JP2003161913A - Optical device and method for manufacturing optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide at a low cost a compact optical device which has excellent optical characteristics and high reliability by joining optical elements without using an adhesive. <P>SOLUTION: In an optical device in which at least one face of a magnetic garnet is joined with a polarizer without using an adhesive and which functions by passing light through the joined plane, the optical device is characterized by the fact that the thickness t2 (m) of the polarizer is 2×10<SP>-5</SP>≤t2≤3×10<SP>-4</SP>and the thickness t2 (m) of the polarizer is 2×10<SP>-5</SP>≤t2≤2×10<SP>-4</SP>, in particular, in the case where the relation between the linear expansion coefficient α1(/°C) of the magnetic garnet and the linear expansion coefficient α2(/°C) of the polarizer is |α1-α2|>2×10<SP>-6</SP>. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device in which optical elements are bonded without using an adhesive and a method for manufacturing the optical device.

[0002]

2. Description of the Related Art In recent years, WDM (Wavelength)
With the increase in the number of wavelengths of division multiplex (wavelength division multiplexing), high integration of an optical communication system is progressing. As a result, there is an increasing demand for miniaturization of optical devices used therein. In many cases, the optical device is configured by bonding an optical element such as a Faraday rotator or a polarizer to a fixed member and combining them. However, in this method, the fixing member is an obstacle and hinders miniaturization of the optical device. Therefore, a method of removing the fixing member and adhering the optical elements to each other has been studied.

The simplest method for joining optical elements is
It is to bond using an organic adhesive. However, the organic adhesive has the drawbacks that outgas is generated, which adversely affects the laser diode, and is weak against irradiation with a high-power laser or exposure in a high temperature and high humidity atmosphere, and the device lacks reliability.

Therefore, without using an organic adhesive,
Various methods for joining optical elements have been studied. An example
For example, one of them is inorganic bonding of low melting point glass and solder.
There is a method of joining optical elements by using them as a material.
Low melting point glass is Bi_TwoO _ThreeLow melting point materials such as PbO
It is a glass for bonding that contains
Must be heated above the softening point of. Also optical
For the purpose of device miniaturization, the transparent surface of the optical element
It is effective to join them together. But such a low
When joining translucent surfaces of optical elements using melting point glass
In the case of softening the low melting point glass, it was applied to the optical element.
The antireflection film reacts with the low melting point glass, and the antireflection function is impaired.
There is a problem such as nau. Therefore, the translucent surfaces are joined together.
Practical application of optical devices using low melting point glass is difficult
It is said that.

On the other hand, when solder is used, it cannot be directly placed on the transparent surface because the solder has no translucency. Therefore, by selectively metallizing the outer frame of the translucent surface,
A joining method is adopted in which the solder is interposed only in the metallized portion. Such a joining method has a problem that a complicated metallization process is required, and a decrease in yield and an increase in cost are unavoidable.

A method of directly bonding optical elements to each other without using any bonding material (see JP-A-7-220923 and JP-A-2000-56265) has also been tried. In this method, the surfaces of the optical element are hydrophilized, and then the hydrophilized surfaces are bonded to each other.
It has been put to practical use in the manufacturing process of I (Silicon On Insulator) wafers. However, when this method is applied to an optical device, there are the following problems and it is difficult to put it into practical use.

That is, the method of directly bonding the optical elements with each other by performing the hydrophilic treatment in this way largely depends on the shape and physical properties of the objects to be bonded. For example, with respect to warpage, it is desirable that the radius of curvature be several hundred meters or more. Also,
It is said that the surface roughness of the object to be bonded is preferably Ra = 0.3 nm or less. Furthermore, the difference in the coefficient of linear expansion between the objects to be joined is also greatly affected.

However, few optical elements satisfy the above requirements. For example, iron-based garnet, which is one of the optical elements generally used in optical devices, often has a large warp because it has a stress distribution in the thickness direction. Moreover, since the polarizing glass has a structure in which metal particles such as silver and copper are dispersed in glass, it is difficult to control the surface roughness. Furthermore, the linear expansion coefficient of these optical elements often differs greatly depending on the material, and the difference in the linear expansion coefficient between the objects to be bonded tends to increase. Therefore, in the bonded body in which the optical elements are directly bonded to each other as described above, peeling easily occurs on the bonded surface by heat treatment, and the adhesiveness and durability of the bonded surface are low.

Further, when such materials having different linear expansion coefficients are directly joined, thermal stress is generated between different materials,
There is a problem that optical distortion is likely to occur due to the concentration thereof on the bonding surface, and optical characteristics such as extinction ratio are deteriorated. Therefore, it is very difficult to apply the direct bonding technique to the optical device.

As described above, at present, it is extremely difficult to bond optical elements without using an organic adhesive to easily manufacture a highly reliable optical device at low cost.

[0011]

Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to:
Join optical elements together without using an organic adhesive,
An object is to provide an optical device that is small in size, has excellent optical characteristics, and has high reliability at low cost.

[0012]

In order to achieve the above object, according to the present invention, at least one surface of a magnetic garnet is bonded without using a polarizer and an adhesive, and light is bonded to the bonding surface. In an optical device that functions by transmitting light, the thickness t2 (m) of the polarizer is
An optical device is provided, wherein 2 × 10 ⁻⁵ ≦ t2 ≦ 3 × 10 ⁻⁴ (claim 1).

In this way, the thickness t2 (m) of the polarizer is
In the case of an optical device satisfying 2 × 10 ⁻⁵ ≦ t2 ≦ 3 × 10 ^−4, it is possible to prevent the magnetic garnet and the polarizer from peeling during the heat treatment step when the magnetic garnet and the polarizer are bonded to each other. It can be a strongly bonded optical device. Furthermore, since no organic adhesive is used, neither outgas is generated nor the joint surface is deteriorated. Therefore, a compact and highly reliable optical device can be provided.

Further, when the relationship between the linear expansion coefficient α1 (/ ° C.) of the magnetic garnet and the linear expansion coefficient α2 (/ ° C.) of the polarizer is | α1-α2 |> 2 × 10 ⁻⁶ , The thickness t2 (m) of the polarizer is 2 × 10 ⁻⁵ ≦ t2 ≦ 2
It is preferably × 10 ⁻⁴ (claim 2).

In this way, the relationship between the magnetic garnet and the linear expansion coefficients α1 and α2 of the polarizer is | α1-α2 |> 2 × 1.
When it is 0 ⁻⁶ , the thickness t2 of the polarizer is 2 × 10 ^−5.
If ≦ t2 ≦ 2 × 10 ⁻⁴ , not only sufficient bonding strength can be obtained, but also thermal stress generated at the bonding surface can be further reduced, so that deterioration of optical characteristics due to optical strain caused by thermal stress is suppressed. it can. Therefore, it is possible to provide a highly reliable optical device having excellent optical characteristics.

At this time, it is preferable that a metal oxide film is formed on the surface of the magnetic garnet which is joined to the polarizer (claim 3), and the metal oxide film is made of Al ₂ O ₃ or Ti.
It is preferable that the metal oxide film is one kind or two or more kinds of metal oxide films selected from O ₂ and SiO ₂ , and the metal oxide films are laminated in a single layer or multiple layers (claim 4).

Since the metal oxide film is formed on the bonding surface of the magnetic garnet with the polarizer in this manner, it functions as an antireflection film, and the bonding with the polarizer can be made stronger. The metal oxide film is Al
One or two or more metal oxide films selected from ₂ O ₃ , TiO ₂ , and SiO ₂ , which are excellent in the effect as an antireflection film because they are laminated in a single layer or multiple layers. Since the bonding strength is remarkably improved, the optical device can have high performance and high reliability.

At this time, it is preferable that the polarizer is a polarizing glass (claim 5). One of the features of the present invention is that the thickness of the polarizer is appropriately set as described above. Therefore, it is required that the optical characteristics of the polarizer are less likely to depend on its thickness. Therefore, it is preferable that the polarizer is a polarizing glass that has little influence on the optical characteristics of the thickness, whereby the thickness of the polarizer can be appropriately set without deteriorating the optical characteristics.

Further, it is preferable that the magnetic garnet is a bismuth-substituted iron garnet (claim 6). Thus, the magnetic garnet is a bismuth-substituted iron garnet with excellent Faraday rotation,
A Faraday rotation angle of 45 degrees can be realized with a thickness of about 0.5 mm, which is effective for downsizing an optical device.

The optical device of the present invention may be an optical isolator (claim 7). The optical isolator is one of the most valuable optical devices, and is an essential device in optical communication. As described above, since the optical device of the present invention is an optical isolator, it is possible to provide an optical device that meets the recent demand for miniaturization of an optical isolator and free organic adhesive.

Next, a method for manufacturing an optical device according to the present invention is a method for manufacturing an optical device by bonding at least one surface of a magnetic garnet to a polarizer without using an adhesive. T2 (m) is 2 ×
^{10 -5 ≦ t2 ≦ 3 × 10} - characterized by joining using a polarizer is ⁴ (claim 8).

As described above, the thickness t2 of the polarizer is 2 × 1.
By manufacturing an optical device using a polarizer satisfying 0 ⁻⁵ ≦ t 2 ≦ 3 × 10 ^−4, it is possible to bond the magnetic garnet and the polarizer with sufficient bonding strength without using an adhesive, and to improve reliability. High optical devices can be manufactured.

Further, when the relationship between the linear expansion coefficient α1 (/ ° C.) of the magnetic garnet and the linear expansion coefficient α2 (/ ° C.) of the polarizer is | α1-α2 |> 2 × 10 ⁻⁶ , The thickness t2 (m) of the polarizer is 2 × 10 ⁻⁵ ≦ t2 ≦ 2
It is preferable to bond them by using a magnetic garnet having a size of × 10 ⁻⁴ and a polarizer (claim 9).

Thus, the relationship between the linear expansion coefficients α1 and α2 of the magnetic garnet and the polarizer is | α1-α2 |> 2 × 10.
^When it is ⁻⁶ , the thickness t2 of the polarizer is 2 × 10 ⁻⁵ ≦
By manufacturing an optical device using a magnetic garnet and a polarizer ^satisfying t2 ≦ 2 × 10 ^−4, it is possible to suppress deterioration of optical characteristics due to optical strain caused by thermal stress generated at a joint surface between optical elements. . Therefore, a highly reliable optical device having excellent optical characteristics can be easily manufactured.

At this time, the magnetic garnet and the polarizer are bonded to each other by polishing, washing, hydrophilizing, and drying the bonding surfaces, and then bonding the bonding surfaces directly or via a solution. After that, it is preferable to perform the heat treatment to bond them (claim 10).

As described above, after the bonding surface of each of the magnetic garnet and the polarizer is subjected to polishing, washing, hydrophilizing treatment and drying steps, they are bonded directly or via a solution, and then heat treatment is performed. The interaction between the chemical species forming the magnetic garnet and the chemical species forming the polarizer effectively works, and sufficient bonding strength can be obtained. Thereby, peeling of the joint surface can be prevented.

Further, at this time, it is preferable that a liquid containing polar molecules as a main component is used alone or as a mixture as a solution used for joining the magnetic garnet and the polarizer (claim 11).

As described above, when the magnetic garnet and the polarizer are bonded together, the bonding force between the magnetic garnet and the polarizer can be further improved by using a liquid containing polar molecules as a main component alone or in combination. You can

Next, it is preferable to bond the magnetic garnet and the polarizer after forming a metal oxide film on the bonding surface of the magnetic garnet with the polarizer (claim 12).

As described above, the bonding strength can be further increased by forming the metal oxide film on the bonding surface of the magnetic garnet with the polarizer and then performing the bonding. Further, since the formed metal oxide film functions as an antireflection film in the optical device, a highly reliable and high performance optical device can be manufactured.

Further, the metal oxide film formed on the magnetic garnet is one or more metal oxide films selected from Al ₂ O ₃ , TiO ₂ and SiO ₂ , and the metal oxide film is a single layer or It is preferable to laminate in multiple layers (claim 13).

As described above, the metal oxide film is formed of Al ₂ O ₃ and T.
By forming one or more metal oxide films selected from iO ₂ and SiO ₂ and stacking them in a single layer or multiple layers, the function of the metal oxide film as an antireflection film is further enhanced, and magnetic garnet and polarized light are used. The bonding force of the child can be significantly increased.

An optical isolator can be manufactured by bonding a polarizer to the magnetic garnet (claim 14). As described above, by manufacturing the optical isolator according to the present invention, it is possible to manufacture a small-sized optical isolator having sufficient bonding strength without using an adhesive.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described below, but the present invention is not limited thereto. In order to provide a compact and highly reliable optical device, the present inventors have joined optical elements with a translucent surface with sufficient bonding strength without using an organic adhesive, and various optical elements at the time of bonding. There is no damage given to the antireflection film of the element,
Moreover, as an optical device in which deterioration of optical characteristics is reduced even in bonding between optical elements having a difference in linear expansion coefficient,
We found that an optical device in which a magnetic garnet and a polarizer were directly bonded was extremely effective if the thickness of the polarizer to be bonded was appropriately selected, and scrutinized various conditions for bonding. By doing so, the present invention has been completed.

That is, in an optical device which is formed by bonding at least one surface of a magnetic garnet to a polarizer without using an adhesive, and functions by transmitting light through the bonding surface, the thickness t2 of the polarizer. (M) is
If the optical device is characterized by satisfying 2 × 10 ⁻⁵ ≦ t2 ≦ 3 × 10 ⁻⁴ , an optical device having sufficient bonding strength can be obtained. In particular, the relationship between the linear expansion coefficient α1 (/ ° C) of the magnetic garnet and the linear expansion coefficient α2 (/ ° C) of the polarizer is | α1-α2 |> 2 × 10.
^When it is ⁻⁶ , the thickness t2 (m) of the polarizer is 2
If the optical device satisfies × 10 ⁻⁵ ≦ t2 ≦ 2 × 10 ⁻⁴ , it is possible to reduce the thermal stress at the bonding surface between the magnetic garnet and the polarizer, which causes optical strain due to the thermal stress. It is possible to suppress deterioration of optical characteristics. Therefore, a compact and highly reliable optical device having sufficient bonding strength and excellent optical characteristics can be provided at low cost.

First, FIG. 1 shows an example of a joining method for joining the magnetic garnet and the polarizer of the present invention. First, the surfaces (bonding surfaces) where the magnetic garnet and the polarizer are bonded are sufficiently polished (process). After that, each joint surface is thoroughly washed (step), and a hydrophilic treatment (step) is performed. At that time, a normal wet cleaning is effective for cleaning the bonding surfaces, but it is more effective to use a short wavelength ultraviolet ray treatment (UV treatment) or a plasma treatment together. Further, for the hydrophilic treatment, an ammonia-hydrogen peroxide mixture (a mixed solution of ammonia water, hydrogen peroxide solution, and pure water), nitric acid, hydrochloric acid diluted solution or these diluted solutions generally used in the semiconductor SOI wafer process is used. A solution containing hydrogen peroxide solution is effective.

Next, washing with pure water is performed to remove the hydrophilic treatment liquid. After washing with pure water, it is desirable to perform drying by an IPA vapor drying method or a spin dryer to prevent uneven drying (step). Next, the pretreated magnetic garnet thus obtained and the polarizer are bonded together. At that time, although it may be directly bonded on the bonding surface, a solution is applied to the bonding surface to facilitate bonding (process),
After that, it is preferable to bond the magnetic garnet and the polarizer (step). As the solution to be applied at this time, it is desirable to use a liquid containing polar molecules such as water and ammonia as a main component, or to use a mixture thereof, and it is particularly desirable to bond them through pure water. By performing the bonding using such a solution, the bonding force between the magnetic garnet and the polarizer can be increased. In addition, it is possible to further improve the bonding strength by adding a soluble substance such as an alkali metal element or a silicate to this solution.

The bonded body bonded according to the above procedure is naturally dried or vacuum dried to be fixed with a weak bonding force (step). After drying, the resulting bonded body has
By performing heat treatment at a temperature of about 200 ° C for several hours,
Sufficient bonding force can be obtained (process). At this time, if the rate of temperature rise in the heat treatment step is too fast, peeling of the joint surface may occur during temperature rise. Therefore, the heating rate is 20
It is desirable to set the temperature to below ° C / h. The atmosphere during the heat treatment is not a problem even in the air, but a reduced pressure atmosphere or an atmosphere containing hydrogen is more preferable. By performing the above steps, it is possible to obtain the optical device 5 in which the polarizer 2 is directly bonded to the magnetic garnet 1 as shown in FIG.

However, when the surfaces of the magnetic garnet and the polarizer are not sufficiently flat, after the magnetic garnet and the polarizer are attached (step), when the bonded body is dried (step), voids are formed on the bonded surface. It occurs and peels off.
Therefore, the present invention prevents such peeling of the bonding surface by setting the thickness of the polarizer to 3 × 10 ⁻⁴ m or less. The mechanism will be described below.

In general, the force required to apply a force to a thin plate to bend it is proportional to the cube of the plate thickness. Therefore, the thinner the object to be bonded, the easier it is to follow irregularities on the surface, and the voids are filled. Therefore, peeling of the joint surface is less likely to occur. In the case of magnetic garnet, a desired Faraday rotation angle can be obtained by Faraday rotation ability × thickness, and therefore the thickness cannot be reduced in order to increase the bonding strength. On the other hand, in the case of a polarizer, particularly in the case of a polarizing glass, a sufficient extinction characteristic can be obtained if the thickness is 2 × 10 ⁻⁵ m or more. Therefore, the thickness should be reduced to improve the adhesion. Is possible.

Actually, the polarizing glass was thinned, and after the process was dried, its adhesion was confirmed. As a result, if the thickness of the polarizing glass is 3 × 10 ⁻⁴ m or less,
It was confirmed that the occurrence of peeling was reduced and an optical device bonded with sufficient bonding strength was obtained.

At this time, when the magnetic garnet and the polarizer are bonded in the bonding process, an antireflection coating optimized for the refractive index of the optical element (polarizer) facing the bonding surface of the magnetic garnet is prepared in advance. It is desirable to give it.

For example, as shown in FIG. 2, when bonding the magnetic garnet 1 and the polarizer 2, a metal oxide film 3 is formed on the bonding surface of the magnetic garnet with the polarizer, and then the magnetic garnet and the polarizer are formed. The metal oxide film 3 thus formed acts as an antireflection film by bonding. Further, by forming the metal oxide film 3 in this way,
The bonding strength between the magnetic garnet 1 and the polarizer 2 can be made stronger.

At this time, the metal oxide film formed on the bonding surface of the magnetic garnet is chemically stable and has a communication wavelength band (0.9
Up to 1.7 μm) and is transparent, and more preferably a surface layer that is easily hydrophilized. In particular, if the metal oxide film is one or two or more metal oxide films selected from Al ₂ O ₃ , TiO ₂ , and SiO ₂ and is a single layer or a multilayered film, it is used as an antireflection film. The effect of is large and the bonding strength is remarkably improved, so that a highly reliable optical device can be obtained.

In order to further improve the performance of the obtained optical device, it is preferable that the anti-reflection film 4 for air is formed on the non-bonding surface of the polarizer 2. However, the present invention is not limited to this. That is, in the optical device of the present invention, the antireflection film does not necessarily have to be formed on the magnetic garnet or the polarizer. Further, the formation of the antireflection film of the polarizer may be performed between any steps of the bonding process shown in FIG.

In general, in an optical device, such as an optical isolator, which is easily affected by the distortion of the optical element, the extinction ratio tends to decrease when stress is applied to the joined optical element. Further, in an optical device in which optical elements are directly bonded without using an adhesive for the miniaturization of the optical device, the optical elements are firmly fixed to each other. Stress (thermal stress) proportional to the difference in linear expansion coefficient between the elements is applied.

Therefore, in an optical device that is directly bonded without using an adhesive, the extinction ratio deteriorates with a change in temperature. The extinction ratio deterioration due to the temperature change tends to be remarkable when the difference in linear expansion coefficient between the optical elements is larger than 2 × 10 ⁻⁶ / ° C.

However, generally, the linear expansion coefficient of bismuth-substituted iron garnet used as a magnetic garnet is 11 × 10 ⁻⁶ / ° C., and the linear expansion coefficient of polarizing glass used as a polarizer is 6.5 ×. It is 10 ⁻⁶ / ° C. Therefore, in the case of an optical device obtained by directly bonding bismuth-substituted iron garnet and polarizing glass, 4.5
A linear expansion coefficient difference of about 10 ⁻⁶ / ° C. occurs. Therefore, a large stress acts on the joint surface between the magnetic garnet and the polarizer due to the temperature change, and a large extinction ratio deterioration occurs in the optical device.

The stress acting on the joint surface between the magnetic garnet and the polarizer depends on the difference in linear expansion coefficient between the optical elements described above, and is proportional to the thickness of each optical element. Therefore, by appropriately setting the thickness of the optical element to be bonded, the stress acting on the bonding surface can be reduced, and thereby the optical strain can be reduced and the deterioration of the extinction ratio can also be reduced. However, in the case of an optical device in which a magnetic garnet and a polarizer are directly bonded, as described above, the magnetic garnet cannot obtain a desired Faraday rotation angle, and therefore its thickness cannot be reduced.

Therefore, in the present invention, in order to prevent the extinction ratio from being deteriorated by appropriately selecting the thickness of the polarizer, an experiment was conducted on the relationship between the linear expansion coefficient difference between the magnetic garnet and the polarizer and the thickness of the polarizer. I conducted a survey. As a result, if the following conditions are satisfied, the difference in linear expansion coefficient between the magnetic garnet and the polarizer is large, that is, even if the optical device has a difference in linear expansion coefficient exceeding 2 × 10 ⁻⁶ , sufficient bonding strength and excellent It has been found that an optical device having excellent optical characteristics can be obtained.

That is, the linear expansion coefficient α of magnetic garnet
The difference between 1 (/ ° C) and the linear expansion coefficient α2 (/ ° C) of the polarizer is
│α1-α2│> 2 × 10^-6The thickness of the polarizer when
The height t2 (m) is t2 ≦ 2 × 10^-4Is an optical device
In this case, deterioration of extinction ratio due to stress can be reduced.
Wear. Furthermore, at this time, the polarizer itself has sufficient extinction characteristics.
To have 2 × 10^-5Thickness over m
Must have. Therefore, the thickness of the polarizer
Is t2 ≧ 2 × 10^-5It is necessary to satisfy the conditions of
is there. That is, the thickness t2 of the polarizer is 2 × 10^-5≤
t2 ≦ 2 × 10 ^-4And preferably 2
× 10^-5≦ t2 ≦ 1.5 × 10^-4Preferred to be
Good

Further, according to the present invention, by appropriately setting the thickness of the polarizer in this way, peeling at the bonding surface is prevented and thermal stress is reduced, whereby the bonding force of the optical device is reduced. Also, the optical characteristics are improved. Therefore, it is required that the optical characteristics of the polarizer are less likely to depend on its thickness. Therefore, it is preferable that the polarizer is a polarizing glass that has little influence of the thickness on the optical characteristics. By doing so, the thickness of the polarizer can be appropriately set without deteriorating the optical characteristics. As the polarizing glass, a glass base material such as borosilicate glass that is generally used and in which metal particles such as silver and copper are dispersed can be used.

Further, at this time, the magnetic garnet is preferably a bismuth-substituted iron garnet excellent in Faraday rotation ability, whereby a Faraday rotation angle of 45 degrees can be realized with a thickness of about 0.5 mm. , Effective for downsizing optical devices.

[0054]

EXAMPLES The present invention will be specifically described below with reference to examples of the present invention, but the present invention is not limited thereto. (Example 1) For an optical element used for bonding, several kinds of polarizing glasses having different thicknesses were prepared as polarizers, and bismuth-substituted iron garnet (wavelength 1.31 μm) was used as magnetic garnet.
Was adjusted to θf = 45 °). Sufficient polishing is applied to these optical elements to obtain a surface roughness Ra of 0.
It was adjusted to 3 nm or less.

Then, regarding the Bi-substituted iron garnet
Is a glass anti-reflection film (Al_TwoO_Three, Ti
O_TwoAnd SiO_TwoSingle layer film or Al_TwoO_Three/ Ti
O_Two/ SiO_Two3 layer film) and glass reflection
Prepare one without a protective film, while
The lath has an anti-reflection film (Al_TwoO
_Three/ SiO_TwoMembrane). Incidentally, these antireflection films are
It was optimized at a wavelength of 1.31 μm. Magnetic garnet and polarization
The detailed physical properties of the child are shown in Table 1 below. Shown in Table 1
The data are for the non-bonded surface of the polarizer and the magnetic garnet.
Measured with anti-reflection coating on both sides of
Is.

[0056]

[Table 1]

FIG. 2 shows the structure of an optical device which is bonded and integrated by using a magnetic garnet having an antireflection film against glass. The anti-glass anti-reflection film 3 is applied to both surfaces of the magnetic garnet 1, and the anti-air anti-reflection film 4 is applied only to the non-bonding surface side of the polarizer 2, and then the anti-glass anti-reflection film 3 of the polarizer 2 and the magnetic garnet 1 is applied. An optical device 5 was produced by joining the protective film 3 with each other.

The procedure for joining the magnetic garnet and the polarizer was performed according to the flow shown in FIG. The main manufacturing conditions of each process are shown below. Polishing: Polishing is performed so that the surface roughness of the magnetic garnet and the polarizer becomes the values shown in Table 1. Cleaning: After UV (ultraviolet) treatment with a low pressure mercury lamp, cleaning with pure water (US (Ultra Sonic, ultrasonic) cleaning) is performed. Hydrophilization treatment: Ammonia water: Hydrogen peroxide water: Pure water =
Immerse in 1: 1: 4 ammonia-hydrogen peroxide mixture. Washing / drying: After washing with pure water (US washing), IPA vapor drying is performed. Liquid coating: Pure water is coated on the joint surface between the magnetic garnet and the polarizer. Laminating: Laminating the magnetic garnet and the polarizer before the coating liquid dries. At this time, the polarization directions of the two polarizers were set to be 45 ° to each other. Drying: vacuum drying for 24 hours after bonding. Heat treatment: 110 ° C., 10 hours in air. The heating rate is 4 ° C./h.

In the above joining process, after the steps were dried, the joining surface of the obtained joined body was inspected to evaluate the adhesion. The results are shown in Table 2. As is clear from Table 2, when the thickness of the polarizing glass was 0.3 mm or less, large peeling did not occur and the adhesion was improved. Further, in the case where the magnetic garnet is provided with a metal oxide film, regardless of whether it is a single-layer film or a three-layer film, peeling does not occur on the bonding surface between the optical elements, and the adhesiveness is further improved. understood.

[0060]

[Table 2]

Next, after the heat treatment of the process, the obtained bonded body (optical device 5) is 1 mm × by a dicer.
It was cut into 1 mm chips. This chip, 105
After treating with a pressure cooker at 100 ° C. for 100 hours, the joint surface was observed and the durability of the joint surface was evaluated. The results are shown in Table 3.

[0062]

[Table 3]

As shown in Table 3, it can be seen that when the polarizing glass has a thickness of 3 × 10 ⁻⁴ m or less, the erosion of the bonding surface is reduced. Further, it was confirmed that the magnetic garnet with the metal oxide film had smaller erosion and had sufficient bonding strength.

(Example 2) Next, a magnetic garnet was prepared.
As an anti-reflective coating for glass on both sides, Al_TwoO _Three/
TiO_Two/ SiO_TwoOne type of Bi replacement with a three-layered film
Iron garnet (coefficient of linear expansion: 11 x 10^-6/ ° C)
As a polarizer, the linear expansion coefficient is 6.5 × 10
^-6/ ° C (Difference in linear expansion coefficient from Bi-substituted iron garnet:
4.5 x 10^-6/ ° C) polarizing glass and 9.0 x 10
^-6/ ° C (Difference in linear expansion coefficient from Bi-substituted iron garnet:
2.0 x 10^-6/ ° C) of two types of polarizing glass,
Prepare several kinds of different thickness for each
It was These optical elements were contacted under the same manufacturing conditions as in Example 1.
Then, a bonded body (optical device 5) was produced. In addition, polarized light
When attaching the glass, make sure that the polarization direction of each is 45 °.
Prepared at an angle, and also Bi-substituted iron garnet
Is θf = 45 ° at the temperature when measuring the optical characteristics.
Was prepared so that

Next, as shown in FIG. 3, the obtained optical device 5 was cut into 1 × 1 mm chips and placed in a cylindrical magnet 6 to form an optical isolator 7. After that, the extinction ratio was measured for the optical isolators having different linear expansion coefficients of the polarizing glass, and the influence of optical distortion was investigated.

The extinction ratio was measured by transmitting the light beam 10 emitted from a light source (not shown) to the optical isolator 7 and detecting the transmitted light beam 10 by the detector 8 as shown in FIG. At this time, the measurement temperature was set to 40 ° C. lower than the optical element temperature in the process. By setting the temperature in this way, the extinction ratio can be measured in the state where the thermal stress is applied to the joint surface.

FIG. 4 shows the extinction ratio with respect to the thickness of polarizing glass.
The graph of is shown. Bi-substituted iron garnet and polarized glass
Difference in linear expansion coefficient is 2.0 × 10^-6/ ° C, polarization
Lath thickness is 2 × 10^-4Large extinction ratio is inferior even if it exceeds m
You can't see the change. On the other hand, the difference in linear expansion coefficient is 4.5 × 1
0^-6In the case of / ° C, the thickness of the polarizing glass is 2 x 10
^-4It can be seen that the extinction ratio deteriorates significantly when m is exceeded.
It From the above, the linear expansion coefficient difference is 2.0 × 10.^-6/
If the temperature exceeds ℃, make the thickness of polarizing glass 2 × 10.^-4m
It is desirable to keep it below, more desirably 1.5 ×
10^-4It is desirable to set it to m or less.

The present invention is not limited to the above embodiment. The above-described embodiment is merely an example, and it has substantially the same configuration as the technical idea described in the scope of claims of the present invention, and has the same operational effect.
Anything is included in the technical scope of the present invention.

For example, in the above-mentioned embodiment, the optical isolator constituted by the minimum unit in which the polarizer is joined to both surfaces of the magnetic garnet is shown, but the present invention is not limited to this, and the polarized light It can also be applied to an optical isolator having a multistage structure in which a child and a magnetic garnet are further combined. Further, in the above-described embodiment,
When bonding the magnetic garnet and the polarizer, pure water is applied to the bonding surface for bonding, but the present invention is not limited to this, and if a sufficient bonding strength is obtained, a liquid is not used. Instead, they may be directly joined.

[0070]

As described above, according to the present invention,
Magnetic garnet and polarizer can be bonded easily and with strong bonding strength without the use of adhesives, and there is no outgas generation or deterioration of the bonding surface, and it has excellent optical characteristics and is compact and highly reliable. The optical device can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of a joining method of the present invention.

FIG. 2 is a schematic diagram showing an example of a configuration of an optical device of the present invention.

FIG. 3 is a schematic diagram of a junction type optical isolator manufactured in a second example.

FIG. 4 is a graph showing a result of measuring an extinction ratio with respect to a thickness of a polarizer.

FIG. 5 is a schematic diagram showing a configuration in an extinction ratio measurement of an optical isolator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic garnet (Bi substituted iron garnet), 2 ... Polarizer (polarizing glass), 3 ... Metal oxide film (anti-glass antireflection film), 4 ... Air antireflection film, 5 ... Optical device, 6 ... Cylindrical type Magnet, 7 ... Optical isolator, 8
… Detector, 10… Ray.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigeru Konishi             2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu             Gaku Kogyo Co., Ltd. Precision Materials Research Laboratory (72) Inventor Ryo Shirasaki             2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu             Gaku Kogyo Co., Ltd. Precision Materials Research Laboratory F-term (reference) 2H099 AA01 BA02 CA11 DA05

Claims (14)

[Claims] 1. An optical device comprising at least one surface of a magnetic garnet bonded to a polarizer without the use of an adhesive, wherein light has a thickness t2, which functions by transmitting light through the bonding surface. (M) is 2 × 10
^-5 <t2 <3x10 < ^-4 > The optical device characterized by the above-mentioned. 2. The linear expansion coefficient α1 of the magnetic garnet
When the relationship between (/ ° C.) and the linear expansion coefficient α2 (/ ° C.) of the polarizer is | α1−α2 |> 2 × 10 ⁻⁶ , the thickness t2 (m) of the polarizer is 2 ×. 10 ⁻⁵ ≦ t2 ≦ 2 × 1
It is ^0-4 , The optical device of Claim 1 characterized by the above-mentioned. 3. The optical device according to claim 1, wherein a metal oxide film is formed on a bonding surface of the magnetic garnet with the polarizer. 4. The metal oxide film formed on the magnetic garnet is one or more metal oxide films selected from Al ₂ O ₃ , TiO ₂ , and SiO ₂ , and the metal oxide film is a single metal oxide film. The optical device according to any one of claims 1 to 3, wherein the optical device is laminated in a layer or in multiple layers. 5. The optical device according to claim 1, wherein the polarizer is polarizing glass. 6. The magnetic garnet is a bismuth-substituted iron garnet, according to claim 1.
The optical device according to claim 1. 7. The optical device according to claim 1, wherein the optical device is an optical isolator. 8. A method of manufacturing an optical device by bonding at least one surface of a magnetic garnet to a polarizer without using an adhesive, wherein a thickness t2 (m) of the polarizer is used.
Is bonded using a polarizer satisfying 2 × 10 ⁻⁵ ≦ t2 ≦ 3 × 10 ⁻⁴ . 9. The linear expansion coefficient α1 of the magnetic garnet.
When the relationship between (/ ° C.) and the linear expansion coefficient α2 (/ ° C.) of the polarizer is | α1−α2 |> 2 × 10 ⁻⁶ , the thickness t2 (m) of the polarizer is 2 ×. 10 ⁻⁵ ≦ t2 ≦ 2 × 1
The method of manufacturing an optical device according to claim 8, wherein the optical garnet of 0 ⁻⁴ and a polarizer are used for bonding. 10. The magnetic garnet and the polarizer are bonded to each other by polishing, washing, hydrophilizing, and drying the bonding surfaces, and then bonding the bonding surfaces directly or through a solution, and thereafter. The method for manufacturing an optical device according to claim 8 or 9, wherein the bonding is performed by performing heat treatment. 11. The optical device according to claim 10, wherein a liquid containing polar molecules as a main component is used alone or as a mixture as a solution used for bonding the magnetic garnet and the polarizer. Production method. 12. The magnetic garnet and the polarizer are bonded together after a metal oxide film is formed on the bonding surface of the magnetic garnet with the polarizer.
1. The method for manufacturing an optical device according to any one of 1. 13. The metal oxide film formed on the magnetic garnet is one or more metal oxide films selected from Al ₂ O ₃ , TiO ₂ , and SiO ₂ , and the metal oxide film is a single layer or The multi-layered structure is laminated in multiple layers.
2. The method for manufacturing an optical device according to 2. 14. The method for manufacturing an optical device according to claim 8, wherein a polarizer is bonded to the magnetic garnet to manufacture an optical isolator.