Highly Efficient Tm3+:LiYF4 Cascade Laser for Telecom Wavelengths

Lasers operating at telecommunication wavelengths around 1.5 μm are demanded, i.e., for optical communication, eye-safe light detection and ranging, materials processing and non-linear frequency conversion. Er3+-based laser systems are well established in this regard. Trivalent thulium (Tm3+) also has potential for laser operation around 1.5 μm utilizing the 3H4→3F4 transition (Fig. 1 a) [1], [2]. However, the long lifetime of ~15 ms of the 3F4 lower laser level facilitates self-termination, preventing continuous-wave (cw) laser operation.