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Inverse design of deformed silicon waveguides for multimode cyclic conversion.
Optics Express
|February 20, 2026
Summary
Researchers developed ultra-compact mode cyclic converters for photonic integrated circuits using inverse design. These devices efficiently convert optical modes, advancing mode-division multiplexing capacity.
Area of Science:
- Photonics and Optical Engineering
- Integrated Optics
- Nanophotonics
Background:
- Mode-division multiplexing (MDM) is crucial for increasing the capacity of photonic integrated circuits (PICs).
- Compact and efficient mode manipulation devices are essential components for bus waveguides in MDM systems.
- Current methods for mode conversion often face limitations in size and efficiency.
Purpose of the Study:
- To present the inverse design of two ultra-compact mode cyclic converters for PICs.
- To demonstrate efficient mutual conversion between different optical modes (TE0/TE1 and TE0/TE1/TE2).
- To explore the potential of inverse design in deformed multimode silicon waveguides for advanced mode manipulation.
Main Methods:
- Utilized a combination of the finite-element method, Bernstein polynomial-based deformation parameterization, and the gradient-based method of moving asymptotes for inverse design.
- Employed a dual-stage optimization strategy for the triple-mode cyclic converter.
- Validated device performance using three-dimensional finite-difference time-domain (3D-FDTD) simulations on a silicon-on-insulator (SOI) platform.
Main Results:
- Achieved two ultra-compact mode cyclic converters with a length of only 7 µm.
- Demonstrated a dual-mode cyclic converter (DMCC) with high conversion efficiencies (-0.053 dB for TE0-to-TE1, -0.043 dB for TE1-to-TE0) and mode purity (99.3%).
- Realized a triple-mode cyclic converter (TMCC) with efficient cyclic conversion (e.g., -0.67 dB for TE0-to-TE1) and high mode purities (up to 98.3%).
- Showcased robustness to fabrication deviations of ±10 nm.
Conclusions:
- Inverse design is a powerful approach for creating efficient, ultra-compact mode cyclic converters in silicon waveguides.
- The developed DMCC and TMCC devices significantly advance the capabilities of mode manipulation for MDM in PICs.
- These findings pave the way for higher-capacity optical communication systems.
