JP7037135B2 - Optical isolator and its manufacturing method - Google Patents

Description

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

The optical isolator is generally composed of a Faraday rotator, a permanent magnet for saturating the Faraday rotator, an incident side polarizing element, and an emitted side polarizing element. Further, as for the Faraday rotator, one in which the plane of polarization of light is adjusted to rotate by 45 degrees by adjusting the thickness of the Faraday rotator itself is used.

Then, in the optical isolator, the linearly polarized light that has passed through the incident side polarizing element and entered in the forward direction with respect to the Faraday rotator is transmitted through the Faraday rotator so that the polarization plane of the incident linearly polarized light is rotated by 45 degrees. It transmits the emitting side polarizing element adjusted so that the amount of transmitted light is maximized at the rotation position. Therefore, it is transmitted to the next optical system as light with almost no loss.

Further, in the optical isolator, when there is reflected return light, the plane of polarization of the linearly polarized light that has passed through the emitter on the emitting side is rotated by 45 degrees by passing through the Faraday rotator, so that the plane of polarization is orthogonal to the splitter on the incident side. It is extinguished because it becomes. In this way, the function of the optical isolator is fulfilled.

By the way, in an optical isolator, an antireflection film is applied to the surface of each optical element such as a Faraday rotator, an incident side polarizing element, and an emitted side polarizing element, and each optical element is integrated with an adhesive (optical isolator). (Called an element) is often used. Although the antireflection film is applied to the entrance / exit end faces of each optical element, light is slightly reflected on the entrance / exit end faces of each optical element to prevent the reflected light from returning to the original optical path. Therefore, the input / output end surface of the optical isolator element may be intentionally tilted several degrees from the surface perpendicular to the optical axis.

Then, as a method of inclining the input / output end surface 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 surface is inclined with respect to a plane perpendicular to the optical axis. A method of producing an optical isolator element having a parallel quadrilateral shape (see Patent Document 2) and adhering the optical isolator element to the inside of a through hole of a cylindrical magnet is known.

The latter method has the advantage that it does not require a holder compared to 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 the plane perpendicular to the optical axis. The end face angle sometimes deviated from the setting at the time of design.

Then, when the input / output end surface angle 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 the desired optical characteristics of the optical isolator at the time of design cannot be obtained.

JP-A-2015-125374 (see FIG. 10) JP-A-2015-084016 (see FIG. 4)

The present invention has been made by paying attention to such a problem, and the problem is that an optical isolator element is provided in a through hole of a cylindrical magnet at an input / exit end face angle as designed without using a holder. It is an object of the present invention to provide an optical isolator that can be bonded and fixed, and a method for manufacturing the same.

Therefore, in order to solve the above problems, the present inventor sets the entrance / exit end face angle of the optical isolator element with respect to the plane perpendicular to the optical axis at the time of design when the optical isolator element is bonded in the through hole of the cylindrical magnet. We investigated and analyzed the cause of the deviation.

Conventionally, when an optical isolator element is bonded inside a through hole of a cylindrical magnet, in consideration of symmetry, the four ridges of the optical isolator element located near the inner wall surface (inner wall surface of the through hole) of the cylindrical magnet ( The four ridges of the optical isolator element formed by connecting the corners of the polarizing element and the corners of the Faraday rotator) and their peripheral parts were bonded to the inner wall surface of the cylindrical magnet with an adhesive.

However, the inner diameter of the cylindrical magnet (inner diameter of the through hole) is set to a slightly larger tolerance so that the optical isolator element can be securely 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 becomes large. Therefore, when the four ridges of the optical isolator element 10 having a parallelepiped shape and the peripheral portions thereof are bonded to the inner wall of the cylindrical magnet 1, the adhesive 20 is used as shown in FIGS. 3 (a) to 3 (b). It is difficult to control the shrinkage direction (the direction of hardening and shrinkage is indicated by an arrow in FIGS. 3a to 3b) due to non-uniform hardening shrinkage, and the central axis β of the optical isolator element 10 and the central 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 with each other and are overlapped or parallel to each other). As a result, the entrance / exit end face angle of the optical isolator element 10 with respect to the plane perpendicular to the optical axis P shown in FIG. 1 (d) is set at the time of design (the entrance / exit end face angle of the optical isolator element is set to θ at the time of design). It turned out that it deviated from. The present invention has been completed by such investigation and analysis.

That is, the first invention according to the present invention is
It comprises a parallel hexahedron-shaped optical isolator element having at least two polarizing elements and one Faraday rotator and bonded to each other on the light transmitting surface thereof, and a cylindrical magnet in which the optical isolator element is housed. The optical isolator element is fixed in the cylindrical magnet by adhering the ridgeline portion and its peripheral portion of the optical isolator element formed by connecting the corners of the polarizing element and the corners of the Faraday rotator to the inner wall of the cylindrical magnet. In the method of manufacturing an optical isolator,
After inserting the optical isolator element into the cylindrical magnet, the adhesive is applied only to the two adjacent ridges of the optical isolator element and their peripheral portions, and then the adhesive is applied only to the two adjacent ridges of the optical isolator element and their surroundings. It is characterized by adhering only the part 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 the coating operation is 0.6 Pa · s or more and 1.7 Pa · s or less.

Further, the third invention according to the present invention is
It comprises a parallel hexahedron-shaped optical isolator element having at least two polarizing elements and one Faraday rotator and bonded to each other on the light transmitting surface thereof, and a cylindrical magnet in which the optical isolator element is housed. The optical isolator element is fixed in the cylindrical magnet by adhering the ridgeline portion and its peripheral portion of the optical isolator element formed by connecting the corners of the polarizing element and the corners of the Faraday rotator to the inner wall of the cylindrical magnet. In the optical isolator
It is characterized in that only the two adjacent ridges of the optical isolator element and their peripheral portions are adhered to the inner wall of the cylindrical magnet.

According to the method for manufacturing an optical isolator according to the present invention.
After inserting the optical isolator element into the cylindrical magnet, the adhesive is applied only to the two adjacent ridges of the optical isolator element and their peripheral parts, and only the above two ridges of the optical isolator element and their peripheral parts are applied. Is adhered to the inner wall of the cylindrical magnet, so that the shrinkage direction when the adhesive is cured and shrunk can be limited to substantially one direction. Therefore, since it is unlikely that the central axis of the optical isolator element and the central axis of the cylindrical magnet intersect each other, it is possible to suppress the deviation of the input / output end face angle of the optical isolator element with respect to the plane perpendicular to the optical axis. It becomes.

1 (a) is a front view of the optical isolator according to the present invention, FIG. 1 (b) is a schematic cross-sectional view taken along the line AA'in FIG. 1 (a), and FIG. 1 (c) is an optical isolator according to the present invention. 1 (d) is an explanatory view of an entrance / exit end face angle (θ) at the time of design with respect to a plane perpendicular to the optical axis P of the optical isolator element 10 fixed to the cylindrical magnet. The input / exit end face angle (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. In the graph showing the relationship with the input / output end face angle (angle after assembly), the reference numeral ◇ indicates that two adjacent ridges of an optical isolator element having a parallelepiped shape and their peripheral portions are adhered to the inner wall of a cylindrical magnet. The relationship between the tip angle and the post-assembly angle of the optical isolator (adhesion of two ridges) is shown. The relationship between the tip angle of the optical isolator (adhesion of four ridges) and the angle after assembly is shown. FIG. 3A is a cross-sectional view of an optical isolator in which four ridges and peripheral portions of an 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 of an optical isolator element having a parallelepiped shape and their peripheral portions are adhered to the inner wall of a cylindrical magnet, and FIG. 4B is a front view thereof. ..

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

(1) Optical Isolator The optical isolator according to the present invention is inserted into a cylindrical magnet 1 having a circular through hole and a through hole of the cylindrical magnet 1 as shown in FIGS. 1 (a) to 1 (d). It is composed of the optical isolator element 10 and the 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 polarizing element 2 on the side where light is incident, a Faraday rotator 3 and a second polarizing element 4 on the side where light is emitted, and these are attached by using an optical adhesive. It has a combined parallelepiped shape. Further, only the two adjacent positions of the ridge line formed by connecting the corners of the first splitter 2 and the corners of the Faraday rotator 3 and the corners of the second splitter 4 and their peripheral portions are cylindrical magnets. It is adhesively fixed to the inner wall of 1.

The parallelepiped means a hexahedron in which three sets of opposing faces are parallel to each other.

In the optical isolator according to the present invention, as shown in FIGS. 4A to 4B, only two adjacent ridges of the optical isolator element 10 and their peripheral portions are adhered to the inner wall of the cylindrical magnet 1. Therefore, it is possible to control the shrinkage direction (the curing shrinkage direction is indicated by an arrow in FIGS. 4a to 4b) when the adhesives 5 and 6 are cured and shrunk in substantially one direction. Therefore, it is unlikely that the central axis β of the optical isolator element 10 and the central axis α of the cylindrical magnet 1 intersect each other (the central axis β of the optical isolator element 10 and the central axis α of the cylindrical magnet 1 are substantially parallel to each other. Therefore, it is possible to suppress the deviation of the input / output end surface angle of the optical isolator element 10 with respect to the surface perpendicular to the optical axis.

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

(2) Optical isolator element As an optical isolator element having a parallel hexahedron shape having at least two deflectors and one Faraday rotator and these being bonded to each other on the light transmitting surface, "for a single type optical isolator". "Optical element" (polarizer / Faraday rotator / deflector), "Double type optical element for optical isolator" (polarizer / Faraday rotator / modulator / deflector / Faraday rotator / Faraday rotator), and "semi-double type optical element for optical isolator" (Faraday rotator / Faraday rotator / Faraday rotator / Faraday rotator) and the like are exemplified.

The shape of the optical isolator element 10 is a parallelepiped (a pair of facing faces having a parallelepiped shape) shown in FIG. 1D, which is composed of a polarizing element having a parallel quadrilateral cross section and a Faraday rotor. , The remaining two pairs of faces facing each other have a square or rectangular shape), or a parallelepiped (cube or rectangular parallelepiped shape) shown in FIG. ) Is exemplified.

(3) Method for manufacturing an optical isolator Next, a method for manufacturing an optical isolator according to the present invention will be described.

First, a cylindrical magnet is placed on a mounting table having a V-groove or the like 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 come into contact with 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 in contact with the inner wall of the through hole of the cylindrical magnet and their peripheral portions 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 will flow without staying in the vicinity of the ridgeline portion of the optical isolator element, and it will be difficult to bond the two adjacent ridgeline portions of the optical isolator element and their peripheral portions. 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 peripheral portion thereof, and as a result, the adhesive area becomes small and sufficient adhesive strength is obtained. Will be difficult. As the type of adhesive to be applied, either a thermosetting type adhesive or an ultraviolet curable type adhesive can be applied, but from the viewpoint of environmental resistance, an adhesive composed of an epoxy resin is preferable.

When a two-component mixed type adhesive is applied, the viscosity increases with the passage of time after mixing the main agent and the curing agent, so that the viscosity becomes 0.6 Pa · s or more and 1.7 Pa · s or less. It is preferable to finish the adhesive application work within the time.

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

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

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

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

Next, a commercially available thermosetting epoxy adhesive (manufactured by Daizo Co., Ltd., model number:) was applied to the two adjacent ridges of the optical isolator element in contact with the inner wall of the through hole of the cylindrical magnet and their peripheral portions using a dispenser. NB3200) was applied. The initial viscosity of this adhesive before curing was 0.66 Pa · s. The adhesive used in this example was a two-component mixed type adhesive, and the viscosity increased with time, but the viscosity at the end of the adhesive application work was 1.7 Pa · s.

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

Further, for comparison, an optical isolator according to a comparative example was also produced in which an adhesive was applied to and cured the four ridges of the optical isolator element, which are the same as those in the example, and their peripheral portions.

FIG. 2 shows a graph comparing the angles of the light transmitting surfaces with respect to the end faces of the cylindrical magnets of the optical isolator elements according to the examples and the comparative examples. Since the end face of the cylindrical magnet is installed perpendicular to the optical axis, the angle of the light transmitting surface of the optical isolator element with respect to the end face of the cylindrical magnet is the angle of the entrance / exit end face of the optical isolator element with respect to the surface perpendicular to the optical axis. Is the same as. Further, in FIG. 2, the reference numeral ◇ indicates the chip angle and the post-assembly of the optical isolator (adhesion of two ridges) according to the embodiment in which the two adjacent ridges of the optical isolator element and their peripheral portions are bonded to the inner wall of the cylindrical magnet. The symbol □ indicates the relationship with the angle, and the chip angle and the post-assembly angle of the optical isolator (4 ridge line bonding) according to the comparative example in which the four ridges of the optical isolator element and their peripheral parts are bonded to the inner wall of the cylindrical magnet. The relationship with each is shown.

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 reference numeral ◇ is relative to the input / output end surface angle (6 ± 0.5 degrees described above) at the time of design. It is within the range of ± 1 degree. On the other hand, it was confirmed that the angle of the light transmitting surface with respect to the cylindrical magnet end face of the optical isolator according to the comparative example indicated by the symbol □ deviates by 5 degrees from the input / output end face angle (6 ± 0.5 degrees) at the time of design. Ru.

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

According to the optical isolator according to the present invention, since the deviation of the input / output end face angle of the optical isolator element with respect to the plane perpendicular to the optical axis is suppressed, it is an industry incorporated in semiconductor modules used in optical communication, optical information systems, and the like. Has the above availability.

1 Cylindrical magnet 2 1st splitter 3 Faraday rotator 4 2nd splitter 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 at design time Input / output end face angle of the element

Claims (3)

It comprises a parallel hexahedron-shaped optical isolator element having at least two polarizing elements and one Faraday rotator and bonded to each other on the light transmitting surface thereof, and a cylindrical magnet in which the optical isolator element is housed. The optical isolator element is fixed in the cylindrical magnet by adhering the ridgeline portion and its peripheral portion of the optical isolator element formed by connecting the corners of the polarizing element and the corners of the Faraday rotator to the inner wall of the cylindrical magnet. In the method of manufacturing an optical isolator,
After inserting the optical isolator element into the cylindrical magnet, the adhesive is applied only to the two adjacent ridges of the optical isolator element and their peripheral portions, and then the adhesive is applied only to the two adjacent ridges of the optical isolator element and their surroundings. A method for manufacturing an optical isolator, which comprises adhering only a portion to the inner wall of a cylindrical magnet. The first aspect of the present invention is that the adhesive is composed of 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. The method for manufacturing an optical isolator according to the description. It comprises a parallel hexahedron-shaped optical isolator element having at least two polarizing elements and one Faraday rotator and bonded to each other on the light transmitting surface thereof, and a cylindrical magnet in which the optical isolator element is housed. The optical isolator element is fixed in the cylindrical magnet by adhering the ridgeline portion and its peripheral portion of the optical isolator element formed by connecting the corners of the polarizing element and the corners of the Faraday rotator to the inner wall of the cylindrical magnet. In the optical isolator
An optical isolator characterized in that only the two adjacent ridges of the optical isolator element and their peripheral portions are adhered to the inner wall of the cylindrical magnet.

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