Achieving exact balance between spatially separated gain and loss is generally regarded as a necessary condition for parity-time- (PT-)symmetric optical systems. We introduce generalized PT- (GPT-)symmetric optical structures, which have an asymmetric and unbalanced gain-loss profile, while exhibiting similar scattering properties and phase transitions as their traditional PT-symmetric counterparts. In particular, we show that the concept of GPT symmetry may help to reduce the threshold gain in achieving newly discovered PT-enabled applications, such as the coherent perfect absorber laser and exceptional points. The concept proposed herein will facilitate the practice of PT-symmetric optical and photonic devices by offering greater design flexibility to tailor gain-loss profiles and their thresholds.
Bibliographical noteFunding Information:
P.-Y. C. would like to thank NSF ECCS-1711409 Grant. H.B. would like to thank KAUST CRG-2953 Grant for supporting the research reported in this publication.
© 2018 American Physical Society.
ASJC Scopus subject areas
- Physics and Astronomy(all)