JP2019219435A - Optical isolator and manufacturing method thereof - Google Patents

Abstract

To provide an optical isolator capable of fitting and fixing an optical isolator element into a through hole of a cylindrical magnet at designed incident and emitting end face angles even if a holder is not used, and to provide a manufacturing method thereof.SOLUTION: An optical isolator includes: a nearly parallelepiped optical isolator element 10 that includes at least two polarizers 2, 4 and one Faraday rotor 3 and allows them to be laminated on the light transmission surface; and a cylindrical magnet 1 for housing the optical isolator element. In the optical isolator element, a ridge line part of the optical isolator element formed by connecting corner parts of the polarizers and a corner part of the Faraday rotor and the peripheral parts are adhered to an inner wall of the cylindrical magnet to fix the optical isolator element into the cylindrical magnet, and only the two adjacent ridge line parts of the optical isolator element and the peripheral parts are adhered to the inner wall of the cylindrical magnet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical isolator incorporated in a semiconductor module used in an optical communication or an optical information system or the like, and more particularly to an optical isolator in which an optical element is adhesively fixed using an adhesive in a through hole of a cylindrical magnet. The present invention relates to improvement of the manufacturing method.

  An optical isolator generally includes a Faraday rotator, a permanent magnet for saturating the Faraday rotator, an incident-side polarizer, and an output-side polarizer. As the Faraday rotator, a Faraday rotator whose thickness is adjusted so that the plane of polarization of light is rotated by 45 degrees is used.

  Then, in the optical isolator, the linearly polarized light that has passed through the incident-side polarizer and entered the forward direction with respect to the Faraday rotator rotates the polarization plane of the incident linearly polarized light by transmitting the Faraday rotator by 45 degrees, At the rotation position, the light passes through the exit-side polarizer adjusted so that the amount of transmitted light is maximized. Therefore, the light is transmitted to the next optical system as light having almost no loss.

  In the case where there is reflected return light in the optical isolator, the plane of polarization of the linearly polarized light that has passed through the output-side polarizer is rotated by 45 degrees by transmitting through the Faraday rotator, and is thereby orthogonal to the incident-side polarizer. It becomes quenched because it becomes. In this way, the function of the optical isolator is performed.

  Incidentally, in an optical isolator, an antireflection film is applied to the surface of each optical element such as a Faraday rotator, an incident-side polarizer, and an output-side polarizer, and each optical element is integrated with an adhesive (optical isolator). Element) is often used. Although the above-mentioned antireflection film is applied to the input / output end face of each optical element, light is slightly reflected at the input / output end face of each optical element, and this reflected light is prevented from returning to the original optical path. Therefore, the input / output end face of the optical isolator element may be intentionally inclined several degrees from a plane perpendicular to the optical axis.

  As a method for inclining the input / output end face of the optical isolator element, a method of fixing the optical isolator element to a holder having an inclined surface (see Patent Document 1), a cross section in which the input / output end face is inclined with respect to a plane perpendicular to the optical axis There is known a method of manufacturing a parallelogram-shaped optical isolator element (see Patent Document 2) and bonding the same in a through hole of a cylindrical magnet.

  The latter method has the advantage of not requiring a holder as compared with the former method, but when the optical isolator element is bonded into the through hole of the cylindrical magnet, the optical isolator element enters and exits from a plane perpendicular to the optical axis. The end face angle sometimes deviated from the design setting.

  Then, when the angle of the input / output end face of the optical isolator element with respect to the plane perpendicular to the optical axis deviates from the setting at the time of design, there is a problem that desired optical characteristics of the optical isolator at the time of design cannot be obtained.

Japanese Patent Application Laid-Open No. 2015-125374 (see FIG. 10) JP-A-2015-084016 (see FIG. 4)

  The present invention has been made in view of such a problem, and an object of the present invention is to place an optical isolator element in a through-hole of a cylindrical magnet at an input / output end face angle as designed without using a holder. An object of the present invention is to provide an optical isolator that can be bonded and fixed and a method of manufacturing the same.

  In order to solve the above problems, the present inventor has set the angle of the input / output end face of the optical isolator element with respect to the plane perpendicular to the optical axis when designing the optical isolator element in the through hole of the cylindrical magnet. We investigated and analyzed the cause of the deviation.

  Conventionally, when an optical isolator element is adhered in a through hole of a cylindrical magnet, considering the symmetry, four ridges of the optical isolator element located near the inner wall surface (the inner wall surface of the through hole) of the cylindrical magnet are considered. The four ridges of the optical isolator element formed by connecting the corner of the polarizer and the corner of the Faraday rotator) and the periphery thereof were bonded to the inner wall surface of the cylindrical magnet with an adhesive.

  However, the inner diameter of the cylindrical magnet (the inner diameter of the through-hole) is set slightly larger to ensure that the optical isolator element can be accommodated in the through-hole of the cylindrical magnet. When a type magnet is used, the clearance (gap) between the inner wall of the cylindrical magnet and the optical isolator element increases. For this reason, when bonding the four ridges of the optical isolator element 10 having a parallelepiped shape and the periphery thereof to the inner wall of the cylindrical magnet 1, as shown in FIGS. It is difficult to control the shrinking direction (the hardening shrinking direction is indicated by an arrow in FIGS. 3A and 3B) due to uneven curing shrinkage, and the center axis β of the optical isolator element 10 and the center axis α of the cylindrical magnet 1 intersect. (It is preferable that the central axis β of the optical isolator element 10 and the central axis α of the cylindrical magnet 1 do not intersect but overlap each other or are parallel to each other). As a result, the angle of the input / output end face of the optical isolator element 10 with respect to the plane perpendicular to the optical axis P shown in FIG. 1D is set at the time of design (the angle of the input / output end face of the optical isolator element is set to θ at the time of design). ). The present invention has been completed through such research and analysis.

That is, the first invention according to the present invention is:
A parallelepiped-shaped optical isolator element having at least two polarizers and one Faraday rotator and bonded to each other at a light transmitting surface thereof, and a cylindrical magnet accommodating the optical isolator element. The ridge of the optical isolator element formed by connecting the corner of the polarizer and the corner of the Faraday rotator and the periphery thereof are adhered to the inner wall of the cylindrical magnet, and the optical isolator is fixed in the cylindrical magnet. In the method of manufacturing an optical isolator,
After the optical isolator element is inserted into the cylindrical magnet, an adhesive is applied only to the two adjacent ridges of the optical isolator element and the periphery thereof, and the two ridges of the optical isolator element and the periphery thereof are applied. Characterized in that only the part is adhered to the inner wall of the cylindrical magnet,
The second invention is
In the method for manufacturing an optical isolator according to the first invention,
The adhesive is composed of a thermosetting adhesive, and the viscosity of the thermosetting adhesive during application is 0.6 Pa · s or more and 1.7 Pa · s or less.

Further, a third invention according to the present invention provides:
A parallelepiped-shaped optical isolator element having at least two polarizers and one Faraday rotator and bonded to each other at a light transmitting surface thereof, and a cylindrical magnet accommodating the optical isolator element. The ridge of the optical isolator element formed by connecting the corner of the polarizer and the corner of the Faraday rotator and the periphery thereof are adhered to the inner wall of the cylindrical magnet, and the optical isolator is fixed in the cylindrical magnet. Optical isolator
Only the two adjacent ridges of the optical isolator element and the periphery thereof are bonded to the inner wall of the cylindrical magnet.

According to the method for manufacturing an optical isolator according to the present invention,
After the optical isolator element is inserted into the cylindrical magnet, the adhesive is applied only to the two adjacent ridges of the optical isolator element and the periphery thereof, and only the two ridges of the optical isolator element and the periphery thereof are applied. Is adhered to the inner wall of the cylindrical magnet, so that the shrinking direction when the adhesive cures and shrinks can be restricted to substantially one direction. Therefore, since it is difficult for the central axis of the optical isolator element and the central axis of the cylindrical magnet to intersect, it is possible to suppress the deviation of the angle of the input / output end face of the optical isolator element with respect to the plane perpendicular to the optical axis. It becomes.

1A is a front view of an optical isolator according to the present invention, FIG. 1B is a schematic cross-sectional view taken along the line AA ′ in FIG. 1A, and FIG. 1C is an optical isolator according to the present invention. FIG. 1 (d) is an explanatory view of an incident / exit end face angle (θ) at the time of design with respect to a plane perpendicular to the optical axis P of an optical isolator element 10 fixed to a cylindrical magnet. The angle of the input / output end face (chip angle) at the time of designing the optical isolator element with respect to the plane perpendicular to the optical axis, and the plane perpendicular to the optical axis of the optical isolator after the optical isolator element is adhered and fixed to the inner wall of the cylindrical magnet. Is a graph showing the relationship between the input and output end face angles (assembled angles) of the optical isolator element having a parallelepiped shape, and the adjacent two ridges and the periphery thereof are adhered to the inner wall of the cylindrical magnet. Shows the relationship between the chip angle of the optical isolator (adhesion with two ridges) and the angle after assembling, and the symbol □ indicates that the four ridges of the optical isolator element having a parallelepiped shape and its peripheral portion are bonded to the inner wall of the cylindrical magnet. The relationship between the chip angle of the optical isolator (four-edge bonding) and the angle after assembly is shown. FIG. 3A is a cross-sectional view of an optical isolator in which four ridges and a peripheral portion of the optical isolator element having a parallelepiped shape are adhered to an inner wall of a cylindrical magnet, and FIG. 3B is a front view thereof. FIG. 4A is a cross-sectional view of an optical isolator in which two adjacent ridges and a peripheral portion of the optical isolator element having a parallelepiped shape are adhered to the inner wall of a cylindrical magnet, and FIG. 4B is a front view thereof. .

  Hereinafter, embodiments of the present invention will be described in detail.

(1) Optical Isolator The optical isolator according to the present invention is, as shown in FIGS. 1A to 1D, a cylindrical magnet 1 having a circular through-hole, and inserted into the through-hole of the cylindrical magnet 1. The optical isolator element 10 and adhesives 5 and 6 for joining the optical isolator element 10 to the inner wall of the through-hole of the cylindrical magnet 1.

  Further, the optical isolator element 10 has a first polarizer 2, a Faraday rotator 3 on the side where light enters, and a second polarizer 4 on the side where light exits, and these are attached using an optical adhesive. It has a fitted parallelepiped shape. Also, only two adjacent ridges formed by connecting the corners of the first polarizer 2 with the corners of the Faraday rotator 3 and the corners of the second polarizer 4 and the periphery thereof are cylindrical magnets only. 1 is adhesively fixed to the inner wall.

  In addition, a parallelepiped means a hexahedron whose three opposing surfaces are respectively parallel.

  Then, in the optical isolator according to the present invention, as shown in FIGS. 4A and 4B, only two adjacent ridges of the optical isolator element 10 and the periphery thereof are bonded to the inner wall of the cylindrical magnet 1. Therefore, it is possible to control the contraction direction (the curing contraction direction is indicated by an arrow in FIGS. 4A and 4B) when the adhesives 5 and 6 cure and contract in substantially one direction. Accordingly, it is difficult for the central axis β of the optical isolator element 10 to intersect with the central axis α of the cylindrical magnet 1 (the central axis β of the optical isolator element 10 is substantially parallel to the central axis α of the cylindrical magnet 1). Therefore, it is possible to suppress the deviation of the angle of the input / output end face of the optical isolator element 10 with respect to the plane perpendicular to the optical axis.

  Further, in the optical isolator according to the present invention, the same optical isolator element and cylindrical magnet as those in the related art can be used.

(2) Optical Isolator Element As a parallelepiped-shaped optical isolator element having at least two polarizers and one Faraday rotator, which are bonded together on their light transmitting surfaces, a “single-type optical isolator” "Optical element" (polarizer / Faraday rotator / polarizer), "Double type optical isolator for optical isolator" combining optical element for optical isolator (Polarizer / Faraday rotator / polarizer / polarizer / Faraday rotator / polarizer) and "semi-double type optical element for optical isolator" (polarizer / Faraday rotator / polarizer / Faraday rotator / polarizer) and the like.

  Further, as the shape of the optical isolator element 10, a parallelepiped shown in FIG. 1D composed of a polarizer having a parallelogram cross section and a Faraday rotator (a set of opposing faces has a parallelogram shape). The remaining two pairs of opposing faces have a square or rectangular shape, or a parallelepiped (cubic or rectangular parallelepiped) shown in FIG. Is exemplified).

(3) Manufacturing Method of Optical Isolator Next, a manufacturing method of the optical isolator according to the present invention will be described.

  First, a cylindrical magnet is mounted on a mounting table on which a V-groove or the like is formed so that its through-hole is horizontal, and an optical isolator element is inserted into the through-hole of the cylindrical magnet. At this time, it is not necessary to align the insertion directions of the optical isolator elements. Due to the weight of the optical isolator element inserted into the through-hole, two adjacent ridges contact the inner wall of the through-hole of the cylindrical magnet.

  Next, an adhesive is applied to two adjacent ridges of the optical isolator element which is in contact with the inner wall of the through hole of the cylindrical magnet and a peripheral portion thereof using a dispenser.

  At this time, the viscosity of the adhesive is preferably 0.6 Pa · s or more and 1.7 Pa · s or less. If the viscosity of the adhesive is too low, the adhesive flows instead of staying in the vicinity of the ridge of the optical isolator element, and it is difficult to bond the two adjacent ridges of the optical isolator element and its peripheral portion. Further, if the viscosity of the adhesive is too high, it is difficult to spread the adhesive over the two adjacent ridges of the optical isolator element and the entire periphery thereof, and as a result, the bonding area becomes small and sufficient bonding strength is obtained. It becomes difficult. As the kind of the adhesive to be applied, any of a thermosetting adhesive and an ultraviolet curing adhesive can be applied, but from the viewpoint of environmental resistance, an adhesive composed of an epoxy resin is preferable.

  When a two-component adhesive is used, the viscosity increases with the lapse of time after the main agent and the curing agent are mixed, so that the viscosity becomes 0.6 Pa · s or more and 1.7 Pa · s or less. It is preferable to finish the operation of applying the adhesive within the time.

  Finally, the optical isolator is completed by curing the adhesive.

  Hereinafter, examples of the present invention will be specifically described.

  A first polarizer, a Faraday rotator, and a second polarizer of 11 mm square are bonded in advance with an adhesive, and are cut with a dicing saw by a method of manufacturing an optical element described in Patent Document 2 to obtain a light transmitting surface. An optical isolator element having a size of 1.4 mm square was manufactured. The light transmitting surface of the optical isolator element is inclined by 6 ± 0.5 degrees from a surface perpendicular to the optical axis.

  In addition, an unmagnetized cylindrical magnet having an outer diameter of 3 mm, an inner diameter of 2 mm, and a length of 2 mm was prepared. The inner diameter of the cylindrical magnet is slightly larger than the diagonal length of the light transmitting surface of the optical isolator element.

  First, the cylindrical magnet was mounted on a mounting table on which a V-groove was formed so that its through-hole was horizontal, and then the prepared optical isolator element was inserted into the through-hole of the cylindrical magnet.

  Then, using a dispenser, a commercially available thermosetting epoxy adhesive (manufactured by Daizo Co., Ltd., model number: 2) on the adjacent two ridges of the optical isolator element that is in contact with the inner wall of the through hole of the cylindrical magnet and the periphery thereof NB3200) was applied. The initial viscosity of the adhesive before curing was 0.66 Pa · s. The adhesive used in the present example was a two-part mixed type adhesive, and although the viscosity increased with time, the viscosity when the application of the adhesive was completed was 1.7 Pa · s.

  Finally, the applied adhesive was cured to complete the optical isolator according to the example.

  For comparison, an optical isolator according to a comparative example was also prepared in which an adhesive was applied to the four ridges of the optical isolator element and the periphery thereof, which were the same as those in the example, and cured.

  FIG. 2 is a graph comparing the angles of the light transmitting surface with respect to the cylindrical magnet end surfaces of the optical isolator elements according to the example and the comparative example. Since the cylindrical magnet end face is installed perpendicular to the optical axis, the angle of the light transmitting surface of the optical isolator element with respect to the cylindrical magnet end face is determined by the angle of the input / output end face of the optical isolator element with respect to the plane perpendicular to the optical axis. Is the same as In FIG. 2, the symbol ◇ indicates the chip angle of the optical isolator (two-edge bonding) according to the embodiment in which the two adjacent ridges of the optical isolator element and the periphery thereof are bonded to the inner wall of the cylindrical magnet. The symbol □ indicates the chip angle and the assembling angle of the optical isolator (four-edge bonding) according to the comparative example in which the four ridges of the optical isolator element and the periphery thereof are bonded to the inner wall of the cylindrical magnet. The relationship with is shown below.

  From the graph of FIG. 2, the angle of the light transmitting surface with respect to the cylindrical magnet end surface of the optical isolator according to the embodiment indicated by the symbol ◇ is larger than the incident / exit end surface angle (6 ± 0.5 degrees described above) at the time of design. It is within ± 1 degree. On the other hand, the angle of the light transmitting surface with respect to the cylindrical magnet end surface of the optical isolator according to the comparative example indicated by the symbol □ was deviated by 5 degrees from the input / output end surface angle (6 ± 0.5 degrees) at the time of design. You.

  Therefore, it is confirmed that the optical isolator element can be bonded and fixed in the through-hole of the cylindrical magnet at the designed input / output end face angle without using the holder by the optical isolator manufacturing method according to the present invention.

  ADVANTAGE OF THE INVENTION According to the optical isolator which concerns on this invention, since the deviation | shift of the entrance / exit end surface angle of an optical isolator element with respect to the surface perpendicular | vertical to an optical axis is suppressed, the industrial built into the semiconductor module used for optical communication, an optical information system, etc. Has the above availability.

Reference Signs List 1 cylindrical magnet 2 first polarizer 3 Faraday rotator 4 second polarizer 5, 6 adhesive 10 optical isolator element 20 adhesive α central axis of cylindrical magnet β central axis of optical isolator element θ optical isolator in design Element entrance / exit end face angle

Claims (3)

A parallelepiped-shaped optical isolator element having at least two polarizers and one Faraday rotator and bonded to each other at a light transmitting surface thereof, and a cylindrical magnet accommodating the optical isolator element. The edge of the optical isolator element formed by connecting the corner of the polarizer and the corner of the Faraday rotator and the peripheral portion thereof are adhered to the inner wall of the cylindrical magnet, and the optical isolator is fixed in the cylindrical magnet. In a method for manufacturing an optical isolator,
After the optical isolator element is inserted into the cylindrical magnet, an adhesive is applied only to the two adjacent ridges of the optical isolator element and the periphery thereof, and the two ridges of the optical isolator element and the periphery thereof are applied. A method of manufacturing an optical isolator, wherein only a portion is adhered to an inner wall of a cylindrical magnet.   2. The method according to claim 1, wherein the adhesive is a thermosetting adhesive, and the viscosity of the thermosetting adhesive during the coating operation is 0.6 Pa · s or more and 1.7 Pa · s or less. A manufacturing method of the optical isolator according to the above. A parallelepiped-shaped optical isolator element having at least two polarizers and one Faraday rotator and bonded to each other at a light transmitting surface thereof, and a cylindrical magnet accommodating the optical isolator element. The ridge of the optical isolator element formed by connecting the corner of the polarizer and the corner of the Faraday rotator and the periphery thereof are adhered to the inner wall of the cylindrical magnet, and the optical isolator is fixed in the cylindrical magnet. Optical isolator
An optical isolator characterized in that only two adjacent ridge portions and a peripheral portion of the optical isolator element are bonded to the inner wall of the cylindrical magnet.