Abstract: A polarized wave coupling optical isolator comprises a plane-parallel birefringent element for optical path control, which is provided to control an optical path according to a polarizing direction, a plane-parallel birefringent element for coupling and splitting, which is provided with a certain interval from the birefringent element for optical path control to couple lights of different optical paths having polarizing directions set orthogonal to each other, and to split lights of the same optical path, a nonreciprocal portion provided between the birefringent element for optical path control and the birefringent element for coupling and splitting, and constructed by including a combination of 45° Faraday rotator and a linear phasor for rotating a plane of polarization by 45°, two input ports installed on the birefringent element side for optical path control, and an output port installed on the birefringent element side for coupling and splitting.

Abstract: A first separating/combining birefringent element 10, first and second optical-path controlling birefringent elements 11, 12, and a second separating/combining birefringent element 13 are spaced apart. Between the first separating/combining birefringent element and the first optical-path controlling birefringent element, a first polarization rotating means 14 is 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 means 17 is arranged.

Abstract: A polarized wave coupling optical isolator comprises a plane-parallel birefringent element for optical path control, which is provided to control an optical path according to a polarizing direction, a plane-parallel birefringent element for coupling and splitting, which is provided with a certain interval from the birefringent element for optical path control to couple lights of different optical paths having polarizing directions set orthogonal to each other, and to split lights of the same optical path, a nonreciprocal portion provided between the birefringent element for optical path control and the birefringent element for coupling and splitting, and constructed by including a combination of 45° Faraday rotator and a linear phasor for rotating a plane of polarization by 45°, two input ports installed on the birefringent element side for optical path control, and an output port installed on the birefringent element side for coupling and splitting.

Abstract: Arranged, with spacing, are a first separating/combining birefringent element 10, first and second optical-path controlling birefringent elements 11, 12, and a second separating/combining birefringent element 13. Between the first separating/combining birefringent element and the first optical-path controlling birefringent element, is arranged first polarization rotating means 14 for changing a polarization direction from an orthogonal to a parallel or from a parallel to an orthogonal. Also, between the second optical-path controlling birefringent element and the second separating/combining birefringent element, is arranged second polarization rotating means 17. The first and second optical-path controlling birefringent elements are oppositely arranged symmetric in optical axis about an arrangement center thereof, between which is arranged a ½-wavelength plate for rotating 90 degrees a polarization direction of a light on a central optical path, thereby structuring an optical circulator.

Abstract: A polarized wave coupling optical isolator comprises a plane-parallel birefringent element for optical path control, which is provided to control an optical path according to a polarizing direction, a plane-parallel birefringent element for coupling and splitting, which is provided with a certain interval from the birefringent element for optical path control to couple lights of different optical paths having polarizing directions set orthogonal to each other, and to split lights of the same optical path, a nonreciprocal portion provided between the birefringent element for optical path control and the birefringent element for coupling and splitting, and constructed by including a combination of 45° Faraday rotator and a linear phasor for rotating a plane of polarization by 45°, two input ports installed on the birefringent element side for optical path control, and an output port installed on the birefringent element side for coupling and splitting.

Abstract: 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.