Perturbation influence of a parity-time optical resonator pair

In this article, we study the perturbation influence on a parity-time (PT) optical resonator pair. Critical characteristics of this type of device, including the sensitivity, dynamic range, and robustness, are formulated and discussed systematically. Through the study of three operational phase regimes, the exceptional point (EP), the PT-symmetry, and symmetric broken phases, we find that the optimal range of the PT resonator pair prefers to be at the PT-broken phase regime near the EP state, considering both the robustness and sensitivity factors. Furthermore, we also find that the device’s dynamic range is proportional to the temporal coupling coefficient κ and gain/loss coefficient γ, which means increasing the coupling and gain/loss coefficients will enable a broader dynamic response. Additionally, we further suggest that: (1) to enhance the sensitivity, γ should be no less than 0.94κ; (2) to achieve a large gain factor of a ⩾ 2, γ must satisfy 0.995κ ⩽ γ ⩽ 1.06κ; and (3) to obtain a larger dynamic range, γ needs to be closer to κ. In particular, for γ = κ, i.e., the EP case, the largest dynamic range of ɛ ⩽ 0.24κ is obtained.