Nanoparticle-on-mirror plasmonic
nanocavities, capable of extreme
optical confinement and enhancement, have triggered state-of-the-art
progress in nanophotonics and development of applications in enhanced
spectroscopies. However, the optical quality factor and thus performance
of these nanoconstructs are undermined by the granular polycrystalline
metal films (especially when they are optically thin) used as a mirror.
Here, we report an atomically smooth single-crystalline platform for
low-loss nanocavities using chemically synthesized gold microflakes
as a mirror. Nanocavities constructed using gold nanorods on such
microflakes exhibit a rich structure of plasmonic modes, which are
highly sensitive to the thickness of optically thin (down to ∼15
nm) microflakes. The microflakes endow nanocavities with significantly
improved quality factor (∼2 times) and scattering intensity
(∼3 times) compared with their counterparts based on deposited
films. The developed low-loss nanocavities further allow for the integration
with a mature platform of fiber optics, opening opportunities for
realizing nanocavity-based miniaturized photonic devices for practical
applications.
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