Ruby laser with an active feedback

An investigation was made of the characteristics of the radiation emitted by a ruby laser with an active positive or negative feedback. Under negative feedback conditions the emission was in the form of smooth pulses modulated by not more than 10% (rms deviation not exceeding 5%) and with an instantaneous width of the spectrum of $\lesssim$ 0.0008 nm. Under positive feedback conditions the laser emitted one or several high-power pulses.