Magneto-optical imaging setup for single vortex observation

A recently developed high-resolution magneto-optical imaging (MOI) setup is reviewed. It is the first MOI system capable of resolving the individual vortices in a type-II superconductor. We give a detailed description of the whole setup, and discuss its measured properties in terms of magnetic sensitivity and signal-noise characteristics. A simple model for the image intensity distribution due to a vortex lattice is developed, and for the intensity profile across a single vortex, we find good agreement between model calculations and experimental data. The minimum vortex spacing resolved experimentally is 1.3 mum. Our analysis shows that increased resolution can most easily be achieved by increasing the light input intensity, but maximum resolution is ultimately limited by the effective extinction ratio through the optical system and mechanical vibrations in the setup. (C) 2003 American Institute of Physics.