JPH089703Y2 - Optical isolator - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an optical isolator utilizing the Faraday effect used for optical communication, optical measurement, etc., for realizing a stable extinction ratio characteristic. Regarding the structure.

[Prior Art] Recently, an optical communication system using a semiconductor laser as a light source,
Optical application equipment using semiconductor lasers has come into widespread use, and there is an increasing demand for optical isolators that eliminate the return light to semiconductor lasers in order to improve the accuracy and stability of those systems and equipment. It was Up to now, optical isolators with various structures have been proposed, but basically, a polarizer / analyzer having a pair of polarizing elements, a Faraday rotator, a magnetic field generating permanent magnet, and a holder for fixing and protecting them. It consists of a case.

The extinction characteristics of the optical isolator depend on the accuracy of the 45 ° plane of polarization by the Faraday rotator, which is a magneto-optical element, and whether or not the polarization planes of the polarizer and the analyzer are relatively accurately 45 ° different. ing. In the forward direction, the light beam emitted from the semiconductor laser passes through the polarizer to become linearly polarized light, and the Faraday rotator rotates the plane of polarization by 45 °.
The 45 ° plane of polarization is maintained by passing through the analyzer adjusted in different directions of the 45 ° plane of polarization. In the opposite direction, the analyzer transmits only the 45 ° plane of polarization, and the Faraday rotator rotates the 45 ° plane of polarization further, resulting in a plane of polarization rotated 90 ° with respect to the plane of incidence. As a result, the light is blocked by the polarizer, and high extinction characteristics are achieved. The Faraday rotator by the liquid phase epitaxial (LPE) method is considered to be the easiest to industrialize from the viewpoint of miniaturization, mass productivity and optical characteristics of optical isolators. Up to now, in order to miniaturize the optical isolator, it has been proposed to insert an optical component inside the cylindrical permanent magnet, and the outer shape of the optical component such as the polarizer, the analyzer and the Faraday rotator to be inserted is a square or hexagonal. From the industrial viewpoint, the Faraday rotator is grown from the crystal grown by the LPE method.
The issue of how to cut out efficiently is very important.

[Problems to be solved by the invention] When the outer shape of the optical component is a quadrangle, there is no waste in using the crystal by the LPE method, but if one side is a for inserting into the cylindrical permanent magnet, the diagonal of √2a A long permanent magnet inner diameter is required, the overall size becomes large, and the corner portion cannot be used when considering the effective cross section of the light beam. If the permanent magnet is formed into a square through hole, the overall size can be relaxed, but it is not preferable because the processing of the permanent magnet becomes expensive.

If the outer shape of the optical component is circular, effective use of light rays,
It is the best in terms of small size, but it has the drawback that the optical parts must be processed into a round shape.Usually ultrasonic processing etc. is applied to take out the circle from the plate-like optical material, but the ineffective part left uncut. However, the yield will decrease. Moreover, ultrasonic processing increases the tendency for cracks and chips to occur in the peripheral area.

Therefore, it has been attempted to cut into a hexagonal shape by a dicing method, and it has an intermediate advantage between the rectangular shape and the circular shape, and the yield is considerably improved. However, since the ineffective portion left uncut is still present, it is not yet suitable for effectively utilizing the expensive crystal by the LPE method.

In view of this point, the present invention aims to effectively use light rays and realize a small shape by defining the outer shapes of these optical components, and to effectively use an expensive crystal by the LPE method.

[Means for Solving the Problems] The present invention provides an optical isolator composed of a polarizer made of polarizing glass, an optical analyzer and a Faraday rotator, and an optical isolator composed of a cylindrical permanent magnet. The outer shapes of the rotor, the polarizer, and the analyzer are formed in an octagonal shape. Considering how many Faraday rotators with a maximum diameter of 2φ can be taken out from a 2-inch LPE film, it was found that the central portion with a crystalline homogeneity was 34 mm ^□.
Taking into consideration the actual measurement value of a circle of 2φ, a hexagon and a square with an inscribed circle of 2φ, the tooth thickness of the dicing blade is 0.1 mm, and the cutting margin of the material is about 0.12 mm, The number and effective area ratio are shown in Table 1.

If the ratio of the number of squares is 100%, it is obviously circular,
Yield deteriorates for both hexagons. In the present invention, the corners of the quadrangle are further cut off to form an octagonal shape, and the shape of the optical isolator is made to be almost circular, thereby reducing the size of the entire optical isolator.

EXAMPLES cut a homogeneous center of 34 mm ^□ square portion of the crystalline from LPE film 2 inches, further cut out a square chip material by the dicing blade, side by side in the thickness direction is set to the jig with these V grooves, An octagonal Faraday rotator 1 was formed by grinding one corner, setting it again so that the next corner could be machined, and grinding, and setting it four times in this manner. It is an example of an optical isolator assembled by optical parts. The outer shapes of the polarizer 2 and the analyzer 3 are also octagonal, and the inner diameter of the permanent magnet 4 is 2.2.
φ, the overall diameter of the optical isolator is 3.6φ and length
A size of 2.5 mm was obtained.

[Advantage of the Invention] According to the present invention, the optical component formed by the polarizer, the analyzer, and the Faraday rotator has a substantially circular outer shape, so that the optical isolator can be extremely downsized, and the Faraday rotation by the LPE method can be performed. Although the child can be effectively used and the number of chip setting steps for grinding the corners is four times, mass productivity is improved by grinding several hundred pieces at a time.

[Brief description of drawings]

 FIG. 1 is an assembly diagram according to an embodiment of the present invention. 1: Faraday rotator, 2: Polarizer 3: Analyzer, 4: Permanent magnet

Claims (1)

[Scope of utility model registration request] 1. An optical isolator comprising a polarizing glass polarizer, an analyzer and an optical component formed of a Faraday rotator and a cylindrical permanent magnet, and a Faraday rotator alone or a Faraday rotator and a polarizer, a detector. An optical isolator characterized by forming the outer shape of a photon into an octagon.