Single Review on past events

Thanks to the invention of photography we are able to capture events, even if they are moving. But how can we observe something that is so fast that our eyes are not able to see? In his presentation on “Ultrafast Science: Shedding Light on Nature's Fastest Events” Daniele Brida explained how this is possible. “If you want to measure something fast you need something even faster”, he pointed out. “Our eyes are not a good instrument for studying fast phenomena.” But which scientific tools can we use to follow events that occur on event faster timescales? A laser is the solution. It can amplify light by stimulating emission of radiation. Whereas ordinary light/sunlight consists of different colors in different waves, standard lasers emit only one color – they are monochromatic –in a peculiar way (coherent) which allows for a lot of storage energy. “If I only have one color, I only have one energy”, says the experimental physicist. “If you fix the energy, time becomes infinitely extended, which means that monochromatic light implies infinitely extended waves.” To obtain really short pulses it is thus necessary to use special lasers that emit a rainbow of different colors at the same time. 

Lasers can, in this way, generate ultrashort pulses down to few femtoseconds (one femtosecond is 10^-15 seconds), and short pulses from ultraviolet to far-infrared (THz). The tunability is important to study different – ultrafast – physical phenomena. Daniele Brida works on the generation of ultrafast pulses and the control of electrons´ motions. His research focuses on ultrafast electronic processes (electron-electron and electron-phonon scattering), electron dynamics in layered materials (e.g. graphene), novel ultrafast sources, as well as nonlinear plasmonics (coherent quantum tunneling).