Patent ID: 8749881

Claim:
A multilayer stack, said stack comprising: a first layer of a first material having an outer surface, a first predefined thickness d H and a refractive index n H between 1.75 and 3.0; and a second layer of a second material having an outer surface, a second predefined thickness d L and a refractive index n L between 1.0 and 3.0, said outer surface of said second layer extending across said outer surface of said first layer, said first layer in direct contact with and extending across said second layer; said first predefined thickness d H and said second predefined thickness d L predefined such that said multilayer stack has a reflection peak of less than 200 nanometers and a dispersion of a center wavelength Δλ c of said reflection peak defined as: Δ ⁢ ⁢ λ c = λ c ⁢  ⁢ θ 0 = 0 0 ⁢ - λ c  θ 0 = 45 0 = 2 ⁢ ( n H ⁢ d H 1 + n L ⁢ d L 1 - n H ⁢ d H 1 - n 0 2 n H 2 - n L ⁢ d L 1 - n 0 2 n L 2 ) is less than 200 nm when said multilayer stack is viewed from 0 degrees and 45 degrees and where λ c at θ o =0° is a center wavelength of said reflection band when said multilayer stack is viewed from 0°, λ c at θ o =45° is a center wavelength of said reflection band when said multilayer stack is viewed from 45° and n o is a refractive index of a medium beyond said multilayer structure.