Cr⁴⁺-doped Y₃Al₅O₁₂ as a saturable absorber for a Q-switched and mode-locked 639-nm Pr³⁺-doped LiYF₄ laser

We experimentally prove that a Cr⁴⁺-doped Y₃Al ₅O₁₂ (YAG) crystal exhibits saturable absorption in visible wavelengths at 639, 607, and 521 nm. From z-scan measurements, the saturation energies measured using laser pulse widths of 25 and 66 ns at 639nm are estimated to ~11:5 and 21.2 mJ/cm², respectively. Therefore, the absorption response time will be shorter than these pulse widths. Using the Cr⁴⁺:YAG saturable absorber, we demonstrate for the first time, to the best of our knowledge, the passive Q-switched and the Q-switched mode-lock Pr³⁺-doped LiYF₄ (YLF) lasers at 639nm pumped by an InGaN diode laser.