Nanophotonics and Photonic Crystals

Nanophotonics is that the method to study the properties of materials in nanometer ranges by means of light, to regulate optical waves with structured materials smaller than their wavelength, or to switch optical properties of matter by the controlled optical fields.

Photonic crystals are macroporous materials with interesting properties, especially optical properties.

Construction strategies of Photonic crystals:

1. One-dimensional photonic crystals: In a one-dimensional photonic crystal, layers of various dielectric constant could also be deposited or adhered together to make a bandgap in a single direction. A Bragg grating is an example of this kind of photonic crystal. One-dimensional photonic crystals are often either isotropic or anisotropic, with the latter having potential use as an optical switch.

2. Two-dimensional photonic crystals: In two dimensions, holes could also be drilled in a substrate that's transparent to the wavelength of radiation that the bandgap is planned to block. Triangular and square lattices of holes are successfully employed.

3. Three-dimensional photonic crystals

There are several structure types that are constructed:

1. Woodpile structure: "Rods" are repeatedly etched with beam lithography, filled in, and covered with a layer of the latest material. Because the process repeats, the channels etched in each layer are perpendicular to the layer below, and parallel to and out of phase with the channels two layers below.
    
2. Inverse opals or Inverse Colloidal Crystals: Spheres are often allowed to deposit into a cubic close-packed lattice suspended in a solvent. Then a hardener is introduced that produces a transparent solid out of the quantity occupied by the solvent. The spheres are then dissolved with an acid like Hydrochloric acid.