Tunable visible laser based on a sapphire crystal with colour centres

An investigation was made of the optical stability of the active medium in the form of Al₂O₃ containing colour centres and subjected to two-channel laser pumping. This laser medium retained its high stability under the action of pumping in the 305 and 460 nm bands because of a dynamic balance between forward and reverse charge-transfer processes in the colour centres under two-stage ionisation conditions. An optical system was proposed and a stable tunable (in the green—orange range at 520 — 630 nm) laser was demonstrated.