High harmonics with spatially varying ellipticity

Jennifer L. Ellis*, Kevin M. Dorney, Daniel D. Hickstein, Nathan J. Brooks, Christian Gentry, Carlos Hernández-García, Dmitriy Zusin, Justin M. Shaw, Quynh L. Nguyen, Christopher A. Mancuso, G. S.Matthijs Jansen, Stefan Witte, Henry C. Kapteyn, Margaret M. Murnane

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


We present a method of producing ultrashort pulses of circularly polarized extreme ultraviolet (EUV) light through high-harmonic generation (HHG). HHG is a powerful tool for generating bright laser-like beams of EUV and soft x-ray light with ultrashort pulse durations, which are important for many spectroscopic and imaging applications in the materials, chemical, and nano sciences. Historically HHG was restricted to linear polarization; however, recent advances are making it possible to precisely control the polarization state of the emitted light simply by adjusting the driving laser beams and geometry. In this work, we gain polarization control by combining two spatially separated and orthogonally linearly polarized HHG sources to produce a far-field beam with a uniform intensity distribution, but with a spatially varying ellipticity that ranges from linearly to fully circularly polarized. This spatially varying ellipticity was characterized using EUV magnetic circular dichroism, which demonstrates that a high degree of circularity is achieved, reaching almost 100% near the magnetic M-edge of cobalt. The spatial modulation of the polarization facilitates measurements of circular dichroism, enabling us to measure spectrally resolved magnetic circular dichroism without the use of an EUV spectrometer, thereby avoiding the associated losses in both flux and spatial resolution, which could enable hyperspectral imaging of chiral systems. Through numerical simulations, we also show the generality of this scheme, which can be applied with either the discrete harmonic orders generated by many-cycle pulses or the high-harmonic supercontinua generated by few-cycle driving laser pulses. Therefore, this technique provides a promising route for the production of bright isolated attosecond pulses with circular polarization that can probe ultrafast spin dynamics in materials.

Original languageEnglish
Pages (from-to)479-485
Number of pages7
Issue number4
Publication statusPublished - 20 Apr 2018


Funding. U.S. Department of Energy (DOE), Office of Basic Energy Sciences (BES) (DE-FG02-99ER14982, DESC0002002); National Science Foundation (NSF) (DGE-1144083); Fundación BBVA; Ministerio de Economía y Competitividad (MINECO) (FIS2016-75652-P); Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO); Barcelona Supercomputing Center - Centro Nacional de Supercomputación (BSC-CSN) (RES-FI-2017-3-0004). Acknowledgment. This work was done at JILA. The authors gratefully acknowledge support from the Department of Energy (DOE) Office of Basic Energy Sciences (AMOS program) for the light science aspect of this work, and also thank the DOE Office of Basic Energy Sciences X-Ray Scattering Program for the magnetic spectroscopy measurements performed for this work. J. E., N. B., and Q. N. acknowledge support from the National Science Foundation Graduate Research Fellowship. C. H.-G. acknowledges a 2017 Leonardo Grant for Researchers and Cultural Creators from the BBVA Foundation and support from the Ministerio de Economía y Competitividad (MINECO). S. W. and M. J. acknowledge support from the Netherlands Organisation for Scientific Research (NWO). C. H.-G. thankfully acknowledges the computer resources at MareNostrum and the technical support provided by Barcelona Supercomputing Center—Centro Nacional de Supercomputación. M. M. and H. K. have a financial interest in KMLabs.

FundersFunder number
Office of Basic Energy Sciences
National Science FoundationDGE-1144083
U.S. Department of Energy
Basic Energy SciencesDE-FG02-99ER14982, DESC0002002
Fundación BBVA
Nederlandse Organisatie voor Wetenschappelijk OnderzoekRES-FI-2017-3-0004
Ministerio de Economía y CompetitividadFIS2016-75652-P
Barcelona Supercomputing Center


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