Ion-exchange in Glasses and Crystals

Since its first observation in 1850, ion-exchange (IEx) has become a fundamental process in many applications involving water treatment, catalysis, chromatography, and the food and pharmaceutical industries. Starting from the early 1900s, another relevant application of IEx has been in the glass industry, with the surface tempering of glass produced by a K+-Na+ ion exchange. Nowadays, photonics has greatly exploited IEx technology: graded-index microlenses, graded-index fibers and integrated optical waveguides and devices are examples of achievements made possible by the IEx process. Moreover, ion-exchange is possible in ferroelectric crystals, too, and has been fundamental for the development of many linear and nonlinear integrated optical devices in lithium niobate and tantalate.