Optical Magnetometer Concepts

摘要

Visidyne has long been active in using ultra-high resolution, at the sub-picometer level optical interferometry to measure physical parameters as: strains, electric fields, and refractive index changes. With support from DARPA-SPO this capability was applied to developing and demonstrating an optics, photonics based magnetometer to detect small magnetic, B-fields associated with underground activities. The motivation for the effort came from the availability of high-activity magneto-optic (MO) materials, crystals that produces large path differences between states of polarization with an applied vector magnetic field, the Faraday effect. These crystals based on e.g., Yttrium Iron Garnets (YIG) were originally developed to serve as in-line isolators or diodes to reduce feedback in laser diode powered fiber optic communication links. Using these crystals, combined with high resolution interferometry allowed us to demonstrate a magnetic field or B-field sensor that in many ways is superior to existing magnetometer concepts, optics based or otherwise, in terms of sensitivity, bandwidth and dynamic range. Small size and low power requirements are features of the sensor.