Pseudo‐Hermitian Systems Constructed by Transformation Optics with Robustly Balanced Loss and Gain
Liyou Luo, Jie Luo, Hongchen Chu, Yun Lai
Abstract
Non‐Hermitian systems with parity‐time symmetry are found to exhibit real spectra of eigenvalues, indicating a balance between the loss and gain. However, such a balance is not only dependent on the magnitude of loss and gain but also easily broken due to external disturbance. Herein, a transformation‐optics approach is proposed to construct a unique class of non‐Hermitian systems with robustly balanced loss and gain, irrespective of the magnitude of loss/gain and the environmental disturbance. Through transformation‐optics operators such as space folding and stretching, loss and gain can be generated and separated in the real space. However, in the virtual space, the loss and gain are still combined to each other, rendering a balance of energy that is far more robust than other non‐Hermitian systems. This amazing feature is verified by finite‐element simulations. This work reveals a class of non‐Hermitian systems in which loss and gain are balanced robustly, thereby denoted as pseudo‐Hermitian systems.