Measuring the Faraday effect in olive oil using permanent magnets and Malus' law

TL;DR

This paper introduces a straightforward setup using permanent magnets and Malus' law to measure the Faraday effect in olive oil, achieving precise phase shift detection and characterizing its Verdet coefficient with dispersion modeling.

Contribution

The study demonstrates a simple, accurate method to measure the Faraday effect in liquids like olive oil, including detailed dispersion analysis of the Verdet coefficient.

Findings

Verdet coefficient of olive oil measured as 192 ± 1 deg T^{-1} m^{-1}

The Verdet coefficient fits a Drude-like dispersion law with specific parameters

Phase shifts as small as ±50 μrads can be reliably detected

Abstract

We present a simple permanent magnet set-up that can be used to measure the Faraday effect in gases, liquids and solids. By fitting the transmission curve as a function of polarizer angle (Malus' law) we average over fluctuations in the laser intensity and can extract phase shifts as small as $\pm$ 50 $\mu$rads. We have focused on measuring the Faraday effect in olive oil and find a Verdet coefficient of $V$ = 192 $\pm$ 1 deg T$^{-1}$ m$^{-1}$ at approximately 20 $^{\circ}$C for a wavelength of 659.2 nm. We show that the Verdet coefficient can be fit with a Drude-like dispersion law $A/(\lambda^2 - \lambda_0^2)$ with coefficients $A$ = 7.9 $\pm$ 0.2 $\times$ 10$^{7}$ deg T$^{-1}$ m$^{-1}$ nm$^2$ and $\lambda_0$ = 142 $\pm$ 13 nm.