FARADAY-EFFECT CURRENT SENSOR WITH IMPROVED SENSITIVITY-BANDWIDTH PRODUCT

We report a new design for a Faraday effect current sensor based on yttrium iron garnet that has substantially greater bandwidth than previous designs and is much easier to fabricate. The measured sensitivity is 0.7 degrees/A, with a -3-dB bandwidth of 500 MHz, which gives an improvement in sensitivity-bandwidth product of approximately 45. A noise-equivalent current of 840 nA/Hz(1/2) was measured at 1.8 kHz by difference-over-sum processing. The use of turning prisms with phase-preserving coatings greatly simplifies construction, improves electrical isolation, and increases sensitivity through proximity effects.