Nanoscale X-ray source by high harmonic generation in a capillary

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Description/Abstract

Short pulse X-ray radiation at nanometer wavelength provides a nanoscale source for a wide range of applications in nanoscience and technology. We demonstrate the generation of coherent ultrafast soft X-rays by high harmonic generation in a capillary filled with argon gas. Harmonics up to the 29th order, at wavelengths down to 25nm, are obtained. The enhancement of particular harmonic intensities and tuning of wavelength position is achieved by controlling the argon ionization level either by changing the average intensity of the laser pulse or by varying the chirp of the laser pulse. We observe an ionization dependent blue shift of the fundamental wavelength that is directly imprinted on the harmonic wavelengths. We now aim to focus the x-ray beam with a tapered fibre to obtain a nanometer size spot for nanoscale imaging of small objects and to directly observe dynamics with simultaneously high temporal and spatial resolution.