Article comprising a magneto-optic material having low magnetic

Details Article comprising a magneto-optic material having low magnetic Article comprising a magneto-optic material having low magnetic

1996-06-12

1998-09-01

Epps, Georgia Y.

Optical: systems and elements

Optical modulator

Having particular chemical composition or structure

359281, G02F 100

Patent

active

058018751

ABSTRACT:
Garnet material according to a particular embodiment of the invention exhibits a substantially rectangular magnetization loop, with .vertline.H.sub.S .vertline.>.vertline.4.pi.M.sub.S .vertline.Oe and .vertline.4.pi.M.sub.s .vertline.<100 G over a predetermined operating range (e.g., -40.degree. to +80.degree. C.), where H.sub.S is the switching magnetic field of the loop, and 4.pi.M.sub.S is the saturation magnetization. The material exhibits improved latching behavior. In a further embodiment of the invention the composition of the garnet material is selected such that the material exhibits hard latching behavior (.vertline.H.sub.s .vertline.>500 Oe) at least at room temperature. Garnet materials according to the invention can advantageously be used in magneto-optic isolators and other magneto-optic devices. For instance, the material enables manufacture of isolators that do not contain a bias magnet. Garnet materials according to the invention generally contain at most relatively small amounts of Gd, Tb and Dy (less than 1.0, 2.1 and 2.5 atoms per formula unit, respectively; with Gd+(Tb/2.1)+(Dy/2.5)<1.0), and generally contain Eu and/or Ho. In a departure from prior practice, compositions according to the invention can have a compensation temperature in the operating temperature range, e.g., at room temperature. An exemplary garnet according to the invention has nominal composition Bi.sub.0.75 Eu.sub.1.5 Ho.sub.0.75 Fe.sub.4.1 Ga.sub.0.9 O.sub.12.

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"Magnetless Faraday Rotator of (BiYO.sub.3 Fe.sub.5 O.sub.12 Waveguide with Stripe Magnetic Domains", by K. Matsuda et al., Applied Physics Letters, vol. 59(5), p. 507 (1991).
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"Fiber Optics", Mitsubishi Gas Chemical Company, Inc., 1995, p. 5.
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