Nonvolatile reconfiguration of chirality via phase-change modulation of radiative interference in quasi-BIC metasurfaces

Phase-change control of chiral quasi-BIC metasurfaces has largely relied on tuning pre-established resonances. Here, we demonstrate nonvolatile reconstruction of chiral quasi-BIC states in a twisted-bilayer silicon metasurface incorporating an Sb₂S₃ interlayer. The phase transition reconstructs the radiative interference between two coherently coupled radiation channels. This enables chirality rewriting within the same TE0-like branch, with the peak circular dichroism (CD) reversing from −0.933 to +0.974. Exploiting opposite-parity vertical modes further yields fixed-wavelength helicity inversion near 1550 nm, with CD changing from −0.896 to +0.954. These results establish radiative-interference reconstruction as a route to nonvolatile helicity control beyond conventional spectral tuning.