Submicrometer periodicity gratings as artificial anisotropic dielectrics

Abstract

Gratings of dielectric material can act as homogeneous birefringent materials if the wavelength of the incident radiation is greater than twice the period of the grating. For the case of square profile gratings, simple equations predict the birefringence versus linewidth-to-period ratio of the gratings. By using x-ray lithography and reactive ion etching, 240-nm period gratings of polymethylmethacrylate and silicon nitride were fabricated with various linewidths. The birefringence of these was measured at 632.8 nm and found to agree closely with the theory. Silicon nitride gratings which act as half-wave and quarter-wave plates in the visible were made.