POINCARE SPHERE INTERPRETATION OF KERR-EFFECT MEASUREMENTS USING A PHOTOELASTIC MODULATOR

There is a growing popularity in the use of photoelastic modulators (PEM's) to measure Kerr loops of magnetic materials. This technique offers several advantages over differential detection, but is more obscure in terms of visualizing how the measured signal actually appears. The Poincare sphere has proved useful in interpreting many polarimetric experiments, but bas not seen use in the recent proliferation of PEM-based detection. This paper describes a highly visual application of the Poincare sphere to magneto-optic detection with a PEM that clarifies how such a large modulation can yield a measurement that is sensitive to small polarization changes in ellipticity and rotation.