Measurement of Faraday rotation using phase-sensitive low-coherence interferometry.

We report a differential phase sensor capable of measuring Faraday rotation in reflection mode with a single measurement and a small field-depth factor. Based on a polarization-maintaining-fiber low-coherence interferometer, the sensor measures phase difference between two decorrelated and oppositely polarized circular states incident on a sample. Sensitivity of the sensor for the Faraday rotation is 0.31 arcmin, allowing applications on small volumes of liquids. The Verdet constants of various liquids, including clear and turbid samples, are measured at 857 nm.