Energy losses in a passive Q-switched ruby laser

An experimental investigation has been performed in order to explain why the output energy from a ruby laser is always reduced when passing from normal laser operation to -switching operation. A saturable absorber was used as the switching element; however, the discussion about the energy losses is valid for every -switching system. Experimental data allow one to evaluate the decrease of the output energy due to the reduced pumping efficiency, to the losses in the optical switch, and to the incomplete depletion of the inversion arising from the spatial inhomogeneity of the standing wave in the resonator and from the relaxation processes in the ruby line.