PhD defence by George Kountouris

Abstract

Many future high-efficiency, low-power micro- and nano-devices for integrated photonics and electronics-photonics applications greatly benefit from the tight confinement of light. Historically, plasmonics using metallic structures enabled extreme light confinement, but metals suffer from considerable losses, limiting their use in practical applications. As a way of addressing this limitation, there has been an increasing effort to achieve similar effects by using other materials. Dielectrics offer negligible losses and could be a particularly interesting alternative to metals, but light confinement in dielectric resonators was long thought to be restricted to dimensions close to the wavelength of light, commonly referred to as the diffraction limit.

Nevertheless, recent work has demonstrated a new way to confine light in dielectric structures well below this limit by cleverly designing the structure’s geometry in order to exploit the interface conditions of the electromagnetic field. The interesting structures in this new field of extreme dielectric confinement (EDC) offer significant spatial confinement without suffering from the high losses of plasmonics. This combination of increased confinement and low losses greatly enhances light-matter interactions, leading to devices with greater efficiency, and potentially low-power nonlinearities, that can have far-reaching consequences for future applications in quantum information technology, and photonic-electronic integration for new-generation processors and neuromorphic photonic computing, with advanced light sources, modulators and detectors.

In this thesis, I study dielectric structures with extreme sub-wavelength confinement, termed extreme dielectric confinement (EDC), and deal with their design and quantum optical properties through finite element and finite-difference time-domain calculations.  Over this thesis, I work on intuitive design, deterministic fabrication of emitters in these structures, and explore time-dynamics with emitters when exciting with short optical pulses.

Supervisors

• Principal supervisor: Professor Jesper Mørk, DTU Electro, Denmark
• Co-supervisor: Senior Researcher Philip Trøst Kristensen, DTU Electro, Denmark

Evaluation Board

• Professor Søren Stobbe, DTU Electro, Denmark
• Professor Riccardo Sapienza, Imperial College London, UK
• Professor N. Asger Mortensen, University of Southern Denmark, Denmark

Master of the Ceremony

• Senior researcher Thomas Christensen, DTU Electro, Denmark