Fdk Corporation

Yoichi Suzuki

Hiromitsu Umezawa

Tsugio Tokumasu

Tomokazu Imura

Hiroshi Rikukawa

A polarization plane switch comprising a Faraday rotator made of an iron-containing garnet single-crystal film and magnetic field applying devices capable of reversing a magnetic field to be applied to the Faraday rotator. The polarization plane switch has a structure in which magnetization of part of the Faraday rotator is unsaturated and that of the remaining portion of it is saturated when a magnetic field is applied to the Faraday rotator by the magnetic field applying device, and a light beam passes through the magnetically saturated portion almost vertically to the film surface. As the above Faraday rotator, it is the most preferable to use a Faraday rotator made of Bi-substituted iron garnet single crystal formed by liquid-phase epitaxy and having a compensation temperature, and thermally treated under the top condition at a temperature between 1,120.degree. and 1,180.degree. C. for 7 hours or less.

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Hamamatsu, Japan

Yoichi Suzuki