Room-temperature photoluminescence spectroscopy of self-assembled In_0.5Ga_0.5As single quantum dots by using highly sensitive near-field scanning optical microscope

We have studied the optical properties of self-assembled In_0.5Ga_0.5As single quantum dots (QDs) at room temperature with a near-field scanning optical microscope. Successful detection of a weak photoluminescence (PL) signal from a single QD at room temperature could be achieved by using a double-tapered fiber probe having the advantages of both high collection efficiency and high spatial resolution. Through the precise examination of PL spectra of many QDs, including broadening and saturation behaviors, the homogeneous linewidth of the ground state emission is evaluated as from 9.8 to 14.5 meV.