Real-space mapping of exciton and biexciton center-of-mass wave functions in a GaAs quantum dot by near-field optical imaging spectroscopy

Near-field optical imaging spectroscopy of naturally occurring GaAs quantum dots (QDs) with a lateral size of approximately 100 nm is presented. Due to the enhancement of spatial resolution up to 30 nm, we successfully mapped out center-of-mass wave functions of exciton and biexciton states confined in a single QD. A clear difference in the shape of the wave functions between these states was observed. This technique can be widely applied to the optical manipulation and control of eigenstgates both in single QDs and in coupled QD systems.