@article{12726, keywords = {Multidisciplinary}, author = {Laura Rego and Nathan Brooks and Quynh Nguyen and Julio San Román and Iona Binnie and Luis Plaja and Henry Kapteyn and Margaret Murnane and Carlos Hernández-García}, title = {Necklace-structured high-harmonic generation for low-divergence, soft x-ray harmonic combs with tunable line spacing}, abstract = {

The extreme nonlinear optical process of high-harmonic generation (HHG) makes it possible to map the properties of a laser beam onto a radiating electron wave function and, in turn, onto the emitted x-ray light. Bright HHG beams typically emerge from a longitudinal phased distribution of atomic-scale quantum antennae. Here, we form a transverse necklace-shaped phased array of linearly polarized HHG emitters, where orbital angular momentum conservation allows us to tune the line spacing and divergence properties of extreme ultraviolet and soft x-ray high-harmonic combs. The on-axis HHG emission has extremely low divergence, well below that obtained when using Gaussian driving beams, which further decreases with harmonic order. This work provides a new degree of freedom for the design of harmonic combs—particularly in the soft x-ray regime, where very limited options are available. Such harmonic beams can enable more sensitive probes of the fastest correlated charge and spin dynamics in molecules, nanoparticles, and materials.

}, year = {2022}, journal = {Science Advances}, volume = {8}, month = {2022-02}, publisher = {American Association for the Advancement of Science (AAAS)}, issn = {2375-2548}, doi = {10.1126/sciadv.abj7380}, }