Microcavity polaritons

Polaritons are compound quasi-particles, which are both light and matter at the same time. In our system they form when light hybridizes with an electronic excitation of matter and can be seen as some form of “heavy” and interacting photons inside a medium.  Such strong coupling between light and matter occurs in many different systems. They have been observed in cold atomic gasses, 2D materials, complex organic materials and even living cells. In our experiment we create polaritons in microscopic optical cavities consisting of semiconductor materials.

There has been considerable interest in studying polaritons in recent years, because they can form (high temperature) Bose-Einstein condensates and inversionless lasing and exhibit rich nonlinear dynamics while still allowing a lot of control over the properties of the particles.  

We are mainly interested in using the interactions between polaritons to create single-polariton quantum states.  Our collaborators from the group of Vincenzo Savona have shown recently that polaritons can exhibit non Gaussian quantum statistics and squeezed polariton states can be created.  We study these quantum states experimentally using nanostructures that confine polaritons in all three dimensions, so-called micropillars (fabricated by our collaborators Karol Winkler and Christian Schneider in Würzburg). When we bring two such micro-pillars close together polaritons can tunnel between the two sites.  However, because of the interactions between polaritons, one polariton that tunneled into the second pillar and back into the first pillar can acquire a different phase than a second polariton in the first pillar and (ideally) destructively interfere with it.  This suppression of the probability to have two polaritons at once at one site can be used to create single polariton states.         

Beyond single-polariton physics we conduct both theoretical and experimental research on quantum statistics of interactions in many-polariton systems in 2D structures (see previous projects ).We are currently in the process of realizing a testbed for room-temperature (organic) polariton experiments utilising an open-cavity geometry.

We also participate in the newly established Quanten-Nano-Zentrum Tirol, offering many opportunities for fabrication of tailor-made polaritonic nanostructures. 

Previous projects 

Entanglement of Polaritons

Research team 

Ulrich Czopak, Denis Karpov, Maximilian Prilmüller, Gregor Weihs

ALUMNI: Mathias Sassermann PhD

BSc & MSc Topics

...for excellent and motivated students...

  • Nanofabrication of photonic devices
  • Open cavity

FWF DACH project:  Polariton-based single-photon sources, I2199-N27


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