Unidirectional Perfect Reflection and Radiation in Double-Lattice Photonic Crystals

Non-Hermitian photonics, in which energy is not conserved, has attracted growing interest lately due to its potential for realizing innovative optical functionalities. Devices in this paradigm typically utilize material-absorption loss, though, which inevitably reduces efficiency. To overcome this issue, this study demonstrates a non-Hermitian waveguide based solely on vertical radiation from a photonic crystal. This device exhibits perfect transmission when light comes from one side, yet perfect reflection from the opposite side, and offers further degrees of freedom in photonics design to accelerate real-world applications.