Strong Photon-Exciton Coupling in the Near-Field Luminescence of Semiconductor Quantum Dots

We present low-temperature near-field scanning optical microscopy (NSOM) measurements of self-organized InP quantum dots (QD) embedded in a GaInP layer. We observed an anomalously strong increase in the emission energy (∼270 meV) of a single QD by changing the tip-to-surface distance over ∼100 nm in the near-field region. The effect indicates the formation of a near-field nanocavity having extremely high photon-exciton mixing and can be interpreted as the observation of the coupled photon-exciton pair