Broadband silicon photonic directional coupler using asymmetric-waveguide based phase control.

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Semiconductor Devices

Background:

• Directional couplers are fundamental components in integrated photonic circuits.
• Achieving broadband operation and precise power splitting across different optical modes remains a challenge.
• Silicon-on-insulator (SOI) platform offers advantages for fabricating compact and efficient photonic devices.

Purpose of the Study:

• To design and demonstrate novel broadband directional couplers.
• To achieve various power splitting ratios (10/90 to 50/50) for both TE and TM modes.
• To explore the use of asymmetric-waveguide based phase control sections for enhanced performance.

Main Methods:

• Utilized asymmetric-waveguide structures for phase control.
• Fabricated devices on the silicon-on-insulator (SOI) platform.
• Characterized coupler performance for both transverse electric (TE) and transverse magnetic (TM) modes.

Main Results:

• Demonstrated broadband directional couplers with bandwidths exceeding 75 nm, some over 100 nm.
• Achieved precise power splitting ratios including 10%/90%, 20%/80%, 30%/70%, 40%/60%, and 50%/50%.
• Realized compact footprints: ≤ 32 μm × 1.3 μm for TE mode and ≤ 13 μm × 1.3 μm for TM mode.

Conclusions:

• Asymmetric-waveguide phase control enables broadband operation in directional couplers.
• The demonstrated devices are suitable for various integrated photonic applications requiring precise mode control and wide bandwidths.
• The compact size and high performance of these couplers make them attractive for advanced photonic circuits on the SOI platform.