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 \({\Theta _{\min }}\) and maximal transmissivity \({T_{\max }}\) can reach \(3.1914\times {10^{- 16}}\) and \(1.5667\times {10^{15}}\) , 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, \({\Theta _{\min }}\) increases monotonically while \({T_{\max }}\) decreases monotonically. Moreover, \({\Theta _{\min }}\) and \({T_{\max }}\) are found to be varied with the periodicity of 1.866152 MHz. Our work provides a new method for optimizing CPA lasers.