Fdk Corporation

Fujitsu Corporation

Tsugio Tokumasu

Hidenori Nakada

Hirotaka Kawai

Isao Kojima

Hiromitsu Umezawa

Teruhisa Sahashi

Tomokazu Imura

Hiroaki Ono

Nobuhiro Fukushima

Mikio Kitaoka

Yuji Goto

Yuko Ota

Takashi Kato

Shohei Abe

Shusuke Wada

Masaharu Hoshikawa

Yoichi Suzuki

Toshihiko Watanabe

Hiroshi Rikukawa

Akitoshi Mesaki

Chiharu Nishida

It is possible to reduce the size of a magneto-optical device, increase the speed of optical control, simplify power supply structure and its control, and maintain a Faraday rotation angle in an arbitrary state even after shut-off of the excitation current. The magneto-optical device includes a magnetic yoke () made of a high-permeability magnetic material, the magnetic yoke including a tabular portion () and four pillar portions () protruding from one side of the tabular portion (), a coil () wound on each of the pillar portions, and a magneto-optical element () arranged in an open-magnetic-circuit region surrounded by the end portions of the four pillar portions. A magnetic field obtained by a coil is applied to the magneto-optical element.

Magneto-optical device

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 variable optical filter comprises a first polarizer, a first phase difference element operable to generate a phase difference, a variable Faraday rotator operable to impart a variable Faraday rotation, a second phase difference element operable to generate a phase difference, and a second polarizer, wherein said polarizers, said variable Faraday rotator, and said phase difference elements are arranged in the mentioned order along the optical axis, and wherein when the angles formed by the optic axes of said first and second phase difference elements and the transmitted polarization azimuth of the first polarizer are assumed respectively to be &#x3c6;and &#x3c6;, these &#x3c6;and &#x3c6;are set to different angles.

Variable optical filter

Optical devices including a Faraday rotation devices improved in wavelength and temperature characteristics and an optical attenuator reduced in wavelength dependence and temperature-dependent loss. The Faraday rotation device has permanent magnets magnetized in an axial direction of through-holes, and Faraday elements having a same Faraday rotation direction with respect to a same magnetization direction. The permanent magnets are directed in the same magnetization direction along an optical path, where part of the Faraday elements are accommodated in the through-hole of the permanent magnet, and the remaining Faraday elements are arranged between the magnets, whereby the Faraday elements are to be applied by magnetic fields in opposite directions. For a device variable in Faraday rotation angle, an electromagnet is provided. An input fiber collimator and polarizer are provided on an input side of with the Faraday elements while an analyzer and output fiber collimator are on an output side.

Faraday rotation device and optical device using same

Farady rotation device and optical device comprising it

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

Growing community of inventors

Minato-ku, Japan

Tsugio Tokumasu