Q-switching in a Cr3+: Yb3+: Ho3+: YSGG crystal laser based on the I-5(6)-I-5(7) (lambda=2.92 mu m) transition

An investigation was made of the generation of giant pulses in a new yttriu m scandium gallium garnet laser crystal doped with holmium (Cr3+:Yb3+:Ho3+: YSGG) operating on the basis of the self-terminating I-5(5) - I-5(7) trans ition. Q-switching was performed by an electro-optical lithium niobate swit ch, a passive switch based on an epitaxial film of indium arsenide on a gal lium arsenide substrate, or a passive switch consisting of water. The 2.92 mu m wavelength dominated giant pulse generation, whereas under free-runnin g conditions the radiation was discretely tunable in the range 2.84-3.05 mu m. Depending on the Q-switching method, pulses of 60-160 ns duration were generated and the pulse energy was similar to 20 mJ. The second and fourth harmonics of the holmium laser radiation were generated and the efficiency of each frequency-multiplication stage was similar to 20%.