Optical isolator

Abstract

Provided is an optical isolator making it possible to improve productivity. 　An optical isolator 1 including: a magnet 7 onto which light is incident in a forward direction and which has a through hole 7a passing through the interior thereof; a Faraday element 2 that allows light to be transmitted through and is provided to the interior of the through hole 7a of the magnet 7; a housing 12 in the interior of which the magnet 7 and the Faraday element 2 are stowed, and which comprises a first opening 12a located on an incidence side and a second opening 12b located on an emission side, the incidence side being the side where light is incident in the forward direction and the emission side being a side from which light exits; a first lid 13 that has a first opening 13a through which light passes and that obstructs the first opening 12a of the housing 12; a second lid 14 that has a second opening 14a through which light passes and that obstructs the second opening 12b of the housing 12; a first polarizer 3 arranged on the incidence side of the first lid 13; a second polarizer 4 arranged on the emission side of the second lid 14; a first polarizer holder 5 in which the first polarizer 3 is stowed; and a second polarizer holder 6 in which the second polarizer 4 is stowed.

Description

Optical isolator

[0001] The present invention relates to an optical isolator.

[0002] An optical isolator is a magneto-optical element that propagates light in only one direction and blocks reflected light from returning. Optical isolators are used, for example, in laser oscillators used in optical communication systems, laser processing systems, etc. Patent Document 1 listed below discloses an example of an optical isolator. In this optical isolator, a Faraday rotator is disposed inside a magnetic structure.

[0003] In Patent Document 1, the magnetic structure is housed in an internal case. The internal case consists of a front portion, a rear portion, and a side portion. The rear portion and the side portion are integrated. In the direction of the optical axis of light passing through the Faraday rotator, the internal case covers the entire magnets that make up the magnetic structure. The internal case is housed in an external case. A pair of polarizers are arranged inside the external case, facing each other with the Faraday rotator sandwiched between them.

[0004] JP 2016-051105 A

[0005] However, there is a risk that the efficiency of processing each component in the optical isolator of Patent Document 1 and the efficiency of assembling the optical isolator cannot be sufficiently high, which may make it difficult to sufficiently increase the productivity of the optical isolator.

[0006] An object of the present invention is to provide an optical isolator that can be manufactured with high productivity.

[0007] An optical isolator according to a first aspect of the present invention comprises: a magnet having a through hole through which light in a forward direction enters and passes therethrough; a Faraday element that transmits the light and is provided inside the through hole of the magnet; a housing that houses the magnet and the Faraday element, the housing having a first opening located on the entrance side and a second opening located on the exit side, where the side through which the light in the forward direction enters is defined as the entrance side and the side through which the light exits is defined as the exit side; a first lid having a first opening through which the light passes and closing the first opening of the housing; a second lid having a second opening through which the light passes and closing the second opening of the housing; a first polarizer arranged on the entrance side of the first lid; a second polarizer arranged on the exit side of the second lid; a first polarizer holder that houses the first polarizer; and a second polarizer holder that houses the second polarizer.

[0008] In the optical isolator of aspect 2, in aspect 1, it is preferable that the area of ​​the first polarizer holder is smaller than the area of ​​the first lid when viewed from the forward direction, and the area of ​​the second polarizer holder is smaller than the area of ​​the second lid when viewed from the forward direction.

[0009] In the optical isolator of aspect 3, in aspect 1 or aspect 2, it is preferable that the first lid and the first polarizer holder are in contact, and the second lid and the second polarizer holder are in contact.

[0010] In the optical isolator of aspect 4, in aspect 3, it is preferable that at least a portion of the first polarizer holder is located inside the first lid body, the first lid body has a first fitting portion that fits together with the first polarizer holder, and at least a portion of the second polarizer holder is located inside the second lid body, and the second lid body has a second fitting portion that fits together with the second polarizer holder.

[0011] In the optical isolator of Aspect 5, in any one of Aspects 1 to 4, it is preferable that the optical isolator further comprises a pipe member arranged inside the through hole of the magnet, the Faraday element is arranged inside the pipe member, the pipe member has a first protrusion protruding from the magnet toward the incident side and a second protrusion protruding from the magnet toward the output side, the first protrusion contacting the inner wall of the first opening of the first lid body, and the second protrusion contacting the inner wall of the second opening of the second lid body.

[0012] In the optical isolator of Aspect 6, in Aspect 5, it is preferable that at least a portion of the first polarizer holder is located inside the first lid, the first lid has a first fitting portion that fits with the first polarizer holder, at least a portion of the second polarizer holder is located inside the second lid, the second lid has a second fitting portion that fits with the second polarizer holder, the first polarizer holder holds the first polarizer so that the first protrusion of the pipe member does not come into contact with the first polarizer, and the second polarizer holder holds the second polarizer so that the second protrusion of the pipe member does not come into contact with the second polarizer.

[0013] In the optical isolator of Aspect 7, in Aspect 6, when a cross section along a direction perpendicular to the forward direction is taken as a transverse cross section, it is preferable that the area of ​​the transverse cross section of the first opening of the first lid body at the portion closest to the incident side is larger than the area of ​​the transverse cross section of the first opening at the portion closest to the output side, the area of ​​the transverse cross section of the second opening of the second lid body at the portion closest to the output side is larger than the area of ​​the transverse cross section of the second opening at the portion closest to the incident side, the first protrusion of the pipe member protrudes at least to a portion of the first opening of the first lid body where the area of ​​the transverse cross section is larger than the area of ​​the transverse cross section of the first opening at the portion closest to the output side, and the second protrusion of the pipe member protrudes at least to a portion of the second opening of the second lid body where the area of ​​the transverse cross section is larger than the area of ​​the transverse cross section of the second opening at the portion closest to the incident side.

[0014] In the optical isolator of aspect 8, in any one of aspects 1 to 7, it is preferable that the first lid body is in contact with the inner wall of the housing, and the second lid body is in contact with the inner wall of the housing.

[0015] In the optical isolator of Aspect 9, in any one of Aspects 1 to 8, it is preferable that the housing has a cylindrical shape.

[0016] In the optical isolator of Aspect 10, in any one of Aspects 1 to 9, it is preferable that the magnet has a first magnetic body, a second magnetic body, and a third magnetic body, each having a through hole, and that the first magnetic body, the second magnetic body, and the third magnetic body are stacked in this order from the incident side, the through hole of the first magnetic body, the through hole of the second magnetic body, and the through hole of the third magnetic body are connected, the first magnetic body is magnetized in a direction perpendicular to the forward direction so that the through hole side is the north pole, the second magnetic body is magnetized in a direction parallel to the forward direction so that the first magnet body side is the north pole, and the third magnetic body is magnetized in a direction perpendicular to the forward direction so that the through hole side is the south pole.

[0017] In the optical isolator of aspect 11, in any one of aspects 1 to 10, when a cross section is taken along a direction perpendicular to the forward direction, it is preferable that the outer shape of the magnet in the cross section is rectangular, and the outer shape of the first polarizer holder in the cross section and the outer shape of the second polarizer holder in the cross section are circular.

[0018] According to the present invention, an optical isolator that can be manufactured with high productivity can be provided.

[0019] FIG. 1 is a schematic perspective view of an optical isolator according to a first embodiment of the present invention. FIG. 2 is a schematic perspective view showing a cross section of the optical isolator according to the first embodiment of the present invention along the light transmission direction. FIG. 3 is a schematic horizontal cross-sectional view of a portion of the optical isolator according to the first embodiment of the present invention where a magnet is located. FIG. 4 is a schematic vertical cross-sectional view showing the positional relationship between a first polarizer holder, a first polarizer, and a first lid in the optical isolator according to the first embodiment of the present invention. FIG. 5 is a schematic horizontal cross-sectional view of the first lid according to the first embodiment of the present invention, as viewed from the forward direction. FIG. 6 is a schematic vertical cross-sectional view showing the first lid according to the first embodiment of the present invention. FIG. 7 is a schematic vertical cross-sectional view showing the first lid according to a modified example of the first embodiment of the present invention. FIG. 8 is a schematic perspective view showing a cross section of the optical isolator according to a second embodiment of the present invention along the light transmission direction. FIG. 9 is a schematic view of a magnet in the second embodiment of the present invention.

[0020] Preferred embodiments will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0021] (First Embodiment) Fig. 1 is a schematic perspective view of an optical isolator according to a first embodiment of the present invention, and Fig. 2 is a schematic perspective view showing a cross section of the optical isolator according to the first embodiment along the direction in which light passes.

[0022] The optical isolator 1 shown in Fig. 1 can be used as a free-space optical isolator. As shown in Fig. 2, the optical isolator 1 includes a Faraday element 2, a first polarizer 3, a second polarizer 4, a first polarizer holder 5, a second polarizer holder 6, a magnet 7, a pipe member 8, a housing 12, a first cover 13, and a second cover 14.

[0023] The magnet 7 has a rectangular cylindrical shape. Specifically, the magnet 7 has a through-hole 7a. More specifically, the magnet 7 has a pair of end faces and a side face 7d. The side face 7d connects the pair of end faces. The through-hole 7a is provided from one end face to the other end face. Light passes through the through-hole 7a in the forward direction.

[0024] That is, in this specification, the forward direction is a direction parallel to the direction in which light passes through the optical isolator, and is the direction in which light passes from the incident side to the outgoing side when passing through the optical isolator. Hereinafter, the side in which light in the forward direction enters will be referred to as the incident side, and the side in which light in the forward direction exits will be referred to as the outgoing side. In each component, a cross section along a direction perpendicular to the forward direction will be referred to as a transverse cross section. Also, a cross section along a direction parallel to the forward direction will sometimes be referred to as a longitudinal cross section.

[0025] FIG. 3 is a schematic cross-sectional view of a portion where a magnet is located in the optical isolator according to the first embodiment.

[0026] The outer shape of the cross section of the magnet 7 is a square. However, the outer shape of the cross section of the magnet 7 is not limited to the above and may be, for example, a quadrangle other than a square, or may be a circle, etc. Therefore, the shape of the magnet 7 is not limited to a rectangular tube and may be, for example, a cylindrical shape.

[0027] The cross-sectional shape of the through-hole 7a in the magnet 7 is square. However, the cross-sectional shape of the through-hole 7a is not limited to the above, and may be, for example, circular.

[0028] A pipe member 8 is provided inside the through hole 7a of the magnet 7. In this embodiment, the pipe member 8 is a metal pipe. The pipe member 8 has a cylindrical shape. Specifically, the pipe member 8 has a through hole 8a. Light passes through the through hole 8a. The cross-sectional shape of the through hole 8a in the pipe member 8 is circular. In this embodiment, SUS304 is used as the material for the pipe member 8. However, the material for the pipe member 8 is not limited to the above.

[0029] Returning to Fig. 2, the Faraday element 2 is provided inside the pipe member 8. More specifically, the Faraday element 2 is disposed in the through hole 8a of the pipe member 8 at a portion that is located inside the through hole 7a of the magnet 7. Note that the pipe member 8 does not necessarily have to be provided. In this case, it is sufficient that the Faraday element 2 is provided inside the through hole 7a of the magnet 7.

[0030] The magnet 7 is housed in a housing 12, a first cover 13, and a second cover 14. Specifically, the housing 12 is cylindrical. More specifically, the housing 12 has a pair of end faces, a side face, and an inner wall 12c. The side face and the inner wall 12c face each other. The side face and the inner wall 12c extend in the forward direction. The side face and the inner wall 12c connect the pair of end faces. One of the pair of end faces is an incident-side end face 12e, and the other is an exit-side end face 12f.

[0031] Furthermore, the housing 12 has a first opening 12a and a second opening 12b. The first opening 12a is located on the incident side. The second opening 12b is located on the output side. When viewed from the forward direction, the magnet 7 is not covered by the housing 12. More specifically, when viewed from either the incident side or the output side, the magnet 7 is not covered by the housing 12.

[0032] The first cover 13 closes the first opening 12a of the housing 12. On the other hand, the second cover 14 closes the second opening 12b of the housing 12. However, the first cover 13 and the second cover 14 do not completely close the housing 12. More specifically, the first cover 13 has a first opening 13a. Similarly, the second cover 14 has a second opening 14a. Light passes through the first opening 13a and the second opening 14a.

[0033] An aluminum alloy is used as the material of the housing 12, the first cover 13, and the second cover 14. However, the materials of the housing 12, the first cover 13, and the second cover 14 are not limited to the above.

[0034] A first polarizer 3 is disposed on the incident side of the first lid 13. On the other hand, a second polarizer 4 is disposed on the exit side of the second lid 14. The first polarizer 3 and the second polarizer 4 face each other with the Faraday element 2 sandwiched between them in the forward direction. In this embodiment, light enters from the first polarizer 3 side, passes through the Faraday element 2, and exits from the second polarizer 4 side.

[0035] The first polarizer 3 and the second polarizer 4 each have a light transmission axis. Light that passes through the first polarizer 3 becomes linearly polarized light according to the light transmission axis. The Faraday element 2 rotates the polarization plane of the linearly polarized light. The angle by which the Faraday element 2 rotates the polarization plane is the rotation angle. The angle of the light transmission axis of the second polarizer 4 relative to the light transmission axis of the first polarizer 3 is set equal to the rotation angle.

[0036] In this embodiment, both the first polarizer 3 and the second polarizer 4 are polarizing beam splitters (PBS). Therefore, P-polarized light or S-polarized light passes through the first polarizer 3 and enters the Faraday element 2. The second polarizer 4 is arranged to pass either the P-polarized light or the S-polarized light that enters the Faraday element 2 in the forward direction. However, the first polarizer 3 and the second polarizer 4 are not limited to PBSs.

[0037] 4 is a schematic vertical cross-sectional view showing the positional relationship between the first polarizer holder, the first polarizer, and the first lid in the optical isolator according to the first embodiment. The first polarizer 3 is housed in the first polarizer holder 5. The first polarizer holder 5 is in contact with the first lid 13. Specifically, the first polarizer holder 5 has a pair of end faces and a side face 5d. The side face 5d extends in the forward direction. The side face 5d connects the pair of end faces. One of the pair of end faces is an incident-side end face, and the other is an exit-side end face 5f. A portion of the side face 5d and the exit-side end face 5f are in contact with the first lid 13.

[0038] Returning to FIG. 2 , the second polarizer 4 is housed in the second polarizer holder 6. The positional relationship between the second polarizer holder 6, the second polarizer 4, and the second lid 14 in the optical isolator 1 according to the first embodiment is the same as the positional relationship between the first polarizer holder 5, the first polarizer 3, and the first lid 13. More specifically, the second polarizer holder 6 is in contact with the second lid 14. Specifically, the second polarizer holder 6 has a pair of end faces and a side face 6d. The side face 6d extends in the forward direction. The side face 6d connects the pair of end faces. One of the pair of end faces is an end face 6e on the incident side, and the other is an end face on the exit side. A portion of the side face 6d and the end face 6e on the incident side are in contact with the second lid 14.

[0039] The outer shape of the cross section of the first polarizer holder 5 is circular. Similarly, the outer shape of the cross section of the second polarizer holder 6 is also circular. Note that the outer shapes of the cross sections of the first polarizer holder 5 and the second polarizer holder 6 are not limited to the above.

[0040] An aluminum alloy is used as the material of the first polarizer holder 5 and the second polarizer holder 6. However, the material of the first polarizer holder 5 and the second polarizer holder 6 is not limited to the above.

[0041] A feature of this embodiment is that the housing 12 has a first opening 12a and a second opening 12b, and the first opening 12a and the second opening 12b are closed by a first cover 13 and a second cover 14. Because the housing 12, the first cover 13, and the second cover 14 are all independent components, processing and manufacturing of these components is easy. For example, multiple housings 12 can be easily obtained by dividing a single pipe-shaped component. Alternatively, for example, the first cover 13 and the second cover 14 can be obtained using the same process. This reduces manufacturing costs for the optical isolator 1. In addition, assembly is easy during manufacturing of the optical isolator 1. This effectively increases productivity of the optical isolator 1. Furthermore, for example, if a component, such as the magnet 7 or the Faraday element 2, disposed within the housing 12 of the optical isolator 1 is damaged, the component can be easily replaced by removing the first cover 13 and / or the second cover 14.

[0042] The configuration of this embodiment will be described in more detail below. As shown in FIG. 4 , the first lid 13 has a recess. Therefore, the first lid 13 has a sidewall surrounding the recess and a bottom. The sidewall of the first lid 13 extends in the forward direction. The sidewall includes a side surface 13d. The side surface 13d is the outer surface of the sidewall. The bottom of the first lid 13 is located on the emission side. That is, the bottom of the first lid 13 is the portion of the first lid 13 located on the magnet 7 side. The first opening 13a is provided in the bottom of the first lid 13. A portion of the first opening 13a is provided to widen toward the incidence side.

[0043] FIG. 5 is a schematic cross-sectional view of the first lid body 13 in the first embodiment, as viewed from the forward direction. FIG. 5 shows a portion corresponding to the cross section taken along line II in FIG. 4 . As shown in FIG. 5 , the outer shape of the first lid body 13 in cross section is square. The first lid body 13 has a first opening 13a located in the center when viewed from the forward direction. The outer shape of the first lid body 13 in cross section may be any shape that can close the first opening 12a of the housing 12 shown in FIG. 2 , and preferably corresponds to the shape of the first opening 12a in cross section. For example, if the shape of the first opening 12a in the housing 12 is square, the outer shape of the first lid body 13 in cross section is also preferably square. Note that the outer shape of the first lid body 13 in cross section is not limited to the above and may be, for example, a quadrangle other than a square, or may be circular, etc. Furthermore, the outer shape of the recess in the first lid body 13 in cross section is circular. The cross-sectional shape of the recess may be any shape that allows a portion of the first polarizer holder 5 to be positioned inside the first lid 13, and preferably corresponds to the cross-sectional shape of the first polarizer holder 5. For example, if the cross-sectional shape of the first polarizer holder 5 is circular, it is preferable that the cross-sectional shape of the recess also be circular. However, the cross-sectional shape of the recess is not limited to the above.

[0044] In the following, unless otherwise specified, the area of ​​a member when viewed from the forward direction is the area of ​​the shape defined by the outer shape of the member. For example, the area of ​​the first lid 13 when viewed from the forward direction does not exclude the area of ​​the first opening 13a unless otherwise specified. The area of ​​the cross section of a member is also the area of ​​the shape defined by the outer shape of the cross section of the member unless otherwise specified.

[0045] The cross-sectional area of ​​the first lid 13 is not constant. Specifically, the first lid 13 has a step portion 13c. The cross-sectional area of ​​the first lid 13 varies at the step portion 13c as a boundary. For example, when comparing the portion through which the dashed-dotted line A passes with the portion through which the dashed-dotted line B passes, as schematically shown in FIG. 6, the area of ​​the shape defined by the outline of the first lid 13 varies. More specifically, the cross-sectional area of ​​the portion through which the dashed-dotted line A passes, i.e., the portion on the incident side of the step portion 13c, is larger than the cross-sectional area of ​​the portion through which the dashed-dotted line B passes, i.e., the portion on the exit side of the step portion 13c.

[0046] Returning to FIG. 2 , the second lid 14 is configured similarly to the first lid 13. Specifically, the second lid 14 has a recess, and a sidewall and bottom surrounding the recess. The sidewall of the second lid 14 extends in the forward direction. The sidewall includes a side surface 14d. The side surface 14d is the outer surface of the sidewall. The bottom of the second lid 14 is located on the incident side. In other words, the bottom of the second lid 14 is the part of the second lid 14 that is located on the magnet 7 side. The second opening 14a is provided in the bottom of the second lid 14.

[0047] The outer shape of the second lid 14 in the cross section is square. The outer shape of the second lid 14 in the cross section may be any shape that can close the second open portion 12b of the housing 12, and preferably corresponds to the shape of the second open portion 12b in the cross section. For example, if the cross section of the second open portion 12b in the housing 12 is square, the outer shape of the second lid 14 in the cross section is also preferably square. Note that the outer shape of the second lid 14 in the cross section is not limited to the above and may be, for example, a quadrangle other than a square, or a circle, etc. Furthermore, the shape of the recess in the second lid 14 in the cross section is circular. The shape of the recess in the cross section may be any shape that can position a part of the second polarizer holder 6 inside the second lid 14, and preferably corresponds to the shape of the second polarizer holder 6 in the cross section. For example, when the outer shape of the cross section of the second polarizer holder 6 is circular, it is preferable that the outer shape of the cross section of the recess is also circular. However, the shape of the cross section of the recess is not limited to the above.

[0048] The cross-sectional area of ​​the second lid 14 is not constant. Specifically, just as the first lid 13 has a step portion 13c, the second lid 14 has a step portion 14c. In the second lid 14, the cross-sectional area changes at the step portion 14c as a boundary. More specifically, the cross-sectional area of ​​the portion on the emission side of the step portion 14c is larger than the cross-sectional area of ​​the portion on the incidence side of the step portion 14c.

[0049] Incidentally, when manufacturing the optical isolator 1, the angle of the first polarizer 3 can be adjusted by rotating the first polarizer holder 5. Similarly, the angle of the second polarizer 4 can be adjusted by rotating the second polarizer holder 6. In this embodiment, a portion of the first polarizer holder 5 is located inside the first lid 13. Specifically, a portion of the first polarizer holder 5 is located inside a recess in the first lid 13. The remaining portion of the first polarizer holder 5 is located outside the recess. This makes it difficult for the first polarizer holder 5 to become misaligned when rotated, and allows the optical isolator 1 to be made compact.

[0050] When the first polarizer holder 5 can be disposed inside the first lid 13, it is sufficient that at least a portion of the first polarizer holder 5 is located inside the first lid 13. For example, the entire first polarizer holder 5 may be located inside the first lid 13. In this case, the optical isolator 1 can be effectively miniaturized.

[0051] The bottom of the first lid 13 is in contact with the output-side surface of the first polarizer holder 5. Meanwhile, the bottom of the second lid 14 is in contact with the input-side surface of the second polarizer holder 6. This allows the arrangement of the first polarizer holder 5 and the second polarizer holder 6 to be stabilized in the optical isolator 1. This increases the vibration resistance and impact resistance of the optical isolator 1. Note that in this specification, the term "communication between members" also applies when members are joined together with an adhesive or the like and an adhesive or the like is located between the members.

[0052] The first cover 13 is fitted to the first polarizer holder 5. Specifically, the sidewall and bottom of the first cover 13 that come into contact with the first polarizer holder 5 are the first fitting portion 13b of the first cover 13. More specifically, the first fitting portion 13b of the first cover 13 is fitted to the side surface 5d and the output-side end surface 5f of the first polarizer holder 5. This effectively stabilizes the positioning of the first polarizer holder 5. This prevents misalignment of the light transmission axis of the first polarizer 3. In addition, the accuracy of the optical axis of the optical isolator 1 can be improved.

[0053] Meanwhile, a portion of the second polarizer holder 6 is located inside the second lid 14. Specifically, a portion of the second polarizer holder 6 is located inside the recess of the second lid 14. The remaining portion of the second polarizer holder 6 is located outside the recess. This allows the second polarizer holder 6 to be rotated along the recess of the second lid 14, making it easier to adjust the angle of the second polarizer 4 and enabling the optical isolator 1 to be made smaller.

[0054] When the second polarizer holder 6 can be disposed inside the second lid 14, it is sufficient that at least a portion of the second polarizer holder 6 is located inside the second lid 14. For example, the entire second polarizer holder 6 may be located inside the second lid 14. In this case, the optical isolator 1 can be effectively miniaturized.

[0055] The second cover 14 is fitted to the second polarizer holder 6. Specifically, the sidewall and bottom of the second cover 14 that come into contact with the second polarizer holder 6 are the second fitting portion 14b of the second cover 14. More specifically, the second fitting portion 14b of the second cover 14 is fitted to the side surface 6d and the incident-side end surface 6e of the second polarizer holder 6. This effectively stabilizes the positioning of the second polarizer holder 6. This prevents misalignment of the light transmission axis of the second polarizer 4. In addition, the accuracy of the optical axis of the optical isolator 1 can be improved.

[0056] In this embodiment, the first polarizer holder 5 and the first lid 13 are fixed with an adhesive. The second polarizer holder 6 and the second lid 14 are fixed with an adhesive. However, the means for fixing the first polarizer holder 5 and the second polarizer holder 6 are not limited to these.

[0057] For example, the first polarizer holder 5 and the second polarizer holder 6 may be fixed by magnetic force. Specifically, for example, a magnetic material may be embedded in the first polarizer holder 5 and the second polarizer holder 6. The first polarizer holder 5 may be indirectly fixed to the magnet 7 by magnetic force via the first lid 13. The second polarizer holder 6 may be indirectly fixed to the magnet 7 by magnetic force via the second lid 14.

[0058] During the manufacture of the optical isolator 1, the angle of the first polarizer 3 can be adjusted by rotating the first polarizer holder 5. The shape of the portion where the first cover 13 and the first polarizer holder 5 are fitted together is circular when viewed from the forward direction. Therefore, before the first cover 13 and the first polarizer holder 5 are fixed together with an adhesive or the like, the side surface of the first polarizer holder 5 can be slid along the inner wall of the first cover 13. This makes it difficult for the first polarizer holder 5 to become misaligned when the first polarizer holder 5 is rotated, and facilitates fine adjustment of the angle of the first polarizer 3.

[0059] Similarly, before the second lid 14 and the second polarizer holder 6 are fixed together with an adhesive or the like, the side surface of the second polarizer holder 6 can be slid along the inner wall of the second lid 14. This makes it difficult for the second polarizer holder 6 to become misaligned when the second polarizer holder 6 is rotated, and facilitates fine adjustment of the angle of the second polarizer 4. However, the first lid 13 and the first polarizer holder 5, and the second lid 14 and the second polarizer holder 6 do not necessarily have to be fitted together.

[0060] When viewed from the forward direction, the area of ​​the first polarizer holder 5 is smaller than the area of ​​the first lid 13. Similarly, when viewed from the forward direction, the area of ​​the second polarizer holder 6 is smaller than the area of ​​the second lid 14. This allows the optical isolator 1 to be suitably small in size.

[0061] In addition, the first polarizer holder 5 and the second polarizer holder 6 can be made lightweight. As a result, when the first polarizer holder 5 and the second polarizer holder 6 are fixed by magnetic force, for example, as described above, the first polarizer holder 5 and the second polarizer holder 6 can be fixed effectively. Therefore, the arrangement of the first polarizer holder 5 and the second polarizer holder 6 can be effectively stabilized. Note that the relationship between the area of ​​the first polarizer holder 5 and the area of ​​the first lid 13, and the relationship between the area of ​​the second polarizer holder 6 and the area of ​​the second lid 14 are not limited to those described above.

[0062] The first cover 13 closes the first opening 12a of the housing 12. Specifically, a portion of the first cover 13 is located inside the housing 12. The first cover 13 contacts the inner wall 12c of the housing 12. This allows the first cover 13 to close the first opening 12a without covering the side surface of the housing 12.

[0063] On the other hand, the second cover 14 closes the second opening 12b of the housing 12. Specifically, a portion of the second cover 14 is located inside the housing 12. The second cover 14 contacts the inner wall 12c of the housing 12. This allows the second cover 14 to close the second opening 12b without covering the side surface of the housing 12.

[0064] The above-described configuration of the first cover 13, the second cover 14, and the housing 12 allows the areas of the first cover 13 and the second cover 14 to be smaller than the area of ​​the housing 12 when viewed from the forward direction. Therefore, the optical isolator 1 can be suitably made small.

[0065] First cover 13 includes a portion located outside housing 12. A step portion 13c is located at the boundary between the portion of first cover 13 located inside housing 12 and the portion located outside housing 12. Housing 12 and first cover 13 are fitted together. More specifically, inner wall 12c and incident-side end face 12e of housing 12 are fitted together with a portion of side face 13d of first cover 13 and the exit-side surface of step portion 13c.

[0066] Similarly, the second cover 14 includes a portion located outside the housing 12. A step portion 14c is located at the boundary between the portion of the second cover 14 located inside the housing 12 and the portion located outside the housing 12. The housing 12 and the second cover 14 are fitted together. More specifically, the inner wall 12c and the exit-side end face 12f of the housing 12 are fitted together with a portion of the side surface 14d of the second cover 14 and the incident-side surface of the step portion 14c.

[0067] The housing 12, the first cover 13, and the second cover 14 are fitted together, thereby improving the vibration resistance and impact resistance of the optical isolator 1. However, the housing 12, the first cover 13, and the second cover 14 do not necessarily have to be fitted together.

[0068] In the present invention, as in this embodiment, it is preferable that the first cover 13 and the second cover 14 are fixed to the housing 12 by screws. However, the means for fixing the first cover 13 and the second cover 14 to the housing 12 is not limited to screws. For example, the first cover 13 and the second cover 14 may be fixed to the housing 12 by an adhesive or the like. Furthermore, the first cover 13 and the second cover 14 may not be fixed to the housing 12 by an adhesive or the like. In this case, for example, if a component such as the magnet 7 or the Faraday element 2 arranged inside the housing 12 of the optical isolator 1 is damaged, the component can be easily replaced by removing the first cover 13 and / or the second cover 14.

[0069] 3, a gap A is provided between the inner wall 12c of the housing 12 and the side surface 7d of the magnet 7. The distance between the inner wall 12c of the housing 12 and the side surface 7d of the magnet 7 is, for example, about 1 mm.

[0070] It is preferable that the housing 12 be made of A5052, an Al-Mg alloy, or A6063, an Al-Mg-Si alloy. This allows the strength of the housing 12 to be suitably increased. It is even more preferable that the housing 12 be made of A6063. In this case, a rectangular tubular member can be easily obtained by extrusion molding. This makes it particularly easy to obtain the housing 12, and increases productivity. Furthermore, the strength of the housing 12 can be increased while the wall thickness can be reduced.

[0071] When A5052 is used as the material for the housing 12, the housing 12 may be formed by, for example, cutting. However, the material for the housing 12 is not limited to the above. For example, A6061, which is an Al-Mg-Si alloy, may also be suitably used as the material for the housing 12.

[0072] It is preferable that the thickness of the housing 12 is 1 mm or more and 3.5 mm or less. In this case, the optical isolator 1 can be made more compact. When A6063 is used as the material of the housing 12, the strength of the housing 12 can be increased even when the thickness of the housing 12 is within the above range. In particular, it is preferable that A6063 is used as the material of the housing 12 and that the thickness of the housing 12 is 1 mm or more and 3.5 mm or less. This makes it possible to more reliably make the optical isolator 1 more compact and more reliably make the optical isolator 1 less susceptible to breakage.

[0073] As shown in FIG. 6 , in the first lid 13, a portion of the first opening 13 a is provided so as to widen toward the incident side. Specifically, the first lid 13 has a portion where the cross-sectional area of ​​the first opening 13 a is constant and a portion where the cross-sectional area of ​​the first opening 13 a increases toward the incident side. More specifically, the portion where the cross-sectional area of ​​the first opening 13 a is constant is the portion on the exit side of the first lid 13, and the portion where the cross-sectional area changes is the portion on the incident side of the first lid 13. Therefore, the cross-sectional area of ​​the portion of the first opening 13 a of the first lid 13 closest to the incident side is larger than the cross-sectional area of ​​the portion of the first opening 13 a closest to the exit side.

[0074] Returning to FIG. 2 , similar to the first lid 13, the second lid 14 also has a portion of the second opening 14 a that widens toward the exit side. Specifically, the second lid 14 has a portion where the cross-sectional area of ​​the second opening 14 a is constant and a portion where the cross-sectional area of ​​the second opening 14 a increases toward the exit side. More specifically, the portion where the cross-sectional area of ​​the second opening 14 a is constant is the incident side portion of the second lid 14, and the portion where the cross-sectional area changes is the exit side portion of the second lid 14. Therefore, the cross-sectional area of ​​the portion of the second opening 14 a of the second lid 14 closest to the exit side is larger than the cross-sectional area of ​​the portion of the second opening 14 a closest to the entrance side.

[0075] As shown in Figure 2, the pipe member 8 is provided inside the through-hole 7a of the magnet 7. The pipe member 8 has a first protrusion 8b and a second protrusion 8c. The first protrusion 8b is a portion that protrudes from the magnet 7 toward the incident side. The second protrusion 8c is a portion that protrudes from the magnet 7 toward the exit side.

[0076] In this embodiment, the first protrusion 8b of the pipe member 8 protrudes into the first opening 13a of the first cover 13. Specifically, the first protrusion 8b contacts the inner wall of a portion of the first opening 13a where the cross-sectional area is constant, and is fixed to the inner wall of that portion with an adhesive.

[0077] On the other hand, the second protrusion 8c of the pipe member 8 protrudes into the second opening 14a of the second cover 14. Specifically, the second protrusion 8c contacts the inner wall of a portion of the second opening 14a where the cross-sectional area is constant, and is fixed to the inner wall of that portion with an adhesive.

[0078] The pipe member 8 is in contact with the inner wall of the first opening 13a in the first cover 13 and the inner wall of the second opening 14a in the second cover 14, thereby stabilizing the positioning of the pipe member 8. The Faraday element 2 is disposed inside the through-hole 8a in the pipe member 8. Therefore, the above configuration also stabilizes the positioning of the Faraday element 2. This improves the accuracy of the optical axis in the optical isolator 1.

[0079] As in this embodiment, it is preferable that the first protrusion 8b of the pipe member 8 is fixed to the inner wall of the first opening 13a in the first lid 13. It is preferable that the second protrusion 8c is fixed to the inner wall of the second opening 14a in the second lid 14. This makes it possible to effectively stabilize the arrangement of the pipe member 8 and the Faraday element 2.

[0080] Alternatively, the pipe member 8 may be fixed with an adhesive to the inner wall of the magnet 7 facing the through-hole 7a. In this case as well, the arrangement of the pipe member 8 and the Faraday element 2 can be effectively stabilized.

[0081] However, the pipe member 8 does not have to be fixed to the inner wall of the first opening 13a in the first cover 13, the inner wall of the second opening 14a in the second cover 14, or the inner wall facing the through-hole 7a in the magnet 7. In this case, when a member such as the magnet 7 or the Faraday element 2 arranged inside the housing 12 of the optical isolator 1 is damaged, the member can be easily replaced by removing the first cover 13 and / or the second cover 14.

[0082] The first protrusion 8b of the pipe member 8 protrudes to a portion of the first opening 13a of the first cover 13 where the cross-sectional area changes. In other words, the first protrusion 8b of the pipe member 8 protrudes to a portion of the first opening 13a of the first cover 13 where the cross-sectional area is larger than the cross-sectional area of ​​the portion closest to the emission side. In this case, when fixing the first protrusion 8b to the inner wall of the first opening 13a, adhesive can easily flow between the pipe member 8 and the inner wall. In addition, the adhesive is less likely to leak outside the first opening 13a. This increases productivity.

[0083] FIG. 7 is a schematic longitudinal cross-sectional view showing a modified example of the first lid body in the first embodiment. As shown in FIG. 7, the first opening 13x of the first lid body 13A has a configuration in which portions with constant cross-sectional areas are connected by a step portion. In this case, the cross-sectional area of ​​the portion of the first opening 13x closest to the incident side is larger than the cross-sectional area of ​​the portion of the first opening 13x closest to the exit side. Even in this configuration, it is preferable that the first protrusion 8b of the pipe member 8 shown in FIG. 2 protrudes at least to the portion of the first opening 13x of the first lid body 13A whose cross-sectional area is larger than the cross-sectional area of ​​the portion of the first opening 13x closest to the exit side. This allows for increased productivity, similar to the above, even when using the first lid body 13A.

[0084] For example, the first protrusion 8b of the pipe member 8 may protrude into the first polarizer holder 5. This also improves productivity. However, as in this embodiment, it is preferable that the first polarizer holder 5 holds the first polarizer 3 with a space provided so that the first protrusion 8b of the pipe member 8 and the first polarizer 3 do not come into contact with each other. This makes it less likely that the first polarizer 3 will be scratched.

[0085] The second protrusion 8c of the pipe member 8 protrudes to a portion of the second opening 14a of the second cover 14 where the cross-sectional area changes. In other words, the second protrusion 8c of the pipe member 8 protrudes to a portion of the second opening 14a of the second cover 14 where the cross-sectional area is larger than the cross-sectional area of ​​the portion closest to the incident side. In this case, when fixing the second protrusion 8c to the inner wall of the second opening 14a, adhesive can easily flow between the pipe member 8 and the inner wall. In addition, the adhesive is less likely to leak outside the second opening 14a. This improves productivity.

[0086] The second opening 14a of the second cover 14 may have a configuration in which portions with constant cross-sectional areas are connected by a step. In this case, the cross-sectional area of ​​the portion of the second opening 14a closest to the exit side may be larger than the cross-sectional area of ​​the portion of the second opening 14a closest to the incident side. Even in this configuration, it is preferable that the second protrusion 8c of the pipe member 8 protrudes at least to a portion of the second opening 14a of the second cover 14 whose cross-sectional area is larger than the cross-sectional area of ​​the portion of the second opening 14a closest to the incident side. This, as described above, can increase productivity.

[0087] For example, the second protrusion 8c of the pipe member 8 may protrude into the second polarizer holder 6. This also improves productivity. However, as in this embodiment, it is preferable that the second polarizer holder 6 holds the second polarizer 4 with a space provided so that the second protrusion 8c of the pipe member 8 and the second polarizer 4 do not come into contact with each other. This makes it less likely that the second polarizer 4 will be scratched.

[0088] The thickness of the pipe member 8 is preferably 0.1 mm or less, more preferably 0.08 mm or less, even more preferably 0.05 mm or less, and even more preferably 0.045 mm or less, which allows the optically effective diameter of the optical isolator 1 to be increased without increasing the size of the optical isolator 1.

[0089] On the other hand, the thickness of the pipe member 8 is preferably 0.02 mm or more, and more preferably 0.03 mm or more, so that the pipe member 8 has sufficient strength.

[0090] In the present invention, an opening may be provided in the side surface of the first polarizer holder 5, as in the first embodiment shown in Fig. 2. Similarly, an opening is provided in the side surface of the second polarizer holder 6. However, openings do not necessarily have to be provided in the side surfaces of the first polarizer holder 5 and the second polarizer holder 6.

[0091] As in the present embodiment, it is preferable that the outer shape of the first polarizer holder 5 and the outer shape of the second polarizer holder 6 are circular in cross section, and that the outer shape of the magnet 7 is rectangular in cross section. By making the outer shapes of the first polarizer holder 5 and the second polarizer holder 6 circular in cross section, it is easy to adjust the angles of the first polarizer 3 and the second polarizer 4. For example, as described above, the side surface 5 d of the first polarizer holder 5 can be slid along the inner wall of the first lid 13. The side surface 6 d of the second polarizer holder 6 can be slid along the inner wall of the second lid 14.

[0092] On the other hand, by making the outer shape of the magnet 7 rectangular, it is possible to increase the magnetic flux density in the magnet 7. Specifically, for example, for a magnet of the same volume, the magnetic flux density in the magnet can be increased by making the outer shape of the cross section rectangular rather than by making the outer shape of the cross section circular or the like. Therefore, in this embodiment, the magnetic flux density of the magnet 7 can be increased even when the optical isolator 1 is made small.

[0093] Second Embodiment Fig. 8 is a schematic perspective view showing a cross section of an optical isolator according to a second embodiment, taken along the direction in which light passes. Fig. 9 is a schematic view of a magnet in the second embodiment.

[0094] 8, this embodiment differs from the first embodiment in that the magnet 27 has multiple magnet bodies. Specifically, the magnet 27 has a first magnet body 27A, a second magnet body 27B, and a third magnet body 27C. Except for the above, the optical isolator of the second embodiment has the same configuration as the optical isolator 1 of the first embodiment.

[0095] The first magnet body 27A, the second magnet body 27B, and the third magnet body 27C are stacked in the forward direction. More specifically, from the incident side, the first magnet body 27A, the second magnet body 27B, and the third magnet body 27C are stacked in this order. The first magnet body 27A, the second magnet body 27B, and the third magnet body 27C each have a through hole. The through holes of the first magnet body 27A, the second magnet body 27B, and the third magnet body 27C are connected to each other, thereby forming a through hole 27a of the magnet 27. A pipe member 8 is provided inside the through hole 27a. A Faraday element 2 is provided inside the pipe member 8.

[0096] 9, the first magnet body 27A is magnetized in a direction perpendicular to the forward direction so that the through-hole side is the north pole. The second magnet body 27B is magnetized in a direction parallel to the forward direction so that the first magnet body 27A side is the north pole. The third magnet body 27C is magnetized in a direction perpendicular to the forward direction so that the through-hole side is the south pole.

[0097] Returning to FIG. 8 , in this embodiment, as in the first embodiment, the housing 12 has a first opening 12a and a second opening 12b, which are closed by a first cover 13 and a second cover 14. Because the housing 12, the first cover 13, and the second cover 14 are all independent components, processing of these components is simplified, reducing costs in manufacturing the optical isolator. Additionally, assembly is simplified in manufacturing the optical isolator. Therefore, productivity of the optical isolator can be effectively improved. Furthermore, for example, if components such as the first magnet 27A, the second magnet 27B, the third magnet 27C, and / or the Faraday element 2 arranged in the housing 12 of the optical isolator are damaged, the components can be easily replaced by removing the first cover 13 and / or the second cover 14.

[0098] DESCRIPTION OF SYMBOLS 1...optical isolator 2...Faraday element 3, 4...first and second polarizers 5, 6...first and second polarizer holders 5d, 6d...side surfaces 5f, 6e...end surfaces 7...magnet 7a...through hole 7d...side surfaces 8...pipe member 8a...through hole 8b, 8c...first and second protrusions 12...casing 12a, 12b...first and second openings 12c...inner wall 12e, 12f...end surfaces 13, 13A...first lid body 14...second lid body 13a, 14a...first and second openings 13b, 14b...first and second fitting portions 13c, 14c...step portions 13d, 14d...side surfaces 13x...first opening 27...magnet 27a...through hole 27A to 27C: First to third magnet bodies

Claims

1. A magnet having a through hole through which light is incident in the forward direction and passes therethrough; a Faraday element that transmits the light and is provided inside the through hole of the magnet; a housing that houses the magnet and the Faraday element, and has a first opening located on the incident side and a second opening located on the exit side, where the side through which the light in the forward direction is incident is the incident side and the side through which the light is exited is the exit side; a first lid that has a first opening through which the light passes and closes the first opening of the housing; a second lid that has a second opening through which the light passes and closes the second opening of the housing; a first polarizer that is arranged on the incident side of the first lid; a second polarizer that is arranged on the exit side of the second lid; a first polarizer holder that houses the first polarizer; and a second polarizer holder that houses the second polarizer. An optical isolator comprising:

2. The optical isolator according to claim 1, characterized in that, when viewed from the forward direction, the area of ​​the first polarizer holder is smaller than the area of ​​the first lid, and when viewed from the forward direction, the area of ​​the second polarizer holder is smaller than the area of ​​the second lid.

3. The optical isolator according to claim 1, characterized in that the first lid and the first polarizer holder are in contact with each other, and the second lid and the second polarizer holder are in contact with each other.

4. The optical isolator of claim 3, characterized in that at least a portion of the first polarizer holder is located inside the first lid, the first lid having a first fitting portion that fits with the first polarizer holder, and at least a portion of the second polarizer holder is located inside the second lid, the second lid having a second fitting portion that fits with the second polarizer holder.

5. An optical isolator as described in claim 1, further comprising a pipe member disposed inside the through hole of the magnet, the Faraday element being disposed inside the pipe member, the pipe member having a first protrusion protruding from the magnet toward the incident side and a second protrusion protruding from the magnet toward the output side, the first protrusion being in contact with the inner wall of the first opening of the first lid, and the second protrusion being in contact with the inner wall of the second opening of the second lid.

6. The optical isolator described in claim 5, characterized in that at least a portion of the first polarizer holder is located inside the first lid, and the first lid has a first fitting portion that fits with the first polarizer holder; at least a portion of the second polarizer holder is located inside the second lid, and the second lid has a second fitting portion that fits with the second polarizer holder; the first polarizer holder holds the first polarizer so that the first protrusion of the pipe member does not contact the first polarizer; and the second polarizer holder holds the second polarizer so that the second protrusion of the pipe member does not contact the second polarizer.

7. An optical isolator as described in claim 6, characterized in that, when a cross section taken along a direction perpendicular to the forward direction is taken as a cross section, the area of ​​the cross section of the first opening of the first lid body at the portion closest to the incident side is larger than the area of ​​the cross section of the first opening at the portion closest to the output side, the area of ​​the cross section of the second opening of the second lid body at the portion closest to the output side is larger than the area of ​​the cross section of the second opening at the portion closest to the incident side, the first protrusion of the pipe member protrudes at least to a portion of the first opening of the first lid body where the area of ​​the cross section is larger than the area of ​​the cross section of the first opening at the portion closest to the output side, and the second protrusion of the pipe member protrudes at least to a portion of the second opening of the second lid body where the area of ​​the cross section is larger than the area of ​​the cross section of the second opening at the portion closest to the incident side.

8. An optical isolator according to claim 1 or 2, characterized in that the first lid is in contact with the inner wall of the housing, and the second lid is in contact with the inner wall of the housing.

9. The optical isolator according to claim 1, wherein the housing is cylindrical in shape.

10. The optical isolator described in claim 1, characterized in that the magnet has a first magnet body, a second magnet body, and a third magnet body, each having a through hole, the first magnet body, the second magnet body, and the third magnet body are stacked in this order from the incident side, the through hole of the first magnet body, the through hole of the second magnet body, and the through hole of the third magnet body are connected, the first magnet body is magnetized in a direction perpendicular to the forward direction so that the through hole side is the north pole, the second magnet body is magnetized in a direction parallel to the forward direction so that the first magnet body side is the north pole, and the third magnet body is magnetized in a direction perpendicular to the forward direction so that the through hole side is the south pole.

11. The optical isolator according to claim 1, characterized in that, when a cross section taken along a direction perpendicular to the forward direction is taken as a transverse cross section, the magnet has a rectangular outer shape in the transverse cross section, and the first polarizer holder and the second polarizer holder have circular outer shapes in the transverse cross sections.

Images