Infiltrated photonic crystal fibres (PCFs) offer a new way of studying nonlinearity in periodic systems. A wide
range of available structures and the ease of infiltration opens up a large range of new experimental opportunities
in bio-physics, nonlinear optics, and the study of long range interactions in nonlinear media. Devices relying
on these effects have many applications, from bio-sensors, to all optical switches. To further understand these
nonlinear interactions and realise their potential applications, the effects of nonlinearity need to be studied on
the short time scale. In this work we study the temporal dynamics of thermally induced spatial nonlinearity
in liquid-filled photonic crystal fibres. Light is injected into a single hole of an infiltrated PCF cladding, and
the subsequent response is measured at a few milliseconds time scale. We experimentally demonstrate the short
time scale behavior of such systems, and characterise the effects of this thermal nonlinearity.
We review our experimental development in the field of optical lattices, emphasizing their unique properties for
control of linear and nonlinear propagation of light. We draw some important links between optical lattices and
photonic crystals, pointing towards practical applications in the fields of optical communications and computing,
beam shaping, and bio-sensing.
We predict theoretically and observe experimentally tunable refraction of beams in optically-induced lattices. By selective excitation of diferent Bloch modes in a tilted lattice, we observe positive and negative refraction for beams associated with the first and the second spectral band, respectively. We demonstrate tunability of the output beam position by dynamically adjusting the lattice depth. At higher laser intensities, the beam broadening due to difraction can be suppressed through nonlinear self-focusing while preserving the general steering properties.