Nonlinear polariton physics: we study the nonlinear dynamics of coherently driven polariton gases. One aspect we are particularly interest in, is the symmetry breaking that can occur in this nonlinear system away from equlibrium - leading to the spontaneous formation of patterns such as hexagons in the far-field emission of the cavity. We have recently demonstrated that these patterns can be externally and all-optically controlled. Our close collaboration with experiment has led to the observation of these patterns in a double-cavity system. We plan to extend our studies with an emphasis on the spinor character of the polariton fields. Future plans also include polariton systems that are promising for room-temperature applications and the interplay of polaritons with incoherent reservoirs.
The optical experiments are done in Jerome Tignon's group at ENS in Paris. On the theory side, we collaborate with Rolf Binder's group at the University of Arizona and Pui Tang Leung's group at the Chinese University Hong Kong.
Quantum optics with semiconductor quantum dots: semiconductor quantum dots have shown great promise as individual deterministic semiconductor source for single photons and entangled photons pairs. Recently we have come to realize that the excitation or de-excitation of the quantum dot biexciton through a direct two-photon process bears certain conceptional advantages. We have shown that through this direct two-photon process, the biexciton can serve as a reliable source of polarization-entangled photon pairs even if fine-structure splitting between the exciton levels is large. In the future, we will link our theoretical studies more closely with experiments and will investigate other promising scenarios aiming at the generation of single photons with polarization and frequency control through a two-photon emission process.
Here we collaborate locally with Artur Zrenner's and Jens Förstner's groups and with the group of Frank Jahnke in Bremen.