Gradiometer Based on Nonlinear Magneto-Optic Rotation, Phase I

This Phase I SBIR project will demonstrate sensitive measurements of magnetic field gradients by nonlinear atomic spectroscopy. The gradients are determined by measuring the magnitudes of the magnetic fields in two atomic vapor cells. A vertical cavity surface emitting laser is used to create an atomic coherence. This coherent state is long lived because of the special construction of the atomic vapor cell. A measurement of the Larmor precession frequency of the coherent state gives a precise measurement of the magnetic field. The field measurement precision should be 0.3 fT in a 1 Hz bandwidth. Two such probes can be tethered at the ends of 80 m cables from a rotating space craft. Typical geophysical gradients of ~ 250 fT can be measured from a single spacecraft with excellent signal/noise. The system uses no cryogenic fluids, no consumable chemicals, and will operate from a few Watts of electrical power. More »