Owing to their vital role in creating and controlling polarized light, birefringent materials are used extensively in various advanced optical systems which in turn impact a large, rapidly increasing range of applications in science and technology. Currently, the fairly small birefringence of MgF2 and the low transmittance of α-BaB2O4 (α-BBO) hinder their efficient application for wavelength below 200 nm. For example, deep-ultraviolet (DUV) birefringent materials for light polarization are urgently needed for DUV lithography. Here we demonstrate based on computational and experimental results that parallel chains of corner-connected planar sp2-hybridized BO3 groups found in Ca(BO2)2 effectively produce large birefringence. Ca(BO2)2 achieves three vital "best" properties including the shortest UV cutoff edge, the largest birefringence, and the highest laser-induced damage threshold (LIDT) compared to all the reported borate birefringent materials. On the basis of a Ca(BO2)2 single crystal, a DUV Glan polarizer has been realized and is more efficient than one constructed with commercially available MgF2.
ASJC Scopus subject areas
- Colloid and Surface Chemistry