Thermomagnetic Writing and Reconstruction Characteristics of Holograms on Amorphous Magnetic Films using Uniform Laser Beams

Abstract

Thermomagnetic writing and reconstruction characteristics of holograms on amorphous magnetic TbFe thin films are studied using laser beams of uniform intensity distribution. Using the uniform laser beams, energy margins of thermomagnetic writing of grating holograms on the films is more than twice as wide than when a ruby laser of approximately a Gaussian intensity distribution is used. The reason is clarified by a calculation of the temperature distribution in the films. First order diffraction efficiency of the holograms is about 1.2 times higher than with the ruby laser. There have been remarkable improvements in the quality of reconstructed images from holograms formed on films by utilizing the uniform laser beams. The reconstructed images of a pattern observed through a doubly exposed hologram is of high quality. It is concluded that this method is very useful for thermomagnetic writing of holograms on amophous magnetic films.