Magneto-optic measurements with a sagnac interferometer

Abstract

We have developed a novel technique for measuring the Faraday effect and the magneto-optic Kerr effect. In a Sagnac interferometer, two optical beams follow identical paths in opposite directions. Effects which break time-reversal symmetry, like magneto-optic effects, will cause destructive interference between the two beams. By measuring the phase shift between circular polarization states reflected from a magnetized sample, we measure the polar magneto-optic Kerr effect to an accuracy of 2 μrad, with a spatial resolution of 2 μm. The interferometric technique provides a number of advantages over conventional polarizer methods, including insensitivity to linear birefringence, the ability to completely determine the magnetization vector in a region, and the ability to sensitively measure magneto-optic effects without an external field.

Key Words:

• Magneto-optic Kerr effect
• magnetism
• fiber optic sensors
• Sagnac interferometer.