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Subcycle nonlinear terahertz optics: a carrier dynamics approach.


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Chai, Xin (2019). Subcycle nonlinear terahertz optics: a carrier dynamics approach. Thèse. Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 144 p.

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The dynamics of free electrons in semiconductors play the central role in strong light-matter interaction with intense terahertz radiations. Terahertz pulse can serve as a transient voltage bias to drive high-field phenomena in solids. Various nonlinear effects can be excited by applying different terahertz field strengths and the observed experimental results are found to be extremely sensitive to the incident terahertz spectrum and its temporal profile. These properties suggest a rich variety of possible optoelectronic applications by controlling the carrier dynamics in semiconductors. In this thesis, we investigate the nonlinear terahertz responses of free charge carriers in semiconductors, such as the n-doped semiconductor In0.53Ga0.47As and graphene, with terahertz time-domain spectroscopy as well as optical pump-terahertz probe spectroscopy. We start by discussing the terahertz responses of monolayer graphene. Then we discuss the significant impact of temporal dynamics in subcycle nonlinear optics. There are several limitations of the conventional Drude model and more importantly, the experimental observations may differ significantly within the well-known THz window. Strong subcycle nonlinear optics can only be achieved by carefully taking into account the time-scale of the variation in the temporal conductivity. Different experimental results are observed using different coherent terahertz sources in the frequency range between 0.1 and 3 THz. To retrieve nonlinear optics in the subcycle regime, we performed nonlinear THz-TDS on a common doped semiconductor material In0.53Ga0.47As, which possesses a much higher carrier density and a high conductivity contrast before and after strong carrier heating induced by intervalley scattering. Our findings suggest an incoherent approach to subcycle control of terahertz high-frequency (or high-harmonic) generation based on intraband carrier scattering effects. These investigations will be important for future terahertz electronics and optoelectronics.

Type de document: Thèse Thèse
Directeur de mémoire/thèse: Ozaki, Tsuneyuki
Mots-clés libres: énergie et matériaux
Centre: Centre Énergie Matériaux Télécommunications
Date de dépôt: 08 nov. 2019 17:38
Dernière modification: 08 nov. 2019 17:38
URI: https://espace.inrs.ca/id/eprint/9014

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