  We demonstrate tunable on-chip single photon sources using the Stark tuning
of single quantum dot (QD) excitonic transitions in short photonic crystal
waveguides (PhC WGs). The emission of single QDs can be tuned in real-time by 9
nm with an applied bias voltage less than 2V. Due to a reshaped density of
optical modes in the PhC WG, a large coupling efficiency \beta>65% to the
waveguide mode is maintained across a wavelength range of 5 nm. When the QD is
resonant with the Fabry-Perot mode of the PhC WG, a strong enhancement of
spontaneous emission is observed leading to a maximum coupling efficiency
\beta=88%. These results represent an important step towards the scalable
integration of single photon sources in quantum photonic integrated circuits.
