Fdk Corporation

Tomokazu Imura

Tsugio Tokumasu

Hiroaki Ono

Hiromitsu Umezawa

Shohei Abe

Shusuke Wada

Yoichi Suzuki

Hiroshi Rikukawa

A first separating/combining birefringent element, first and second optical-path controlling birefringent elements, and a second separating/combining birefringent elementare spaced apart. Between the first separating/combining birefringent element and the first optical-path controlling birefringent element, a first polarization rotating meansis arranged for changing a polarization direction from an orthogonal relationship to a parallel relationship, or from a parallel relationship to an orthogonal relationship. Also, between the second optical-path controlling birefringent element and the second separating/combining birefringent element, a second polarization rotating meansis arranged. The first and second optical-path controlling birefringent elements are oppositely arranged symmetrically on optical axis about an arrangement center thereof, between which is arranged a &#xbd;-wavelength plate for rotating a polarization direction of a light on a central optical path 90 degrees, thereby structuring an optical circulator. With a similar structure, an optical switch can be structured by using a &#xb1;45-degree variable Faraday rotator in the first and second polarization rotation switch means.

Optical circulator and optical switch

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.

Polarization plane switch and optical switching device using the same

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Minato-ku, Japan

Tomokazu Imura