Figure 3: Measuring the electric and magnetic local density of states with ED and MD transitions.

(a) Schematic illustrating self-interference effects for ED and MD emission near an air–mica interface. The dashed lines indicate the light reflected by the interface. Owing to different field symmetries, the resulting interference is opposite for ED and MD emitters. (b) Experimental s-polarized BFP spectra showing interference fringes characteristic of standing waves formed by the reflection from the interface. (c) Longer-acquisition BFP spectra highlighting the difference between the emissions for the ED transition centred at 580.8 nm and the MD centred at 582.2 nm. (d) S-polarized momentum cross-sections visualizing the symmetry difference between predominantly ED emission at 580.9 nm (blue line) and predominantly MD emission at 581.3 nm (red line). (e) S-polarized relative electric LDOS, (blue), and relative magnetic LDOS, (red). Solid lines show experimental relative LDOS values obtained by fitting the observed counts near 581.1 nm (±0.5 nm), as described in the Supplementary Methods. The shaded regions indicate the 95% confidence intervals for the fits. The dotted and dashed lines show the theoretical LDOS values for two related three-layer systems: air/Eu³⁺:Y₂O₃/glass (dotted lines) and oil/Eu³⁺:Y₂O₃/glass (dashed lines). To allow for direct comparison, the theoretical results were scaled by a constant factor.