The first laser (which is the abbreviation of the words Light Amplification by Stimulated Emission of Radiation) was created in 1961 by Theodore Maiman (b.1927) at the Hughes Research Laboratories. He used a rod of synthetic ruby as the lasing medium. The crystalline structure of ruby is similar to the one of corundum, i.e. a crystal of aluminum oxide (Al2O3), in which the small part of atoms of aluminum (about 0,05 %) is replaced with ions Cr +++. Ruby rod is illuminated by intense impulse of light, which is generated by helical xenon discharge lamp as shown in animation. The ends of ruby rod are highly polished and silvered to serve as laser mirrors. The impulse of light creates the inverse population of electrons in ruby rod and due to the presence of mirrors the laser generation is excited. The duration of the laser impulse is a little bit shorter than the pump impulse of the flash lamp.
A short while after the initial announcement of the first successful optical laser, other labs around the world jumped on the bandwagon trying out many different substrates and ions such as rare earths like Nd, Pr, Tm, Ho, Er, Yb, Gd even Uranium was successfully lased ! Many different substrates were tried such as Yttrium Aluminum Garnet (YAG), glass (which was easier to manufacture), CaF2. As manufacturing techniques improved these lasers rapidly made the transition from the lab bench to commercial applications.