Recent advances in nonlinear optics have enabled the generation of structured attosecond pulses with controllable angular momentum properties, including extreme-ultraviolet beams with spin and orbital angular momentum, and high-harmonics with selftorque --- time-dependent orbital angular momentum.
We use a Hartmann wavefront sensor to measure single-shot wavefronts of high-order harmonics to study how they vary with generation parameters. We then use a new type of sensor with spectral resolution.
Here we demonstrate control over the refraction of XUV radiation by using a gas jet with a density gradient across the XUV beam profile. In a first set of experiments, a gas-phase prism and a gas-phase lens are demonstrated.
By studying the spatial profiles of high-order harmonics generated in a gas jet, we show how harmonic beam profiles can be controlled and demonstrate that harmonics can be generated as converging beams thereby focused without XUV optics
By controlling the intensity profile and wavefront of XUV high-order harmonics generated in a gas jet, we establish the possibility of focusing harmonic beams to micrometer spot size and achieve efficient spectral filtering without resorting to any XUV optics.
We establish an extreme ultraviolet lock-in detection scheme, allowing the isolation and amplification of weak chiral signals, by achieving a direct time-domain polarization control. We demonstrate it by a phase-resolved measurement of magnetic circular dichroism.
