Widely tunable 1.94-mm Tm:BaY2F8 laser

A novel BaY2F8 crystal doped with thulium ions is grown and extensively investigated. Owing to the large number of vibronic levels and to a favorable electron-phonon coupling, extremely wide absorption and emis-sion bands around 1.9 mm are observed. A room-temperature Tm: BaY2F8 laser tunable over a 210-nm in-terval, from 1849 to 2059 nm, is demonstrated.