An instrument has been constructed that can produce any degree of elliptical polarization from linear to circular in the vacuum uv range 1050 Å to 1450 Å using a piezobirefringent retarder of LiF. The apparatus is conveniently described by the Mueller matrices. One of the piezobirefringence constants, P11 - P12, ranged from 4.0-10.0 × 10-13 cm2/dyn for various samples of LiF, and the index of refraction at 1216 Å was 1.79 ± 0.14.
Harold Metcalf and James C. Baird, "Circular Polarization of Vacuum Ultraviolet Light by Piezobirefringence," Appl. Opt. 5, 1407-1410 (1966)