Abstract
Quantum emitters coupled to plasmonic nanostructures can act as exceptionally bright sources of single photons, operating at room temperature. Plasmonic mode volumes supported by these nanostructures can be several orders of magnitude smaller than the cubic wavelength, which leads to dramatically enhanced light–matter interactions and drastically increased photon production rates. However, when increasing the light localization further, these deeply subwavelength modes may in turn hinder the fast outcoupling of photons into free space. Plasmonic hybrid nanostructures combining a highly confined cavity mode and a larger antenna mode circumvent this issue. We establish the fundamental limits for quantum emission enhancement in such systems and find that the best performance is achieved when the cavity and antenna modes differ significantly in size. We experimentally support this idea by photomodifying a nanopatch antenna deterministically assembled around a nanodiamond known to contain a single nitrogen–vacancy (NV) center. As a result, the cavity mode shrinks, further shortening the NV fluorescence lifetime and increasing the single-photon brightness. Our analytical and numerical simulation results provide intuitive insight into the operation of these emitter–cavity–antenna systems and show that this approach could lead to single-photon sources with emission rates up to hundreds of THz and efficiencies close to unity.
Highlights
Solid-state quantum emitters (QEs) are key elements of future quantum communication and information processing technologies as sources of single photons [1]
The corresponding analytical estimate for θ = 12◦ (0◦) gives a total decay rate enhancement of about 150 times (3000 times). These numbers are computed by normalizing the decay rates to those of a dipole located in a nanodiamond on glass substrate, as in the numerical simulation. It indicates that our analytical theory provides a theoretical limit for the given cavity and antenna mode volumes that is commensurate with the performance of a nanopatch antennas (NPAs)
We have systematically studied coupled systems of QEs, ultrasmall plasmonic cavities and larger nanoantennas
Summary
Solid-state quantum emitters (QEs) are key elements of future quantum communication and information processing technologies as sources of single photons [1]. This effect shortens the emitter excited state lifetime and yields a higher emitted photon rate It can be achieved in either high-Q dielectric cavities with diffraction-limited mode volumes, or in low-Q plasmonic structures with sub-diffraction mode volumes. This approach implies coupling a small volume plasmonic cavity with a larger plasmonic mode serving as a nanoantenna. We find that the maximum theoretically predicted radiative rate enhancement strongly depends on the cavity and antenna mode volumes. This enhancement factor can reach over a million times while maintaining near-unity efficiency for realistic emitter and nanostructure parameters
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