Linked Publication
What if you could simulate a photonic device in milliseconds instead of minutes or hours?
This is no longer just an idea. With our recently published design framework ROMEO (Rapid Optical Eigenmode Optimizer), we’re beginning to see what’s possible when simulation times are drastically reduced.
As photonics continues to expand into new applications, there’s growing demand for ultra-efficient, compact, and broadband photonic devices. Algorithmically optimized (or inverse-designed) structures offer a promising approach, but the physical simulations required often dominate the computational cost. To make meaningful progress, we need much faster (and still accurate) simulation techniques. That’s where ROMEO comes in.
The Path to ROMEO#
Modern AI-driven software tools can revolutionize physical simulation algorithms, enabling faster and more effective device optimization. The Eigenmode Expansion (EME) method, despite its potential for leveraging modern matrix algebra and parallel processing, has remained largely untapped for this purpose—until now.
- The Problem: While GPUs are lightning-fast at scattering matrix operations, calculating scattering elements in EME is traditionally too slow for iterative optimization workflows.
- The Solution: To tackle this, former student Mehmet Can Oktay (now at Ghent/imec) built a database of pre-computed scattering elements. This allows us to represent light scattering in arbitrary continuous geometries, like tapers, by cascading scattering matrices in parallel using PyTorch on a GPU.
Unprecedented Speed and Accuracy#
Using this framework, we demonstrated the ability to simulate arbitrary tapers in just 40 milliseconds.
In our recent publication in the Journal of Lightwave Technology, we showed ROMEO’s application to designing photonic components—including tapers, splitters, and crossings—in just seconds.
- Performance: Losses below 0.1 dB
- Bandwidth: Ultra-wideband operation (exceeding 100-200 nm)
- Verification: Confirmed by 3D-FDTD simulations and recent SiEPIC tapeouts.
Special thanks to the SiEPIC openEBL team for making the experimental verification possible!
What’s Next?#
ROMEO is just the beginning. We are looking to explore:
- Fabrication tolerance: Directly integrating lithography models (e-beam or DUV) into the optimization.
- Ultra-broadband designs: Optimizing performance over even wider wavelength ranges.
- New geometries: Extending ROMEO beyond continuous waveguide structures to free-form inverse designs.
- Active devices: Employing data-driven EME for optimizing modulator and detector geometries.
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