Fig. 3.

Experimental demonstration of selective far-field excitation and detection with both Q1 and Q2 in the nanosystem. a Excitation enhancement spectra for Q1 (solid data points; in order to measure for Q1, Q1 is selectively detected) and Q2 (hollowed data points; in order to measure for Q2, Q2 is selectively detected) when excited with elliptical polarizations for optimal selective excitation of Q1 (blue data points; elliptical polarization e1) or Q2 (red data points; elliptical polarization e2) at 740 nm wavelength. Solid (dashed) curves are simulated excitation enhancement spectra for Q1 (Q2). b Polar plot of the emission polarization measurement when Q1 (blue solid data points) is selectively excited (using elliptical polarization e1) or when Q2 (red hollowed data points) is selectively excited (using elliptical polarization e2). The solid and dashed curves are simulated results. c Same as a but with excitation polarizations optimized at 760 nm wavelength. d Excitation enhancement factor at 740 nm wavelength as a function of $\phi$ (at two fixed $\theta$ values). Solid data points (experiment) and solid curves (simulation) are for Q1, while hollowed data points (experiment) and dashed curves (simulation) are for Q2. e Excitation ratio at 740 nm wavelength as a function of $\phi$ (at two fixed $\theta$ values). Solid data points (experiment) and solid curves (simulation) are the excitation ratio ${\sigma }_{\mathrm{Q}1}\mathrm{∕}{\sigma }_{\mathrm{Q}2}$, while hollowed data points (experiment) and dashed curves (simulation) are the excitation ratio ${\sigma }_{\mathrm{Q}2}\mathrm{∕}{\sigma }_{\mathrm{Q}1}$. The blue (red) circles in d and e indicate the polarizations for optimal selective excitation of Q1 (Q2) shown in a. The yellow-green circles indicate the polarization e3 (inset at the left of d) to equally excite Q1 and Q2