# Ellipsometric measurements on a mirror.

• Hannavdwerk
In summary, the values of Psi and Delta obtained when measuring a mirror under an Ellipsometer depend on the definition of the ellipsometric angles and the reflectivities, which are influenced by the complex refractive index and angle of incidence. Nulling ellipsometry is often used to measure changes in these angles caused by the adsorption of substances onto the mirror's surface. For more in-depth information, Azzam and Bashara's book on ellipsometry is a valuable resource.
Hannavdwerk
Hi,

During my internship I worked with an Ellipsometer.
Now I'm wondering, what values of Psi and Delta do you get when you measure a mirror under an Ellipsometer?
Are there any phaseshifts at all? Because there are no layers on the mirror right?
It's fully reflective in total..

Hanna

It depends. Given a definition of the ellipsometric angles ψ and Δ as:

tan(ψ) exp(iΔ) = Rp/Rs,

Where Rp is the reflection coefficient for p-polarized light and Rs the coefficient for s-polarized light. ψ is then related to the ratio of reflectivities and Δ the relative phase shift experienced by s- and p-polarized light.

The reflectivities are given by the (complex) refractive index and angle of incidence, so ψ and Δ depend on both those quantities. Thus, 'nulling ellipsometry' is often used to measure how those angles change when something adsorbs onto the reflective surface by setting the instrument (compensator, polarizer, and analyzer angles), to zero when measuring the bare surface.

Azzam and Bashara's book has infinite detail about ellipsometry.

## 1. What is the purpose of performing ellipsometric measurements on a mirror?

Ellipsometric measurements on a mirror are used to determine the optical properties of the mirror, such as its reflectance and transmittance. This information can be used to assess the quality of the mirror and to optimize its performance in various applications.

## 2. How is an ellipsometric measurement performed on a mirror?

An ellipsometer is used to perform an ellipsometric measurement on a mirror. This instrument measures the change in polarization of light as it reflects off the mirror's surface. The resulting data is then analyzed to determine the optical properties of the mirror.

## 3. What factors can affect the accuracy of ellipsometric measurements on a mirror?

The accuracy of ellipsometric measurements on a mirror can be affected by factors such as the quality of the mirror's surface, the wavelength of light used, and the angle of incidence of the light. Careful calibration and proper handling of the mirror can also impact the accuracy of the measurement.

## 4. What are the advantages of using ellipsometric measurements on a mirror?

Ellipsometric measurements on a mirror offer several advantages over other methods of measuring optical properties. These include non-destructive testing, high sensitivity, and the ability to measure both transparent and opaque materials.

## 5. How are ellipsometric measurements on a mirror used in practical applications?

Ellipsometric measurements on a mirror are commonly used in industries such as optics, semiconductor manufacturing, and thin film coatings. They can be used to evaluate the quality of mirrors during production, monitor changes in optical properties over time, and aid in the development of new mirror materials and designs.

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