Numerical simulations of tunable ultrashort power splitters based on slotted multimode interference couplers

Area of Science:

• Photonics
• Optoelectronics
• Materials Science

Background:

• Multimode interference (MMI) couplers are essential components in photonic integrated circuits.
• Conventional MMI couplers face limitations in size and tunability.
• Graphene's unique electronic properties offer potential for tunable photonic devices.

Purpose of the Study:

• To present an ultracompact tunable device for power splitting and switching.
• To leverage graphene's tunable Fermi energy level in a slotted MMI coupler.
• To achieve miniaturization and enhanced performance in the mid-infrared spectrum.

Main Methods:

• Integration of a slotted silicon structure within an MMI coupler.
• Utilizing monolayer patternless graphene to tune device characteristics.
• Operating in the mid-infrared wavelength range (9-11 μm).

Main Results:

• Achieved a 4.5-fold reduction in device length compared to conventional MMI couplers.
• Demonstrated a two-fold improvement in power transmission.
• Device footprint is ultra-compact (0.30 × 0.65 μm²), smaller than λ/10.
• Exhibited nearly uniform power transmission over a 2 μm bandwidth.
• Showed high fabrication tolerance with <5% power variation for >15% dimension variations.

Conclusions:

• The proposed device is the smallest power splitter and switcher to date.
• Its tunability, compact size, and broadband operation make it ideal for dense photonic integrated circuits.
• The device performance is primarily limited by achievable Fermi energy levels in graphene.