Browse Prior Art Database

Magneto Optic Element

IP.com Disclosure Number: IPCOM000093112D
Original Publication Date: 1967-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

MacDonald, RE: AUTHOR [+3]

Abstract

This memory cell consists of a film of gadolinium-iron garnet sandwiched between two thin metal films. The latter are deposited on a transparent substrate. The entire structure is surrounded by an electric coil.

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Magneto Optic Element

This memory cell consists of a film of gadolinium-iron garnet sandwiched between two thin metal films. The latter are deposited on a transparent substrate. The entire structure is surrounded by an electric coil.

The optical transmissivity of the sandwich is a function of the direction in which the garnet is magnetized. The garnet can be magnetized in either of two directions depending upon the direction of current in the electric coil. The wavelength of maximum transmissivity is substantially shifted when the direction of magnetization of the garnet is shifted. On reversing the magnetization, the wavelength of maximum transmission is shifted by delta n, due to a difference in refractive indices delta n, where delta lambda/lambda = delta n/n.

The shift in peak transmission wavelength delta lambda is approximately 20 angstroms at lambda = 4,300 angstroms in the garnet. A bandwith, at half transmission, of less than 100 angstroms, at a peak transmission better than 30%, can be obtained when this structure is employed. The resulting ratio of the transmission coefficients is approximately two for a monochromatic circularly polarized light beam. A bandwith as small as 10 angstroms at a peak transmission as high as 80% can be achieved when the metal films are replaced by multiple dielectric films.

One way of reading information from the device is to direct light at the structure at some angle other than 90 degrees. The amount of refraction of the l...