Intracavity second-harmonic pulse generation at 261 and 320 nm with a Pr³⁺:YLF laser Q-switched by a Co²⁺:MgAl₂O₄ spinel saturable absorber

We demonstrated the power scaling of a passively Q-switched Pr³⁺:LiYF₄ (YLF) laser at 523, 607, and 640 nm with a Co²⁺:MgAl₂O₄ (MALO) saturable absorber and analyzed the experimental results with a numerical simulation based on rate equations. A maximum pulse energy of 33.5 µJ was obtained with a pulse width of 30.9 ns and a repetition rate of 64.0 kHz at 640 nm. We demonstrated ultraviolet pulse generation at 261 and 320 nm by intracavity frequency doubling and obtained 63.3-ns pulses with a pulse energy of 7.0 µJ and a repetition rate of 64.6 kHz at 320 nm as well as 356-ns 261-nm pulses with a pulse energy of 0.2 µJ at a repetition rate of 82.0 kHz. To the best of our knowledge, a 261-nm pulse is the shortest wavelength laser directly generated from the intracavity second-harmonic generation of passively Q-switched lasers.