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Abstract The application high intensity ultrafast lasers to compact plasma-based electron accelerators has recently been an extremely active area of research. Here, for the first time, we show experimentally and theoretically that carefully sculpting an intense ultrafast pulse in the spatio-temporal domain allows ponderomotive pressure to be used for direct acceleration of electron bunches from rest to relativistic energies. With subluminal group velocity and above-threshold intensity, a laser pulse can capture and accelerate electrons, pushing on them like a snowplow. Acceleration of electrons from rest requires a substantial reduction of group velocity. In this demonstration experiment, we achieve a group velocity of ∼0.6c in a tilted pulse by focusing the output of a novel asymmetric pulse compressor we developed for the petawatt-class ALEPH system at Colorado State University. This direct laser-electron approach opens a route towards exploiting optical spatio-temporal control techniques to sculpt electron beams with desired properties such as narrow energy and angular distributions. The tilted-pulse snowplow technique can be scaled from small-scale to facility-scale amplifiers to produce short electron bunches in the 10 keV−10 MeV range for applications including ultrafast electron diffraction and efficient injection into laser wakefield accelerators for acceleration beyond the GeV level. 

Lightwave pulse shaping in the picosecond regime has remained unaddressed because it resides beyond the limits of state-of-the-art techniques, due to either its inherently narrow spectral content or fundamental speed limitations in electronic devices. The so-called picosecond shaping gap hampers progress in all areas correlated with time-modulated light–matter interactions, such as photoelectronics, health and medical technologies, and energy and materials sciences. We report on a novel nonlinear method to simultaneously frequency-convert and adaptably shape the envelope of light wave packets in the picosecond regime by balancing spectral engineering and nonlinear conversion in solid-state nonlinear media, without requiring active devices. We capture computationally the versatility of this methodology across a diverse set of nonlinear conversion chains and initial conditions. We also provide experimental evidence of this framework producing picosecond-shaped, ultranarrowband, near-transform-limited light pulses from broadband, femtosecond input pulses, paving the way toward programmable lightwave shaping at gigahertz-to-terahertz frequencies. 

Vigorous efforts to harness the topological properties of light have enabled a multitude of novel applications. Translating the applications of structured light to higher spatial and temporal resolutions mandates their controlled generation, manipulation, and thorough characterization in the short-wavelength regime. Here, we resort to high-order harmonic generation (HHG) in a noble gas to upconvert near-infrared (IR) vector, vortex, and vector-vortex driving beams that are tailored, respectively, in their spin angular momentum (SAM), orbital angular momentum (OAM), and simultaneously in their SAM and OAM. We show that HHG enables the controlled generation of extreme-ultraviolet (EUV) vector beams exhibiting various spatially dependent polarization distributions, or EUV vortex beams with a highly twisted phase. Moreover, we demonstrate the generation of EUV vector-vortex beams (VVB) bearing combined characteristics of vector and vortex beams. We rely on EUV wavefront sensing to unambiguously affirm the topological charge scaling of the HHG beams with the harmonic order. Interestingly, our work shows that HHG allows for a synchronous controlled manipulation of SAM and OAM. These EUV structured beams bring in the promising scenario of their applications at nanometric spatial and sub-femtosecond temporal resolutions using a table-top harmonic source. 

Ultrafast laser pulse beams are four-dimensional, space–time phenomena that can exhibit complicated, coupled spatial and temporal profiles. Tailoring the spatiotemporal profile of an ultrafast pulse beam is necessary to optimize the focused intensity and to engineer exotic spatiotemporally shaped pulse beams. Here we demonstrate a single-pulse, reference-free spatiotemporal characterization technique based on two colocated synchronized measurements: (1) broadband single-shot ptychography and (2) single-shot frequency resolved optical gating. We apply the technique to measure the nonlinear propagation of an ultrafast pulse beam through a fused silica window. Our spatiotemporal characterization method represents a major contribution to the growing field of spatiotemporally engineered ultrafast laser pulse beams. 

We present a novel, versatile framework to generate W-level temporally shaped, near transform-limited, UV picosecond pulses via non-colinear sum frequency generation and demonstrate it producing temporally flattop, high-power UV pulses capable of enhancing femtosecond- and attosecond-level electron and Xray free electron lasers brightness. 

We present a novel, versatile framework to generate W-level temporally shaped UV picosecond pulses via non-colinear sum frequency generation and demonstrate it producing temporally flattop, high-power UV pulses capable of enhancing femtosecond- and attosecond-level X-ray free electron lasers. 

Using a novel pulse compressor for the CSU ALEPH facility, we demonstrate direct ponderomotive acceleration of electrons with 1.5J, tilted ultrafast pulses. The < 500keV electrons are directed normal to the tilted pulse front as predicted.