A superior coherent perfect absorber and laser constructed from the periodic ring optical waveguide network based on extremum spontaneous PT-symmetric breaking points.

In this study, we propose a superior coherent perfect absorber and laser (CPA laser) constructed from the one-dimensional (1D) two-material (TM) parity-time (PT) symmetric periodic ring optical waveguide network (PROWN). A novel method based on seeking the exact extremum spontaneous PT-symmetric breaking points is used for determining the imaginary part of the refractive indices of the materials composed of waveguides. The minimal overall output coefficient [Formula: see text] and maximal transmissivity [Formula: see text] can reach [Formula: see text] and [Formula: see text], respectively, which are 9 orders of magnitude smaller and larger than the previously reported values, respectively. It is also found that with the increment of unit cells, [Formula: see text] increases monotonically while [Formula: see text] decreases monotonically. Moreover, [Formula: see text] and [Formula: see text] are found to be varied with the periodicity of 1.866152 MHz. Our work provides a new method for optimizing CPA lasers.