Fabrication of high-quality PMMA/SiO$_x$ spaced planar microcavities for strong coupling of light with monolayer WS$_2$ excitons

Abstract

Exciton polaritons in atomically-thin transition metal dichalcogenide crystals (monolayer TMDCs) have emerged as highly promising to enable topological transport, ultra-efficient laser technologies, and collective quantum phenomena such as polariton condensation and superfluidity at room temperature. However, integrating monolayer TMDCs into high-quality planar microcavities to achieve the required strong coupling between the cavity photons and the TMDC excitons (bound electron-hole pairs) has proven challenging. Previous approaches had to compromise between the adverse effects on the strength of light-matter interactions in the monolayer, the cavity photon lifetime, and the lateral size of the microcavity. Here, we demonstrate a scalable approach to fabricating high-quality planar microcavities with integrated monolayer WS2 layer-by-layer by using polymethyl methacrylate/silicon oxide (PMMA/SiOx) as cavity spacer. Because the exciton oscillator strength is well protected by the PMMA layer against the required processing steps, the microcavities investigated in this work, which have quality factors of above 10 3 , can operate in the strong light-matter coupling regime at room temperature. This is an important step towards fabricating patterned microcavities for engineering the exciton-polariton potential landscape, which is essential for enabling many proposed technologies.

Anomalous dispersion and negative-mass dynamics of exciton polaritons in an atomically thin semiconductor

“…Recent works have also showed the significant role of phonons in exciton-photon interaction [25]. In addition, the fabrication process used in this work can cause an enhancement of non-radiative channels as evidenced by the increase in linewidths of the bare exciton PL (see SI) [33]. Dissipative coupling can also arise via coupling to a 'hidden' photon mode [35], but this mode with opposite polarisation is not present in our planar DBR-based microcavities.…”

“…To uncover the effects of dissipative coupling, we also need to reduce the coherent coupling strength V . We achieved this with our recently developed technology for integrating monolayer WS 2 into PMMA/SiO x spaced planar microcavitites [33].…”