  Photonic integrated circuits are an enabling technology in modern
communications systems. The continually increasing demands for higher-speed and
lower operating power devices have resulted in the continued impetus to shrink
photonic components. In this work, we demonstrate a primitive nanophotonic
integrated circuit element composed of a single silver nanowire and
single-layer molybdenum disulfide (MoS2) flake. We show that nanowire plasmons
can excite MoS2 photoluminescence via direct plasmon-to-exciton conversion
along the wire and plasmon-to-photon-to-exciton conversion at the MoS2-covered
wire end. We also find that the reverse process is possible: MoS2 excitons can
decay into nanowire plasmons that can then be routed via the nanowire on-chip.
Finally, we demonstrate that the nanowire may serve the dual purpose of both
exciting MoS2 photoluminescence via plasmons and recollecting the decaying
excitons.
