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Title: Optical near-field dynamics of active 2D semiconductors
Author: Guazzotti, Stefano
ISNI:       0000 0004 7969 8906
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2019
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When structures with a strong confinement of the electromagnetic fields are considered, the near-field dynamics becomes integral to the description of a semiconductor. Not only it provides feedback from the environment, as is the case in a laser system, but it further mediates the interaction between different, otherwise independent, positions. In such a context, a full-field spatio-temporal description is essential to faithfully describe the dynamics of either an extended semiconductor system or a set of spatially separated emitters. This thesis highlights the importance of combining a complex (many-body and band-resolved) model of semiconductor carrier dynamics with a full-field description of the electromagnetic fields by presenting some applications. With the recent rise in popularity of atomically thin materials, semiconductors can be embedded in increasingly smaller optical environments, whose properties can only be studied by self-consistently combining carrier and field dynamics. The ability to calculate the linear and non-linear response of a system under arbitrary excitation conditions is shown. This is performed without any prior knowledge of the electromagnetic environment and can thus be extended to complex geometries. By embedding active materials in a tailored environment, the complex interaction of the two can be exploited to engineer the optical response of the system by using a self-consistent modelling technique. The complex dynamical interaction between field and gain in a semiconductor laser is another example of a system in which a self-consistent model is required. Here, a set of one-dimensional simulations is reported showing how the output of a semiconductor laser is highly sensitive to perturbation arising from sub-wavelength dynamics of the gain medium. By introducing a random patterning of the laser cavity, a novel approach to the suppression of dynamical instabilities in a laser output is demonstrated. This scheme, based on complex wave interference, is introduced by spatially perturbing the optical environment.
Supervisor: Hess, Ortwin ; Phillips, Chris Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral