High-speed fiber-optic sensor for magnetic-field mapping

A fiber-optic sensor was fabricated with a magnetostrictive multilayer thin-film coating synthesized to have a combination of properties favorable for resolving mm scale inhomogeneities in low level magnetic fields (approx. 100 mOe) varying at MHz rates. High-frequency detection is achieved by mixing signal and local oscillator fields varying at frequencies f and f + fmr/2, into the mechanical resonance of the sensor at fmr. These sensors are expected to be useful for the noninvasive detection of RF magnetic fields, and for mapping the eddy current induced magnetic-field anomalies in nondestructive test evaluation.