Ultrafast polarization-tunable monochromatic extreme ultraviolet source at high-repetition-rate

Abstract

Abstract We report on the development of a high-order harmonic generation (HHG)-based ultrafast high-repetition-rate (250 kHz) monochromatic extreme ultraviolet (21.6 eV) source with polarization tunability, specifically designed for multi-modal dichroism in time- and angle-resolved photoemission spectroscopy. Driving HHG using an annular beam allows us to spatially separate the high-power 515 nm driving laser from the XUV beamlet while preserving the linear polarization axis angle tunability. This enables controlling the polarization state of the XUV radiation with a fixed all-reflective phase-shifter. This scheme leads to a source brightness of 5.7 × 10 12 photons s−1 at 21.6 eV (up to 4 × 10 11 photons s−1 on target) with ellipticities as high as 90%.