7. Conclusion

The control of electromagnetic fields on wavelength scales is a crucial issue. In this respect, diffraction gratings can be considered as the first optical components of nanophotonics, a research and development theme aimed at controlling light at sub-micron or even nanometric scales.

At the end of the 20th century, diffraction gratings paved the way for the development of photonic crystals, and later metamaterials. Metamaterials are materials structured on a scale well below the wavelength to extend the choice of optical materials with negative or near-zero refractive indices. By way of illustration, a planar metal layer that reflects light very well can be made totally absorbent with sub-wavelength structuring