Highly Polarized Light Emission of Monolayer WSe 2 Coupled with Gap‐Plasmon Nanocavity

As contemporary star materials, 2D monolayer semiconductors have drawn huge research interests owing to their striking electrical and optical properties, rendering them ideal candidates as building blocks for novel optoelectronic devices. Towards light emitting devices with extended functions, it is necessary to manipulate the polarization of light emission from monolayer semiconductors. However, most of these monolayer semiconductors exhibit no or very limited polarization sensitivity inherited from their structural anisotropy, making it challenging to develop highly polarized light sources. Herein, by embedding monolayer tungsten diselenide (WSe2) in a nanowire-on-film nanocavity, highly polarized light emission is demonstrated, featuring degree of polarization (DoP) of ≈99%. The highly anisotropic light emission originates from the near-field coupling between the WSe2 monolayer with the polarization-dependent gap plasmons of the nanowire-on-film nanocavity. Moreover, as the width of the nanowire essentially defines the gap-plasmon resonance of the nanowire-on-film nanocavity, the anisotropy of the highly polarized light emission is systematically tuned by changing the nanowire width. The findings pave the way for engineering anisotropic optical properties of monolayer semiconductors and will boost the development of functional polarization-sensitive 2D optoelectronic devices.