Four-dimensional light shaping: manipulating ultrafast spatiotemporal foci in space and time

Control over the focus of a light field in both space and time can be achieved by exploiting the spectral dispersion of ultrashort pulses. The scheme has been developed by Martin Booth and co-workers from the University of Oxford, UK, Friedrich-Alexander University Erlangen-Nuremberg, Germany and Innsbruck Medical University, Austria. The team passed spatially chirped ultrashort laser pulses through a phase hologram and then focused them using an objective lens. The light pulses were chirped using a pair of blazed gratings, while the phase hologram was encoded into a liquid-crystal spatial light modulator. Focusing gave two- and three-dimensional arrays of focused spots that are strongly confined in the lateral and axial directions. This approach is expected to be useful for applications involving nonlinear optics such as two-photon microscopy and direct laser writing.