Ultrafast quantum photonics enabled by coupling plasmonic nanocavities to strongly radiative antennas

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.

Intrinsic luminescence blinking from plasmonic nanojunctions

“…Here, the PL spectrum is the time average of the series shown in Fig. 1 d. This demonstrates that PL from the metal is enhanced by orders-of-magnitude due to the combined effect of large near-field coupling to the nanocavity modes and efficient far-field coupling through the antenna effect 8 .…”

“…By inserting molecules or low-dimensional materials in plasmonic nanojunctions, their intrinsic optical, electronic, and vibrational properties can be investigated with unprecedented sensitivity 2 – 4 . Furthermore, these properties can be modified by leveraging giant values of the Purcell factor 5 – 8 , optomechanical coupling rate 9 , 10 , or vacuum Rabi splitting 11 —values that typically surpass those of dielectric cavities. The generation of photo-excited charge carriers inside the metal can be enhanced by the plasmonic resonance and field enhancement, with potential applications in photo-catalysis 12 – 14 and nanoscale light sources 7 .…”

Chip‐Compatible Quantum Plasmonic Launcher

“…[10] Theoretically, the use of plasmonic structures can lead to single-photon production rates that are several orders of magnitude larger than those offered by dielectric nanostructures. [5,11] Leveraging on these ultrafast emission rates, plasmonic nanostructures could enable the on-demand production of indistinguishable photons, [12] possibly even at noncryogenic temperatures. [13][14][15] In this approach, one limitation is that plasmonic materials typically exhibit relatively high ohmic losses.…”

“…For instance, with the nanoparticleon-metal structures, [16] the plasmon outcoupling to far-field takes place on a time scale comparable to the photon loss rate. [11,17] Record-breaking performance was demonstrated with Integrated on-demand single-photon sources are critical for the implementation of photonic quantum information processing systems. To enable practical quantum photonic devices, the emission rates of solid-state quantum emitters need to be substantially enhanced and the emitted signal must be directly coupled to an on-chip circuitry.…”

“…For instance, with the nanoparticle‐on‐metal structures, [ 16 ] the plasmon outcoupling to far‐field takes place on a time scale comparable to the photon loss rate. [ 11,17 ] Record‐breaking performance was demonstrated with emitters coupled to crystalline silver nanopatch antennas, [ 18–20 ] leading to detected single‐photon rates exceeding 35 million counts per second (Mcps).…”