We propose a class of spectral singularities emerging from the coincidence of two independent singularities with highly directional responses. These spectral singularities result from resonance trapping induced by the interplay between parity-time symmetry and Fano resonances. At these singularities, while the system is reciprocal in terms of a finite transmission, a simultaneous infinite reflection from one side and zero reflection from the opposite side can be realized.
Hamidreza Ramezani, et. al., (2014) Unidirectional spectral singularities.Physical Review Letters113:26. DOI: http://doi.org/10.1103/PhysRevLett.113.263905
Physical Review Letters