Fast imaging polarimeter for magneto-optical investigations

A new imaging polarimeter for magneto-optical investigations is described. Improvements over conventional magneto-optics are: it (i) is insensitive to uneven illumination, (ii) determines also the sign of the magnetic field, and (iii) has significantly improved sensitivity at small magnetic fields. The typical root-mean-square (rms) noise level is 0.7 mT Hz(-1/2) for a single pixel, corresponding to a polarization rotation of 0.03 deg Hz(.)(-1/2) With limited temporal and spatial averaging, the rms error in magnetization profiles can be reduced to < 10 muT, corresponding to 4x10(-4) deg. Time resolution is 12 frames per second. Demonstration of the performance of the polarimeter is given for measurements of the local field above superconductors and for measurements of the rotation angle of sugar dissolved in water. (C) 2001 American Institute of Physics.