Broadband subwavelength optical resonators have the ability to enhance the spontaneous emission rate and brightness of solid-state emitters. Recently, high-index dielectrics have been proposed as an alternative to plasmonic materials to design optical resonators with low ohmic losses. In this study, the interaction between a silicon nanoantenna and solid-state emitters is characterized by tuning the position of a 100 nm diameter fluorescent sphere in the vicinity of an e-beam fabricated silicon disk using scanning-probe microscopy. If the nanodisk resonance matches the emission wavelength of the fluorescent molecules, we observe enhanced decay rates at short distances; while, for an out-of-resonance antenna, the fluorescence lifetime is locally increased. Furthermore, our experiments highlight the ability of silicon antennas to increase far-field collection efficiencies, in agreement with numerical simulations (D. Bouchet et al, Phys. Rev. Applied 6, 064016 (2016)).
The intensity of spontaneous emission from fluorescent dye molecules can be further enhanced, by more than two orders of magnitude, in the nanoscale gap between silicon nanodisks. This is evidenced at the single molecule level using fluorescence correlation spectroscopy with freely diffusing emitters (R. Regmi et al, Nano Lett. 16, 5143 (2016)).
These results demonstrate the potential of silicon antennas for the manipulation of solid-state emitters at the nanoscale and at room temperature.
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