Investigating Thermo-optical Nonlinearities in Graphene

Kumar, Abhijeet (2018) Investigating Thermo-optical Nonlinearities in Graphene. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Abhijeet Kumar (13MS027)) 13MS027.pdf - Submitted Version Restricted to Repository staff only Download (6MB)

Abstract

Due to its several remarkable properties, graphene has gained tremendous research attention in the last decade. Owing to linear Dirac dispersion, graphene exhibits strong optical behavior, and hence one also expects a strong optical non-linear response by graphene over large wavelength regime. Strong self-focusing and self-defocusing phenomena within a medium under its interaction with incident light with high intensity makes the refractive index of the medium intensity dependent, which is studied using several experimental techniques such as spatial self-phase modulation and z-scan. Two conflicting theories, namely electronic and thermal effect, are popular to account for the intensity-dependent refractive index variation in a nonlinear medium. We study here, these effects, and make attempts to distinguish these two effects and to investigate one's dominance. Depending on laser and sample characteristic, these techniques can be used to distinguish purely electronic or thermal nonlinearities. In this way, both the experiments in this research converge towards a common goal{to investigate thermo-optic nonlinearities in graphene and graphene oxide.

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