ABSTRACT
Chapter 19, Birefringent Ray Trace, presents ray tracing algorithms for anisotropic materials, incorporates polarization ray tracing matrices with birefringent interface, and addresses the handling of double refraction/ray doubling.
The optical properties of birefringent materials depend on the direction of the light’s polarization, as opposed to isotropic materials which have identical properties in all directions. Isotropic materials are characterized by scalar dielectric constant or refractive index, while anisotropic materials are characterized by 3×3 dielectric tensors and 3×3 gyrotropic tensors. Ray tracing through birefringent materials is different from ray tracing isotropic materials. Rays refracting into anisotropic media are decomposed into two rays with different propagation directions and orthogonal polarizations. These two rays are eigen-modes and propagate without change of polarization state. The ray tracing details are different for each type of birefringent materials, including uniaxial, biaxial, and optically active materials.
This chapter describes the interaction of light with birefringent materials, with algorithms relating the split light fields before and after birefringent interfaces and a method to track the multiple rays generated due to ray doubling. The ray tracing algorithm for birefringent ray intercepts tracks the electric field orientations, complex Fresnel coefficients, refractive indices of each eigenmode and the ray direction change, both propagation vector and Poynting vector, through birefringent interfaces using the polarization ray tracing matrix. This anisotropic algorithm handles double refraction and reflection, coated anisotropic interfaces, evanescent rays, including total internal reflection and inhibited reflection.
