I have a material's $n,k$ file, containing the complex index of refraction for every wavelength: $n(\omega)+ i\ k(\omega)$.

Now I would like to convert it to the dielectric constants: $\epsilon_{\mathrm{real}} + i\ \epsilon_{\mathrm{im}}$

How can I do it?


You don't mention anything about $\mu_r$, the material's relative permeability, so I'll assume you're dealing with optical frequencies, in which case we can treat $\mu_r=1$, due to most materials of interest being non-magnetic at optical frequencies. In that case, the relationship between the complex relative permittivity (also known as the complex dialectric constant) and the complex refractive index is given by

$$\epsilon_{\mathrm{real}} + i\ \epsilon_{\mathrm{im}}=(n+i\ k)^2\ \ ,$$

which can be broken into real and imaginary components as

$$\epsilon_{\mathrm{real}}=n^2-k^2$$ and $$\epsilon_{\mathrm{im}}=2nk\ \ .$$


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.