Browse Prior Art Database

Magneto Optical Waveguide

IP.com Disclosure Number: IPCOM000082916D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 31K

Publishing Venue

IBM

Related People

Giess, EA: AUTHOR [+3]

Abstract

A magneto-optical waveguide, capable of switching and modulating light, has been devised employing a thin layer of magnetic film.

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Magneto Optical Waveguide

A magneto-optical waveguide, capable of switching and modulating light, has been devised employing a thin layer of magnetic film.

Prior art devices serving as magneto-optical waveguides are made by epitaxially growing a thin layer of magnetic film, e.g., Y(2,5)

Gd(0.5)Fe(4)GaO(12), on top of a garnet substrate, e.g., Gd(3)Ga(5)O(12). The refractive index of the magnetic film is larger than that of the substrate, so that the interface between the film and substrate acts as a waveguide. A light beam can be guided in the film using conventional input and output couplers.

Due to the Faraday effect, when a magnetic field is applied to the magnetic film, a transverse electric (TE) mode input will give rise to a transverse magnetic (TM) mode at the output of the light coupler, or a TM mode input will give rise to a TE mode at the output. The mode conversion efficiency is limited to a few percent, due to the mismatch between the phase velocities of TE and TM modes.

Such inefficient conversion can be overcome by periodically reversing the magnetic domains along the direction of propagation of light, at locations where the phase difference between "free" and "forced" waves reaches 180 Degrees or a multiple thereof. In order to achieve such periodic reversal of magnetic field, a series of rectangular islands of permalloy is deposited in a periodic pattern on a transparent wafer. Such periodic pattern serves as a chain of small permanent magnets that produce an external field that is spatially modulated in sign and amplitude.

This waveguide comprises a chemically polished substrate 2 of garnet (Gd(3)Ga(5)O(12)), on which a film 4 of (Gd(0.5)Y(2.5))(Fe(4)Ga(1))O(12) was grown by liquid phase epitaxy to a thickness of a few microns. A grating 6 provides an input coupler for the optical waveguide and grating 8 is its output coupler. The output light of a He-Ne l...