Contrast Reversal of Magneto-Optical Domain Image by Photo-Elastic Modulator

Two methods were employed to study the fast contrast reversal of magnetic domain images by a photoelastic modulator (PEM). A PEM combined with a quarter-wave plate acts as a polarization rotator, and enables domain observation with fast contrast reversal under exposure to pulsating light. Contrast reversal in as little as 10 ¿s is possible. However, the PEM is driven sinusoidally, hence the domain contrast is modulated, resulting in a low average contrast. When a PEM was employed as a phase compensator with a garnet film polarization rotator, it could dynamically compensate for unwanted contributions from the ellipticity of the sample and the garnet rotator. This combination provided not only fast contrast reversal, but even higher contrast compared with that obtained in conventional methods involving the mechanical rotation of an analyzer. In the latter method, a domain image contrast of 0.82 was derived theoretically, and a contrast of 0.76 was obtained experimentally, for domains with ¿k=0.19° and ¿k=0.13°, whereas the contrast using the conventional mechanical method was 0.72.