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Garnet Write for Holograms

IP.com Disclosure Number: IPCOM000090501D
Original Publication Date: 1969-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

McDonnell, JA: AUTHOR

Abstract

Certain classes of materials, notably gadolinium iron garnet, yttrium-iron garnet, lithium niobate, etc., have properties, for example, optical transparency, ferromagnetism up to the Curie point, Faraday effect for rotating the plane of polarization, and heat insulating, which render the materials suitable for holographic read-write systems in which polarized light is employed. The system is prepared for writing by subjecting hologram plate 1 to a magnetic flux by,for example, applying current through coil 2 surrounding plate 1. The light from laser source 3 is projected through an optical system which includes lens 4 and mode filter 5. The exiting divergent beam is divided into object beam 6a and reference beam 6b. Both are made to converge through a mask upon plate 1 by mirrors 7a and 7b.

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Garnet Write for Holograms

Certain classes of materials, notably gadolinium iron garnet, yttrium-iron garnet, lithium niobate, etc., have properties, for example, optical transparency, ferromagnetism up to the Curie point, Faraday effect for rotating the plane of polarization, and heat insulating, which render the materials suitable for holographic read-write systems in which polarized light is employed. The system is prepared for writing by subjecting hologram plate 1 to a magnetic flux by,for example, applying current through coil 2 surrounding plate 1. The light from laser source 3 is projected through an optical system which includes lens 4 and mode filter 5. The exiting divergent beam is divided into object beam 6a and reference beam 6b. Both are made to converge through a mask upon plate 1 by mirrors 7a and 7b. Object 8, in this instance a transparency, is placed in the path of beam 6a which contains coded information to be recorded on plate 1. Alternatively, a solid object can be used instead of the transparency by replacing mirror 7a.

The laser is selected to provide a frequency of light which is readily absorbed by the holographic material. By proper adjustment of the intensity and duration of the laser emission, those points in the hologram at which the modulated and reference beams reinforce can be arranged to absorb sufficient energy to exceed the Curie temperature. This results in unmagnetized points, while those points which interfere do not absorb enough energy to exceed the Curie point, thus resulting in magnetized points. The heat insulating property is important. By selecting the proper duratio...