Brief Review of the Development of Laser Crystal Physics

Abstract

Quantum electronics has developed from the concept of stimulated emission introduced by Einstein [1]. Yet it did not become a field of scientific research in its own right until the appearance of the well-known investigations by Basov and Prokhorov [2], as well as Townes et al. [3], in which this phenomenon was used for the amplification and generation of electromagnetic oscillations in the microwave region. In 1958 Schawlow and Townes [11] analyzed the possibility of generating and amplifying electromagnetic oscillations over the optical and near-optical range by stimulated emission. They considered the basic theory, and put forward some concrete suggestions concerning the choice of active media and methods for their excitation. In particular, they showed that for this purpose, one can use materials activated by lanthanide (Ln) ions. In the summer of 1960, a year and half later, Maiman announced in the journal Nature the development of a pulsed synthetic ruby laser (Al2O3-Cr3+ crystal) emitting in the red region of the visible spectrum (0.6943 $μ$m) [12]. These reports presented an obvious extension of quantum electronics to the optical range.