Broadband 2 × 2 adiabatic 3  dB coupler using silicon-on-insulator sub-wavelength grating waveguides

Area of Science:

• Photonics and Waveguide Technology
• Integrated Optics
• Nanophotonics

Background:

• Sub-wavelength gratings (SWGs) offer unique optical properties for waveguide design.
• Adiabatic couplers are crucial for efficient power splitting in photonic integrated circuits.
• Silicon-on-insulator (SOI) platforms are widely used for high-performance photonic devices.

Purpose of the Study:

• To design and demonstrate a compact, broadband 2x2 adiabatic 3 dB coupler.
• To achieve efficient power splitting using SWGs in SOI waveguides.
• To characterize the performance over a broad wavelength range.

Main Methods:

• Utilized two SWG waveguides supporting two transverse electric modes.
• Employed tapered waveguide widths for adiabatic mode evolution.
• Fabricated a 50 μm long coupler on a silicon-on-insulator platform.

Main Results:

• Achieved broadband 3 dB power splitting over a 130 nm wavelength range.
• Demonstrated power splitting with an imbalance of no greater than ±0.3 dB.
• Exhibited low excess losses of less than 0.5 dB.

Conclusions:

• The developed SWG adiabatic coupler is a compact and efficient solution for broadband power splitting.
• This technology is suitable for various integrated photonic applications requiring precise power division.
• The results highlight the potential of SWGs for advanced photonic device design.