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2011 — Jacek Kasprzak, ERG (reintegration grant) SUPERRAD

SUPERRAD stands for superradiance (SR). The goal of this Marie-Curie European Reintegration Grant 2010 SUPERRAD is to achieve the first comprehensive evidence for SR within an ensemble of individual emitters embedded in a semiconductor matrix.

Superradiance (SR) refers to spontaneous and self-organized build up of coherent radiation within an ensemble of N quasi-degenerate emitters.The physics behind the SR can be understood by picturing each emitter as a tiny antenna sending out electromagnetic waves. At the high density a phase-locking between dipoles can occur, so that the emitted fields coherently add up in phase, generating an intensity N2 times stronger - as if originating from a single, macroscopic dipole - N times larger than that of an individual emitter. The symmetry breaking and the ordering leading to the establishment of a common phase in a superradiant state are closely related to other phase transitions like photon lasing, spin SR, Bose-Einstein condensation and ferromagnetism. Apart from the fundamental aspect, the research for SR is motivated by the prospects in producing ultra-short, intense, coherent light pulses without the need of optical resonators- in alternative to lasers.

The prerequisite for creating a SR is a spectral uniformity of participating transitions. For that reason the SR was first observed in atomic and molecular ensembles. More recently, SR was reported for Rydberg atoms. A spectacular and clean evidence for a SR were also provided by employing atomic Bose-Einstein condensates. In last years significant efforts were invested so as to provide a direct proof for SR in a nanostructured semiconductor.

The goal of this Marie-Curie European Reintegration Grant SUPERRAD is to achieve the first comprehensive evidence for SR within an ensemble of individual emitters embedded in a semiconductor matrix. The research for SR in solids has been hindered by the inhomogeneous broadening in ensemble of emitters. To overcome this difficulty an exotic magneto-plasma has recently been used to demonstrate SR, see Nature Phys. 8, 219-224 (2012). Conversely, in SUPERRAD we employ more common donor-bound excitons. To provide a conclusive signatures of SR we search for a burst of directional radiation, whose duration and delay with respect to the excitation are a function of the number of excitons, as well as their spatial phase locking.

Contact : Jacek Kasprzak

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