KHC2O4·B(OH)3: A nonlinear optical crystal with large birefringence in the short‐wavelength ultraviolet region.

Exploring nonlinear optical crystals with large birefringence in the short‐wavelength ultraviolet (SWUV) regions (≤300 nm) is a valuable pursuit. Herein, KHC2O4·B(OH)3, which is composed of infinite [HC2O4]− and [B(OH)3] chains, was successfully grown via the slow evaporation method. The [HC2O4]− and [B(OH)3] chains endow KHC2O4·B(OH)3 with the largest birefringence (0.164@1064 nm) of all B(OH)3‐containing compounds that have been reported in the SWUV regions. Moreover, it possesses a moderate second‐harmonic generation response (0.3 × KH2PO4) and a short UV cutoff edge of 254 nm. The electron localization function diagram indicates the large birefringence originates from the HC2O4 and B(OH)3 groups. This work provides a new method to investigate crystals with large birefringence in the B(OH)3‐based oxalate system. [ABSTRACT FROM AUTHOR]