Abstract:
Temporal cavity solitons (CSs) are localized pulses of light that can persist indefinitely in passive,
coherently-driven, Kerr resonators. They were first experimentally observed by Leo et al. in
a macroscopic optical fibre ring resonator in 2010 and proposed as ideal candidates for bits in
all-optical buffers. More recently, they have been found to also manifest themselves in coherently-driven Kerr microresonators, and they are now understood to be the time-domain structures that
underpin the so-called Kerr microresonator frequency comb, whose numerous applications range
from telecommunications to astronomy. It is commonly held that temporal CSs only exist under
the condition of anomalous dispersion, but recent theoretical studies surprisingly predicted that
higher-order dispersion can enable the sustainment of CS-like `bright' pulse structures even in the
regime of normal dispersion. However, to the best of our knowledge, no conclusive experimental
observations of such bright normal dispersion CSs have yet been reported.
In this Thesis, we present direct experimental observations of bright temporal cavity solitons
in the regime of normal dispersion. Our experiments are performed in a custom-built macroscopic
fibre ring resonator that exhibits a zero-dispersion wavelength in the telecommunication
spectral region; by driving the resonator with a widely-tunable external cavity diode laser, we are
able to systematically explore CS existence under conditions where higher-order dispersion plays
a significant role. We observe clear signatures of bright CSs when operating under the condition
of normal dispersion, and our experimental observations are in remarkable agreement with theoretical predictions. We also investigated the dynamics of the normal dispersion CSs, and find
experimental evidence of their theoretically predicted bifurcation structure (so-called collapsed
snaking). Finally, we experimentally explore how CSs transition from normal to anomalous
dispersion regime, and discuss the dynamical origins of the different soliton states.