Single-mode condition for a rib waveguide on the SOI platform: a revisit with new perspective

Area of Science:

• Integrated photonics
• Waveguide design
• Optical engineering

Background:

• Rib waveguides are fundamental in integrated photonics due to low loss and controllability.
• Achieving single-mode operation in large cross-section rib waveguides is a key challenge.
• Existing methods may lack precision for specific structural configurations.

Purpose of the Study:

• To revisit and analyze single-mode conditions in rib waveguides.
• To establish accurate empirical single-mode conditions for silicon-on-insulator (SOI) rib waveguides.
• To provide guidelines for designing reliable silicon photonic integrated circuits.

Main Methods:

• Utilized an insightful mode-matching method for analysis.
• Derived theoretically exact single-mode conditions.
• Established empirical single-mode conditions for various cross-sections.

Main Results:

• Developed a true single-mode condition (HE₁₁ exclusive) and a quasi-single-mode condition (HE₁₁ and EH₁₁).
• Empirical conditions demonstrated high accuracy for SOI rib waveguides.
• Verified findings using both silicon (Si) and silicon nitride waveguides.

Conclusions:

• The established single-mode conditions are vital for advanced integrated photonics.
• These conditions facilitate the creation of high-density, low-loss, and reliable photonic circuits.
• The findings contribute to the optimization of waveguide design in silicon photonics.