Design of Deep-Ultraviolet Zero-Order Waveplate Materials by Rational Assembly of [AlO2F4] and [SO4] Groups

Zero-order waveplates are widely used in the manufacture of laser polarizer waves, which are important in polarimetry and the laser industry. However, there are still challenges in designing deep-ultraviolet (DUV) waveplate materials that satisfy large band gaps and small optical anisotropy simultaneously. Herein, three cases of aluminum sulfate fluorides: Na2AlSO4F3, Li4NH4Al(SO4)2F4, and Li6K3Al(SO4)4F4, with novel [AlSO4F3] layers or isolated [AlS2O8F4] trimers were designed and synthesized by the rational assembly of [AlO2F4] and [SO4] groups through a hydrothermal method. Experiments and theoretical calculations imply that these three possess short cutoff edges (λ < 200 nm) and small birefringence (0.0014–0.0076 @ 1064 nm), which fulfils the prerequisite for potential DUV zero-order waveplate materials. This work extends the exploration of DUV zero-order waveplate materials to the aluminum sulfate fluoride systems.