What is it about?
High-order harmonic generation (HHG) provides scalable sources of coherent extreme ultraviolet radiation with pulse duration down to the attosecond time scale. Efficient HHG requires the constructive interplay between microscopic and macroscopic effects in the generation volume, which can be achieved over a large range of experimental parameters from the driving field properties to those of the generating medium. Here, we present a systematic study of the harmonic yield as a function of gas pressure and medium length. Two regimes for optimum yield are identified, supporting the predictions of a recently proposed analytical model. Our observations are independent on the focusing geometry and, to a large extent, on the pulse duration and laser intensity, providing a versatile approach to HHG optimization.
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Why is it important?
How to optimize high-order harmonic generation in gases is a frequently asked question. Thre phase matching conditions lead to two optimal efficient high harmonic generation regions on the pressure medium length space as summarized in well written recent reviews (see https://www.nature.com/articles/s42254-022-00522-7 ). In this work jointly conducted at ELI-ALPS Research Institute and at the Lundh Laser Center, led by the 2023 Nobel Laureate Physict A. L’Huillier, the experimental validation of such prediction is established for the first time.
Perspectives
We present in this work the first experimental validation of the hyperbolic phase-matching model, first published in “How to optimize high-order harmonic generation in gases,” Nat. Rev. Phys. 4(11), 713–722 (2022). The model allows us to identify the parameter space for phasematching of high-order harmonics with a simple one-dimensional parametric curve. The analytic calculation required is simple and depends on only a few parameters, the gas medium, driving laser wavelength, and harmonic order. To test that the model has no explicit dependence on the specific focusing geometry, laser intensity and pulse duration, we show results of experiments performed at two different sources, the GHHG Sylos Long beamline at ELI-ALPS and the Intense XUV Beamline of the Lund Laser Centre, where these parameters are varied.
Subhendu KAHALY
Extreme Light Infrastructure Hu Nonprofit Ltd
Read the Original
This page is a summary of: Two phase-matching regimes in high-order harmonic generation, Optics Express, September 2023, Optical Society of America (OSA),
DOI: 10.1364/oe.488298.
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