Improvement of vortex imaging in magneto-optical technique and Bitter decoration

We propose a method that improves spatial resolution of magnetic imaging technique to study vortex arrangements in type-II superconductors. Using an indicator film coated with niobium, we have succeeded in resolving single vortices in magneto-optical images. The quality of the observed images is consistent with the calculated results in which characteristics of the present optical system are taken into account. According to this calculation, improvements of the optics or direct deposition of niobium film onto the garnet layer enables us to obtain vortex images in a single-shot image. This observation of vortices in the niobium-coated indicator film indicates the possibility of observations of vortex arrangements in many kinds of superconductors including high-Tc superconductors. This idea of flux squeezing can also be effective in Bitter decoration to increase the operation fields higher than 1 kOe even in high-Tc superconductors.