Non-linear optical effects in cold and hot rubidium gases

Look around you. Everything you see is the result of interactions between light and matter. After all, every ray of light
entering your eyes has interacted with matter.
And this is not our only source of information that heavily relies on this interaction. Messages sent over the internet travel as packets of light through glass fibre cables, are
received in the device and converted to an electronic signal
using this interaction. In the future electronic devices might
be replaced completely by photonic devices, in which the signal can remain a photon. But even then, the manipulations
to the signal must still be performed through light-matter
interaction, because photons cannot interact with one another directly.
Therefore matter is required to mediate the interaction to
alter the signal in the desired way. As photonic chips become smaller and smaller, the interactions approach their fundamental limit. It is therefore important to acquire a fundamental understanding of
the interaction between light and matter. In this thesis, the
fundamental building block of matter, the atom, is used to
probe this fundamental interaction on the nanoscale. Rubidium atoms are laser cooled, trapped and brought into the field of light confined in nanophotonic samples. The enhanced light field due to the confinement cause non-linear effects in the interaction with atoms. To further investigate these non-linearities, experiments of intense laser beams in heated rubidium gases are performed, which show that several non-linear effects are required to describe the interaction.