Van der Waals waveguide quantum electrodynamics probed by infrared nano-photoluminescence

Atomically layered van der Waals (vdW) materials exhibit remarkable properties, including highly confined infrared waveguide modes and the capacity for infrared emission in the monolayer limit. Here we engineered structures that leverage both of these nano-optical functionalities. Specifically, we encased a photoluminescing atomic sheet of MoTe2 within two bulk crystals of WSe2, forming a vdW waveguide for the embedded light-emitting monolayer. The modified electromagnetic environment offered by the WSe2 waveguide alters MoTe2 spontaneous emission—a phenomenon we directly image with our interferometric nano-photoluminescence technique. We captured spatially oscillating nanoscale patterns prompted by spontaneous emission from MoTe2 into waveguide modes of WSe2 slabs. We quantify the resulting Purcell-enhanced emission rate within the framework of a waveguide quantum electrodynamics model, relating the MoTe2 spontaneous emission rate to the measured waveguide dispersion. Our work marks a substantial advance in the implementation of all-vdW quantum electrodynamics waveguides. A nano-optical probe of the Purcell effect in a van der Waals waveguide is demonstrated, exploiting its highly confined infrared waveguide modes and the capacity for infrared emission in the monolayer limit of atomically layered van der Waals materials.