A white-light method of optically reading ferroelectric domains in bismuth titanate crystals is described. This method is based upon the difference in birefringencc in opposite domains in a properly oriented crystal. The white-light operation is made possible by using a second bismuth titanate crystal which compensates one of the domains in the opcrating crystal to zero total retardation for the dark or ‘off state. The oppositely switched domain provides a total retardation of - 200 nm for first-order white transmission in the ‘on’ state. Contrast ratios of = 20 and efficiences of 1 16y; were measured on an operating crystal pair illuminated by a tungsten light source. This white-light read method in combination with one of several available write methods may prove useful in projection display or optical storage applications.
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