Alkali metal sulfate: A new non-n-conjugated deep-ultraviolet quasi-phase matching crystal

Nonlinear optical crystals with ferroelectricity could realize frequency conversion based on the quasi-phase matching principal, which could effectively break the limitation of the inherent birefringence. Here, an alkali metal sulfate crystal, LiKSO4, is found, which combines a short absorption cutoff edge of 160 nm, a large second harmonic generation response of 4 x KH2O4 and the typical ferroelectric polarization reversal into a single structure. Besides, it possesses an optimized Sr(2)Be(2)B(2)O7-like structure with-S-O -Li-bonds in the adjacent layers, which effectively avoids the layer growth tendency. Therefore, this manuscript provides the first sulfate deep ultraviolet quasi-phase matching crystal, which opens a new horizon for the development of deep-ultraviolet nonlinear optical materials.

Automated summary

A ferroelectric alkali metal sulfate crystal, LiKSO4, is found to combine a short absorption cutoff edge, a large second harmonic generation response, and the typical ferroelectric polarization reversal into a single structure. It possesses an optimized structure with effective layer connections, offering new possibilities for the development of deep-ultraviolet nonlinear optical materials.