PT-Symmetry on-a-Chip: Harnessing Optical Loss for Novel Integrated Photonic Functionality

The development of non-Hermitian parity-time (PT) symmetric quantum mechanics has offered a powerful platform to engineer novel device functionality for integrated photonics. In this chapter, we review the chip-scale applications of PT-symmetry in photonic devices, including the implementation of the unidirectional reflectionless PT metamaterial, coherent asymmetric light-light switching, and orbital angular momentum (OAM) laser on-chip. We study the optical analogy of non-Hermitian PT systems, manipulate the complex refractive index properties such as gain/loss modulation, and investigate the unique wave transport characteristics near the exceptional point (EP) to achieve these intriguing on-chip functionalities.