Calculate dielectric function from n and k

In summary, the speaker is asking for advice on how to calculate the dielectric function of a thin silicon film using the real and imaginary components of the refractive index. They provide a link to a potential formula and mention the importance of getting the signs of the permittivity correct. Another participant clarifies that the assumption of \mu = \mu_0 is not necessary in optics as all magnetic effects are included in the wavenumber dependence of the dielectric constant.
  • #1
bad80
1
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Dear All,

I am trying to calculate the dielectric function of a thin silicon film from the real and imaginary values of the refractive index, which I have for wavelengths between 300 and 900 nm. If I have the n and k values (real and imaginary components of the refractive index), could anyone advise me as to how excactly to calculate the dielectric function from these values?

Am I correct in thinking the formulae shown under the 'Relation to dielectric constant' section in the following link are the right formulae to use?

http://en.wikipedia.org/wiki/Refractive_index

Any advice would be greatly appreciated.

Thanks.
 
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  • #2
Assuming that the material is nonmagnetic ([itex]\mu = \mu_0[/itex]), you can just use [itex]\epsilon = (n+ i k)^2[/itex]. Of course, you have to be careful to make sure you get the signs of the real and imaginary parts of the permittivity right.
 
  • #3
In optics, the statement [tex] \mu=\mu_0[/tex] is not an assumption about the material being non-magnetic, but a definition. All magnetic effects are taken care of by the wavenumber dependence of the dielectric constant.
 

FAQ: Calculate dielectric function from n and k

1. What is the dielectric function?

The dielectric function, denoted as ε, is a complex quantity that describes the response of a material to an applied electric field. It is a fundamental property of a material that characterizes its ability to store and transmit electric energy.

2. How is the dielectric function calculated from n and k?

The dielectric function can be calculated from the refractive index (n) and extinction coefficient (k) using the following formula: ε = n2 - k2. Both n and k are experimentally measured quantities that provide information about the optical properties of a material.

3. What is the physical significance of the real and imaginary parts of the dielectric function?

The real part of the dielectric function (ε1) represents the material's ability to store electric energy, while the imaginary part (ε2) describes its ability to dissipate this energy. In other words, ε1 and ε2 correspond to the material's electric permittivity and conductivity, respectively.

4. Can the dielectric function be used to determine the optical properties of a material?

Yes, the dielectric function is directly related to the optical properties of a material, such as its reflectance, transmittance, and absorbance. By knowing the dielectric function, we can predict and understand how a material will interact with light.

5. How does the dielectric function change with the frequency of the applied electric field?

The dielectric function is frequency-dependent, meaning that it can change at different frequencies of the applied electric field. This is because the response of a material to an electric field is influenced by the energy levels and interaction of its constituent particles, such as electrons and atoms. As the frequency changes, the behavior of these particles also changes, resulting in a different dielectric function.

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