Integrated dual-mode 3 dB power coupler based on tapered directional coupler

Area of Science:

• Photonics
• Integrated Optics
• Optical Communications

Background:

• Mode division multiplexing (MDM) is crucial for increasing optical communication capacity.
• Efficiently coupling multiple spatial modes is a key challenge in MDM systems.
• Silicon-on-insulator (SOI) platform offers advantages for integrated photonic devices.

Purpose of the Study:

• To propose and demonstrate a dual-mode 3 dB power coupler for MDM systems.
• To achieve a 50:50 coupling ratio for both TM0 and TM1 modes.
• To realize a compact device with low loss and low crosstalk.

Main Methods:

• Design of a tapered directional coupler with asymmetrical structure on SOI.
• Optimization of the tapered waveguide width for a short common coupling length.
• Fabrication and characterization of the dual-mode power coupler at 1550 nm wavelength.

Main Results:

• Demonstration of a dual-mode 3 dB power coupler with a 50:50 coupling ratio for TM0 and TM1 modes.
• Achieved a short common coupling length of ~15.2 μm for both modes.
• Measured insertion loss < 0.7 dB and crosstalk of -14.3 dB (TM0) and -18.1 dB (TM1).

Conclusions:

• The proposed dual-mode power coupler is effective for MDM systems.
• The device exhibits excellent performance in terms of coupling ratio, loss, and crosstalk.
• This compact SOI device is a promising component for future high-capacity optical networks.