MMI couplers without slotting. The device has a footprint of only 0.30 × 0.65 μm2 (<λ/10), making it the smallest power splitter and switcher. Over the bandwidth of 2 μm, the power transmission of the proposed device is nearly uniform. Extending the operating bandwidth is limited only by the practically achievable Fermi energy of graphene. For the fabrication tolerance, the numerical results show that the relative power variations are lower than 5%, even though the dimension variations are greater than 15%. With its advantages of tunability, compact footprint, and broadband operation, the proposed device is suitable for highly dense photonic integrated circuits.
Highlights
To achieve high data transmission rates in optical networks or to build on-chip photonic integrated circuits, various optical devices, including power, wavelength, and polarization splitters, play pivotal roles in manipulating optical signals[1,2,3]
Multimode interference (MMI) couplers are waveguide structures widely used in various optical devices, including power, wavelength, and polarization splitters, switchers, and add-drop multiplexers[21,22,23,24,25,26]
Some researchers have applied the tunability of graphene to the design of multimode interference (MMI) couplers for broadband applications with fixed device dimensions operating in the mid-IR28–30
Summary
The real parts of the effective index of the first four modes of the proposed device with WMMI = 300 nm, hMMI = 50 nm, and WS = 30 nm versus the Fermi energy at wavelengths λ = 9.0 and 11.0 μm are shown, respectively. The direct imaging of the proposed structure cannot be obtained for shorter wavelength (
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
