Time-resolved photoemission microspectroscopy based on fs-VUV laser light

A novel photoemission microspectrometer based on focused VUV coherent radiation is presented for simultaneous realization of <100 fs time resolution, <30 meV energy resolution, and sub-micrometer lateral resolution. VUV light at 140 nm wavelength (8.9 eV photon energy) is generated by frequency upconversion of a regeneratively amplified Ti:sapphire laser of 100 fs pulse duration. The VUV light is focused on a sample surface by a Schwarzschild objective of 0.29 numerical aperture. Photoelectrons are detected by a time-of-flight electron spectrometer. The width of the Fermi edge feature of cooled (30 K) polycrystalline copper was observed to be narrower than 40 meV. The energy resolution is close to the Fourier-transform-limited bandwidth of the laser light. Two-photon photoemission with 420 nm light revealed that the lateral resolution is very close to the diffraction-limited spot diameter of 0.9 μm. The microspectrometer is also equipped with a photoemission electron microscope for time-resolved sub-100 nm imaging.