Time-resolved and angle-resolved photoemission spectroscopy (trARPES) is a powerful method to detect the non-equilibrium electronic structure in solid systems. In this study, we report a trARPES apparatus with tunable photon energy selectively among 12, 16.8, and 21.6 eV at a repetition rate of 400 kHz. The energy and temporal resolutions of the three harmonics are determined as 104/111/157 meV and 276/190/154 fs, respectively. The photon flux on the sample is estimated to be 1010–1011 photons/s by using a photodiode. Finally, the performance of this setup is verified by both equilibrium and non-equilibrium ARPES measurements on topological materials Zr2Te2P and Bi2Se3. Meanwhile, the importance of the tunability of the extreme ultraviolet (XUV) source is highlighted by comparing experimental results measured with the three different photon energies.
High-order harmonic generation (HHG) has a broad spectrum covering vacuum ultraviolet to extreme ultraviolet (XUV) bands, which is useful for applications involving material analyses at different information depths. Such an HHG light source is perfect for time- and angle-resolved photoemission spectroscopy. Here, we demonstrate a high-photon flux HHG source driven by a two-color field. Applying a fused silica compression stage to reduce the driving pulse width, we obtained a high XUV photon flux of 2 × 1012 phs/s @21.6 eV on target. We designed a classical diffraction mounted (CDM) grating monochromator that can achieve a wide range of photon energy from 12 to 40.8 eV, while the time resolution is improved by reducing the pulse front tilt after the harmonic selection. We designed a spatial filtering method to adjust the time resolution using the CDM monochromator and significantly reduced the pulse front tilt of the XUV pulses. We also demonstrate a detailed prediction of the energy resolution broadening which is caused by the space charge effect.
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