Development of a 10.8-eV tabletop femtosecond laser with tunable polarization for high-resolution angle-resolved photoemission spectroscopy.

The development of extreme ultraviolet sources is critical for advancing angle-resolved photoemission spectroscopy (ARPES), a powerful technique for probing the electronic structure of materials. Here, we report the construction of a tabletop 10.8-eV femtosecond laser through cascaded third-harmonic generation, which operates at a repetition rate of 1 MHz and delivers a photon flux of ∼1012 photons/s. The system achieves a high energy resolution of ∼11.8 meV and tunable polarization. This flexibility enables detailed studies of orbital and (pseudo)spin characteristics in quantum materials. We demonstrate the capabilities of this laser-ARPES system by investigating several prototypical materials, showcasing its potential for elucidating complex phenomena in quantum materials.