By using GaAs as an output coupler as well as a saturable absorber, passive Q-switching of an arc-lamp pumped Nd:YAG laser has been demonstrated. The shortest pulse duration obtained was 77.6 ns, corresponding to a pulse energy of 34 μJ. The laser average output power was 2.1 W with a power density in GaAs at 1.5×103 W cm−2. No optical damage to GaAs was observed without any active cooling. © 1999 Society of Photo-Optical Instrumentation Engineers.