nonlinear optics

We will present our recent results regarding the observation of soliton explosions in an all-normal dispersion fibre laser. Using a real time dispersive Fourier transform we were able to make single shot measurements of the spectrum showing how the explosion happens in frequency space and how this translates to the temporal behaviour of the pulse. Simulations of the generalised nonlinear Schrodinger equation agree well with the experimental results and highlight the regions between stability and chaos in such systems. Further investigations highlight the presence of optical rogue waves and chimera states in such a laser which will be discussed in the presentation.

We review recent progress in the study of linear and nonlinear propagation in ferroelectric super-crystals. The three-dimensional super-lattice of spontaneous polarization vortices leads to giant broadband refraction across the entire visible spectrum. Absence of diffraction, chromatic dispersion, and propagation normal to the crystal facets is compatible with giant values of index of refraction larger that 25. The huge values of optical susceptibility greatly enhance second-harmonic generation efficiency with broadband spectral and angular acceptance.

Spontaneous symmetry breaking is central to our understanding of physics and explains many natural phenomena, from cosmic scales to sub-atomic particles. Its use for applications requires devices with a high level of symmetry, but engineered systems are always imperfect. Surprisingly, the impact of such imperfections has barely been studied, and restricted to a single asymmetry. Here, we experimentally study spontaneous symmetry breaking in presence of two controllable asymmetries. We remarkably find that the characteristic features of spontaneous symmetry breaking, while dramatically destroyed by one asymmetry, can be entirely restored when a second asymmetry is introduced. In essence, asymmetries are found to balance each other. Our study illustrates aspects of the universal unfolding of the pitchfork bifurcation, and provides new insights into a key fundamental process. It also has practical implications, showing that asymmetry can be exploited as a new degree of freedom. In particular, it would enable sensors based on symmetry breaking or exceptional points to reach divergent sensitivity even in presence of imperfections. Our experimental implementation built around an optical fibre ring additionally constitutes the first observation of the polarization symmetry breaking of passive driven nonlinear resonators.

Ultra-high-Q microresonators can confine extremely large amounts of optical energy in tiny mode volumes. This talk will focus on recent realizations of nonlinear interaction of counterpropagating light in these resonators. Particularly, above a certain threshold power, light of a given frequency can only circulate in one direction. Experimental and theoretical results show spontaneous symmetry breaking that follows from the interaction of the counterpropagating light. The resulting nonreciprocity of the light propagation in the microresonators can be used for novel applications including integrated photonic isolators and circulators.