  Two-dimensional transition metal di-chalcogenide semiconductors provide
unique possibilities to investigate strongly confined excitonic physics and a
plasmonic platform integrable to such materials constitutes a hybrid system
that can be of interest to enable manipulation of their cumulative optical
properties. Here we report tuning of excitonic emission from monolayer WSe2,
mechanically exfoliated on top of a periodic two dimensional plasmonic array of
elliptical gold (Au) nanodiscs. By exploiting the polarization-dependent nature
of plasmonic resonance of the nano plasmonic array (NPA), the photoluminescence
(PL) emission from the overlaid monolayer WSe2 could be significantly
manipulated. PL is preferentially enhanced at the NPA covered regions of the
ake when excited closer to the plasmonic resonant frequencies and previously
unpolarized WSe2 PL emission gained ~ 20 up to 40 % degree of linear
polarization at room temperature. Obtaining significant spectral overlap
between the PL spectrum of WSe2 and the polarization tunable plasmonic
resonance of the NPA plays a crucial role in this observation. The results
demonstrate active tunability of optical emission from WSe2 by using an
otherwise passive plasmonic environment and open the possibility of achieving
atomically thin linearly polarized emitters at room temperature. In addition to
fundamentally interesting physics of such interactions this can be highly
desirable for ultrathin orientation sensitive opto-electronic device related
applications.
