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 K 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.