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Accueil > Evénements > Séminaires > Archives 2016 > Quantum theory of superra
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Quantum theory of superradiant thermal emitters - Simon Huppert - Jeudi 17 mars 2016 à 10 h 30

INSP - UPMC - 4 place Jussieu - 75005 Paris - Barre 22-12, 4e étage, salle 426

Simon Huppert (candidat au poste Maître de conférences à l’INSP)

Abstract

The thermal radiation produced by a heated surface depends both on its temperature and on its optical absorption. In semiconductor nanostructures with high electronic density, absorption in the mid-infrared range is characterized by a collective mode in which all electrons in the conduction band oscillate in phase [1]. This mode has a superradiant nature : its spontaneous emission time can be as short as few tens of femtoseconds, hence dominating any non-radiative scattering event in such structures [2].

In this seminar I will present a quantum model of superradiant thermal emission. Starting from a microscopic description of the collective electronic excitations, this model allows the calculation of the emitted power through the resolution of quantum Langevin equations, including the coupling of the collective excitations with electronic and photonic baths [3]. I will show that the emitted power is controlled by the ratio between the spontaneous emission rate and the non-radiative decay rate of the collective oscillation. This property leads to the counter-intuituve result that beyond the critical coupling condition (when both rates are equal), superradiance actually reduces the emissivity. Furthermore, superradiant thermal radiation displays an emission pattern very different from that of a mere oscillating dipole, with a preferential direction that depends strongly on the electronic density. The accuracy of this quantum theory has been confirmed by angle-resolved emission measurements [3]. This model is also well suited to explore quantum optical effects arising in the the so-called ultra-strong coupling regime [4], such as the dynamical Casimir effect and the production of squeezed states of light [5].

[1] A. Delteil et al., Phys. Rev. Lett. 109, 246808 (2012)
[2] T. Laurent et al., Phys. Rev. Lett. 115, 187402 (2015)
[3] S. Huppert et al., ACS Photonics, 2 (12), 1663–1668 (2015)
[4] S. Huppert et al., (submitted)
[5] S. Fedortchenko, S. Huppert et al., arXiv:1601.08104 (2016)