Fabrication, modeling, and characterization of form-birefringent nanostructures

A 490-nm-deep nanostructure with a period of 200 nm was fabricated in a GaAs substrate by use of electron-beam lithography and dry-etching techniques. The form birefringence of this microstructure was studied numerically with rigorous coupled-wave analysis and compared with experimental measurements at a wavelength of 920 nm. The numerically predicted phase retardation of 163.3 degrees was found to be in close agreement with the experimentally measured result of 162.5 degrees, thereby verifying the validity of our numerical modeling. The fabricated microstructures show extremely large artificial anisotropy compared with that available in naturally birefringent materials and are useful for numerous polarization optics applications.