Morphology-induced redistribution of surface plasmon modes in two-dimensional crystalline gold platelets

The 2D optical field intensity distribution in sub-micron, ultrathin, and crystalline gold platelets is investigated by two-photon luminescence (TPL) microscopy. In particular, the evolution of the TPL maps as the particle morphology undergoes a transition from triangular to hexagonal reveals that the signatures of the high-order surface plasmon states sustained by the platelets follows the same C3v to C6v symmetry redistribution. Experimental observations are precisely accounted for by theoretical simulations based on the Green dyadic method.