Determination of the excitation rate of quantum dots mediated by momentum-resolved Bloch-like surface plasmon polaritons.

Abstract

When light emitters are being placed in close proximity to a plasmonic system, not only the emission but also the excitation can be strongly enhanced and both yield the surface plasmon polariton (SPP) mediated fluorescence enhancement. Here, we combine the rate equation model and coupled mode theory to formulate the excitation rate of light emitters located on a periodic metallic array. The rate is expressed in terms of quantities that can be measured by angle- and polarization-resolved reflectivity and photoluminescence spectroscopy. As a demonstration, we have studied the excitation rate of CdSeTe quantum dots deposited on a 2D Au nanohole array as a function of the propagation direction of the (-1,0) Bloch-like SPPs. At the excitation wavelength of 633 nm, we find the rate remains almost constant at ~44 ps-1 regardless of the propagation direction of SPPs, which move from the Γ-X towards the Γ-M direction in the first Brillouin zone, and the crossing of the (-1,0) and (0,-1) SPPs along the Γ-M direction where two bright and dark modes are formed. The results are supported by the finite-difference time-domain simulations. We conclude the excitation rate is an intrinsic parameter and the enhanced excitation of the quantum dots arises entirely from field enhancement.