Beauty transcends the purpose as love is beyond the needs. Our research is love for the world's beauty.
High-field THz pulses from table-top settings are incredibly appealing for boosting a large number of intriguing investigations, especially in the non-perturbative regime of light-matter interaction. The vast majority of the available schemes for intense THz generation rely on optical rectification from second order nonlinear media. We proposed and demonstrated a new scaling mechanism for the emission of long wavelength radiation via laser-induced gas ionisation. We show that the emission of Terahertz radiation from transient transverse photocurrents increases with the wavelength of the ionising radiation. Employing this new mechanism, we achieved record-breaking peak electric fields for single-cycle pulses in the >15 μm spectral range. See the paper published in Physical Review Letters in 2013.
Other research avenues include parametric processes and nonlinear imaging with Kerr media driven by intense THz pulses.
One of the latest results (see Highlights) shows the phase insensitive scattering of a THz field off an intense 800 nm pulse in Diamond, one of the most fascinating nonlinear media. See the paper published in Photonics in 2017. This it also my first publication as last author 🙂
Not everything is as it seems, and appearance can be misleading. Going beyond the obvious, we have shown how the dynamics of a scene can be perceived "time-reversed" if scattering light sources propagate at superluminal speed. Rest assured, there is no violation of the fundamental laws of physics in our experiments, but the results are nonetheless inspiring. See the paper published in Science Advances in 2016.
Do you want to see how a pulse propagates inside a fibre? Check out our 2017 Scientific Reports paper on this topic. Below, two movies showing a pulse undergoing nonlinear propagation (changing its colours), and a GHz train of linearly propagating pulses, respectively.
Nonlinear propagation in photonics crystal fibres
GHz train linear propagation
Intense laser pulses can trigger the breakdown of air at potential lower than the standard one. We have shown how proper beam shaping can allow electric discharges to be guided along curved paths, avoiding obstacles, or even healing after crashing on a dielectric stopper. See the paper published in Science Advances in 2015 and the video below!
New materials & time-varying media
The light interaction with matter can be enhanced by the dispersion properties of the material. One of the most interesting cases occurs when the real part of the dielectric permittivity approaches zero (Epsilon Near Zero - ENZ). We have recently shown how nonlinear effects are enhanced at the wavelengths where this condition is met. See our recent Physical Review Letters published in 2016.
More recently, we have shown that material properties can be fine-tuned by a suitable combination of light pulses of a different colour. This way, we were able to drive two independent nonlinear processes realising novel effects.
The ability to control the two nonlinearities independently allowed us to increase and tune the film modulation bandwidth, and also to change the wavelength of the testing pulse! See these new results in the Nature Communications published in 2017.
Part of these research activities was funded by the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement n° . The project acronym was KOHERENT. See the project website for more details (KOHERENT Website).