Non-Hermitian zero-mode laser in a nanophotonic trimer

Non-Hermitian zero modes in arrays of coupled optical elements can be tailored to feature a number of interesting properties. In addition to being immune to coupling disorders and remaining pinned at the center of the spectrum, they are not dark modes in general (light intensity does not necessarily vanish in one sublattice), their energy eigenvalues are not restricted to the center of the complex plane, and they can be brought to laser oscillation by carefully patterning the spatial pump profile. In this work, we report on the direct observation of a lasing zero mode in a non-Hermitian three-coupled nanocavity array. We show efficient excitation for nearly equal pump power in the two extreme cavities. Furthermore, its efficiency can be dynamically controlled by pumping the center cavity. The realization of zero-mode lasing in large arrays of coupled nanolasers has potential applications in laser-mode engineering and it opens up promising avenues in optical computing.