Experimental signatures of zero modes in a non-Hermitian coupled nanocavity system

Melissa Hedir

Zero modes are symmetry protected modes in a cavity network whose energy eigenvalues have zero real part. In Hermitian systems, they may originate from the sublattice (or chiral) symmetry, implying that zero modes are dark ones and they are robust agains large frequency detuning between subtattices. In non-Hermitian systems, such as gain/loss coupled cavity arrays, zero modes result from particle-hole symmetry instead; they are no longer dark but feature π/2 phase jumps between adjacent cavities. However, in this case the detuning plays an important role which makes their observation challenging. Here we demonstrate the existence of non Hermitian zero modes in 3 coupled photonic crystal cavities via photoluminescence experiments at selected pump-spot locations.