Title: Nonlinear fibre optics for ultrafast phenomena
Name: Dr. Francesco Tani
Time：15:00, August 5, 2019
Venue: Yizhi Hall

Abstract:
Soliton dynamics offers a wide range of powerful tools for nonlinear manipulation of ultrashort light pulses. Gas-filled hollow-core fibres provide access to such dynamics together with an excellent control over the interplay between linear and nonlinear effects. As a result, the dynamics of ultrashort pulses propagating in this system can be harnessed to realise novel light sources, and to investigate several ultrafast phenomena. In particular, pulses over a broad spectral range can be shortened to a few femtoseconds via soliton self-compression – an ideal source for high harmonic generation. This soliton dynamics can lead to resonant dispersive wave emission, a mechanism which yields ultrashort wavelength-tuneable pulses in the deep and vacuum ultraviolet (UV) and which can be also exploited to probe transient changes of the gas polarisability.

In this talk, I will introduce the properties of gas-filled fibres, and report results on the generation of a few femtosecond pulses with energies in the microjoule range both in the infrared and UV spectral regions. The repetition rate can be scaled to megahertz level and the phase stability of these pulses can be maintained via keeping under control photoionisation driven instabilities. Finally, I will discuss the spatio-temporal dynamics of plasmas generated inside the hollow-core fibre and the experimental techniques which we developed to investigate such dynamics.

Biography:
Francesco Tani received received his master degree in theoretical physics from the university of Rome La Sapienza in 2010 with a thesis on laser-plasma acceleration. In 2014 he received a PhD in physics from the Max Planck Institute, where he investigated the nonlinear dynamics of ultrashort pulses propagating in gas-filled photonic crystal fibre and exploited these to develop novel light sources and for high harmonic generation. In 2016 after two years as a postdoctoral research fellow in the same institute, he became team leader of the ultrafast nonlinear optics sub-group.