Probing microcavity switching events on the picosecond time scale using quantum dots as a broadband internal fluorescent source

Abstract

We report on ultrafast all-optical switching experiments performed on pillar microcavities containing a collection of quantum dots (QDs). Using QDs as a broadband internal light source and a detection setup based on a streak camera, we track in parallel the frequencies of a large set (>10) of resonant modes of an isolated micropillar during the entire duration of switching events and with a 2 ps temporal resolution. Being much faster and more convenient than standard approaches based on pump–probe spectroscopy, this method is very well suited for in-depth studies of cavity switching, noticeably in view of applications in the field of quantum photonics. We report as a first demonstrative example an investigation of the switch-on time constant τon dependence as a function of the pump power and the observation of a remarkably low value of τon(≈1.5 ps) for optimized pumping conditions. As a second illustration, we report the observation of a transient lifting of the degeneracy of a polarization-degenerate cavity mode, induced by a non-centrosymmetric injection of free carriers.