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

TL;DR

This paper presents a scalable method for fabricating high-quality PMMA/SiO$_x$-spaced planar microcavities with monolayer WS$_2$, achieving strong light-matter coupling at room temperature, crucial for advanced polariton-based technologies.

Contribution

The authors develop a layer-by-layer fabrication technique using PMMA/SiO$_x$ that preserves exciton oscillator strength and achieves high-quality microcavities with strong coupling at room temperature.

Findings

Microcavities with quality factors above 10^3 were achieved.

Strong light-matter coupling demonstrated at room temperature.

Scalable fabrication method compatible with wafer-scale production.

Abstract

Exciton polaritons in atomically-thin transition metal dichalcogenide crystals (monolayer TMDCs) have emerged as a promising candidate 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 to integration had to compromise between various 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 an integrated monolayer WS$_2$ layer-by-layer by using polymethyl methacrylate/silicon oxide (PMMA/SiO$_x$) as a cavity spacer. Because the exciton oscillator strength is well protected against the required processing steps by the PMMA layer, 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 wafer-scale and patterned microcavities for engineering the exciton-polariton potential landscape, which is essential for enabling many proposed technologies.