Study of the momentum-resolved plasmonic field energy of Bloch-like surface plasmon polaritons from periodic nanohole array.

Abstract

The angular surface plasmon mediated fluorescence from a two-dimensional Au nanohole array has been studied by reflectivity spectroscopy and Fourier-space photoluminescence microscopy. By using the rate equation model and temporal coupled mode theory, we determine the momentum-dependent coupling rate of light emitters to (-1,0) Bloch-like surface plasmon polaritons (SPPs) in the first Brillouin zone. The rate increases gradually when the SPPs propagate away from the Γ-X direction and split into two at the Γ-M point where two coupled modes are formed. In addition, both the spectral density-of-states (SDOS) and the plasmonic field energy are found to govern the momentum dependence. We also examine the behavior of the field energy as a function of the SPP propagation direction and it agrees well with the finite-difference time-domain simulations, showing the energy plays a major role in controlling the angular emission intensity. Our results devise a new method in studying the momentum-dependent plasmonic field energy and they are expected to provide insight in directional emission from periodic arrays.