Room-temperature strong coupling between CdSe nanoplatelets and a metal–DBR Fabry–Pérot cavity

Abstract

The generation of exciton–polaritons through strong light–matter interactions represents an emerging platform for exploring quantum phenomena. A significant challenge in colloidal nanocrystal-based polaritonic systems is the ability to operate at room temperature with high fidelity. Here, we demonstrate the generation of room-temperature exciton–polaritons through the coupling of CdSe nanoplatelets (NPLs) with a Fabry–Pérot optical cavity, leading to a Rabi splitting of 74.6 meV. Quantum–classical calculations accurately predict the complex dynamics between the many dark state excitons and the optically allowed polariton states, including the experimentally observed lower polariton photoluminescence emission, and the concentration of photoluminescence intensities at higher in-plane momenta as the cavity becomes more negatively detuned. The Rabi splitting measured at 5 K is similar to that at 300 K, validating the feasibility of the temperature-independent operation of this polaritonic system. Overall, these results show that CdSe NPLs are an excellent material to facilitate the development of room-temperature quantum technologies.

Cavity Controlled Upconversion in CdSe Nanoplatelet Polaritons

“…To investigate this possibility, we simulated polariton PL spectra with different Q-factors (Figure e) for the fixed experimental conditions in Figure d to understand the effect of cavity loss on polariton dynamics. For small Q-factors (Q = 30), the PL intensity is primarily in the LP branch, in agreement with previous measurements of polariton PL for nanomolecular exciton-polaritons involving organics, − carbon nanotubes, , and previous CdSe NPL cavity systems. , In contrast, for large Q-factors (Q = 3000) there is even greater PL intensity from the UP relative to the (Q = 300) measurements and simulation. This trend is also observed in the dynamics of the excited UP populations defined for energies above 2.437 eV weighted by photonic character (which are proportional to the emission intensity) in the simulation (Figure f) where the higher Q simulations have larger weighted steady-state populations of UP states.…”

“…We hypothesized that increasing the Q-factor of the FP cavity would enable different polariton photophysical behavior, due to the significant effect of cavity loss on polariton population dynamics. , Thus, our low Q-factor cavity serves as a control experiment and an important benchmark for our quantum dynamics simulations to accurately describe any emergent behavior associated with varying cavity loss for the CdSe NPL polariton systems. As illustrated in Figure a, compared to a cavity that is entirely filled with NPLs, we calculated that adding inert spacer layers between the NPLs and the mirrors would greatly increase the FP cavity Q-factor. Indeed, adding two 200 nm SiO 2 spacer layers between the NPL layer and the two mirror surfaces provided a Q-factor of approximately 300, compared to a Q-factor of about 70 without the spacers (Figure S1).…”

Dark State Concentration Dependent Emission and Dynamics of CdSe Nanoplatelet Exciton-Polaritons

“…Early studies on dark states have resorted to pump probe and two-dimensional infrared spectroscopy , through which relaxation rates from the UP and LP states into the manifold of dark states have been determined. Alternatively, a means to directly access the dark state manifold is provided by off-resonant pumping, early implementations of which have involved cavity-embedded J-aggregates. , Recently, off-resonant pumping has been applied to cavity-embedded cadmium selenide (CdSe) nanoplatelets (NPLs), , where subsequent detection of emission unveiled the importance of phonons in mediating polariton transitions . These advances notwithstanding, the systematic study of dark states remains in its infancy.…”