Abstract
Topological photonics have provided new insights for the manipulation of light. Analogous to electrons in topological insulators, photons travelling through the surface of a topological photonic structure or the interface of two photonic structures with different topological phases are free from backscattering caused by structural imperfections or disorder. This exotic nature of the topological edge state (TES) is truly beneficial for nanophotonic devices that suffer from structural irregularities generated during device fabrication. Although various topological states and device concepts have been demonstrated in photonic systems, lasers based on a topological photonic crystal (PhC) cavity array with a wavelength-scale modal volume have not been explored. We investigated TESs in a PhC nanocavity array in the Su–Schrieffer–Heeger model. Upon optical excitation, the topological PhC cavity array realised using an InP-based multiple-quantum-well epilayer spontaneously exhibits lasing peaks at the topological edge and bulk states. TES characteristics, including the modal robustness caused by immunity to scattering, are confirmed from the emission spectra and near-field imaging and by theoretical simulations and calculations.
Highlights
Topological insulators, an emerging field in condensed matter physics, are a fascinating research subject owing to their intriguing properties based on coexisting insulating bulk and conducting surface states[1]
Topological edge states (TESs) should significantly improve the functional robustness of resultant photonic devices owing to their intrinsic immunity against structural imperfections and irregularities, which may be created during device fabrication, making topological photonics a promising and powerful technology of the future
Corresponding photonic band structures are calculated using a unit cell composed of two adjacent resonators
Summary
Topological insulators, an emerging field in condensed matter physics, are a fascinating research subject owing to their intriguing properties based on coexisting insulating bulk and conducting surface states[1]. We implement the structure by arranging identical PhC nanocavities in the SSH dimer chain configuration within a two-dimensional (2D) PhC backbone composed of an InAsP/InP multiple-quantum-well (MQW) epilayer and demonstrate lasing action at the associated TESs (as well as bulk states).
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