This repository provides a set of scripts to perform the singular value decomposition of the effective T-matrix and the S-matrix of various structures. In particular, they can be used to investigate bound states in the continuum in metasurface-based systems. The following systems are covered:

• Periodic metasurface of dielectric spheres
• Periodic metasurface on a substrate
• Finite array
• Double-layer metasurface of dielectric rods

To use these codes, you have to install treams

pip install treams

For acoustic systems, also install acoustotreams

pip install acoustotreams

When using this code please cite:

N. Ustimenko, I. Fernandez-Corbaton, and C. Rockstuhl, Singular value decomposition to describe bound states in the continuum in periodic metasurfaces, Phys. Rev. B 113, 235418 (2026).