Lucent Technologies Inc.

Triquint Technology Holding Co.

Integrated Photonics, Inc.

Vincent Jerome Fratello

Charles D Brandle, Jr

Steven J Licht

Robert Ralph Abbott

George W Berkstresser

Kathleen M Paget

Charles David Brandle, Jr

Steve J Licht

Irina Mnushkina

Shanthi Subramanian

Faraday rotator garnet thick films have improved specific Faraday rotations without requiring a bias magnet. Films of nominal composition Bi (Eu Ho ) Fe Ga O are grown lattice matched to available &lcub;Gd Ca &rcub;&lsqb;Ga Mg Zr &rsqb;(Ga )O substrates. The film is prepared with Z &lE;0.45, which allows higher concentrations of Bi to be included in the film than prior compositions. The increased amount of Bi results in a higher specific Faraday rotations for the film. For devices such as non-reciprocal optoelectronic devices that require 45-degree rotators, the increased specific Faraday rotation results in the use of thinner films of reduced path length as well as increased crystal growth yields.

Article comprising a faraday rotator that does not require a bias magnet

Improvements in the production of high-performance latching magneto-optic garnet materials are provided. It has been recognized that high-Europium magneto-optic garnets will offer superior properties in devices such as isolators, circulators and interleavers. However, formation of, e.g., (BiEu) (FeGa) O on conventional, congruent composition, garnet substrates is difficult, due to poor lattice matching between the magneto-optic garnet and such conventional substrates. The invention addresses this problem, by utilizing a single crystal substrate composed essentially of a solid solution of two or more garnet materials. By use of a solid solution of two or more garnets, e.g., two congruent garnet compositions, an acceptable lattice parameter is able to be attained. Useful solid solutions include gadolinium scandium gallium garnet and gadolinium scandium aluminum garnet, or gadolinium scandium gallium garnet and terbium scandium gallium garnet.

Process for fabricating an article comprising a magneto-optic garnet material

In an arrangement substantially like an optical isolator, appropriate choice of the composition of the magneto-optic element can result in a variable optical attenuator. The composition is selected to vary in the direction of light propagation, and also is selected such that the magneto-optic element comprises a compensation wall. The compensation wall is movable in response to a change in the temperature of the magneto-optic element, whereby the attenuation of the device is changed.

Article comprising a variable optical attenuator

Garnet material according to a particular embodiment of the invention exhibits a substantially rectangular magnetization loop, with .vertline.H.sub.S .vertline.&gt;.vertline.4.pi.M.sub.S .vertline.Oe and .vertline.4.pi.M.sub.s .vertline.&lt;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.&gt;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)&lt;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.

Article comprising a magneto-optic material having low magnetic moment

Garnet material according to the invention exhibits a substantially rectangular magnetization loop, with .vertline.H.sub.S .vertline.&gt;.vertline.4.pi.M.sub.S .vertline.Oe, 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 'latching' behavior, and 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 permanent magnet. 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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Basking Ridge, NJ, United States of America

Vincent Jerome Fratello