  Symmetry-protected zero modes in arrays of coupled optical elements have
attracted considerable attention because they are expected to be robust against
coupling disorders. In the Hermitian limit, zero modes are dark ones, i.e. the
intensity in one sublattice vanishes; yet, in a non-Hermitian counterpart, zero
modes can be bright and feature {\pi}/2 phase difference between sublattices.
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.
