Patent ID: 7324281

Claim:
An optical element, comprising: a first layer of a first anisotropic material having a first surface, the first layer having a first optical index of refraction corresponding to a first internal axis and a second optical index of refraction corresponding to a second internal axis, the first and second indices being different, the first anisotropic material being biaxial; and a second layer of a second material different from the first anisotropic material and having a second surface in intimate contact with the first surface, the second layer having a third optical index of refraction that is a geometric mean of the first and second optical indices of refraction, wherein the second material is rotated relative to the first anisotropic material, and wherein the first anisotropic material and second material are materials having principal material axes, and wherein the angle of rotation of the second material relative to the first anisotropic material substantially satisfies the relationship: β 1 ⁢ ɛ 1 2 = β 2 ⁢ ɛ 2 2 β 1 ⁢ cos 2 ⁢ ϕ 1 + 1 β 1 ⁢ sin 2 ⁢ ϕ 1 = β 2 ⁢ cos 2 ⁢ ϕ 2 + 1 β 2 ⁢ sin 2 ⁢ ϕ 2 where: ε 1 is a dielectric constant of the first anisotropic material relative to its principal material axis; ε 2 is a dielectric constant of the second material relative to its principal material axis; β 1 ε 1 is a dielectric constant of the first anisotropic material relative to a second material axis of the first material; β 2 ε 2 is a dielectric constant of the second material relative to a second material axis of the second material; and φ 1 is an orientation angle of the principal material axis of the first anisotropic material and φ 2 is an orientation angle of the principal material axis of the second material, φ 2 is defined relative to a normal angle to the second surface.