Photonic crystal-based compact hybrid WDM/MDM (De)multiplexer for SOI platforms

Area of Science:

• Photonics
• Optical Communications
• Nanotechnology

Background:

• Wavelength-division multiplexing (WDM) and mode-division multiplexing (MDM) are key technologies for increasing optical fiber communication capacity.
• Integrating WDM and MDM functionalities into a single compact device is crucial for advanced optical networks.
• Photonic crystals offer unique properties for designing compact and efficient optical devices.

Purpose of the Study:

• To propose and evaluate a novel compact hybrid wavelength- and mode-division (de)multiplexer (MDM).
• To demonstrate the multiplexing of two eigenmodes (TM0 and TM1) and two wavelengths (1550 nm and 1300 nm) within a single device.
• To assess the performance of the proposed device in terms of insertion loss and crosstalk for potential on-chip integration.

Main Methods:

• Design of a hybrid WDM/MDM device using 2D photonic crystals with a square lattice and Silicon (Si) rods.
• Implementation of wavelength multiplexing using two identical multimode interference couplers.
• Implementation of mode-division multiplexing using an asymmetric directional coupler and tapers to prevent back-reflections.

Main Results:

• The proposed device achieves a compact footprint of 29 μm × 12 μm, suitable for on-chip integration.
• Simulation results show insertion losses below -1.0927 dB for all four channels.
• Crosstalk levels are demonstrated to be below -11.9024 dB for all four channels, indicating high signal isolation.

Conclusions:

• A compact and efficient hybrid wavelength- and mode-division (de)multiplexer has been successfully designed and simulated.
• The device leverages 2D photonic crystals and standard integrated optics components for multiplexing multiple wavelengths and modes.
• The achieved performance metrics (low loss, low crosstalk, compact size) make this device a promising candidate for future high-capacity optical communication systems.