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Theses

Étude physique des limites en puissance des lasers à cascade quantique

Abstract : This thesis work is devoted to the theoretical and experimental study of the limiting factors of quantum cascade lasers (QCL) output power. It exposes a global modeling of their electro-optical properties. Laser operation is described in particular by including the electronic structure, non-radiative electron scattering mechanisms and the electron-photon coupling along the laser cavity. This model allowed us to successfully reproduce all the characteristics (current and optical power as a function of the applied voltage) of a QCL over the whole range of operating temperatures. This model was used to calculate the electron temperature in QCL. It showed that scattering by LO phonons is the only mechanism by which the gas of electron can transfer energy towards the lattice. Elastic scattering mechanisms are sources of energy for the electron gas. Two physical parameters allow to fully describe the electron temperature in the device: the electronic thermal resistance of the heterostructure and the temperature current coupling factor. Taking into account the electron-photon coupling shows that it may influence the electronic distribution over energy levels. Therefore, the gain of the active zone of the laser is reduced in the presence of this coupling. This effect, called gain saturation, plays an important role on the output performances of QCL. Minimizing this effect can increase the maximum power output of the laser by a factor of two. This study allowed us to propose new design rules of active regions to improve the QCL output performances. The experimental characterization of some of these structures has validated the approach we have followed towards performances improvement.
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Submitted on : Monday, July 4, 2011 - 11:21:04 PM
Last modification on : Wednesday, July 25, 2018 - 1:23:49 AM
Long-term archiving on: : Monday, November 12, 2012 - 10:06:21 AM

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Ezzeddine Ouerghemmi. Étude physique des limites en puissance des lasers à cascade quantique. Optique [physics.optics]. Ecole Polytechnique X, 2011. Français. ⟨NNT : 2011EPXX0072⟩. ⟨pastel-00605931⟩

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