Saturable absorption mode-locking based on intersubband transitions in quantum wells at 2 µm

Passive Mode-Locking of a Tm:YLF Laser

“…While only active modelocking has been demonstrated previously with bulk Tm-or Ho-lasers, more recently single-walled carbon nanotube saturable absorbers (SWCNT-SA) were successfully applied to mode-lock for the first time a Tm:KLu(WO 4 ) 2 laser at 1.95 µm [1]. Alternatively, Ho 3+ -lasers operating at somewhat longer wavelengths, with Tm 3+ used as a sensitizer, were also successfully mode-locked but using semiconductor saturable absorbers: 10 ps pulses near 2.09 µm with Ho,Tm:YAG [2] and 0.57-ps pulses near 2.05 µm with Ho,Tm:KYW [3] were reported. Very recently, again applying semiconductor saturable absorbers for passive mode-locking, pulses with durations around 0.5 ps were generated with Tm-and Tm,Ho:glasses [4] and the first passively mode-locked fluoride crystal, Tm:GdLiF 4 , isomorphic to YLF, delivered 17 ps pulses with broad sub-50 ps tuning range from 1868 to 1926 nm [5].…”