Abstract:
Switching waves (SWs) are travelling wavefronts connecting two stable states of a coher-
ently driven passive Kerr resonator. Known to exist in other nonlinear dynamical systems
for decades, they have received particular attention in optical resonators due to the plat-
form’s ease of use and manipulability. More recently, SWs have been found to be crucial
to generating normal dispersion frequency combs in the form of interlocking SWs [or dark
cavity solitons (CSs)], platicons, and normal dispersion CSs.
Although the dynamics of SWs in optical Kerr resonators have been previously studied,
their temporal profile has received little to no experimental attention. This thesis presents
a systematic study of the temporal profile of individual and interlocking SWs in a normal
dispersion coherently driven passive Kerr fibre ring resonator. We perform our experi-
ments under a pulsed-pumping regime in a large fibre ring cavity with custom-built fibre
couplers. With our cavity detuning control system and high bandwidth photodetectors,
we can measure SW profiles under a large variety of cavity conditions and find excellent
agreement with the established theoretical models. Furthermore, we directly observe in
remarkable detail the interlocking of two SWs to form a stable, dark, localised structure.
Finally, we investigate the presence of period-2 modulation instability (P2-MI), which we
find to coexist with our interlocking SW structures. By mapping the evolution of this
MI with the cavity detuning, we found excellent agreement with the predicted values
obtained from Floquet theory. In addition to this, we directly measure via heterodyne
detection the roundtrip-to-roundtrip change in phase of the P2-MI spectral components,
finding that the π change in phase required by the P2-MI temporal pattern elements is
encoded within the corresponding spectral components.
