Experimental observation of leaky modes and plasmons in a hybrid resonance element

We provide experimental evidence of a hybrid photonic device supporting simultaneously surface-plasmon polaritons and resonant leaky modes. A fabricated metallo-dielectric structure exhibits a pronounced plasmonic resonance at 799 nm wavelength and a modal resonance at 669 nm in transverse magnetic polarization. In transverse electric polarization, a weak modal resonance appears at 725 nm wavelength. We identify the corresponding modes by computing the attendant internal field distributions. Numerically computed spectra are in good agreement with our measurements. Since traditional modal and plasmonic devices find many uses, their hybrid versions may enable the extension of their applicability.