A remarkable solar-blind ultraviolet nonlinear optical crystal with comprehensive performance and enhanced thermal stability

Abstract

Solar-blind ultraviolet (UV) nonlinear optical (NLO) crystals are urgently demanded for their important applications in modern lasers. Herein, a remarkable solar-blind UV NLO crystal, K[H₂N(CH₂COO)₂], was rationally obtained by tuning alkali metal cations. Interestingly, it was noted that the [H₂N(CH₂COO)₂] groups were held between the helical chains in an ordered arrangement that superimposed their microscopic second-order susceptibilities. Notably, K[H₂N(CH₂COO)₂] exhibited comprehensive NLO performance, including a strong phase-matching SHG response of 1.6 × KDP at 1064 nm and 0.6 × BBO at 532 nm, a suitable birefringence of 0.124 at 1064 nm, a high LDT up to 332 MW cm⁻², a distinct UV cutoff edge of 216 nm, a wide high-transparency window covering 246–1554 nm, the shortest phase-matching wavelength extending to 250 nm and easy growth of centimetre-sized crystals. K[H₂N(CH₂COO)₂] remained thermally stable up to 210 °C in an air atmosphere. This research offers a new approach to further explore solar-blind UV NLO crystals.