Reflective receiver protectors with non-Hermitian CT-symmetric spectral protection of nonlinear defect modes

Reciever protectors (RP) shield sensitive electronics from high-power electromagnetic signals that might damage them. Typical RP schemes range from simple fusing and PIN diodes to superconducting circuits and plasma cells -- each having a variety of drawbacks ranging from unacceptable system downtime and self-destruction to significant insertion losses and power consumption. We introduce a class of non-Hermitian photonic receiver protectors that are self-protected from overheating effects induced via high-level incident electromagnetic radiation, due to a self-regulating impedance mismatching mechanism that turns them into near-perfect reflectors. At low-power incident signals, these receiver protectors demonstrate high transmittance via a nonlinear defect mode. In this limit, they also demonstrate a high tolerance to fabrication imperfections due to topological protection, imposed via a charge-conjugation symmetry.