Relationship Between a Cross Sectional Shape and Developing Conditions in a Grating Made by Magnetic Lithography

A new method, previously reported, for fabricating optical diffraction gratings involves writing a periodic magnetic pattern in a magnetic memory medium and using a magnetic fluid as magnetic toner to render the pattern visible. Using this method, an optical grating can easily be prepared even on convex and concave surfaces. Because the optical characteristics of such relief-type gratings are determined by the cross-sectional shape, it is important that the cross-sectional shape be studied prior to application of the method in encoder plates or optical components. When the grating constant is small, the positions at which the magnetic fluid is deposited change from domain walls to magnetic domains. By analyzing the Fraunhofer diffraction pattern of such gratings, the relationship between cross-sectional shape and developing conditions was investigated. According to the results, the shape is that of a sinusoidal or circular arc when the grating constant is less than 10 μm.