Robust lasing from locally embedded non-Hermitian defects

A hallmark of topological physics has been allowing for wave propagation control and confinement in disordered media. A wide range of approaches have been developed to acquire robust lasing states in non-Hermitian systems, emerging from the existence of an exceptional point (EP) which induces topological phase transition. However, the key challenge in creating these states remains in the demand for high external pump power and addition of balanced loss in the system. By introducing a coupling defect in a lattice made of microring resonators with trivial topology, we observe robust lasing modes that are not necessarily localized at the edge of the lattice. Our theoretical and experimental work circumvents requirements for generation of topological laser modes and pave the way to go beyond edge mode lasing.