JPH01131520A - Optical isolator - Google Patents

Abstract

PURPOSE:To improve an isolation ratio without generating the misalignment in the optical axis of an analyzer by forming the contact surface of an intermediate holding body and groove for fixing the analyzer to a cylindrical face and aligning the central axis of the cylindrical face to the optical axis running the center of a Faraday rotor. CONSTITUTION:The intermediate holding body 8 is disposed between the groove 7 for fixing the analyzer and the analyzer 3. The contact surface of the intermediate holding body 8 and the groove 7 for fixing the analyzer is made into the cylindrical face 9. The central axis of the cylindrical face 9 is aligned to the optical axis 10 running the center of the Faraday rotor 4. The analyzer can, therefore, be rotated around the optical axis running the center of the Faraday rotor along the cylindrical face of the intermediate holding body 8 at the time of fixing the analyzer 3 to the box body 1. Generation of the misalignment in the optical axis of the analyzer is thereby obviated and the isolation ratio is easily improved.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an optical isolator.

More specifically, the present invention relates to a device that prevents reflected light from end faces of optical fibers, lens systems, and connectors in optical communications, writable video discs, and the like that use semiconductor lasers as light sources.

The basic configuration of conventional optical isolators is that the polarization directions are 45° to each other.
K 45° between differently arranged polarizer and analyzer
In this configuration, a magneto-optic crystal having a thickness such that a Faraday rotation angle of 1 is obtained is placed as a Faraday rotator, and permanent magnets for applying an external saturation magnet of t4 gold to the magneto-optic crystal are placed around the magneto-optic crystal.

The principle of an optical isolator is shown in FIG. Figure 5 (shows the polarization plane of the next light incident on al in the forward direction. Polarizer 11
Among the incident light 12a, the linearly polarized light 12b that has passed through the polarizer 11 is rotated by 45° by the Faraday rotator 13. The linearly polarized light 12c rotated by 45° is polarized by polarizers 11 and 4.
The light passes through an analyzer 14 arranged at a 5° difference and is emitted. FIG. 5 [b] shows the polarization plane of light incident in the opposite direction. Of the incident light 15a, the linearly polarized light 15b that has passed through the analyzer 14 has a non-reciprocal nature of Faraday rotation, so the direction of Faraday rotation is determined only by the direction of the magnetic field 16, regardless of the direction of incidence of the light. Because it is decided,
When passing through the Faraday rotator 13, it is further subjected to a Faraday rotation of 45 degrees, and is perpendicular to the polarization direction of the polarizer 11, so that it cannot pass through. An optical isolator allows light to pass in only one direction.

The configuration of a conventional optical isolator will be explained based on FIG. 3. In Fig. 3, reference numeral 21 denotes a case frame, with a polarizer 22 on one end wall 21a, an analyzer 23 on the other end wall 21b, and a square Faraday shape in the middle part. They are arranged so that their polarization directions differ from each other by 45 degrees. For this reason, the fixing groove 26 of the polarizer 22 is rectangular, whereas the fixing groove 27 of the analyzer 23 is shaped like an inverted triangle, that is, a V-shape.
2 and the analyzer 23 are directly fixed in the fixing grooves 26 and 27 by synthetic resin or the like. Problems to be Solved by the Invention According to the above conventional configuration, the Faraday rotation angle of the Faraday rotator is 45°. Misalignment or case frame 21
Due to factors such as manufacturing accuracy, in order to improve the actual isolation ratio, as shown in Figure 4, the analyzer 23
In some cases, it may be necessary to install it at a certain angle θ with respect to its fixing member 1'1127. For this reason, analyzer 2
There is a problem in that the optical axis 28 of No. 3 is deviated from the optical axis 29 which passes through the center of the Faraday rotator 24 when the optical axis 28 is normally fixed, and the effective beam diameter becomes small.

Furthermore, when tilting the analyzer 23 with respect to the fixing groove 27,
It becomes difficult to align the analyzer 23, and the gap between the fixing groove 27 and the fixing groove 27 is filled with synthetic resin 30 to fix it, but there is a problem in that the optical axis 28 of the analyzer 23 changes slightly when the resin hardens. Ta.

Therefore, an object of the present invention is to provide an optical isolator that can solve the above problems.

Precautions to Solve the Problems In order to solve the above problems, the optical isolator of the present invention includes a box, a polarizer disposed on one end wall of the box,
An optical isolator comprising an analyzer disposed on the other end wall of the box, and a permanent magnet disposed at the center of the box between the polarizer and the analyzer and having a Faraday rotator, An intermediate holder is arranged between the analyzer and the analyzer fixing groove formed on the other end wall of the box, and the contact surface between the intermediate holder and the analyzer fixing groove is made into a cylindrical surface. In addition, the center axis of this cylindrical surface is made to coincide with the center of the Faraday rotator and the optical axis.

Effects According to the above configuration, when fixing the analyzer to the box, the analyzer can be rotated around the optical axis passing through the center of the Faraday rotator along the cylindrical surface of the intermediate holder.
The isolation ratio can be easily improved without causing any deviation of the optical axis of the analyzer.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, 1 is a case frame (box), on one end wall 1a of which a polarizer 2 is arranged, and on the other end wall 1.
An analyzer 3 is disposed at b, and a cylindrical permanent magnet 5 having a Faraday rotator 4 at the center is disposed at the center of the case frame 1 between the polarizer 2 and the analyzer 3. ing. The polarizer 2 is fixed in the rectangular fixing groove 6 as in the prior art, but the analyzer 3 is fixed so that its polarization direction can be easily adjusted. That is, an intermediate holder (also referred to as a core) 8 is arranged between the analyzer fixing groove 7 and the analyzer 3, and the contact surface between the intermediate holder 8 and the analyzer fixing groove 7 is a cylindrical surface 9. At the same time, the central axis of this cylindrical surface 9 passes through the center of the Faraday rotator 4, and the optical axis 10
is matched to

Therefore, as shown in FIGS. 2(a) and (b),
The inner side of the intermediate holder 8 is formed into a 7-shape to support the lower part of the analyzer 3 which is different from the polarizer 2 by 45 degrees, and the outer side is formed into a cylindrical shape.

In the above configuration, when the analyzer 3 is fixed to the case frame 1, as shown in FIGS. Next, Figure 1 (bl) and Figure 2 (b)
As shown in FIG.
The intermediate holding body 8 may be rotated and fixed using synthetic resin or the like at a position where the isolation ratio is the best.

Effects of the Invention According to the configuration of the present invention described above, the analyzer is fixed to the fixing groove of the box via the intermediate holder having an inner cylindrical surface, so that the analyzer can be fixed along the cylindrical surface and at the Faraday. The rotor can be easily rotated around the optical axis passing through the center of the rotor, and therefore the optical axis of the analyzer does not shift as in the conventional case, and the isolation ratio can be improved. There is no need to fill it with synthetic resin, and the optical axis does not change.

[Brief explanation of the drawing]

Figures 1 (a) and (bl) are overall perspective views showing the schematic configuration of an optical isolator in one embodiment of the present invention and the procedure for fixing the analyzer, and Figures 2 (al and (b) are diagrams of the same analyzer. A front view of main parts showing the fixing procedure, FIGS. 3 to 5 are drawings explaining a conventional example, FIG. 3 is a perspective view of the entire optical isolator, FIG. 4 is an enlarged front view of the analyzer, and FIG. (at
and (b) a perspective view illustrating the principle of an M optical isolator. 1...Case frame, 1a...One end wall, 1b.
・・Other end wall portion, 2・Polarizer, 3・Analyzer, 4・
... Faraday rotator, 5... Permanent magnet, 7... Analyzer fixing groove, 8... Intermediate holder, 9... Cylindrical surface,
10... Optical axis. Agent Hiroshi Morimoto Cane 2nd illustration Luno 3rd drawing S (?> rbn-17゜

Claims (1)

[Claims] 1. A box, a polarizer placed on one end wall of the box, an analyzer placed on the other end wall of the box, and the center position of the box between these polarizers and the analyzer. An optical isolator is an optical isolator consisting of a permanent magnet arranged at An optical isolator in which the contact surface between the intermediate holder and the analyzer fixing groove is a cylindrical surface, and the central axis of the cylindrical surface is aligned with the optical axis passing through the center of the Faraday rotator.