Ultrafast polarization-tunable monochromatic extreme ultraviolet source at high-repetition-rate
Antoine Comby, Debobrata Rajak, D. Descamps, S. Petit, Valérie Blanchet, Y. Mairesse, J. Gaudin, Samuel Beaulieu
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>5.7</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mn>12</mml:mn> </mml:mrow> </mml:msup> </mml:math> photons s −1 at 21.6 eV (up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>4</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mn>11</mml:mn> </mml:mrow> </mml:msup> </mml:math> photons s −1 on target) with ellipticities as high as 90%.