Measurement of the Faraday Effect



We performed an experiment to measure the Faraday rotation of polarized light passing through a magnetic field, as well as measuring the Verdet constant of a glass tube with a length of 0.1 m. Linearly polarized light from a HeNe laser was sent through a magnetic field created by a solenoid. The light then passed through an adjustable polarizer and was detected by a photodiode. Using the photodiode, we measured how the intensity of the light changed when turning the polarizer through 360 degrees. We performed this experiment both with and without a glass tube inside the solenoid. We plotted the data as a function of voltage versus angle in plotly in order to find the angle where the voltage measured by the photodiode changed most rapidly. By keeping the polarizer at its most sensitive angle, we plotted voltage versus magnetic field and measured how the voltage changed with magnetic field. We used the lock-in amplifier to make the voltage measurement more accurate.


To observe Faraday effect in this lab, which says that the rotation of plane of polarization of light changes when applying a magnetic field:

\begin{equation} I=I_{0}cos2[\theta_{1}−\theta_{0}]\nonumber \\ \end{equation}

where \(I_{0}\) is the original light intensity and I is the light intensity passing through two polarizers at angles \(\theta_{1}\) and \(\theta_{0}\). To experimentally determine the Verdet constant of a glass tube, which describes the strength of Faraday effect for a particular material:

\begin{equation} \varphi_{B}=C_{v}BL\nonumber \\ \end{equation}

where \(\varphi\) is the shift in polarization, B is the strength of applied magnetic field and L is the length of the glass tube.


more introduction. Explanation of polarization? Transmission of originally unpolarized light through two polarizers?

Light intensity \(I\) after passing through two polarizers at angles \(\theta_{1}\) and \(\theta_{0}\) is predicted to be

\begin{equation} I=I_{0}\cos^{2}[\theta_{1}-\theta_{0}]\\ \end{equation}

where \(I_{0}\) is the original light intensity.

An example for zero field is shown in Fig. \ref{fig:PolarizationDataAtZeroField}