Enhancing Coherent Light-Matter Interactions through Microcavity-Engineered Plasmonic Resonances

Quantum manipulation is challenging in localized-surface plasmon resonances (LSPRs) due to strong dissipations. To enhance quantum coherence, here we propose to engineer the electromagnetic environment of LSPRs by placing metallic nanoparticles (MNPs) in optical microcavities. An analytical quantum model is first built to describe the LSPR-microcavity interaction, revealing the significantly enhanced coherent radiation and the reduced incoherent dissipation. Furthermore, when a quantum emitter interacts with the LSPRs in the cavity-engineered environment, its quantum yield is enhanced over 40 times and the radiative power over one order of magnitude, compared to those in the vacuum environment. Importantly, the cavity-engineered MNP-emitter system can enter the strong coupling regime of cavity quantum electrodynamics, providing a promising platform for the study of quantum plasmonics, quantum information processing, precise sensing, and spectroscopy.

Figure 1

(a) A quantum emitter coupled to a MNP in a microcavity-engineered electromagnetic environment. (b) Schematic of the interaction in the system. The cavity results in a peak in vacuum density of state, marked by the red region. (c) Power outputs in logarithmic scale of the LSPR to each channel versus the pump-cavity detuning ${\mathrm{\Delta }}_{p,c}={\omega }_p-{\omega }_c$: radiation with cavity ${\varphi }_r$ (red solid curve), radiation without cavity ${\varphi }_{r,0}$ (red dashed curve), absorption with cavity ${\varphi }_d$ (black dots), and absorption without cavity ${\varphi }_{d,0}$ (black dash-dotted curve).

Figure 2

(a) Quantum yield (left axis) and normalized dipolar mode absorption (right axis) versus the pump-cavity detuning ${\mathrm{\Delta }}_{p,c}$. The black solid curve (dashed line) plots quantum yield $\eta$ (${\eta }_0$) with (without) the cavity. (b) Enhancement factor of quantum yield $\eta /{\eta }_0$ versus the distance $D$ and the cavity $Q$ factor. (c) Radiative power spectrum with the cavity ${\mathrm{\Phi }}_r$ (red solid curve) and without the cavity ${\mathrm{\Phi }}_{r,0}$ (black dashed curve). (d) Enhancement factor of radiative power ${\mathrm{\Phi }}_r/{\mathrm{\Phi }}_{r,0}$ versus the distance $D$ and the cavity $Q$ factor. In (a) to (d), the parameters are $\{J,G,{\gamma }_s,{\gamma }_m\}=\{-144,-7200,3,83\}\mu \mathrm{eV}$; the cavity, emitter, and dipolar LSPR are on resonance, i.e., ${\omega }_c={\omega }_e={\omega }_1$. In (b) and (d), ${\mathrm{\Delta }}_{p,c}={\mathrm{\Delta }}_0$.

Figure 3

(a) Temporal evolution of the population $⟨{\widehat{\sigma }}_{+}(t){\widehat{\sigma }}_{-}(t)⟩$ on the emitter for $Q={10}^5$ (red solid curve), $Q={10}^4$ (blue dash-dotted curve), $Q={10}^3$ (green dots), and without the cavity (black dashed curve). (b) Radiation power of the emitter with respect to the pump-emitter detuning ${\mathrm{\Delta }}_{p,e}={\omega }_p-{\omega }_e$ for $Q={10}^4$ (red solid curve) and without the cavity (black dashed curve). In (a) and (b), included angle $\theta =60°$, the emitter-MNP distance $D=5\mathrm{nm}$, cavity mode volume is $0.1{\mu \mathrm{m}}^3$, plasmonic mode volume is $400{\mathrm{nm}}^3$, detunings ${\omega }_1-{\omega }_e=0.6\mathrm{eV}$ and ${\omega }_c-{\omega }_e=1.5\mathrm{meV}$.

Figure 4

(a) Emission spectra (in logarithmic scale) of the emitter for various ${\mathrm{\Delta }}_{e,c}$. From bottom to top, ${\mathrm{\Delta }}_{e,c}$ increases from $-10\mathrm{meV}$ to 10 meV with a 2 meV step. (b) Detunings and (c) linewidths of the two eigenmodes formed in the strongly coupled cavity-engineered plasmonic mode and the emitter. Parameters are the same as in Fig. 3.