In this paper, we study the influence of quasiresonant and nonresonant excitation on the interference properties of single photons emitted from quantum dots (QDs). The quasiresonant excitation scheme leads to an increase of interference visibility of photons emitted from the same QD to 69% compared to 12% for nonresonant excitation. Furthermore, we demonstrate quantum interference of photons emitted from separate QDs which are simultaneously excited into their $p$ shell. We can readily extract a two-photon interference visibility as high as (39 ± 2)% for nonpostselected coincidences exceeding the predicted value based on coherence and radiative decay times of the quantum dot emission ($\sim$25%). We account for this observation by treating the emission of both quantum dots as inhomogeneously broadened ensembles of Fourier-limited photons and observe good congruence between experiment and model.

• Received 16 July 2013
• Revised 23 November 2013

DOI:https://doi.org/10.1103/PhysRevB.89.035313