A subwavelength grating structure made in an isotropic medium induces form birefringence effects, and the artificially produced optical axis is parallel to the grating vector. The phase shift between the two orthogonal electric-field components exiting this grating varies linearly with the thickness of the grating. When a grating with subwavelength period is formed on a uniaxial birefringent material with the grating vector aligned parallel to its natural optical axis, the total effect enhances the birefringence of the material. As a result, the thickness of the material can be reduced and still produce the same phase shift. If the natural optical axis and the induced optical axis lie within the surface plane and have an angular separation between them, the phase shift varies nonlinearly with the thickness of the grating.
© 1996 Optical Society of America
Chien-Wei Han and Raymond K. Kostuk, "Enhanced phase shift in a zeroth-order beam from subwavelength grating structures formed in uniaxial birefringent materials," J. Opt. Soc. Am. A 13, 1728-1736 (1996)