Reflection coefficient

[lumiza]

Would you provide more information on how the reflection coefficient has been calculated in the Refractive Index Info software. Is it based on the Fresnel equations, with the refractive index of material being a functionsof the wavelength?

Thanks

Lumi

[mikhail]

Hi Lumi,

yes, reflection is calculated at the specified wavelength using Fresnel equations

[sensij]

If I understand correctly, the Fresnel equations are only valid for perfect insulators. The reflectance i get when using them for the metals listed does not match the shown values. However, if I include the extinction coefficient the numbers match at normal incidence. I'm not sure how to incorporate that term into the S-pol and P-pol equations though.

[mikhail]

Fresnel equations work in all cases, but you have to use complex refractive index n'=n+ik. In the case of oblique incidence all angles have to be treated as complex numbers too.

[AnaitaJones]

How does it work? Can yo explain it with example?

[mikhail]

Example: Aluminum at 0.6 microns

Real and imaginary part of the complex index of refraction from the database:
n = 1.26232
k = 7.1855

Complex index of refraction:
n' = 1.26232 + i*7.1855

Reflectance at normal incidence:
R = abs( (n'-1)/(n'+1) ) ^2 = 0.91103

See http://en.wikipedia.org/wiki/Fresnel_equations for the equations