Refraction is described using the complex index of refraction n*:

The material forming the highly reflective layer (18) is chosen to have a complex index of refraction whose real part (n) is less than about 0.4.

From these signals, the complex index of refraction, (I) or the complex reflection coefficient (II), can be calculated.

The anti-reflective film is formed from a material having a complex refractive index such that reflectance is reduced at each of the two interfaces.

Said support comprises a substrate (1) with complex refractive index n2 and a layer (2) of refractive index n1 and thickness e1.

The synthesized core rod has a complex refractive index profile.