Abstract
In recent years, peculiar physical phenomena enabled by non-Hermitian systems, especially the parity-time (PT)-symmetric systems, have drawn tremendous research interests. Particularly, special spectral degeneracies known as exceptional points (EPs) and coherent perfect absorber-laser (CPAL) points where zero and infinite large eigenvalues coexist are the most popular topics to be studied. To date, the discussions of EPs that serve as transition boundaries between broken PT-symmetry phase and exact PT-symmetry phase have been intensively presented. However, the theoretical analysis and experimental validations of CPAL points are inadequate. Different from EPs, CPAL points, as a special solution of broken PT-symmetry phase, may exhibit even further counterintuitive physical features, which may have significant implications to study non-Hermitian physics. Here, we review some recent advances of CPAL phenomena in different sub-disciplines of physics, including optics, electronics and electromagnetics, and acoustics. Additionally, we also provide an envision of future directions and applications of CPAL systems.