Systematic design of loss-engineered slow-light waveguides.

Area of Science:

• Photonics and Optical Engineering
• Materials Science and Engineering
• Computational Electromagnetics

Background:

• Slow-light waveguides are crucial for optical signal processing and buffering.
• Existing designs often face trade-offs between slow light (high group index) and bandwidth, or suffer from high propagation losses.
• Topology optimization offers a powerful approach for designing complex optical structures with tailored properties.

Purpose of the Study:

• To systematically design free-topology slow-light waveguides with an enlarged group index bandwidth product (GBP).
• To implement loss engineering techniques to minimize propagation losses in these waveguides.
• To compare the performance of free-topology designs against traditional fixed-topology approaches.

Main Methods:

• Utilized topology optimization to achieve free-form waveguide geometries.
• Employed complex band structure calculations to evaluate propagation losses, incorporating effective dissipation for manufacturing imperfections.
• Implemented loss engineering by minimizing the imaginary part of eigenvalues corresponding to guided modes.

Main Results:

• Demonstrated significant suppression of propagation losses in free-topology dispersion-engineered waveguides through loss engineering.
• Showcased that free-topology loss-engineered waveguides achieve a substantially enhanced GBP compared to fixed-topology designs.
• Observed only a marginal increase in propagation losses for free-topology designs with significantly improved GBP.

Conclusions:

• Free-topology optimization combined with loss engineering is an effective strategy for designing high-performance slow-light waveguides.
• The proposed method enables simultaneous enhancement of GBP and reduction of propagation losses.
• This approach offers a pathway to overcome limitations in current slow-light waveguide technologies.