Quantum Optics Seminar by Joanna M. Zajac – Niels Bohr Institute - University of Copenhagen

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Quantum Optics Seminar by Joanna M. Zajac

Joanna M. Zajac, School of Physics, Cardiff University, United Kingdom

Strong coupling between a Fabry-Perot cavity mode and a quantum well exciton give rise to thenew quasi-particles microcavity exciton-polaritons. Microcavity polaritons were for the first timereported in 1992 in Ref 1 and since then, the field developed dynamically.

Fundamental physics was explored in these systems including a quantum phase transitions ofmicrocavity polaritons2, and demonstration of superfluidity3. However, in polariton physics, samples with desirable properties play a crucial role and there is still much room for the improvement of samples quality. Semiconductor microcavities commonly suffer from disorder, for both the exciton and the photon components of polaritons, which strongly modifies quantum effects and makes them difficult to interpret.

In this talk, I will discuss the main sources of photonic disorder in microcavity samples, such as lattice mismatch between constituent layers within GaAs/AlAs distributed Bragg reflectors which give rise to cross-hatch dislocation4 disorder and point-like-defects5 originating from Ga cell splitting during molecular beam epitaxial growth of the microcavity which give rise to localized polaritons states with discreet energy spectrum. Further to this, I will present novel samples design in which we have achieved significant strain compensation.

The second part of my talk is dedicated to quantum many-body effects in low disordered microcavities. In particular, I will present theoretical and experimental results on polariton parametric scattering into ghost branches6 which arise due to energy and momentum conservation of polaritons. Theory and experiment give good qualitative agreement.  

  • Ref 1. C. Weisbuch et al. Phys. Rev. Lett., 69:3314–3317, 1992.
  • Ref 2. J. Kasprzak et al., Nature, 443:409–414, 2006.
  • Ref 3. A Amo et al., Nature Physics, 5:805–810, 2009.
  • Ref 4. Zajac et al., Appl Phys Lett, 101, 041114 (2012).
  • Ref 5. Zajac et al., Phys Rev B, 85, 165309 (2012).
  • Ref 6. Zajac et al., arXiv:1210.1455