Photonic Crystal Molecules: Towards an experimental demonstration of spontaneous symmetry breaking

We develop a key element in order to implement Photonic Crystal Molecules for a demonstration of spontaneous symmetry breaking: the coupling control. In particular, we numerically show that the mode splitting in two-evanescently coupled Photonic Crystal L3 cavities (three holes missing in the ΓK direction of the underlying triangular lattice) can be controlled through barrier engineering. The potential barrier is formed by the air-holes in between the two cavities. By changing the hole radius of the central row in the barrier up to 30%, the frequency splitting can be strongly reduced. Moreover, the sign of the splitting can be reversed in such a way that the fundamental mode can be either the symmetric or the anti-symmetric one without altering neither the cavity geometry nor the inter-cavity distance.