Isolated Moiré flat bands for augmented reality and beyond

AR demands optical devices transparent to environment light but strongly scattering to specific frequencies. Ideal solutions for simultaneously achieving a large angular bandwidth and a narrow spectral bandwidth are flat photonic bands isolated in frequency space. We develop a coupled-mode model yielding a systematic theory for generating flat bands in the lowest bands of unconventional photonic moiré structures. This enables identification of optimal tradeoffs between frequency isolation and angular bandwidth, and we propose designs that offer strong scattering over more than 80 degrees of angular bandwidth and a narrow spectral bandwidth (< 20 nm in the visible), within a broad band of transparency.