JPH01131519A - Optical isolator - Google Patents

Abstract

PURPOSE:To facilitate handling of an optical isolator by inclining the respective light incident faces of a polarizer, analyzer and Faraday rotor at the same angle with the light incident face of a box body which is the perpendicular plane of an incident optical axis so that the light incident face of the box body can be positioned perpendicular to incident light. CONSTITUTION:The respective light incident faces of the polarizer 2, the analyzer 2 and the Faraday rotor 4 are inclined at the same angle with the light incident face of the box body 1 which is the perpendicular face of the incident optical axis. The incident light 6 from a light source, therefore, enters perpendicularly the light incident face 1a of the case 1 and is changed in direction at an angle theta by the polarizer 2; thereafter, the light is emitted in a backward direction at the angle -theta from the light incident face 2b, i.e., is emitted in parallel with the incident optical axis (a). The exit light 7 is similarly emitted in parallel with the incident optical axis (a) through the Faraday rotor 4 and the analyzer 3. Since the light incident faces 1a, 1b of the case 1 is thereby positioned perpendicular to the incident light, mounting of the optical isolator, i.e., handling of the optical isolator is facilitated.

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 for preventing radiation from the 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 structure of the conventional optical isolator is that the polarization directions are mutually K45.
°45° between differently placed polarizer and analyzer
In this configuration, a magneto-optic crystal having a thickness that provides a Faraday rotation angle of is placed as a Faraday rotator, and permanent magnets are placed around the magneto-optic crystal to apply an external saturation magnetic field to the magneto-optic crystal.

Figure 3 shows the principle of an optical isolator. FIG. 3 1al shows the state of the polarization plane of the t-light incident 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. Figure 3 (1b) shows the state of the polarization plane of friendly light incident in the opposite direction. Of the incident light 15a, the linearly polarized light 15b that has passed through the analyzer 14 is due to the non-reciprocity of Faraday rotation. Because the oral direction of Faraday rotation is determined only by the direction 16 of the magnetic field, regardless of the incident direction of the light,
When passing through the Faraday rotator 130, the light undergoes a further 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. 2. In FIG. 2, 21 is a case, on one end of which is a polarizer 22, on the other end a polarizer 22, and at an intermediate position is a Faraday rotator 24 and this Faraday rotator 24.
A cylindrical permanent magnet 25 that covers the periphery of each is provided on its own. The light incident surfaces 22a and 23 of these polarizer 22, analyzer 23, and Faraday rotator 24
a and 24a are parallel to each other and parallel to the light entrance surface 21a of the case 21, and each light entrance surface 22a
, 23a, and 24a from returning to the light source (for example, a semiconductor laser), the incident optical axis is not perpendicular to the light incident surface 21a of the case 21, that is, the incident light 26 is The light was incident on the incident surface 21a at an appropriate angle.

Problems to be Solved by the Invention According to the above-mentioned conventional configuration, the incident light 26 must be incident on the optical isolake, that is, the light incident surface 21a of the case 21, and be inclined at an appropriate angle, and its handling is difficult. The problem was that it was difficult.

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

Means for Solving the Problems In order to solve the above problems, the optical isolator of the present invention arranges a polarizer and an analyzer in a box so that their polarization directions differ from each other by 45 degrees. A Faraday rotator and a permanent magnet that saturates the magnetization of the Faraday rotator are arranged between the polarizer and the analyzer, and the light incident surfaces of the polarizer, analyzer, and Faraday rotator are aligned perpendicularly to the incident optical axis. The light incident surface of the box is inclined at the same angle as the light incident surface of the box.

Effect: According to the above configuration, each of the light incident surfaces of the polarizer, analyzer, and Faraday rotator are inclined at the same angle with respect to the light incident surface of the box, which is a plane perpendicular to the incident optical axis. Even if the incident light is perpendicular to the box, the reflected light will not return to the light source.

Therefore, handling of the optical isolator becomes easy.

Example An embodiment of the present invention will be described below with reference to FIG.

In Fig. 1, 1 is a case (box), inside of which a polarizer 2 is arranged at one end, and an analyzer 3 is arranged at the other end. A Faraday rotator 4 is disposed at an intermediate position between the Faraday rotator 4 and a permanent magnet 5 that saturates the magnetic field of the Faraday rotator 4.
are arranged around the Faraday rotator 4. That is, this permanent magnet 5 is the light input/output surface 4a of the Faraday rotator 4.

4b e fi and has a cylindrical shape that covers its surroundings. Then, each light incident surface 2a, 3a, 4 of the polarizer 2, analyzer 3, and Faraday rotator 4
a is the light incidence surface of case 1 (
For example, it is inclined at a predetermined angle (θ) with respect to the window member Ha. Of course, the light entrance surface 2a and the light exit surface 2b of the polarizer 2 are the same as the light entrance surface 3a and the light exit surface 3b of the analyzer 3.
The light entrance surface 4a and the light exit surface 4b of the Faraday rotator 4 are parallel to each other. Moreover, the above-mentioned inclination angle (θ) is for each light entrance surface 2a.

The angle is such that the reflected light from 3a and 4a does not return to the light source. Note that the permanent magnet 5 is also tilted at an angle (θ) in accordance with the Faraday rotator 4.

In the above configuration, the incident light 6 from the light source enters the light incident surface 1a of the case 1 perpendicularly, and after being changed in direction by the polarizer 2 at an angle (θ), the incident light 6 is incident on the light incident surface 1a of the case 1. The light is emitted in the opposite direction at an angle (-θ), that is, it is emitted in parallel to the incident light tV43a.

Similarly, the output light 7 passes through the Faraday rotator 4 and the analyzer 3, and exits in parallel to the incident optical axis a. Of course, each light input/output surface 2a, 2b, 3a, 3b
, 4a.

The reflected light 8 at 4b does not return to the light source. In this way, since the polarizer 2, analyzer 3, and Faraday rotator 4 are tilted with respect to the light incidence surface 1a of the case 1 to prevent reflected light from returning to the light source, the light incidence surface 1a of the case 1,
lb can be made perpendicular to the incident light, which facilitates installation of the optical isolator, ie, handling of the optical isolator.

Effects of the Invention According to the configuration of the present invention, each of the light incident surfaces of the polarizer, analyzer, and Faraday rotator are inclined at the same angle to the light incident surface of the box that is perpendicular to the incident optical axis. Since the reflected light is prevented from returning to the light source, the light input/output surface of the box can be made perpendicular to the incident light, making installation of the optical isolator, that is, handling of the optical isolator extremely easy.

[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 a conventional optical isolator, and FIG.
Figures (al and (bl) are perspective views explaining the principle of the optical isolator. 1... Case, 2... Polarizer, 3... Analyzer, 4
...Faraday rotator, la, 2a, 3a
, 4a... Light incidence surface, 5... Permanent magnet. Agent Yoshihiro MorimotoFigure 1

Claims (1)

[Claims] 1 A polarizer and an analyzer are arranged in a box so that their polarization directions differ from each other by 45 degrees, and a Faraday rotator and a permanent magnet that saturates the magnetization of the Faraday rotator are placed between the polarizer and the analyzer. Arrange the magnets so that each light entrance surface of the polarizer, analyzer, and Faraday rotator is
An optical isolator tilted at the same angle with respect to the light incident surface of the box, which is a plane perpendicular to the incident optical axis.