Borosilicates as deep-ultraviolet transparent nonlinear optical crystals: Structural motifs, performance limits and future directions

Abstract

Short-wavelength nonlinear optical (NLO) crystals can convert a specific wavelength of light to ultraviolet (UV) and deep-UV region. To date, most of the commercialized UV and deep-UV NLO materials are borate crystals. By combining the merits of borates and silicates, borosilicates exhibit some unique advantages of rich structural types, moderate second harmonic generation (SHG) response, and high UV transmittance. This paper summarizes the known NLO borosilicates which can be grouped into two types according to the linkage modes of B–O and Si–O units: (1) borosilicates with B–O–Si covalent bond, and (2) borosilicates with isolated B–O and Si–O units. The structural features, SHG intensities, and UV cutoff edges of these borosilicates are discussed. Finally, future perspectives in this field are presented.