Radiative Rate Enhancements in Ensembles of Hybrid Metal-Semiconductor Nanostructures

We report on radiative decay rate modifications of dipole emitters in the proximity of anisotropic metal nanostructures. Using time, angle, and polarization resolved photoluminescence spectroscopy, we show that resonant interactions between surface plasmons in gold nanodisks and excitons in semiconductor nanocrystals require both spectral and orientational overlap resulting in radiative rate enhancements with directional characteristics. Numerical simulations of emission decay dynamics based on local electric field enhancements are in excellent agreement with experimental results.

Figure 1

(a) Atomic force microscope image of a square array of Au disks. (b) Definition of the angle and polarizations in the extinction setup. (c) and (d), $p$- and $s$-polarized extinction maps of the Au disk array as a function of $\theta$ and wavelength. Indicated are in-plan ${\mathrm{SP}}^{\parallel }$ and out-of-plane ${\mathrm{SP}}^{\perp }$ resonances and the PL wavelength of the NCs (yellow line).

Figure 2

(a) Schematic of the angle and polarization resolved PL dynamics setup. (b) $p$- and $s$-polarized PL decay dynamics collected at 50°. (c) and (d), $p$- and $s$-polarized PL dynamics obtained at 0°, 30°, and 50° collection angles.

Figure 3

FDTD calculations based on a $p$-polarized plane wave that is incident at 50° with a wavelength that corresponds to the ${\mathrm{SP}}^{\perp }$ resonance at 50°: (a) Cross section of the field enhancement around an Au disk that is part of a square array. (b) Top view of the field enhancement at the $z$ position shown in (a). The Au disk is indicated as a circle. (c) Calculated extinction at 50° [25]. (d) Measured (red line) and modeled PL dynamics based on SP-induced radiative (solid black line) and nonradiative (dashed black line) rate change.