Deep-ultraviolet (DUV) nonlinear optical (NLO) crystals: An application in photonic technologies

An overview on deep-ultraviolet nonlinear optical (DUV NLO) materials was summarized from an extensive literature survey and analyzed the results. Deep-UV NLO crystals are of worldwide interest for the generation of coherent light with wavelength below 200 nm by the direct second-harmonic generation (SHG) output from solid-state lasers. Despite a number of materials shows NLO, only few are available for deep-UV second-harmonic generation (SHG). It is limited by the fundamental requirements of the structure-directing optical properties. KBe2BO3F2 (KBBF) is the sole exception and it exhibits a sufficiently large SHG response and good phase-matchability, but it suffers from the processing difficulties. Various parameters used for the characteristics of DUV NLO Crystals were discussed. Classifications of NLO materials i.e., π-conjugated and non-π-conjugated materials were also discussed. NLO materials of phosphates with their properties were also discussed, which were introduced in recent past by the researchers. In addition, NLO materials (UV and DUV) play significant roles in various applications, were discussed in this article.