Complex refractive index mesurement from reflectivity data

In summary, the conversation discusses the methods of obtaining the complex refractive index of a material from reflectivity measurements. It is mentioned that the Kramers Kronig relations can be used to infer some of the data, but there is also a direct method using ellipsometry. Another alternative is using the ratio of reflection of plane and parallel polarized light, although there is still one unknown parameter. Finally, it is suggested that ellipsometry can directly measure n, k, e1, and e2, while reflectivity data from a photospectrometer can also be used with a specific formula.
  • #1
Gobil
59
0
hi All,

Just wondering how you get the complex refractive index of a material from relectivity measurements at a single angle. I understand you must infer some of the data, using the Kramers Kronig relations, is this right?

Is there a direct way of calculating it? I see from an article on elipsometry that is you have the ratio of the reflction of plane and parallel polarised light

from wiki

Ps/Pp = tan(Phi)exp(ixdelta)

where delta is the phase shift, and the amplitued is tan(Phi), but here you still have one unkown. Any ideas on doing this without the kramers kronig relation?

cheers
Gobil
 
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  • #2
ellipsometry measures n, k and e1, e2 directly. however if you have reflectivity data from photospectrometer then you may use R=(n-1)^2+K^2/(n+1)^2+k^2, you will have to account for multiple reflections
 

1. What is a complex refractive index?

A complex refractive index is a measure of how much a material bends light as it passes through it. It is a combination of the material's real refractive index, which describes how fast light travels through the material, and its imaginary refractive index, which describes how much the light is absorbed by the material.

2. How is the complex refractive index measured from reflectivity data?

The complex refractive index can be calculated from reflectivity data using the Fresnel equations, which describe the relationship between the incident angle, reflectivity, and the refractive indices of two materials at an interface. By analyzing the reflectivity data at different angles, the complex refractive index can be determined for a specific material.

3. What are some common techniques for measuring complex refractive index from reflectivity data?

Some common techniques for measuring complex refractive index from reflectivity data include ellipsometry, spectroscopic ellipsometry, and reflectance anisotropy spectroscopy. These techniques use different methods to analyze the reflectivity data and calculate the complex refractive index.

4. Why is measuring the complex refractive index important?

Measuring the complex refractive index is important for understanding the optical properties of materials. It can provide information about the material's composition, structure, and thickness, which are important for many applications such as thin film coatings, photovoltaic devices, and optical sensors.

5. Are there any limitations to measuring complex refractive index from reflectivity data?

Yes, there are limitations to measuring complex refractive index from reflectivity data. These include the assumption of a single-layer material, the need for accurate and precise reflectivity measurements, and the inability to measure the complex refractive index of materials with high absorption coefficients. Additionally, the results may be affected by surface roughness or contamination on the material's surface.

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