Being a superposition of photons and excitons in the strong coupling regime, exciton-polaritons
inherit properties from both the constituents. We are interested in the interaction
arising from their matter component, since the enhancement of the interaction strength
compared to that in nonlinear optical materials in the weak coupling regime might lead to the
development of new technological platforms, where light can be controlled by light thanks to
Kerr-like nonlinearity.
In Chapter 1, we define exciton-polaritons and introduce the fundamental many-body
phenomena in which they are involved, like Bose-Einstein condensation and solitons.
In Chapter 2, we describe the active media used in polaritonics, especially the two
employed in this thesis, i.e. transition-metal dichalcogenide (TMDC) monolayers and GaN.
In Chapter 3, we outline the different geometries utilised to confine the light and make it
interacts with excitons, specifically microcavities and waveguides.
In Chapter 4, we detail the experimental setups we used to study exciton-polaritons in
TMDC-microcavities and GaN-waveguides.
In Chapter 5, we report on the preliminary results obtained on bare MoSe2 monolayers
and when we embedded them in our open-access microcavity.
In Chapter 6, we narrate about the interesting results achieved on TMDC-polaritons,
focusing on the giant trion-polariton interaction strength, which lays the foundation for a
new generation of nonlinear devices in the IR spectral range, foreshadowing highly efficient
polariton blockade.
In Chapter 7, we observe for the first time nonlinear self-modulation of UV pulses
operating up to room temperature, opening the way for potential technological platform for
ultrafast nonlinear optics without cryogenics in the UV spectral range.
Finally, in Chapter 8, we summarise all the results obtained and trace possible future
outcome in polaritonics, ranging from topological studies to superconductivity.
Appedices A and B are the theoretical models underneath the two experimental Chapters
6 and 7, respectively.
