Achieving Zero-Detuned and Polarized Bragg Polaritons in Monolayer MoS₂ above Room Temperature

Monolayer transition metal dichalcogenides (TMDs), with their large exciton binding energies, are promising platforms for exploring exciton-polariton physics and developing integrated polaritonic devices that can operate at and above room temperature. Resonant exciton-photon coupling and polarized exciton-polaritons are highly desirable for on-chip applications, such as optical switches and logic gates. However, both achieving zero detuning, rather than the more accessible positive or negative detuning regimes, and realizing polarization-resolved light-matter interactions remain challenging at elevated temperatures. Here, we demonstrate zero-detuned and polarized Bragg polaritons at 333 K in a superacid-treated monolayer MoS2 integrated with a distributed Bragg reflector. By thermally tuning the system and splitting the intrinsic transverse electric and transverse magnetic modes, we generate polarized Bragg polaritons. Polarization-resolved and angle-dependent reflectivity spectra reveal a polarization-sensitive behavior between parallel and perpendicular directions. The coupled oscillator model confirms the existence of Bragg polaritons, with anisotropic effective masses and Hopfield coefficients. Polaritonic devices operating at elevated temperatures enhance thermal stability and alleviate self-heating effects, which are essential for sustaining performance under practical operating conditions. Our findings demonstrate the realization and control of polarization-tunable Bragg polaritons in monolayer TMDs under realistic thermal conditions, paving the way for polarization-sensitive polaritonic circuits in on-chip switches and logic gates.