Optimal interfacing with coupled-cavities slow-light waveguides: mimicking periodic structures with a compact device

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Waveguide Technology

Background:

• Slow-light structures, particularly coupled cavities, are crucial for advanced optical signal processing.
• Efficient interfacing (input/output coupling) remains a significant challenge, limiting device performance.
• Impedance mismatch at the edges of slow-light waveguides causes signal reflections and loss.

Purpose of the Study:

• To design and analyze optimal input/output (I/O) couplers for coupled cavity slow-light structures.
• To achieve high I/O coupling efficiency and minimize reflections.
• To investigate the impact of coupler design parameters and fabrication imperfections.

Main Methods:

• Designing I/O couplers by adding auxiliary cavities with tailored coupling coefficients.
• Utilizing impedance matching principles to align the slow-light waveguide with I/O waveguides.
• Simulating and analyzing coupling efficiency, bandwidth, and reflection suppression.

Main Results:

• Achieved I/O coupling efficiencies exceeding 99.9%.
• Demonstrated a bandwidth larger than 50% of the slow-light waveguide's bandwidth.
• Practically eliminated reflections at the edges of the slow-light structure.
• Analyzed the slow-light structure as a super-cavity and the effect of coupler design variations.

Conclusions:

• The proposed I/O coupler design enables highly efficient interfacing with slow-light structures.
• The method effectively suppresses reflections, enhancing overall device performance.
• The design is robust against errors and disorder in the coupling sections, paving the way for practical applications.