Subwavelength grating based mode (de)multiplexer for 3D photonic integrated circuits

Area of Science:

• Photonics
• Integrated Optics
• Nanophotonics

Background:

• Three-dimensional (3D) photonic integrated circuits (PICs) require efficient mode (de)multiplexers.
• Existing devices often face limitations in bandwidth, size, or fabrication complexity.

Purpose of the Study:

• To propose and optimize a broadband 3D mode (de)multiplexer based on subwavelength gratings (SWGs).
• To enhance coupling strength and operating bandwidth for 3D PICs.

Main Methods:

• Utilized subwavelength grating (SWG) waveguides arranged in a 3D configuration across two vertical layers.
• Employed a 3D full-vectorial finite difference time domain (FDTD) method for device optimization.
• Investigated the impact of SWG structure and bus-access offset on performance.

Main Results:

• Achieved 1-dB bandwidths exceeding 300 nm (TE0), 107 nm (TE1), and 128 nm (TE2).
• Demonstrated compact device dimensions with short coupling lengths of 5.0 µm (TE1) and 1.75 µm (TE2).
• Reported low insertion losses of 0.12 dB (TE0), 0.27 dB (TE1), and 0.29 dB (TE2).

Conclusions:

• The proposed SWG-based 3D mode (de)multiplexer offers broadband operation with high performance.
• The design exhibits excellent coupling efficiency, low loss, and compact footprint.
• The device demonstrates robustness against fabrication variations, making it suitable for practical 3D PICs.