Optical wave propagation in form-birefringent media and waveguides

Characteristics of a periodic structure waveguide with a finite width are studied theoretically and numerically. Propagation constants of two orthogonally polarized fundamental modes converge to values which are different from each other, when the total periodic structure width exceeds twice the wavelength. The asymptotic characteristic equation is derived analytically. The normalized frequency of the high-index layers must be less than unity in order that the optical energy does not localize in the high-index layers. Both the magnitude of the birefringence and the effective refractive index in the form-birefringent media can be controlled by varying the thickness of the high-index layer and the thickness ratio of the high- and low-index materials.