Mapping Magnetic Fields with Near-Field Scanning Optical Microscopy*

We present the implementation of a near-field scanning optical microscope (NSOM) to observe

the three components of the magnetic field generated by a set of coils. While previous

instruments have been developed that can measure these fields at the nanoscale, they are capable

of differentiating only one field component at a time. Our device, however, is capable of three-

dimensional measurement simultaneously at the macro scale using orthogonally positioned

magnetic probes based on induction coils. This novel approach enables the possibility of

mapping electromagnetic fields by using Maxwell’s equations to derive the electric field

associated with the measured magnetic field. Over the course of our study, we mapped both

circular and polygonal loops of wire. Our results closely aligned with theoretically simulated

predictions.