  We experimentally observe the effect of photo-generated carriers on the
spectral diffusion of a quantum dot (QD) coupled to a photonic crystal (PC)
cavity. In this system, spectral diffusion arises in part from charge
fluctuations on the etched surfaces of the PC. We find that these fluctuations
may be suppressed by photo-generated carriers, leading to a reduction of the
measured QD linewidth by a factor of ~2 compared to the case where the
photo-generated carriers are not present. This result demonstrates a possible
means of countering the effects of spectral diffusion in QD-PC cavity systems
and thus may be useful for quantum information applications where narrow QD
linewidths are desired.
