Anti-Parallel Dipole Coupling of Quantum Dots via an Optical Near-Field Interaction

We observed the optically forbidden energy transfer between cubic CuCl quantum dots coupled via an optical near-field interaction using time-resolved near-field photoluminescence (PL) spectroscopy. The energy transfer time and exciton lifetime were estimated from the rise and decay times of the PL pump-probe signal, respectively. We found that the exciton lifetime increased as the energy transfer time fell. This result strongly supports the notion that near-field interaction between QD makes the anti-parallel dipole coupling. Namely, a quantum-dots pair coupled by an optical near field has a long exciton lifetime which indicates the antiparallel coupling of QDs forming a weakly radiative quadrupole state. key words: optical near-field interaction, anti-parallel electric dipole pair, near-field spectroscopy, coupled quantum dots