Collective Strong Light-Matter Coupling in Hierarchical Microcavity-Plasmon-Exciton Systems

Abstract

Polaritons are compositional light-matter quasiparticles that arise as a result of strong coupling between a vacuum field of a resonant optical cavity and electronic excitations in quantum emitters. Reaching such a regime is often hard, as it requires materials possessing high oscillator strengths to interact with the relevant optical mode. Twodimensional transition metal dichalcogenides (TMDs) have recently emerged as promising candidates for realization of the strong coupling regime at room temperature. However, these materials typically provide coupling strengths in the range of 10-40 meV, which may be insufficient for reaching strong coupling with low quality factor resonators. Here, we demonstrate a universal scheme that allows a straightforward realization of strong and ultra-strong coupling regime with 2D materials and beyond. By intermixing plasmonic excitations in nanoparticle arrays with excitons in a WS2 monolayer inside a resonant metallic microcavity, we fabricate a hierarchical system with the combined Rabi splitting exceeding 500 meV at room temperature. Photoluminescence measurements of the coupled systems show dominant emission from the lower polariton branch, indicating the participation of excitons in the coupling process. Strong coupling has been recently suggested to affect numerous optical-and material-related properties including chemical reactivity, exciton transport and optical nonlinearities. With the universal scheme presented here, strong coupling across a wide spectral range is within easy reach and therefore exploring these exciting phenomena can be further pursued in a much broader class of materials.

Triplet harvesting in the polaritonic regime: A variational polaron approach

“…So far, we have addressed the N = 100 case in detail. In fact, strong light-matter coupling with such small number of molecular emitters has been reported using plasmonic nanoparticle environments [61,62]. However, most microcavity systems have much larger N values.…”

Circular dichroism mode splitting and bounds to its enhancement with cavity-plasmon-polaritons

“…Unpolarized transmission spectrum of the coupled system at normal incidence shows the presence of two peaks at around 620 and 900 nm in Fig. 6b, unambiguously indicating emergence of the mode splitting due to strong coupling of plasmonic oscillators to the cavity mode 28 . Transmission spectrum also reveals a middle peak at around 700 nm, which originates from the nanocrescents anisotropy, as discussed above.…”

Recent Progress on Exciton Polaritons in Layered Transition‐Metal Dichalcogenides

“…Such a hierarchical coupling significantly increased the coupling strength due to the high quality factor of the cavity. As a result, they observed a huge Rabi splitting energy exceeds ≈500 meV at room temperature, which is the highest reported Ω R in TMD polaritons …”

“…Plasmonic cavities also have different configurations, commonly formed by mirrors and plasmonic nanostructures. [104][105][106] As shown in Figure 5e, TMD atomic layers with different thicknesses are placed inside the cavity formed between gold nanoparticles and a gold mirror [104] (a similar approach is used by Han et al [105] ). The strong plasmonic field confined inside such a cavity couples strongly with excitons to form hybrid PEPs.…”

“…As a result, they observed a huge Rabi splitting energy exceeds ≈500 meV at room temperature, which is the highest reported Ω R in TMD polaritons. [106] Tamm plasmons are a special type of plasmonic modes formed at the boundary between a DBR mirror and metal. [107] Unlike conventional surface plasmon polaritons that are subdiffractional with high wavevectors, Tamm plasmons are sitting inside the light cone, so they can be excited directly by an optical beam.…”