  The delivery of optical signals from an external light source to a nanoscale
waveguide is highly important for the development of nanophotonic circuits.
However, the efficient coupling of external light energy into nanophotonic
components is difficult and still remains a challenge. Herein, we use an
external silica nanofiber to light up an organic-inorganic hybrid
nano-waveguide, namely a system composed of a polymer filament doped with
MoS$_{2}$ quantum dots. Nanofiber-excited nano-waveguides in a crossed geometry
are found to asymmetrically couple excitation signals along two opposite
directions, with different energy dissipation resulting in different colors of
the light emitted by MoS$_{2}$ quantum dots and collected from the waveguide
terminals. Interestingly, rainbow-like light in the hybrid waveguide is
achieved by three-in-one mixing of red, green, and blue components. This
hetero-dimensional system of dots-in-waveguide represents a significant advance
towards all-optical routing and full-color display in integrated nanophotonic
devices.
