Photoluminescence up-conversion of single quantum dots in a microcavity.

We have studied photoluminescence upconversion in single self-assembled InGaAs quantum dots that are embedded in a planar optical microcavity. Upconversion is generally thermal and can be characterized unambiguously due to the absence of inhomogeneous broadening. A side-excitation photoluminescence technique allows us to detect arbitrarily close to the laser line thereby distinguishing otherwise unresolvable energy splittings. This allows the investigation of upconversion as a function of both temperature and energy separation.