The measurement of the Faraday effect in alternating magnetic fields: a new and simple method

Abstract

A method of measuring the peak value of the Faraday rotation induced by a sinusoidal magnetic field is described. No rotating part is needed. The method is general and may, in theory, be used at any frequency. An accuracy better than 1% is reached, for rotation between 0.2 degrees and 60 degrees , at frequencies below about 20 kHz. The device has been tested with a water Faraday rotator for two field amplitudes and at three frequencies. This device may also be of interest in building sinusoidal magnetic field sensors or in studying the variation of the Faraday effect with modulation frequency.

Faraday Rotation Dispersion Measurements of Diamagnetic Organic Liquids and Simultaneous Determination of Natural Optical Rotatory Dispersion Using a Pulsed Magnetic Field

“…2b, Bl = 5.44 × 10 -5 Ec (T m), was obtained by the least-square method, and was used for calibrating the allied magnetic flux density. Most measurement techniques for FR employ modulation of the magnetic field 24,25 or the polarization state. 4,21,26 In these methods, an electromagnet under a weak magnetic field of ~100 mT is usually utilized in combination with a lock-in amplifying technique.…”

All-Optical Measurements of the Verdet Constant in Achiral and Chiral Liquids: Toward All-Optical Magnetic Spectroscopies

“…( ) (18) where χ is an (real) amplitude ratio factor and φ is a relative phase factor. For example, for χ = 1 and φ = ± π/2, one recovers the circular polarization states given in eq 10.…”

“…Clearly, the empirical law given in eq provides a means to find directly the Verdet constant of a material under a given magnetic field strength and for a definite optical path length by measuring the Faraday rotation angle. Using this law, the Verdet constants of various diamagnetic and paramagnetic media, including gases, liquids, and solids, have since been determined experimentally and at several wavelengths. − Most of these measurements relied on magnetic fields produced either by direct current, , alternating current, − or pulsed methods . Except for the latter method, generated magnetic flux densities are relatively weak (<1 T) and measured Faraday rotation angles are small (<1°).…”