title: Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness.
abstract: The brightness of a light source defines its applicability to nonlinear phenomena in science. Bright low-frequency terahertz (<5 THz) radiation confined to a diffraction-limited spot size is a present hurdle because of the broad bandwidth and long wavelengths associated with terahertz (THz) pulses and because of the lack of THz wavefront correctors. Here using a present-technology system, we employ a wavefront manipulation concept with focusing optimization leading to spatio-temporal confinement of THz energy at its physical limits to the least possible three-dimensional light bullet volume of wavelength-cubic. Our scheme relies on finding the optimum settings of pump wavefront curvature and post generation beam divergence. This leads to a regime of extremely bright PW m(-2) level THz radiation with peak fields up to 8.3 GV m(-1) and 27.7 T surpassing by far any other system. The presented results are foreseen to have a great impact on nonlinear THz applications in different science disciplines.
authors.affiliation: Paul Scherrer Institute, SwissFEL, 5232 Villigen, Switzerland.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Shalaby
authors.affiliation: 1] Paul Scherrer Institute, SwissFEL, 5232 Villigen, Switzerland [2] Ecole Polytechnique Federale de Lausanne, 1015 Lausanne, Switzerland.
authors.forename: Christoph P
authors.initials: CP
authors.lastname: Hauri