In non-Hermitian systems, the singularities refer to poles or zeros of the scattering and transfer matrices. Here, we investigate the kinds of singularities in a non-parity-time-symmetric multilayer structure which mainly consists of double layers of silver grating and one layer of phase-change material Ge2Sb2Te5 (GST). When the GST is in its crystalline phase, a unidirectional zero-reflection singularity, i.e., exceptional point (EP) is achieved with the aid of Fano resonance. Interestingly, a coherent perfect absorber (CPA)-laser singularity adjacent to the EP is observed in the Fano peak. M...
