University of Colorado

Colorado State University Research Foundation

Tenio V Popmintchev

Henry C Kapteyn

Margaret Mary Murnane

Dimitar V Popmintchev

Jorge J Rocca

David M Gaudiosi

Margaret M Mumane

Brendan A Reagan

Michael E Grisham

Ming-Chang Chen

Alon Bahabad

A method for extending and enhancing bright coherent high-order harmonic generation into the VUV-EUV-X-ray regions of the spectrum involves a way of accomplishing phase matching or effective phase matching of extreme upconversion of laser light at high conversion efficiency, approaching 10in some spectral regions, and at significantly higher photon energies in a waveguide geometry, in a self-guiding geometry, a gas cell, or a loosely focusing geometry, containing nonlinear medium. The extension and enhancement of the coherent VUV, EUV, X-ray emission to high photon energies relies on using VUV-UV-VIS lasers of shorter wavelength. This leads to enhancement of macroscopic phase matching parameters due to stronger contribution of linear and nonlinear dispersion of both atoms and ions, combined with a strong microscopic single-atom yield.

Generation of VUV, EUV, and X-ray light using VUV-UV-VIS lasers

Phase-matched high-order harmonic generation of soft and hard X-rays is accomplished using infrared driving lasers in a high-pressure non-linear medium. The pressure of the non-linear medium is increased to multi-atmospheres and a mid-IR (or higher) laser device provides the driving pulse. Based on this scaling, also a general method for global optimization of the flux of phase-matched high-order harmonic generation at a desired wavelength is designed.

Phase-matched generation of coherent soft and hard X-rays using IR lasers

A pre-ionized medium created by a capillary discharge results in more efficient use of laser energy in high-order harmonic generation (HHG) from ions. It extends the cutoff photon energy, and reduces the distortion of the laser pulse as it propagates down the waveguide. The observed enhancements result from a combination of reduced ionization energy loss and reduced ionization-induced defocusing of the driving laser as well as waveguiding of the driving laser pulse. The discharge plasma also provides a means to spectrally tune the harmonics by tailoring the initial level of ionization of the medium.

High-order harmonic generation in a capillary discharge

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Tenio V Popmintchev