Fig. 1: The principle and experimental system of cavity-enhanced optical Stark effect (OSE).

a Illustration of the red-detuned chiral OSE. The circularly polarized pump leads to Floquet states (\(\left\vert {{\rm{X}}}-{{\rm{h}}}\nu \right\rangle\) and \(\left\vert {{\rm{g}}}+{{\rm{h}}}\nu \right\rangle\)), which hybridize with the ground and excited state of excitons \(\left\vert {{\rm{g}}}\right\rangle\) and \(\left\vert {{\rm{X}}}\right\rangle\), resulting in blueshifted dressed states \(\left\vert {{{\rm{g}}}}^{{\prime} }\right\rangle\) and \(\left\vert {{{\rm{X}}}}^{{\prime} }\right\rangle\). A weak probe pulse measures the shifted transition energy. b Schematic of the half-wavelength cavity with a monolayer WSe₂ at the antinode. The simulated field distribution at the cavity resonance is plotted on the left side, showing a 200-fold enhancement of the resonant field at the antinode. Optical measurements are performed through transparent Sapphire. c Reflectance spectra of the \({{\rm{SiN}}}/{{{\rm{SiO}}}}_{2}\) bottom distributed Bragg reflector (DBR) (blue) with a side-band minimum at the exciton resonance, the ZnS/MgF₂ top DBR (red) with high reflectance at the laser and exciton energies, and the complete cavity (black) showing cavity (1.67 eV) and exciton (1.74 eV) resonances. The solid/dashed curves are the measured/simulated results, respectively.