Analysis of influence factors of Faraday rotation measurement by magneto-optic modulation

Abstract

The ultrasensitive measurement of Faraday rotation finds application in many scientific and technological applications. Various polarimetry techniques are used to measure such rotation. The measurement of Faraday rotation based on magneto-optic modulation is most commonly used owing to its effectiveness at low-frequency range. Phenomenologically Faraday rotation in a magneto-optical glass depends upon the characteristics parameter Verdet constant, interaction length and applied axial magnetic field. In this paper, the influence of various factors on the precise measurement of Faraday rotation in magneto-optical glass has been theoretically analyzed and investigated by simulation and experiments. The theoretical analysis shows that the precision of measurement of Faraday rotation is affected by the various factors associated with experimental modalities. The factors namely cross polarization angle, modulation depth, homogeneity of the magnetic field, and extinction ratio of the polarizers have been analyzed. The results show that there is a characteristics impact of systematic variation of the relative polarizer and analyzer orientation. The precision of measurement is influenced by modulation depth and homogeneity of applied magnetic field. The optimum cross polarization angle is dependent on the extinction ratio of polarizers used. Based on the analysis a framework has been proposed to improve the precision of Faraday measurements.