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Journals and Conferences
High-harmonic generation (HHG) traditionally combines ~100 near-infrared laser photons to generate bright, phase-matched, extreme ultraviolet beams when the emission from many atoms adds constructively. Here, we show that by guiding a mid-infrared femtosecond laser in a high-pressure gas, ultrahigh harmonics can be generated, up to orders greater than 5000,… (More)
We demonstrate fully phase-matched high harmonic emission spanning the water window spectral region important for nano- and bioimaging and a breadth of materials and molecular dynamics studies. We also generate the broadest bright coherent bandwidth (≈300 eV) to date from any light source, small or large, that is consistent with a single subfemtosecond… (More)
Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high… (More)
By driving the high harmonic generation process with multi-cycle mid-infrared laser pulses, we demonstrate bright isolated, attosecond soft X-ray pulses for the first time.
High-harmonic generation is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Because of reduced quantum diffusion of the radiating electron wave function, the… (More)
We demonstrate bright coherent X-ray supercontinua generated through fully phase-matched upconversion of mid-IR laser light into the keV spectral region. The ultrabroad bandwidths can support pulse durations of few attoseconds, scalable to zeptosecond time scales.
Phase matching of circularly polarized high-order harmonics driven by counter-rotating bichromatic lasers was recently predicted theoretically and demonstrated experimentally. In that work, phase matching was analyzed by assuming that the total energy, spin angular momentum and linear momentum of the photons participating in the process are conserved. Here… (More)
We present a semi-classical study of the effects of the Lorentz force on electrons during high harmonic generation in the soft and hard X-ray regions driven by near- and mid-infrared lasers with wavelengths from 0.8 to 20 μm, and at intensities below 10<sup>15</sup> W/cm<sup>2</sup>. The transverse extent of the longitudinal Lorentz drift is compared for… (More)
We model soft x-ray high harmonic generation and propagation driven by mid-infrared lasers. We find that multi-cycle laser pulses are ideal for generating shorter bright isolated attosecond pulses via time-gated phase-matching in high-density extended media.
We present a new regime of UV-driven high harmonic generation, where the larger refractive index of ions counterbalances the plasma dispersion. Bright harmonic emission from ions is observed for the first time that extends up to 280 eV.