The FELBE THz/IR FEL: Overview of the Facility and User Activities

The FELBE User Facility at the ELBE Center for High-Power Radiation Sources offers a pair of FELs that deliver beam to eight different user labs. The FELs are driven by a two-stage Superconducting RF (SRF) linac, which produces a quasi-CW beam (13 MHz/1 mA) at an energy of up to 36 MeV. The tuning range spanned by the two FELs extends from the mid IR to THz (5 – 250 m). The spectral range and ultrashort pulse width (p ≈ 0.7 – 25 ps) are ideal for time-resolved measurements of many types of transient processes in low-dimensional materials [1], quantum structures [2], and correlated systems [3]. The high pulse energy can also drive nonlinear phenomena [4] and strong coupling [5] in light-matter interactions. The FELBE User Labs are equipped with instrumentation and synchronized ultrashort table-top lasers (i.e. Ti:Sa oscillators, regens, OPAs, SFG/DFG) which facilitate various classes of degenerate (single-color), and non-degenerate (two-color) pump-probe experiments. Optical cryostats and an 8 T split coil magnet are also available for low temperature and magnetic field dependent studies. Furthermore, the FELBE beamline extends into the adjacent High Field Magnet Lab (HLD) for performing magneto-optical spectroscopy measurements at fields up to 70 T [6]. The high repetition rate and tunability of the FELBE beam has uniquely enabled revolutionary methods in scattering-Scanning Nearfield Optical Microscopy (s­SNOM) to image novel light-matter interactions with resolution far below the diffraction limit [7]. Proposals for beamtime on FELBE and the other secondary sources at ELBE are invited from users twice a year.
(https://www.hzdr.de/FELBE).

[1] T. Venanzi, et al., ACS Photonics 8, 2931-2939 (2021).
[2] J. Schmidt, et al., Optics Express 28, 25358-25370 (2020).
[3] M. M. Jadidi, et al., Phys. Rev. B 102, 245123 (2020).
[4] F. Meng, et al., Phys. Rev. B 102, 075205 (2020).
[5] B. Piętka, et al., Phys. Rev. Lett. 119, 077403 (2017).
[6] M. Ozerov, et al., Phys. Rev. Lett. 113, 157205 (2014).
[7] T. V. A. G. de Oliveira, et al., Adv. Mater. 33, 2005777 (2021).