Optics-free focusing down to micrometer spot size and spectral filtering of XUV harmonics

Controlling the wavefront of an extreme ultraviolet (XUV) high-order harmonic beam during the generation process offers to focus the beam without resorting to any XUV optics. By characterizing the XUV intensity profile and wavefront, we quantitatively retrieve both the size and the position of the waist of each generated harmonics and show that optics-free focusing leads to focused XUV spot with micrometer size. We use this remarkable coherent effect to demonstrate efficient and adjustable spectral filtering of the XUV light, along with a strong rejection of the fundamental beam, without using any XUV optics

Optics-free ffocusing and application to spectral filtering of XUV beam

Poster session III (Tu4A)International audienceWe experimentally characterize XUV intensity profiles and wavefronts, and demonstrate XUV beams focusing without resorting any optics. We use this coherent effect to spectrally filter group of harmonics. Simulations show possible control of attosecond temporal structure

Optics-Free Focusing and Application to Spectral Filtering of XUV Beam

International audienceWe experimentally characterize XUV intensity profiles and wavefronts, and demonstrate XUV beams focusing without resorting any optics. We use this coherent effect to spectrally filter group of harmonics. Simulations show possible control of attosecond temporal structure

Spectral filtering of high-order harmonics via optics-free focusing

Controlling the wavefront of an extreme ultraviolet (XUV) high-order harmonic beam during the generation process offers the capability of modifying the beam properties without resorting to any XUV optics. By characterizing the XUV intensity profile and wavefront, we quantitatively retrieve both the size and the position of the waist of each harmonic generated in an argon jet. We show that optics-free focusing can occur under specific generating conditions leading to XUV focii of micrometer size. We also demonstrate that each focus is located at distinct longitudinal positions. Using this remarkable XUV wavefront control combined with near focus spatial selection, we experimentally demonstrate efficient and adjustable spectral filtering of the XUV beam, along with a strong rejection of the fundamental beam, without using any XUV optics. The experimental results are compared with simulations providing the impact of the filtering on the temporal profile of the XUV field. It shows that the attosecond structure is preserved and that the beam is more homogeneous after the filtering, thereby reducing the longitudinal focii shift. This is a major step to achieve high XUV intensity and probing ultrafast processes with an improved resolution

Spatiotemporal control of attosecond XUV beams

International audienceSpectral and spatial control of XUV beams is demonstrated combining divergence control at the generating plane with intermediate-field spatial filtering. This control is reproduced by simulations and shows a net improvement of attosecond beam homogeneity

Optics-less focusing of XUV high-order harmonics

By experimentally studying high-order harmonic beams generated in gases, we show how the spatial characteristics of these ultrashort extreme-ultraviolet (XUV) beams can be finely controlled when a single fundamental beam generates harmonics in a thin gas medium. We demonstrate that these XUV beams can be emitted as converging beams and thereby get focused after generation. We study this optics-less focusing using a spatially chirped beam that acts as a probe located inside the harmonic generation medium. We analyze the XUV beam evolution with an analytical model and obtain very good agreement with experimental measurements. The XUV foci sizes and positions vary strongly with the harmonic order, and the XUV waist can be located at arbitrarily large distances from the generating medium. We discuss how intense XUV fields can be obtained with optics-less focusing and how the order-dependent XUV beam characteristics are compatible with broadband XUV irradiation and attosecond science