  We present investigations of the propagation length of guided surface plasmon
polaritons along Au waveguides on GaAs and their coupling to near surface
InGaAs self-assembled quantum dots. Our results reveal surface plasmon
propagation lengths ranging from 13.4 {\pm} 1.7 {\mu}m to 27.5 {\pm} 1.5 {\mu}m
as the width of the waveguide increases from 2-5 {\mu}m. Experiments performed
on active structures containing near surface quantum dots clearly show that the
propagating plasmon mode excites the dot, providing a new method to spatially
image the surface plasmon mode. We use low temperature confocal microscopy with
polarization control in the excitation and detection channel. After excitation,
plasmons propagate along the waveguide and are scattered into the far field at
the end. By comparing length and width evolution of the waveguide losses we
determine the plasmon propagation length to be 27.5 {\pm} 1.5 {\mu}m at 830 nm
(for a width of 5 {\mu}m), reducing to 13.4 {\pm} 1.7 {\mu}m for a width of 2
{\mu}m. For active structures containing low density InGaAs quantum dots at a
precisely controlled distance 7-120 nm from the Au-GaAs interface, we probed
the mutual coupling between the quantum dot and plasmon mode. These
investigations reveal a unidirectional energy transfer from the propagating
surface plasmon to the quantum dot. The exquisite control of the position and
shape afforded by lithography combined with near surface QDs promises efficient
on-chip generation and guiding of single plasmons for future applications in
nanoscale quantum optics operating below the diffraction limit.
