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Project title: Spontaneous symmetry breaking and dissipative processes in single quantum dot lasers. Lasing as a phase transition.

Acronym: SSB-QD-Laser

Project code: PN-III-P4-ID-PCE-2016-0221

Funded by:  Romanian National Authority for Scientific Research, UEFISCDI

Contractor: CIFRA-INCDFM

Project director: Dr. Paul Gartner

Start Date: 12 July 2017

End Date: 31 December 2019

Project Summary:
The problem of the onset of lasing as a nonequilibrium phase transition is a debated issue in the case of few- or single-emitter systems, with several nonequivalent lasing criteria being used in the literature. We address this problem by analyzing the spontaneous breaking of the rotation symmetry in the phase space of coherent photonic states. Anomalous averages should appear as a sign of instability to symmetry-spoiling infinitesimal perturbations in the lasing regime, and only there. This way we propose a simple lasing criterion which also identifies the excitation threshold point. The problem will be treated using the P-representation of the photonic density operator, which is defined on the phase space. The accuracy of the simpler, approximate rate equation solution will be checked against the full solution. The result will be generalized to coupled cavity arrays.
A second objective concerns the quantum dot carrier dynamics interacting with a gas of electrons or holes in the spectral continuum provided by either the wetting layer or the barrier bulk states. A similar problem is successfully treated for the carrier-phonon interaction, using the polaronic unitary transform. This goes beyond the usual Born-Markov of the system-reservoir interaction by including quasi-particle renormalization by the same interaction. We treat the problem of a fermionic reservoir on the same footing by identifying the analog unitary transform in the S-matrix of the scattering problem on the quantum dot as scattering center. This procedure will provide accurate calculations of dissipation rates and exciton emission lineshapes as a function of temperature and continuum carrier populations. These are both controllable parameters in a quantum dot device.

Project team:

1. Paul Gartner - Experienced Researcher

2. Viorel Dinu - Experienced Researcher

3. Marian Nita - Experienced Researcher

4. Valeriu Moldoveanu - Experienced Researcher

5. Mugurel Tolea - Experienced Researcher

6. Bogdan Ostahie - Postdoc Researcher

7. Stefan Stanciu - PhD Student

Contact:

Dr. Paul Gartner

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Postal address: Atomistilor street, no. 405A, Magurele, 077125, Romania

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