Faraday multipass rotator for use in high accuracy polarimetric or ellipsometric devices

A highly efficient low magnetic field Faraday rotator is presented. A cavity filled with transparent liquid for visible and infrared radiation with a high Verdet coefficient is used. Light travels the cavity several times giving us the advantage of nonreciprocity of the Faraday effect. This cavity is designed in such a way (regarding geometry and the nature of reflecting materials) that it introduces no detectable alteration of the state of polarization of the light, except, under the effect of an applied field, a pure rotation of the polarization plane given by the Faraday law. A rotator using this sort of cavity has potential, in the form of a Faraday modulator, in high precision ellipsometric and polarimetric devices working in the visible and near infrared and using polarization modulation.