Dielectric mirrors are made of multiple layers of transparent materials, each of which reflects a small fraction of the light that hits it. At a specific layer thickness, the reflected light waves merge and amplify, intensifying the reflection. In earlier dielectric mirrors, the efficiency of the mirror fell as the angle of reflected light increased - until at a critical angle no light at all was reflected. This effect is known as Brewster's law.

However, the new polymer mirrors have alternating layers of positive and negative "birefringent" materials such as polymethylmethacrylate and polyester. Light passing through the birefringent polymer splits into two rays that travel through the material at different speeds. By controlling the interactions of the reflected light beams, the researchers were able to minimise the effect of Brewster's law and induce light to reflect off the polymer mirror, no matter what its initial angle of approach.