We have compared two solid-state saturable absorbers for Q-switching of longitudinally diode-pumped Nd:YAG
laser operating at wavelength 1444 nm: vanadium doped garnet (V3+:Y3Al2O5, V:YAG), and cobalt doped spinel
(Co2+:MgAl2O4, Co:MALO). V:YAG crystal with initial transmission 91% was 2.2mm thick. Co:MALO crystal
with initial transmission 91% was 2.0mm thick. Q-switched laser consisted of the Nd:YAG composite rod (8mm
long Nd-doped part, 4mm long undoped YAG part) and the saturable absorber placed in 80mm long hemispheric
cavity. As an output coupler was used concave mirror (r = 150mm) with reflectivity 98% on lasing wavelength.
Giant pulses were obtained with both passive Q-switches. When V:YAG saturable absorber was used, 55 ns long
(FWHM) pulses were generated with peak power 0.47kW (pulse energy 26 &mgr;J). Using Co:MALO, more powerful
pulses were obtained (40 ns long, 1.0kW peak power, 45 &mgr;J energy). Advantage of less efficient V:YAG consist
in possibility of diffusion bonding between Q-switch and laser active medium which allows to prepare miniature
compact laser device. This concept was demonstrated by using of Nd:YAG/V:YAG monolith crystal (4mm long
undoped YAG part, 8mm long Nd:YAG part, 0.5mm long V:YAG part - initial transmission 97% @ 1444 nm).
This monolithic crystal, originally designed for 1338nm lasing, was placed into 23mm long cavity resonating
at wavelength 1444 nm. For output coupler reflectivity 96% pulses 39 ns long with peak power 0.64kW were
generated at wavelength 1444 nm.