Light emission in complex networks from single-photons to lasing

Abstract

Light-matter interaction, which is at the heart of the science and technology
of light, can be controlled and designed in materials structured at the
nanometre length-scale, for enhanced light emission and absorption, and
down to the single photon level.
The aim of this thesis is to investigate complex photonic geometries, i.e.
systems where the collective interaction of a large number of constituents
denes the optical properties with emergent phenomena beyond the sum of
the response of the individual constituents. In particular, a central topic is
the emission of light from sources located in dielectric and plasmonic networks
with dierent degree of disorder and correlation. Experimental and
theoretical evidence of coupling of single photons to propagating modes
in nano-waveguides, emission enhancement in plasmonic structures, and
collective emission in disordered lasing systems are presented.
Large coupling of individual quantum dots embedded in free-standing
sub-wavelength waveguides is experimentally demonstrated. These waveguides
are fabricated by electrospinning, a scalable technique suitable for
the realisation of large interconnected systems.
Light emission enhancement is investigated in plasmonic self-assembled
systems and lithographic structures, which build on the framework of optical
antennas and allows isolating local and global contributions to the local
density of states around a topological percolation phase transition.
One of the most important cooperative eects between multiple emitters
is lasing. Random lasing is investigated numerically and experimentally
in diusive systems with particular attention to the spectral properties of
the emission and its relation with the physical and chemical parameters
of the surrounding environment, which can be exploit to tune the lasing
emission, thus providing a novel sensing scheme. These results provide
the building blocks to construct a photonic network of emitters coupled by
simple optical links.

Date of Award	2016
Original language	English
Awarding Institution	King's College London
Supervisor	Riccardo Sapienza (Supervisor)