Realization of Bound States in the Continuum in Anti-PT-Symmetric Optical Systems: A Proposal and Analysis

Novel physical concepts that originate from quantum mechanics, such as non-Hermitian systems (dealing mostly with PT and anti-PT symmetry) and bound states in the continuum (BICs), have attracted great interest in the optics and photonics community. To date, BICs and anti-PT symmetry seem to be two independent topics. Here, a parallel cascaded-resonator system is proposed for the first time to achieve BICs and anti-PT symmetry simultaneously. It is found that the requirements for the Fabry-Perot BIC and anti-PT symmetry can both be satisfied when the phase shift between any two adjacent resonators is an integer multiple of pi. The cascaded-resonator systems consisting of different numbers of resonators are further analyzed and their robustness to fabrication imperfections is demonstrated. The proposed structure can readily be realized on an integrated photonic platform, and can enable many applications that benefit from the advantages of both BICs and anti-PT symmetry, such as optical delay and storage, all-optical nonlinear processing, high-sensitivity sensing, and chiral mode switching.

Automated summary

Novel physical concepts originating from quantum mechanics, such as non-Hermitian systems and bound states in the continuum, have attracted significant interest in the optics and photonics community. In this study, a parallel cascaded-resonator system is proposed for the first time to achieve both bound states in the continuum and anti-PT symmetry simultaneously. The requirements for Fabry-Perot bound states in the continuum and anti-PT symmetry can be met by adjusting the phase shift between adjacent resonators. The proposed structure can be implemented on an integrated photonic platform and has potential applications in various fields such as optical delay and storage, nonlinear processing, sensing, and mode switching.