Compact, high-performance, and fabrication friendly two-mode division multiplexer based on a silicon bent directional...

Area of Science:

• Photonics and Optical Communications
• Integrated Optics
• Semiconductor Devices

Background:

• Increasing demands for optical communication capacity necessitate advanced multiplexing techniques.
• Mode division multiplexing (MDM) offers a promising solution for capacity enhancement.
• Existing MDM devices often face challenges in terms of size, performance, and fabrication cost.

Purpose of the Study:

• To propose a compact and high-performance silicon mode division multiplexer (MDM) for optical communication.
• To demonstrate a cost-effective fabrication process for the proposed MDM device.
• To analyze the performance characteristics, including loss, crosstalk, efficiency, and bandwidth.

Main Methods:

• Design of an asymmetric bent directional coupler with an ultrasmall coupling length.
• Utilization of single-layer silicon waveguides for CMOS-compatible fabrication.
• Three-dimensional finite-difference time-domain (FDTD) simulations to evaluate device performance.

Main Results:

• Achieved low insertion loss of 0.87 dB and low crosstalk of -21.8 dB at 1.55 µm.
• Demonstrated high mode conversion efficiency of 98.3%.
• Exhibited a broad bandwidth of 110 nm covering C and L bands with crosstalk below -10 dB.
• Confirmed fabrication tolerance for coupling gap and waveguide width variations.

Conclusions:

• The proposed silicon MDM is a compact, high-performance, and cost-effective solution for optical communication capacity enhancement.
• The device's broad bandwidth and fabrication tolerance make it suitable for practical applications.
• The single-step CMOS-compatible fabrication process simplifies manufacturing and reduces costs.