Terahertz spectroscopy using quantum-cascade lasers Heinz-Wilhelm Hübers, Heiko Richter, Martin Wienold, Xiang Lü, Lutz Schrottke and Holger T. Grahn Photoniques, 101 (2020) 27-32 Published online: 29 April 2020 DOI: 10.1051/photon/202010127