Q-switched Nd:YAG/V:YAG monolith microlaser

A specially developed monolith crystal, which combines in one piece cooling undoped part (undoped YAG crystal), active laser part (YAG crystal doped with Nd3+ ions) and saturable absorber (YAG crystal doped with V3+ ions), was used for construction of longitudinally diode pumped Q-switched Nd:YAG laser operating at wavelength 1342 nm. The monolith consists of 4 mm long undoped part bounded to the pumping face of 8 mm long active part doped by Nd3+ ions (1 at.%). Opposite side of crystal was bounded to the V:YAG saturable absorber 530 mu m thick which gives the initial transmission of saturable absorber 88 %. The diameter of whole monolith was 5 mm. This combination of active crystal and saturable absorber allows to realize more compact resonator with the shortest cavity length of 33 mm only. The monolith was mounted in an adjustable watercooled cupreous ring. Temperature of cooling water was in a range from 12 to 14 degrees C. As a pumping source the CW-operating laser diode emitting radiation at wavelength 808 nm with the maximum output power 20 W at the end of the fiber (fiber core diameter 400 gm, numerical aperture 0.22) was used. The diode radiation was focused into the active Nd:YAG crystal by two achromatic doublet lenses with the focal length of 75 mm. The measured diameter of pumping beam focus inside the crystal was 360 gm. The resonator of the Nd:YAG laser was formed by a planar dielectric mirror with high transmission for the pumping radiation (T > 98 % @ 808 nm) together with the high reflectance for the generated radiation (R = 100 % 0 1340 nm), and by a concave (100 mm or 146 mm) dielectric mirror serving as an output coupler. As this coupler a various dielectric reflectors (with the reflectivity from 82 % up to 94 %) was used with the reason to obtain the shortest giant pulse with the maximum power. As the optimal, the stable CW Q-switched output at wavelength 1342 nm with length of pulses 11 ns with repetition rate 6.4 kHz and peak power 6. 1 kW, was obtained.