Investigation of relaxation oscillations in the output from a ruby laser

Measurements have been made on the `spike7rsquo; pulses produced by the relaxation oscillation in the output from a laser using a 90 deg ruby crystal. Pulse shape, width and height, the time interval between successive pulses, and the polarization of the pulses have been accurately measured. The rate equations describing the laser oscillation have been solved for operation of the laser close to threshold. The solution predicts a shape for individual pulses of the form cosh¿2K(t ¿ t0) and this has been verified by the experiments. It is well known that the ruby laser operates in narrow `filaments¿. The solution to the rate equations enabled the diameter and population inversion of the contributing filament to be obtained. Also the measurements on the pulse interval gave the number of filaments active in the crystal at a given time. All the pulses were found to be equally linearly polarized to 99.92%.