Optically pumped cell for novel visible decay of inhomogeneous magnetic field or of rf frequency spectrum

We have constructed a simple laser-pumped device for a visible and real-time display of an inhomogeneous magnetic field in three dimensions. Photographic records of such displays in the form of constant-field contours spaced 5 mG apart are presented. Our device is capable of high spatial resolution, and we have observed contour lines as sharp as 0.02 cm full width. Such real-time high-resolution contours cannot be obtained by conventional point-by-point mapping. Our device can also be used as an unconventional rf frequency spectrum analyzer.