JPH01306815A - Optical isolator - Google Patents

Abstract

PURPOSE:To facilitate handling by disposing the two opposite side surfaces of a polarizer and analyzer with inclination by the same angle perpendicularly to the light incident and exit surfaces, disposing the two side surfaces in parallel with the optical axis and further disposing the light incident and exit surfaces of the polarizer and analyzer with inclination in the direction opposite to the optical axis. CONSTITUTION:The polarizer 3 and the analyzer 4 are disposed with the polarization directs at 45 deg. with each other. The two side surfaces 3b, 3b' and 4b, 4b' of the polarizer 3 and the analyzer 4 opposed to each other are disposed with the inclination by the same angle theta perpendicularly to the light incident and exit surfaces 3a and 4a. The respective two side surfaces 3b, 3b' and 4b, 4b' of the polarizer 3 and the analyzer 4 are installed in parallel with the optical axis and the light incident and exit surface 3a of the polarizer 3 and the light incident and exit surface 4a of the analyzer 4 are installed with the inclination in the direction opposite to the optical axis. The misalignment in the optical axis of the incident light on and exit light from the optical islator is, therefore, eliminated and the installation of the light incident and exit surfaces of the case 5 of the optical isolator perpendicularly to the optical axis is enabled. The handling is facilitated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to optical isolators. More specifically, the present invention relates to an optical isolator that prevents reflected light from end faces of optical fibers, lens systems, and connectors in optical communications using semiconductor lasers and the like as light sources, writable video discs, and the like.

Conventional technology In general, an optical isolator uses a magneto-optic crystal as a magneto-optic element, which is thick enough to obtain a Faraday rotation angle of 45 degrees between a polarizer and an analyzer whose polarization directions are arranged at 45 degrees to each other. The basic configuration is to arrange permanent magnets around a magneto-optic crystal to apply an external saturation magnetic field to the crystal.

The principle of the optical isolator is as shown in Figure 3.
Figure (a) shows the polarization plane of light incident in the forward direction. Of the light 8a incident on the polarizer 7, the linearly polarized light 8b that has passed through the polarizer 7 is rotated by 45° by the magneto-optical element 9. The linear polarization 8c rotated by 45° is polarizer 7 and 4.
The light passes through an analyzer lO arranged at 5° and exits. 11 indicates the direction of the magnetic field.

On the other hand, FIG. 4(b) shows the polarization plane of light incident in the opposite direction. Due to the non-reciprocity of Faraday rotation, the direction of Faraday rotation of the linearly polarized light 121) that the light 12a has passed through the analyzer 1O is determined only by the direction of the magnetic field 11, regardless of the direction of incidence of the light. Magneto-optical element 9
When passing through, it is further subjected to a Faraday rotation of 45'', which is perpendicular to the polarization direction of the polarizer, and it is no longer able to pass through.

Conventionally, this type of optical isolator has had a configuration as shown in FIG. In FIG. 4, 13 is a permanent magnet, 14 is a magneto-optical element, 15 is a polarizer, 16 is an analyzer, 17 is a case, 18a is incident light from a semiconductor laser, etc., +8b is output light after passing through an optical isolator, ! 8c is surface reflected light, which is light reflected from each of the polarizer 15, the magneto-optical element 14, and the analyzer 16. Polarizer 15, magneto-optical element 14
The light input/output surfaces of the analyzer 16 were all arranged parallel to the light input/output surface of the case 17. Therefore, the surface reflected light 18c
In case 1, the
The light input/output surface of No. 7 and the optical axis of the incident light 18a were tilted from the vertical at an appropriate angle.

Problems to be Solved by the Invention In the conventional configuration as described above, the output light +8b from the optical isolator is shifted by δ from the incident optical axis as shown in FIG.

Further, the light input/output surface of the case 17 of the optical isolator must be tilted from the vertical at an appropriate angle with respect to the optical axis of the incident light, making handling difficult.

The purpose of the present invention is to solve the above-mentioned problems, eliminate the misalignment of the optical axis between the incident light to the optical isolator and the output light from the optical isolator, and align the exit surface of the optical isolator case with the optical axis. It is intended to be able to be mounted vertically and to facilitate handling.

Means for Solving the Problems In order to achieve the above object, the present invention provides a polarizer and an analyzer whose polarization directions are arranged at 45 degrees to each other, and a magneto-optical element disposed between the polarizer and the analyzer. and a permanent magnet disposed around the magneto-optical element in order to saturate the magnetization of the magneto-optical element, and the two opposing sides of the polarizer and the analyzer are arranged so as to allow light to enter and exit the magneto-optical element. The polarizer and the analyzer are arranged so as to be inclined by the same angle from perpendicular to the plane, and the two side surfaces of the polarizer and the analyzer are parallel to the optical axis, and the light entrance and exit surfaces of the polarizer and the analyzer are parallel to the optical axis. The optical isolator is arranged so as to be inclined in the opposite direction to the optical axis.

Effect: With the above configuration, the optical axes of light incident on the optical isolator and light emitted from the optical isolator are aligned, and the light input/output surface of the case of the optical isolator can be mounted perpendicular to the optical axis.

Example The drawings shown as examples of the present invention will be explained.

In FIG. 1, l is a permanent magnet, 2 is a magneto-optical element, and 3 is a permanent magnet.
4 is a polarizer, and 4 is an analyzer. The polarizer 3 and the analyzer 4 are arranged with their polarization directions at 45° with respect to each other. Two opposing sides 3b, 3b' and 4b, 4b of the polarizer 3 and analyzer 4
' are arranged to be inclined by the same angle θ from perpendicular to the light input/output surfaces 3a and 4a, and the two side surfaces 3b, 3b' and 4b, 4b' of the polarizer 3 and analyzer 4 are parallel to the optical axis. Further, the light input/output surface 3a of the polarizer 3 and the light input/output surface 4a of the analyzer 4 are installed so as to be inclined in opposite directions with respect to the optical axis. 5 is a case, 6a is incident light from a semiconductor laser, etc., 6
b shows the emitted light after passing through the optical isolator. The setting of the inclination angle θ of the two side surfaces 3b, 3b' and 4b, 4b'' of the polarizer 3 and the analyzer 4 is such that when the incident light 6a enters the light incident surface of the case 5 perpendicularly, the polarizer 3 and the analyzer The setting may be made so that the surface reflected light of the photons 4 does not return to the semiconductor laser or the like.

The light input/output surfaces of the Faraday rotator and the case 5 are perpendicular to the optical axis.

FIG. 2 shows another embodiment of the polarizer 3 according to the above-mentioned embodiment.
This shows a case where the light input/output surface 3a of the analyzer 4 and the light input/output surface 4a of the analyzer 4 are tilted in opposite directions with respect to the optical axis.

In the embodiment, the incident light 6a and the output light 6b respectively coincide with the optical axis, the two opposing sides of the polarizer 3 and the analyzer 4 are parallel to the optical axis, and the respective first input/output surfaces 3a and 4b are aligned with the optical axis. Since the case 5 is arranged so as to be inclined in the opposite direction, the light incident surface of the case 5 only needs to be arranged perpendicular to the incident light 6a, making it easy to handle.

Effects of the Invention Since the present invention has the above-described configuration, it eliminates the misalignment of the optical axis between the incident light to the optical isolator and the output light from the optical isolator, and aligns the light input/output surface of the optical isolator case with the optical axis. Since it can be installed vertically, it has the advantage of being easier to handle.

[Brief explanation of the drawing]

FIG. 1 is a side view of an optical isolator according to an embodiment of the present invention, FIG. 2 is a side view of an optical isolator showing another embodiment of the present invention, FIG. 3 is a diagram explaining the principle of the optical isolator, and FIG. FIG. 2 is a side view of a conventional optical isolator. 1... Permanent magnet 2... Magneto-optical element 3... Polarizer 4... Analyzer 3 a - Light input/output surfaces 3b, 3b' of polarizer... Two opposing side surfaces of polarizer 4a
...Light entrance/exit surfaces 4b, 4b' of the analyzer...Two opposing sides 5 of the analyzer...
・Case 6a...Incoming light 6b...Outgoing light 6
c...Surface reflected light

Claims (1)

[Claims] a polarizer and an analyzer whose polarization directions are arranged at 45 degrees to each other; a magneto-optical element disposed between the polarizer and the analyzer; and a magneto-optic element for saturating the magnetization of the magneto-optic element. a permanent magnet disposed around the polarizer, and two opposing side surfaces of the polarizer and the analyzer are arranged so as to be inclined by the same angle from perpendicular to the light input/output surface, and the polarizer and the analyzer, and each of the two sides of the analyzer,
An optical isolator characterized in that the light input/output surfaces of the polarizer and the analyzer are arranged parallel to an optical axis and tilted in a direction opposite to the optical axis.