Efficient visible laser operation of Tb:LiYF₄ and LiTbF₄

We report laser operation of two Tb³⁺-activated gain media, Tb:LiYF₄ and LiTbF₄, in yellow or/and green spectral region. A record-high slope efficiency of 63% among Tb³⁺-lasers and maximum output power of 1.17 W (incident power of 2.79 W) at around 544 nm were obtained with a c-cut 15%Tb:LiYF₄ crystal. The yellow laser characteristics in σ-polarization were studied. A slope efficiency of 21% at 582 nm was achieved. More importantly, we succeeded in laser operation of LiTbF₄ for the first time to the best of our knowledge. Laser oscillation at around 544 nm yielded a maximum slope efficiency of 45%. This points toward the possibility of producing high-energy pulsed lasers using LiTbF₄, which features a high active-ion concentration as well as relatively long lifetime.