Design criteria to optimize the near perfect anti-reflection coating

We present design criteria to demonstrate nanostructured high performance anti-reflection coatings that allows over 98.5% transmission over a broad visible spectral range with cone angles up to 120°. We propose a methodology to relate the nanostructures with different shapes and sizes as an equivalent of the graded index (GRIN) film. Starting from GRIN film we find the rate of change of refractive index with reference to the film thickness, we then design nanostructures such that their effective refractive index (RI) satisfies the above equality to achieve broadband wide-angle low reflection coating. With the theory presented we can accurately predict the reflectance performance of the nanostructure. We will present the simulation results of the angular and spectral dependences of nanocone anti-reflection structures, with the principle applicable to all other types of nano-structures anti-reflection coatings.