Novel approaches to tailor and tune light-matter interactions at the nanoscale

TL;DR

This thesis introduces innovative methods for controlling light-matter interactions at the nanoscale, including tunable plasmonic cloaks, manipulation of quantum emitter decay rates, and enhanced near-field heat transfer, with potential applications in nanophotonics.

Contribution

It presents new schemes using magneto-optical materials and external magnetic fields to actively control electromagnetic responses and energy transfer at the nanoscale, advancing the field of light-matter interaction engineering.

Findings

Magnetic fields can switch and mitigate cloaking effects in plasmonic devices.

Quantum emitter decay rates can be tuned via magnetic fields near graphene structures.

Near-field heat transfer is significantly enhanced at the percolation threshold.

Abstract

In this thesis we propose new, versatile schemes to control light-matter interactions at the nanoscale. In the first part of the thesis, we envisage a new class of plasmonic cloaks made of magneto-optical (MO) materials. We demonstrate that the application of a uniform magnetic field B in these cloaks may not only switch on and off the cloaking mechanism, but also mitigate the electromagnetic (EM) absorption. We also prove that the scattered field profile can be effectively controlled by changing B. The second part of the thesis is devoted to the study of light-matter interactions mediated by fluctuations of the vacuum EM field. Firstly, we demonstrate that the Purcell effect can be effectively suppressed for an excited atom near a cloaking device. Furthermore, the decay rate of a quantum emitter near a graphene-coated wall under the influence of an external magnetic field is studied. We show that the MO properties of graphene strongly affect the atomic lifetime and that B allows for an unprecedented control of the decay channels of the system. In addition, we discuss the dispersive interaction between an atom and suspended graphene in a magnetic field. For large atom-graphene separations and low temperatures we show that the interaction energy is a quantized function of B. Besides, we show that at room temperature, thermal effects must be taken into account even in the extreme near-field regime. Finally, the third part of the thesis deals with the study of near-field heat transfer. We analyze the energy transfered from a semi-infinite medium to a composite sphere made of metallic inclusions embedded in a dielectric host medium. We show that the heat transfer can be strongly enhanced at the percolation phase transition. We show that our results apply for different effective medium models and are robust against changes in the inclusions' shape and materials.