Relationship between the refractive index and absorption

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SUMMARY

The relationship between the refractive index and light absorption is established through the Kramers-Kronig relations, which connect the real part of the refractive index (η) and the imaginary part (κ) representing absorption. A higher refractive index does not directly imply higher absorption; rather, both components are interdependent and must be analyzed across all frequencies for accurate deductions. Additionally, the intensity of light does not correlate with the refractive index, as refractive index variations depend on the medium's properties and light's wavelength.

PREREQUISITES
  • Understanding of Kramers-Kronig relations
  • Familiarity with complex refractive index (n = η + iκ)
  • Knowledge of Kerr nonlinearity and saturable absorption
  • Basic principles of light-matter interaction
NEXT STEPS
  • Research Kramers-Kronig relations in detail
  • Explore complex refractive index calculations
  • Study Kerr nonlinearity and its applications
  • Investigate the effects of wavelength on refractive index
USEFUL FOR

Geologists, physicists, optical engineers, and anyone involved in material science or light absorption studies will benefit from this discussion.

asdfghhjkl
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Hello,

I was wondering is there a relation between the refractive index of the material and the amount of light the material absorbs (e.g. the higher n means higher absorption)? If so what is then a relation between the intensity of the light and the refractive index?

p.s. I am trying to apply this to some geological thin section observations, thus a simple explanation would be appreciated.

Thank you :)
 
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asdfghhjkl said:
Hello,

I was wondering is there a relation between the refractive index of the material and the amount of light the material absorbs (e.g. the higher n means higher absorption)? If so what is then a relation between the intensity of the light and the refractive index?

p.s. I am trying to apply this to some geological thin section observations, thus a simple explanation would be appreciated.

Thank you :)
There is no relation between the intensity of light and the refractive index.Refractive index depends on the speed of light through the medium.It varies with wavelength too.
 
Last edited:
Ok, thank you.
 
asdfghhjkl said:
Ok, thank you.
Please give thanks by using the "thanks" button. :biggrin:
 
There is a relation between absorption and refractive index which is known as Kramers Kronig relation:
http://www.rp-photonics.com/kramers_kronig_relations.html
However, to deduce the one from the other, you need to know the absorption or refractive index ideally for all frequencies.
 
asdfghhjkl said:
Hello,

I was wondering is there a relation between the refractive index of the material and the amount of light the material absorbs (e.g. the higher n means higher absorption)? If so what is then a relation between the intensity of the light and the refractive index?

Echoing DrDu, absorption is often modeled by allowing the refractive index to be complex-valued (say n = η + iκ) the real part η is the 'refractive' component and the imaginary part κ the 'absorption' component. The components are not independent but related through the Kramers-Kronig relation.
 
The intensity-dependent component of the refractive index is known as the Kerr nonlinearity (real part) and saturable absorption (imaginary part).

Claude.
 

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