Periodic Reporting for period 4 - HISOL (High Energy Optical Soliton Dynamics for Efficient Sub-Femtosecond and Vacuum-Ultraviolet Pulse Generation)
Okres sprawozdawczy: 2021-01-01 do 2021-06-30
In this work I proposed to use a new regime of high-energy optical soliton dynamics to revolutionize our access to the shortest, sub-femtosecond, high-energy optical pulses in the near-infrared down to the vacuum-ultraviolet range: a region of huge importance to spectroscopy, but poorly served by current sources.
Solitons, a central concept in nonlinear physics, are particle-like nonlinear wave-packets or pulses that maintain their shape upon propagation and interaction. They appear in many areas of physics, including plasmas, magnetic circuits and the atmosphere. Optical solitons form through the balance of linear effects such as dispersion or diffraction, and the intensity dependent refractive index. A wide range of fascinating and useful soliton dynamics have been discovered in solid-core fibres at up to kilowatt peak powers and nanojoule energies, including: pulse self-compression, the emission of radiation analogous to the Čerenkov radiation, inter-soliton collisions, and soliton self-frequency red-shifting due to interactions with molecular oscillations (the Raman effect). By orchestrating soliton dynamics in both time and frequency an extreme transient polarization of the electrons and molecules of the nonlinear medium can be created and a supercontinuum can be formed. Supercontinua can contain the spectral content, for example, of sunlight, spanning from the ultraviolet to infrared, but possess other properties usually associated with lasers, such as directionality and extreme brightness.
The objectives of my proposal are:
1. To study a new regime of ultra high intensity and energy temporal optical soliton dynamics in gas and plasma media in large-bore hollow capillaries. I aim to achieve millijoule energy-scale, soliton dynamics, and thus combine high-field laser science with the physics of solitons.
2. To use these soliton dynamics to create a coherent, ultrafast, table-top and tunable light sources deep into the vacuum ultra-violet (100 nm to 200 nm, 6 eV to 12 eV). I plan to exceed the energy and pulse characteristics of any other known sources in the VUV region.
3. To use these soliton dynamics to produce millijoule scale sub-femtosecond pulses in the visible-infrared spectral region—the shortest isolated optical pulses ever generated there.
4. To combine points 2 and 3 above, in one experiment, to perform sub-femtosecond VUV pump-probe spectroscopy experiments.
Nuclear motion and charge dynamics occur on femtosecond and attosecond timescales respectively. Therefore, to probe the evolution of molecular structure and its interplay with electron dynamics, in real-time, requires pump-probe spectroscopy experiments operating on these time-scales. A very wide variety of atoms, molecules and solids have electronic resonances in the VUV spectral region. To observe the excitation and evolution of electronic wave-packets in these systems, similar to what has been achieved in the XUV region using high-harmonic based attosecond sources, requires a sub-femtosecond VUV source. Indeed, it has been suggested that one might even be able to control the motion of the electronic wave-packets. However, there is a distinct lack of sources in the vacuum ultraviolet (VUV) range (see state of the art below). The tunable, sub-femtosecond, VUV source I propose will address this need. More generally, many of the techniques that provide access to the fundamental properties of matter, such as attosecond transient absorption spectroscopy, photoemission spectroscopy, or photoionization mass-spectroscopy, would directly benefit from a sub-femtosecond VUV source.
Our results have been published in 10 journal papers, with another 5 papers under preparation with the latest results. Furthermore, we have disseminated the results at over 20 conferences, with more than 13 invited talks. A significant part of our dissemination efforts are aimed towards spreading this technology to other leading research groups and to industry. We have open-sourced our numerical modelling code, so that the whole community can make use of it. We have also built more than 10 collaborations with world-leading research groups and facilities, to help install our light-source technology for use in a wide range of scientific applications.