JP3645700B2 - Optical isolator element and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical isolator element used for removing return light generated when light emitted from a light source is introduced into various optical elements and optical fibers, and a method for manufacturing the same.
[0002]
[Prior art]
Light emitted from a light source such as a laser light source is incident on various optical elements and optical fibers, but some of the incident light is reflected and scattered when passing through the various optical elements and optical fibers. A part of the reflected or scattered light returns to the light source side, and an optical isolator is used to block this return light. Conventionally, this type of optical isolator has been configured by installing a flat Faraday rotator between two polarizers and placing these three components in a ring-shaped magnet via a component holder. . The Faraday rotator has a thickness that rotates the plane of polarization of light having a predetermined wavelength at the saturation magnetic field intensity by 45 °, and the two polarizers are rotationally adjusted so that their transmission directions are shifted by 45 °. ing. The optical isolator having such a configuration requires a rotation adjustment work for each product, and requires a large number of assembly steps. For this reason, a method for manufacturing an optical isolator element by the following steps (1) to (5) has been proposed.
[0003]
(1) A step of laminating one or two or more flat-plate Faraday rotators and two or more polarizers via a temporary fixing adhesive.
[0004]
(2) The process of cutting the optical element laminated | stacked by the said process (1) in strip shape.
(3) A step of cleaning the optical element cut in the step (2) and removing the temporarily fixing adhesive applied in the step (1).
[0005]
(4) A step of aligning one or two or more flat-plate Faraday rotators and two or more polarizers that have been formed into a strip shape in the step (3), and bonding the substrate to the cut surface in the step (2).
[0006]
(5) A step of cutting a plurality of optical isolator elements by cutting the optical element and the substrate integrated in the step (4) into blocks. FIG. 3 shows the configuration of the optical isolator element manufactured by the above process. As shown here, in the optical isolator element 16, the flat-plate Faraday rotator 2 and the polarizers 3, 3 ′ are disposed on the substrate 17, and are bonded by an adhesive member 18.
[0007]
In the optical isolator element manufactured by the above process, a large optical element is optically adjusted and then cut into a large number of optical elements, so a large number of uniform and excellent optical isolator elements can be easily manufactured. It is possible to reduce the number of assembling steps and is excellent in mass productivity. Further, when an inorganic material such as a metal flat plate or a glass flat plate is used for the member to be the substrate and an inorganic material such as low melting glass or solder is used for the bonding member, organic outgas is not generated. For this reason, an optical isolator element can be installed in the semiconductor laser package, and the apparatus can be downsized and the characteristics can be stabilized.
[0008]
[Problems to be solved by the invention]
When using an adhesive member that requires heat treatment, such as low-melting glass or solder, for bonding the optical element and the substrate, due to the difference in linear expansion coefficient between each optical element and the substrate, the member constituting the optical isolator element Thermal stress is generated, and cracks and optical characteristics are deteriorated.
[0009]
[Means for Solving the Problems]
In view of the above problems, the present invention provides an optical isolator element comprising a substrate bonded to at least one end of each optical element in which one or two or more Faraday rotators and two or more polarizers are laminated. In the above, the bonding member for bonding these optical elements and the substrate and the material of the substrate are different for each optical element, and the linear expansion coefficient of the substrate bonded to each optical element is the optical element to be bonded. The substrate members are bonded together by welding.
Further, the substrate and the bonding member are made of an inorganic material.
Further, the substrate is made of metal.
Further, the optical isolator element is characterized by performing at least the following steps (1) to (6).
(1) A step of laminating one or two or more flat-plate Faraday rotators and two or more polarizers via a temporary fixing adhesive.
(2) The process of cutting the optical element laminated | stacked by the said process (1) in strip shape.
(3) A step of cleaning the optical element cut in the step (2) and removing the temporarily fixing adhesive applied in the step (1).
(4) A step of adhering a substrate member made of a different material for each optical element to one or two or more flat-plate Faraday rotators and the two or more polarizers cut into strips in the step (3). .
(5) The process of aligning the 1 or 2 or more flat Faraday rotator to which the board | substrate member was adhere | attached by the said process (4), and 2 or more polarizers, and adhere | attaching the said board | substrate members by welding.
(6) A step of cutting a plurality of optical isolator elements by cutting the optical element and the substrate integrated in the step (5) into blocks.
[0015]
The present invention is configured as described above, and the linear expansion coefficient of the substrate bonded to each optical element is in the vicinity of the linear expansion coefficient of each optical element to be bonded. Thermal stress is small. Further, since the substrates bonded to the optical elements are bonded to each other by welding, no thermal stress is generated here. Further, in the optical isolator element of the present invention, a large number of optical isolator elements having excellent characteristics can be easily produced for the step of cutting out a large number after performing optical adjustment with a large substrate, It is possible to reduce assembly man-hours and is excellent in mass productivity.
[0016]
In addition, all members constituting the optical isolator element are made of an inorganic material, and organic outgas is not generated. Therefore, an optical isolator element can be installed in the semiconductor laser package, and the apparatus can be downsized and the characteristics can be stabilized.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing an embodiment of an optical isolator element of the present invention. As shown here, in the optical isolator element 1, the flat Faraday rotator 2 and the polarizers 3, 3 ′ are bonded on the substrates 4, 5, 5 ′ by bonding members 6, 7, 7 ′. The linear expansion coefficients of the substrate members 4, 5, 5 ′ are set in the vicinity of the linear expansion coefficients of the optical elements 2, 3, 3 ′ to be bonded to each of the substrate members 4, 5, 5 ′. Are bonded by welding.
[0018]
The Faraday rotator 2 is made of, for example, a bismuth-substituted garnet crystal, and the thickness thereof is set so that the polarization plane of the incident light rotates 45 ° when a saturation magnetic field in the direction of the optical axis L of the incident light is applied. When an optical isolator element using a bismuth-substituted garnet crystal is used for the Faraday rotator, the optical isolator element 1 needs to be arranged in a magnet in order to apply a magnetic field to the Faraday rotator 2. In the embodiment, the configuration of a holder and the like for holding the magnet and the optical isolator element 1 is omitted. If a self-bias type Faraday rotator is used, the optical isolator operates without a magnet, so that no magnet is required.
[0019]
The two polarizers 3 and 3 ′ are composed of absorption polarizers or birefringent polarizers. When an absorptive polarizer is used, the transmission polarization planes of the two polarizers 3, 3 ′ may be shifted by 45 ° around the optical axis 8. A metal flat plate is used as a member used for the substrates 4, 5, 5 ′. In addition, an inorganic material such as solder or low-melting glass is selected for the bonding members 6, 7, 7 ′, and the Faraday rotator 2 and the polarizers 3, 3 ′ are bonded to the substrates 4, 5, 5 ′. As a result, the optical isolator element is entirely composed of an inorganic material, and no outgas is generated.
[0020]
In general, a semiconductor laser chip made of GaAs or the like has an oxide film formed on its surface by a slight residual oxygen, and a decrease in oscillation efficiency is observed. Therefore, the package in which the semiconductor laser chip is installed is hermetically sealed with an inert gas such as nitrogen gas. Of course, it is impossible to install components that generate outgas in the sealed package. Outgas is mainly generated from organic materials, but the optical isolator element of the present invention hardly generates outgas as described above, and is small in size. It becomes possible to install it. Therefore, a high performance and very small semiconductor laser module can be provided.
[0021]
FIG. 2 is a diagram showing an example of a manufacturing procedure of the optical isolator element 1 according to the present invention. First, as shown in FIG. 2A, one flat Faraday rotator 2 and two polarizers 3, 3 ′ are prepared, and each optical element is laminated via a temporary fixing adhesive 9. With respect to the two polarizers 3 and 3 ′, it is desirable that the transmitted polarization directions 10 and 10 ′ are shifted by 45 ° in a superposed state.
[0022]
Next, as shown in FIG. 2B, the laser light having the wavelength to be used is passed in the direction of the optical axis 8 and the transmitted polarization direction of the polarizers 3 and 3 ′ while confirming the intensity and polarization plane of the transmitted laser light. Is adjusted to a position rotated 45 ° relative to the optical axis 8. Thereafter, the temporary fixing adhesive 9 is cured to obtain a laminated optical element 11. However, when the optical characteristics required for the optical isolator are low, the optical adjustment using the laser beam may not be performed, and the arrangement of the optical elements may be matched from the appearance, and the temporary fixing adhesive 9 may be cured. Subsequently, as shown in FIG. 2C, the optical element 11 laminated with the temporary fixing adhesive is cut to obtain a strip-shaped optical element 12. A dotted line in the figure indicates a cut portion. Thereafter, the temporary fixing adhesive 9 between the optical elements is washed and removed to separate each optical element.
[0023]
Next, as shown in FIG. 2 (d), the Faraday rotator 2 and the polarizers 3 and 3 ′ processed into a strip shape, and the substrate members 4, 5, and 5 ′ bonded to the Faraday rotator 2 and the polarizers 3 and 3 ′ are bonded. , 7 and 7 ′. Here, the linear expansion coefficients of the substrate members 4, 5, 5 ′ are set in the vicinity of the optical elements 2, 3, 3 ′ bonded thereto, and the optical elements 2, 3, 3 ′ and the substrate member 4 are set. Even if heat treatment is performed when bonding 5, 5 ′, the generation of thermal stress can be kept low. A metal flat plate or the like is used as the board members 4, 5, 5 ′, and solder, low-melting glass or the like is used as the bonding members 6, 7, 7 ′. When solder is used, a metallized film is applied to the cut surfaces of the optical elements 4, 5, 5 ′ and the bonding surfaces of the substrate members 6, 7, 7 ′. An example of the solder material is Sn63 / Pb37 (melting point 185 ° C.), and an example of the metallized film is a three-layer film of Ti / Ni / Au used metal whose forming method is RF magnetron sputtering.
[0024]
Next, the strip-shaped optical elements 13 to which the substrate members are bonded are aligned. At this time, as shown in FIG. 2E, the arrangement of each optical element is equal to the arrangement in the step of cutting into strips, and the cut surface is brought into contact with the flat surface 14 and aligned. If the arrangement of the polarizers 3 and 3 ′, particularly the arrangement in the rotation direction around the optical axis, varies, the optical characteristics are deteriorated as compared with the optical characteristics obtained during the optical adjustment described above. Since the arrangement in the rotation direction of 3, 3 ′ is accurately reproduced, the optical characteristics are not deteriorated. Thereafter, the substrate members 4, 5, 5 ′ bonded to the optical elements are welded to integrate the constituent members.
[0025]
Next, as shown in FIG. 2 (f), the integrated component 15 is cut into blocks, and a plurality of optical isolator elements 1 are cut out. A dotted line in the figure indicates a cut portion. If the block shape is a parallelogram at the time of cutting, each optical element is inclined with respect to the incident light optical axis when the optical isolator is used. The incident can be prevented.
[0026]
The setting example of each member is shown below about the said Example. When a polarizer having a linear expansion coefficient of 65 × 10 ⁻⁷ is used, 45Ni—Fe having a linear expansion coefficient of 70 × 10 ⁻⁷ is used as a substrate member to be bonded thereto, and linear expansion is used as an adhesive member. A low melting glass having a coefficient of 69 × 10 ⁻⁷ is used. Further, if the linear expansion coefficient garnet used was a 110 × 10 ^-7, linear expansion is a SUS430 linear expansion coefficient of 110 × 10 ^-7 as a substrate member to be bonded thereto, as the adhesive member A low melting glass having a coefficient of 110 × 10 ⁻⁷ is used. As a method for bonding the substrates together, YAG welding is used, and the constituent members are integrated without melting the low melting point glass used for bonding the optical element and the substrate member.
[0027]
In the optical isolator element of the present invention, since the linear expansion coefficient of the substrate bonded to each optical element is close to the linear expansion coefficient of each optical element to be bonded, thermal stress generated even when using a bonding method by heat treatment Is small. Further, since the substrates bonded to the optical elements are bonded to each other by welding, no thermal stress is generated here. In addition, optical adjustment is performed on a large substrate, and then a large number of elements are cut out, so that a large number of uniform and excellent optical isolator elements can be easily manufactured, reducing the number of assembly steps, and mass production. Excellent in properties.
[0028]
Further, all members constituting the optical isolator element are made of an inorganic material, and organic outgas is not generated. Therefore, an optical isolator element can be installed in the semiconductor laser package, and the device can be downsized and the characteristics can be stabilized.
[0029]
In this embodiment, the configuration of an optical isolator element having two polarizers and one Faraday rotator was used. However, the present invention is not limited to this, and more polarizers and Faraday rotators were used. Even if it is an element for optical isolators, the same effect as the said Example can be acquired.
Although it has been described that the material of both the substrate and the bonding member is different for each optical element of the present embodiment, the material of the substrate is the same and only the material of the bonding member may be different. On the contrary, the material of the bonding member is the same, and only the substrate may be different.
[0030]
【The invention's effect】
As described above, the optical isolator element and the manufacturing method thereof according to the present invention have the following excellent effects.
[0031]
(1) Since the linear expansion coefficient of the substrate bonded to each optical element is in the vicinity of the linear expansion coefficient of each optical element to be bonded, the thermal stress generated even when using the bonding method by heat treatment is small. Further, since the substrates bonded to the optical elements are bonded to each other by welding, no thermal stress is generated here.
[0032]
(2) In the method for manufacturing an optical isolator element, optical adjustment of a large number of optical isolator elements can be performed at a time, and the number of assembling steps can be reduced.
[0033]
(3) All members constituting the optical isolator element are made of an inorganic material, and no organic outgas is generated. Therefore, an optical isolator element can be installed in the semiconductor laser package, and the device can be downsized and the characteristics can be stabilized.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing one embodiment of an optical isolator element of the present invention.
FIGS. 2A to 2F are diagrams showing a manufacturing procedure of an optical isolator element according to the present invention. FIGS.
FIG. 3 is a schematic structural view showing a conventional optical isolator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,16: Optical isolator element 2: Faraday rotator 3, 3 ': Polarizers 4, 5, 5': Substrate members 6, 7, 7 ': Adhesive member 8: Optical axis 9: Adhesion for temporary fixing Agents 10 and 10 ': Transmission polarization direction 11: Stacked optical element 12: Strip-shaped optical element 13: Strip-shaped optical element 14 to which a substrate member is bonded: Flat surface 15: Integrated configuration Member 17: Substrate 18: Adhesive member

Claims (4)

In an optical isolator element comprising a substrate bonded to at least one end of each optical element in which one or more Faraday rotators and two or more polarizers are laminated, these optical elements and the substrate The material of the bonding member for bonding the substrate and the substrate is different for each optical element, and the linear expansion coefficient of the substrate bonded to each optical element is in the vicinity of the linear expansion coefficient of each optical element to be bonded, An optical isolator element, wherein substrate members are bonded together by welding. 2. The optical isolator element according to claim 1, wherein the substrate and the bonding member are made of an inorganic material. 3. The optical isolator element according to claim 1, wherein the substrate is a metal. 4. The optical isolator element according to claim 1, wherein the optical isolator element is manufactured by at least the following steps (1) to (6).
(1) A step of laminating one or two or more flat-plate Faraday rotators and two or more polarizers via a temporary fixing adhesive.
(2) The process of cutting the optical element laminated | stacked by the said process (1) in strip shape.
(3) A step of cleaning the optical element cut in the step (2) and removing the temporarily fixing adhesive applied in the step (1).
(4) A step of adhering a substrate member made of a different material for each optical element to one or two or more flat-plate Faraday rotators and the two or more polarizers cut into strips in the step (3). .
(5) The process of aligning the 1 or 2 or more flat Faraday rotator to which the board | substrate member was adhere | attached by the said process (4), and 2 or more polarizers, and adhere | attaching the said board | substrate members by welding.
(6) A step of cutting a plurality of optical isolator elements by cutting the optical element and the substrate integrated in the step (5) into blocks.

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