Generation of bright phase-matched circularly-polarized extreme ultraviolet high harmonics

• DOI: 10.1038/nphoton.2014.293
• Publication Date: 2014-12-08T16:43:30Z
• Authors: Ofer Kfir; Patrik Grychtol; Emrah Turgut; Ronny Knut; Dmitriy Zusin; Dimitar Popmintchev; Tenio Popmintchev; Hans Nembach; Justin M. Shaw; Avner Fleischer; Henry Kapteyn; Margaret Murnane; Oren Cohen
• Keywords: Physical sciences; Physical Sciences; 0103 physical sciences; Mathematical sciences; physics.optics; 01 natural sciences; 7. Clean energy; Mathematical Sciences; Optoelectronics & Photonics; 3. Good health

Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollowcore waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution.