Photonic Magnetic Field Sensor
VISIDYNE INC BURLINGTON MA
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Small, in-line polarization rotators or isolators to reduce feedback in fiber optic links can be the basis for excellent magnetic field sensors. Based on the giant magneto-optical GMO or Faraday effect in iron garnets, they with a magnetic field of a few hundred Gauss, 20 mT for an interaction length for an optical beam of a few millimeters achieve a polarization rotation or phase shift of 45 deg 18 cycle. When powered by a small laser diode, with the induced linear phase shift recovered at the shot noise limit, we have demonstrated sensitivities at the 3.3 nTHz12 level for frequencies from 1 Hz to frequencies into the high kHz range. Through further improvements an increase in interaction length, better materials and by far the greatest factor, the addition of a flux concentrator, sensitivities at the pTHz12 level appear to be within reach. We will detail such a design and discuss the issues that may limit achieving these goals.
- Magnetic and Electric Field Detection and Detectors