This pattern creates a continuously graded refractive index
profile from air to the material's surface, which essentially provides a pathway for light rays to enter the material and prevents them from reflecting back out.
industry to come up with a practical cloaking device coating that uses graded refractive index
nanocomposite materials to reduce an object's electromagnetic signature, making it appear flat.
Graded refractive index
is of interest for both transformation optics including hyperlenses  and invisibility cloaks .
Instead of shaping the lens to aid eyesight, Isabelle Calderara, a chemist at the contact lens maker Essilor in Creteil, and her colleagues have made a lens that focuses light with a graded refractive index
. In other words, the lens' power to bend light rays changes from the center to the edge, a technique that can potentially be used to make more practical corrective lenses for far-sightedness.
Recently, several continuous design methodologies and implementation by using nanoporous materials have been published on high-performance broadband graded refractive index AR coatings [2-5].
Significant research has focused on finding graded refractive index profiles which minimize reflection for a given AR coating thickness.
In order to answer the above-mentioned question, a systematic study on design of graded refractive index profile for broadband omnidirectional antireflection coatings is performed in this paper.
Using the concepts borrowed from biology, namely, selection, recombination and mutation, optimal graded refractive index profile can be obtained.
Therefore, in this paper, genetic programming algorithm is employed to design and optimize the graded refractive index profile for broadband omnidirectional antireflection coatings in order to decrease the average reflectance of AR coatings to the greatest extent.
The combination of step and graded refractive index
profiles, such as in Figure 1(d), is considered in  for the design of dispersion compensating fibers.