Fig. 1.

Base structure. a Schematic illustration of the epitaxially grown base structure with a mechanical exfoliated MoSe₂ monolayer on top of the GaInP cap. The Bragg wavelength of the bottom AlAs/AlGaAs DBR and the GaAs/AlAs QWs are designed to be resonant to the MoSe₂ A–exciton. b Photoluminescence and reflectivity spectra of the structure without flake. The peak at 749 nm named X corresponds to the excitonic electron—heavy hole transition at the gamma—point of the GaAs QWs (see Supplementary Note 1 and Supplementary Fig. 1), which matches the absorption resonance. The reflectivity spectrum is dominated by a stop band which ranges from 710 to 790 nm with a calculated reflectivity of over 99.9 % from 740 to 765 nm. c White light reflection of the structure with and without the MoSe₂ monolayer. d Absorption of the MoSe₂—monolayer by norming the on-flake reflection to the off-flake reflection shows a strong absorption at the A-exciton energy, 1.666 eV, and a weak absorption at the trion energy, 1.634 eV