Near-field optical mapping of strong exciton-plasmon coupling in 2-dimensional semiconductor

The strong interaction of emitters with plasmonic cavities has been studied intensively during the last decade. Much of the experimental works have focused on applying the far-field optical approaches to read out the coupled states, manifested by the separated peaks in the scattering or emission spectra. However, in the 2-dimensional (2D) semiconductors related strong coupling systems, the splitting effect in the emission spectrum is hidden by the far-field background read from the objective lens, since the plasmonic modulated coupling events occur in an optical volume much smaller than the diffraction limit spot size. This work proposes a unique near-field measurement configuration to read out the strong exciton-plasmon coupling from the 2D WSe₂ placed on the plasmonic nano trenches. By hyperspectral mapping, we can precisely locate the positions of the strong coupling and study the difference in coupling strength.