Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Physics

Supervisor

Mahi Singh

Abstract

In this thesis, nanophotonic switching mechanisms and light-matter interactions are explored in photonic and metallic heterostructures and nanocomposites. These heterostructures are made using various combinations of photonic crystals (PCs), quantum dots (QDs), and graphene or metal nanoparticles (MNPs).

PC heterostructures are formed by combining different PCs so that photons in a specific energy range can propagate in certain regions along one direction and cannot propagate in others. This band structure engineering is used to form photonic quantum wells (PQWs) that have discrete energy states along one dimension. By simulating the photon transmission along the direction of confinement, resonant photon tunnelling is shown to occur at discrete energies. Double PQW (DPQW) heterostructures are also considered, where it is found that resonant states appear in split pairs due to coupling between PQWs.

Nonlinear DPQW heterostructures are also investigated, whereby two regions in the structure are made of Kerr-nonlinear PCs. Here it is shown that the application of an external pump laser field can be used to optically switch the resonant frequencies of bound states in the DPQW.

Energy transfer in a heterostructure made by embedding a QD-graphene nanodisk nanocomposite in a Kerr-nonlinear PC has been studied. Here it is shown that energy transfer occurs between the QD and graphene due to a dipole-dipole interaction. Energy transfer occurs for two distinct frequencies of an external probe laser field, and can be switched by changing the separation between the QD and graphene or by applying a pump laser field to the PC.

An alternative QD-graphene nanocomposite was investigated, where the local field created by plasmons in graphene is used to manipulate two-photon absorption in the QD. An external gate voltage is applied to graphene to modify the plasmon resonance frequency and therefore the frequency at which the local field enhancement has its maximum value. It is demonstrated that two-photon absorption in this nanocomposite can be switched on or off by modifying the gate voltage.

Finally, nonlinear second harmonic (SH) generation and two-photon photoluminescence (TPPL) has been studied experimentally and theoretically in QD-MNP hybrid systems. It is found that a secondary laser field resonant with the plasmons in the MNP can be used to enhance SH generation in the QDs.

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