• • Birefringence of 0.165 at 532 nm exceeds the 0.1 threshold required for DUV applications, enabling compact polarization control in lithography and spectroscopy.
• • UV cutoff edge below 188 nm ensures transparency in the DUV region, surpassing commercial CaCO3 (240 nm) and enabling sub-200 nm operation.
• • Bandgap >6.2 eV, as required for DUV transmittance, achieved through fluorine substitution and hydrogen bonding that eliminate dangling O bonds.
• • Theoretical analysis pinpoints the [HCO3·F·HCO3] block as the origin of anisotropy, providing a design rule for engineering carbonate-based DUV birefringents.