Non-Hermitian physics and engineering in silicon photonics

Silicon photonics has been studied as an integratable optical platform where numerous applicable devices and systems are created based on modern physics and state-of-the-art nanotechnologies. The implementation of quantum mechanics has been the driving force of the most intriguing design of photonic structures, since the optical systems are found of great capability and potential in realizing the analogues of quantum concepts and phenomena. Non-Hermitian physics, which breaks the conventional scope of quantum mechanics based on Hermitian Hamiltonian, has been widely explored in the platform of silicon photonics, with promising design of optical refractive index, modal coupling and gain-loss distribution. As we will discuss in this chapter, the unconventional properties of exceptional points and parity-time symmetry realized in silicon photonics have created new opportunities for ultrasensitive sensors, laser engineering, control of light propagation, topological mode conversion, etc. The marriage between the quantum non-Hermiticity and classical silicon platforms not only spurs numerous studies on the fundamental physics, but also enriches the potential functionalities of the integrated photonic systems.