Q-switching in a Cr3+:Yb3+:Ho3+:YSGG crystal laser based on the 5I6 — 5I7 (λ = 2.92 μm) transition

An investigation was made of the generation of giant pulses in a new yttrium scandium gallium garnet laser crystal doped with holmium (Cr³⁺:Yb³⁺:Ho³⁺:YSGG) operating on the basis of the self-terminating ⁵I₆ — ⁵I₇ transition. Q-switching was performed by an electro-optical lithium niobate switch, a passive switch based on an epitaxial film of indium arsenide on a gallium arsenide substrate, or a passive switch consisting of water. The 2.92 μm wavelength dominated giant pulse generation, whereas under free-running conditions the radiation was discretely tunable in the range 2.84 — 3.05 μm. Depending on the Q-switching method, pulses of 60 — 160 ns duration were generated and the pulse energy was ≈ 20 mJ. The second and fourth harmonics of the holmium laser radiation were generated and the efficiency of each frequency-multiplication stage was ≈ 20%.