A polymer layer includes a first in-plane refractive index extending along a first direction of the polymer layer, a second in-plane refractive index less than the first in-plane refractive index extending along a second direction of the polymer layer orthogonal to the first direction, a third refractive index along a direction orthogonal to both the first direction and the second direction, and a plurality of wrinkles extending along a surface of the polymer layer, where a difference between the first in-plane refractive index and the second in-plane refractive index is at least approximately 0.05, and the third refractive index is greater than the second in-plane refractive index.