Multi-μJ 12 μm Femtosecond GaSe-based OPCPA at 1 kHz Repetition Rate Pia Fuertjes, Martin Bock, Lorenz von Grafenstein, Uwe Griebner and Thomas Elsaesser EPJ Web Conf., 267 (2022) 01022 Published online: 18 October 2022 DOI: 10.1051/epjconf/202226701022