JP2003270436A - Method for manufacturing optical device, and optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a small and highly reliable optical device by bonding optical elements without using an organic adhesive. <P>SOLUTION: The method for manufacturing the optical device by bonding the optical elements without using the adhesive comprises the steps of: applying polish, cleaning, and hydrophilic processing at least to each of the surfaces to be bonded of the optical elements; bonding the surfaces to be bonded of the optical elements; applying heat treatment by raising temperature at a first temperature rise rate of V1(°C/hr) to a first temperature T1(°C) and at a second temperature rise rate of V2(°C/hr) slower than the first temperature rise rate V1 to a second temperature T2(°C). <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 a method for manufacturing an optical device in which optical elements are joined and integrated without using an adhesive and an optical device manufactured by this method.

[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.

For example, Japanese Unexamined Patent Publication (Kokai) No. 6-75189 discloses an optical isolator in which optical elements are bonded and integrated with each other using an organic adhesive such as resin. However, the optical isolator bonded with such an organic adhesive has poor moisture resistance and heat resistance, and outgas is generated, so that the optical axis of the optical isolator is misaligned and other optical parts are adversely affected. was there.

Therefore, without using an organic adhesive,
Various methods for joining optical elements have been studied. For example, as one of them, there is a method of bonding optical elements to each other using low melting glass or solder as an inorganic bonding material.
The low-melting glass is a bonding glass mainly composed of a low-melting material such as B ₂ O ₃ or PbO, but it needs to be heated to a temperature higher than the softening point of the glass at the time of bonding. Further, for the purpose of downsizing the optical device, it is effective to join the light transmitting surfaces of the optical element to each other. However, when joining translucent surfaces of optical elements using such low-melting-point glass, the low-melting glass reacts with the anti-reflection film applied to the optical element when the low-melting glass is softened by heating, and anti-reflection There is a problem that the function is lost. Therefore, it is difficult to put an optical device using a low melting point glass to join the translucent surfaces to practical use.

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 metallizing 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. Further, the coefficient of thermal expansion of these optical elements often differs greatly depending on the material, and the difference in coefficient of thermal expansion 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.

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.

[0010]

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 of the present invention is to provide a method for manufacturing a compact and highly reliable optical device.

[0011]

In order to achieve the above object, according to the present invention, in a method for manufacturing an optical device by bonding optical elements to each other without using an adhesive, at least the optical element is used. After polishing, washing, and hydrophilizing the respective joint surfaces, the optical elements are bonded to each other at the joint surfaces, and then the first temperature increase rate V1 (° C / hr) up to the first temperature T1 (° C). ) And then the second temperature T
The optical device is characterized in that the optical elements are joined together by performing a heat treatment for heating up to 2 (° C.) at a second temperature rising rate V2 (° C./hr) slower than the first temperature rising rate V1. A manufacturing method is provided (Claim 1).

As described above, after the optical elements are bonded to each other at the joint surface, the first temperature increase rate V1 is reached up to the first temperature T1.
By performing a heat treatment of increasing the temperature at a second temperature increase rate V2 slower than the first temperature increase rate V1 to a second temperature T2, The bonding strength of the bonding surface can be further increased by adhering during the temperature increase up to the temperature T1 and then increasing the temperature up to the second temperature. As a result, peeling of the bonding surface due to thermal stress generated during heat treatment can be prevented, and an optical device bonded with sufficient bonding strength can be manufactured. Further, since the joining is performed without using the organic adhesive, outgas is not generated. Further, since the optical device thus bonded has an excellent bonding state, it also has a low forward insertion loss and excellent optical characteristics. Therefore, a small-sized, highly reliable, high-performance optical device can be manufactured at low cost.

At this time, in the heat treatment, a third temperature T3 is provided between the first temperature T1 and the second temperature T2.
(° C.) is set and the temperature is raised up to the third temperature T3 at a third temperature increase rate V3 (° C./hr) slower than the first temperature increase rate V1 and higher than the second temperature increase rate V2. It is preferable to do so (claim 2).

In this way, the third temperature T3 (° C.) is set between the first temperature T1 and the second temperature T2, and the temperature is slower than the first temperature increase rate V1 up to the third temperature T3. By increasing the temperature at the third temperature increase rate V3 that is faster than the second temperature increase rate V2, the bonding strength between the optical elements can be made stronger, and peeling that occurs during heat treatment is further prevented. can do.

At this time, at the time of performing the heat treatment, it is preferable to maintain at least one of the first temperature T1, the second temperature T2, and the third temperature T3 for a certain period of time (claim). 3).

As described above, by holding at least one of the first temperature T1, the second temperature T2, and the third temperature T3 for a certain period of time, the bonding strength of the bonding surface can be further increased.

Further, the first heating rate V1 is 60
C./hr or less (Claim 4), the first temperature T1 is T1 <150, and the second temperature T2 is 150 ≦ T2 ≦ 400 (Claim 5). ).

By setting the first heating rate V1, the first temperature T1, and the second temperature T2 in this way,
Sufficient bonding strength can be obtained. In addition, in-plane variations in bonding strength can be reduced, so that peeling of the bonding surface can be prevented.

In the heat treatment, the temperature rising rate in the temperature range of less than 150 ° C. is 60 ° C./hr or less, and 1
The rate of temperature increase in the temperature range of 50 ° C. or higher is preferably 10 ° C./hr or lower (claim 6).

Thus, in the heat treatment, the temperature rising rate in the temperature range of less than 150 ° C. is 60 ° C./hr or less,
If the rate of temperature rise in the temperature range of 150 ° C. or higher is 10 ° C./hr or lower, a large thermal stress is not abruptly applied during heat treatment, and therefore peeling that occurs on the joint surface can be effectively prevented. it can.

Furthermore, it is preferable that the heat treatment is performed in a reduced pressure atmosphere or an atmosphere containing hydrogen. As described above, the heat treatment atmosphere is a reduced pressure atmosphere or an atmosphere containing hydrogen, whereby the bonding strength of the bonding surface can be further strengthened.

At this time, when the optical elements are bonded to each other at the bonding surface, it is preferable that the bonding surfaces are bonded directly or via a solution, and then the heat treatment is performed to bond them.

As described above, by bonding the bonding surfaces of the optical elements directly or via the solution, the interaction between the chemical species constituting each optical element works effectively, and sufficient bonding strength is obtained. You can

Further, at this time, when the optical elements are bonded to each other through a solution, it is preferable that a liquid containing polar molecules as a main component is used alone or as a mixture as the solution (claim 9).

As described above, when the optical elements are joined together via the solution, the joining force between the optical elements can be further improved by using the liquid containing polar molecules as the main component, either alone or as a mixture. It is possible to prevent peeling of the joint surface.

At this time, the bonded optical elements may be at least a magnetic garnet and a polarizer (claim 10). In this way, the optical element to be bonded is
By using at least a magnetic garnet and a polarizer, the obtained optical device can be an optical device that functions as an optical isolator. The optical isolator is one of the most valuable optical devices, and is an essential device in optical communication. Therefore, according to the present invention, it is possible to provide a small-sized optical isolator having a sufficient junction strength.

Further, at this time, it is preferable to bond the optical element after forming a metal oxide film on at least one bonding surface of the optical element to be bonded (claim 1).
1).

In this way, a metal oxide film is formed on at least one bonding surface of the optical element to be bonded, for example, in the case of bonding the magnetic garnet and the polarizer, a metal oxide film is formed on the bonding surface of the magnetic garnet and the polarizer. By joining them, the joining strength of the joining surface can be further increased. 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.

At this time, it is formed on the bonding surface of the optical element.
The metal oxide film_TwoO_Three, Ta _ThreeO₅, TiO_Two,
SiO_TwoOne or more metal oxides selected from
Forming a film and laminating the metal oxide film in a single layer or multiple layers
Is preferred (claim 12).

The metal oxide film thus formed is formed of Al ₂
One or more metal oxide films selected from O ₃ , Ta ₃ O ₅ , TiO ₂ , and SiO ₂ are formed, and by laminating the metal oxide films in a single layer or multiple layers, an antireflection film for the metal oxide film is obtained. The function can be further enhanced, and the bonding force between the optical elements can be significantly enhanced.

The optical device manufactured by the manufacturing method of the present invention is an optical device in which optical elements are bonded with sufficient bonding strength without using an organic adhesive,
No generation of outgas or deterioration of joint surface. Further, since the bonding state of the bonding surface is also excellent, the forward insertion loss of the optical device can be reduced. Therefore, a compact, highly reliable, and high-performance optical device can be obtained (claim 13).

Further, the optical device manufactured by the manufacturing method of the present invention can be an optical isolator (claim 14).

As described above, the optical isolator is one of the most useful ones among the optical devices.
Therefore, since the optical device of the present invention is an optical isolator, it is possible to provide an optical device that has been strongly demanded in recent years, and which is compatible with downsizing of an optical isolator and free of an organic adhesive. Furthermore, it has sufficient bonding strength,
Since the bonding state is also excellent, it is possible to provide an optical isolator with high reliability and high performance.

[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 method for manufacturing a small and highly reliable optical device, the inventors of the present invention bond optical elements to each other on a light-transmitting surface without using an organic adhesive, and various optical elements at the time of bonding. As a method for manufacturing an optical device, which is free from damage given to the antireflection film, and which is capable of obtaining sufficient bonding strength even for an optical element having a warp or surface roughness,
Join optical elements together without using an adhesive,
After bonding the optical elements to each other, it was found that it is extremely effective to perform the heat treatment under the optimum conditions to bond the optical elements to each other, and the present invention was completed by examining various conditions related to the bonding. It was

That is, the method for manufacturing an optical device of the present invention is a method for manufacturing an optical device by bonding optical elements to each other without using an adhesive, and polishing at least the bonding surface of each of the optical elements. After performing the washing, hydrophilizing, and drying steps, the optical elements are bonded to each other at the joint surface, and then heated to a first temperature T1 (° C) at a first heating rate V1 (° C / hr). , Then the second temperature T2
Manufacturing of an optical device in which optical elements are bonded to each other by performing a heat treatment in which the temperature is raised to (° C.) at a second temperature raising rate V2 (° C./hr) slower than the first temperature raising rate V1. Is the way.

According to the method for manufacturing an optical device of the present invention as described above, the adhesive strength of the joint surface between the optical elements can be remarkably increased, and peeling of the joint surface due to the thermal stress generated during the heat treatment can be prevented. it can. In addition, since no organic adhesive is used, outgas is not generated and other optical components are not adversely affected. Further, since the deterioration of the joint surface is reduced, it is possible to suppress the deterioration of the optical characteristics of the obtained optical device. Therefore, a small-sized, highly reliable, high-performance optical device can be manufactured at low cost.

First, a bonding method for bonding optical elements according to the present invention will be described below with reference to FIG. 3 by taking an example of manufacturing an optical device using a magnetic garnet and a polarizer as an optical element. . 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. that time,
Although the bonding may be performed directly on the bonding surface, it is preferable to apply a solution to the bonding surface (step) and then to bond the magnetic garnet and the polarizer to each other for facilitating the bonding (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 carrying out the joining using such a solution, the joining force between the magnetic garnet and the polarizer can be further enhanced. 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 adhered by the above procedure is naturally dried or vacuum dried to fix it with a weak bonding force (step).

After drying, as shown in FIG. 1, the obtained joined body was heated to a first temperature T1 (° C.) at a first heating rate V1.
The temperature is raised at (° C./hr), and then to the second temperature T2 (° C.), the second heating rate V2 slower than the first heating rate V1.
A heat treatment (process) of raising the temperature at (° C./hr) (that is, V1> V2) is performed. By performing such heat treatment, the bonding surfaces of the optical elements are bonded to each other during the temperature increase up to the first temperature T1, and the bonding strength of the bonding surfaces is further increased during the subsequent temperature increase up to the second temperature T1. Can be increased. Therefore, it is possible to manufacture an optical device bonded with a sufficient bonding strength.

Further, as shown in FIG. 2, a third temperature T3 (° C.) is set between the first temperature T1 and the second temperature T2, and the first temperature T3 is set to the third temperature T3. Temperature rising rate V1
By performing a heat treatment that is slower and at a third temperature increase rate V3 (° C./hr) (that is, V1>V3> V2) that is faster than the second temperature increase rate V2, the bonding strength of the bonding surface is further increased. It can be made strong, and peeling can be further prevented.

At this time, the third temperature T3 and the second temperature T
In the temperature range between the two, the fourth temperature T4, the fifth temperature T5, etc. are set so that T3 <T4 <T5 <...
Effect of further increasing the bonding strength at the bonding surface by performing heat treatment with the fourth temperature rising rate V4 up to 4 and the fifth temperature rising rate V5 up to T5 set to V3>V4>V5>...> V2 However, there is a problem in that the number of steps in the heat treatment step is further increased and the heat treatment time is prolonged. Therefore, it is preferable to perform the heat treatment in up to three stages, and the temperature and temperature rising rate after the fourth may be appropriately set as necessary.

When performing the heat treatment, it is preferable to maintain at least one of the first temperature T1, the second temperature T2, and the third temperature T3 for a certain period of time, whereby the joint surface is further maintained. It is possible to increase the bonding strength of.

At this time, if the first temperature raising rate V1 up to the first temperature T1 is too fast, thermal stress is abruptly applied during the temperature raising, so that peeling may occur at the joint surface. Therefore, it is preferable to set the first heating rate V1 to 60 ° C./hr or less.

Further, at this time, the first temperature T1 is T1 <
At 150, the second temperature T2 is preferably 150 ≦ T2 ≦ 400. When the first temperature T1 is 150 ° C. or higher, a large thermal stress is generated in a state where the adhesive strength is weak,
There is a possibility that peeling may occur at the joint surface or that the variation in adhesive strength within the joint surface may become large. However, if the first temperature T1 is too low, adhesion between the optical elements may be insufficient and peeling may occur. Therefore, the first temperature T1 is preferably T1> 90. Further, when the second temperature T2 is lower than 150 ° C., sufficient bonding strength cannot be obtained, while when it is higher than 400 ° C., the optical element is deteriorated and an optical device having sufficient optical characteristics is obtained. May not be.

At this time, the rate of temperature rise during the heat treatment is 150
In the temperature range of less than ℃, 60 ℃ / hr or less, 150
In the temperature range of 0 ° C or higher, it is preferably 10 ° C / hr or lower. If the temperature is raised faster than these in each temperature range, the joint surface will not be able to withstand the increase in thermal stress due to the temperature change, and peeling will occur, and the in-plane variation of the joint strength will increase. there is a possibility.

Although the atmosphere for the heat treatment is not problematic in the air, it is more preferable to use a reduced pressure atmosphere or an atmosphere containing hydrogen. By performing the heat treatment in such an atmosphere, the bonding strength of the bonding surface can be further strengthened.

In the above-mentioned joining process, when the optical elements are joined together, it is desirable to apply an antireflection coating optimized to the refractive index of the optical element facing the joining surface of the optical elements in advance.

For example, in the case of bonding the magnetic garnet and the polarizer in the above direct bonding method, a metal oxide film is formed on the bonding surface of the magnetic garnet with the polarizer, and then the magnetic garnet and the polarizer are bonded together. By
The formed metal oxide film acts as an antireflection film. Further, by forming the metal oxide film in this way,
The bonding strength between the magnetic garnet and the polarizer can be made stronger.

At this time, the metal oxide film formed on the bonding surface of the optical element is chemically stable and has a communication wavelength band (0.9-1.
7 μm) and transparent, and more preferably a surface layer that is easily hydrophilized. Therefore, the metal oxide film is one or more metal oxide films selected from Al ₂ O ₃ , Ta ₃ O ₅ , TiO ₂ , and SiO ₂ , and is a single layer or a multi-layered layer. As a result, the effect as an antireflection film is large and the bonding strength is remarkably improved, so that an optical device with high reliability can be obtained.

In this way, according to the present invention, as shown in FIG. 4, for example, the polarizer 2 is provided on both sides of the magnetic garnet 1.
It is possible to obtain an optical device 5 that functions as an optical isolator in which are directly bonded. In FIG. 4, as described above, the optical device in which the magnetic garnet 1 is provided with the metal oxide film 3 acting as an antireflection film against glass, and the polarizer 2 is provided with the antireflection film 4 against air. Shows an example. However, the present invention is not limited to this. That is, in the optical device of the present invention, the antireflection film may not necessarily be formed on the bonding interface of the magnetic garnet or the polarizer. Also,
The antireflection film 4 of the polarizer may be formed between any steps of the above bonding process.

With the optical device manufactured in this manner, peeling of the bonding surface due to thermal stress generated during heat treatment is prevented, and an optical device having sufficient bonding strength can be obtained. In addition, since it is joined without using an organic adhesive, outgas is not generated. Furthermore, since the bonding state of the bonding surfaces is excellent, it is possible to obtain an optical device with reduced forward insertion loss.

[0054]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited thereto. (Example 1) The optical element used for bonding was a polarizer,
Prepare polarizing glass with a shape of 15 × 15 × 0.2 mm,
As the magnetic garnet, a bismuth-substituted iron garnet (adjusted to θf = 45 ° at a wavelength of 1.31 μm) having a shape of 15 × 15 × 0.35 mm was prepared.

FIG. 4 shows the structure of an optical device in which a magnetic garnet and a polarizer are joined. Bi substituted iron garnet 1
The antireflection film 3 (Al ₂ O ₃ / TiO _{2) on} both surfaces of the glass
/ SiO ₂ three-layer film), while the anti-reflection film 4 (Al ₂ O ₃ / Si) is formed only on the non-bonding surface side of the polarizing glass 2.
After applying the O ₂ film), the bonding surface of the polarizing glass 2 and the bonding surface of the anti-glass anti-reflection film 3 of the Bi-substituted iron garnet 1 were bonded to each other to fabricate an optical device 5. The antireflection films 3 and 4 were optimized at a wavelength of 1.31 μm.

The procedure for joining the Bi-substituted iron garnet and the polarizing glass was performed according to the flow shown in FIG. The main manufacturing conditions of each process are shown below. Polishing: Surface roughness of magnetic garnet and polarizer is 0.3
The polishing is performed so that the thickness becomes less than or equal to nm. 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 application: Pure water is applied to the bonding surface of each optical element. Lamination: Before the coating liquid dries, the two polarizers are prepared so that the polarization directions thereof are 45 ° with each other, and the magnetic garnet and the polarizer are laminated together. Drying: vacuum drying for 24 hours after bonding. Heat treatment: Heat treatment is performed in a hydrogen atmosphere of 0.2 atm under different heat treatment conditions. Conditions for the first, second, and third heat treatments are shown below, and detailed heat treatment conditions for each sample are shown in Table 1.

1) First heat treatment: The first temperature T1 is 90
~ 160 ° C, 20 ° C / hr heating rate (V1)
The temperature was raised. (Note that the samples of Examples 18 and 19 shown in Table 1 were held at the first temperature T1 for 10 hours.) 2) Second heat treatment: the second temperature T2 was 140 to 450 ° C.
And the temperature was raised at a temperature raising rate (V2) of 1 to 15 ° C./hr. (Note that the samples of Examples 18 and 19 shown in Table 1 were held at the second temperature T2 for 10 hours.) 3) Third heat treatment: The third temperature T3 was set to 160 ° C. and 10 The temperature was raised at a temperature raising rate (V3) of ° C / hr (Example 8). Alternatively, the third temperature T3 is set to 200 ° C., and the temperature is raised at a heating rate (V3) of 5 ° C./hr (Example 19).

After the heat treatment of the step, the obtained bonded body (optical device 5) was placed in a closed container at 105 ° C. for 10 hours.
It was maintained for 0 hour (hereinafter referred to as a pressure cooker test). Then, the joint surface of the joint was observed and the joint surface was evaluated.

Next, as shown in FIG. 5, 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. The forward insertion loss of each of the produced optical isolators was measured with a laser beam having a wavelength of 1.31 μm. Table 1 below shows the heat treatment conditions of each sample, the observation results of the joint surface before and after the pressure cooker test, and the measurement results of the forward insertion loss before and after the pressure cooker test.

[0060]

[Table 1]

As shown in Table 1, the heat treatment according to the present invention, that is, the temperature is raised to the first temperature T1 at the first heating rate V1, and then to the second temperature T2, the first heating rate is set. It can be seen that the samples of Examples 1 to 19, which were subjected to the heat treatment of raising the temperature at the second temperature rising rate V2 slower than V1, were bonded with sufficient bonding strength. On the other hand, in Comparative Examples 1 and 2 in which the second heat treatment was not performed, the joint strength of the joint surface was not sufficient, and after the pressure cooker test, peeling occurred in more than half of the joint surface.

Further, by comparing the results of Examples 3 and 8, the third temperature T3 is set between the first temperature T1 and the second temperature T2, and the third temperature T3 is set up to the third temperature T3. By increasing the temperature at the third temperature increase rate V3 which is slower than the first temperature increase rate V1 and higher than the second temperature increase rate V2, the bonding strength can be further increased and the forward insertion loss can be reduced. You can see that That is, by performing the third heat treatment, an optical device with higher reliability and higher performance can be obtained.

From the first to seventh embodiments, the first temperature T1
When T1 <150, it can be seen that the forward insertion loss is reduced and the optical characteristics are excellent. on the other hand,
When the first temperature T1 was 90 ° C. or lower (Example 1), some peeling was observed on the joint surface after the pressure cooker test. Therefore, the first temperature T1 is preferably T1> 90. Further, Examples 3 and 9-13
From the comparison between the results of Example 14 and Example 14, it can be seen that if the second temperature T2 is 150 ≦ T2 ≦ 400, an optical device with further reduced forward insertion loss can be obtained.

Further, by comparing the results of Examples 3 and 15 and Examples 16 and 17, if the rate of temperature rise in the temperature range of 150 or higher is 10 ° C./hr or less, the joint surface is not removed even after the pressure cooker test. It is possible to further reduce delamination, reduce forward insertion loss, and obtain an optical device with higher performance and higher reliability.

Further, from the comparison of the results of Examples 3 and 18, it can be seen that the joint strength can be further increased by maintaining the first temperature T1 and the second temperature T2 for a certain period of time. Furthermore, from the results of Example 19, it was confirmed that by performing the third heat treatment and holding at T1 and T2 for a certain period of time, an optical device having further excellent bonding strength and optical characteristics was obtained.

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 embodiment, the magnetic garnet and the polarizer are used as the optical element, and the optical isolator constituted by the minimum unit in which the polarizer is bonded to both surfaces of the magnetic garnet is shown. The present invention is not limited to this, and can also be applied to an optical isolator having a multistage structure in which a polarizer and a magnetic garnet are further combined. Also, when joining the magnetic garnet and the polarizer through a transparent optical material such as transparent glass,
The manufacturing method of the present invention can be applied.

Further, in the above-described embodiment, when the magnetic garnet and the polarizer are bonded, pure water is applied to the bonding surface to carry out the bonding, but the present invention is not limited to this. If sufficient bond strength can be obtained, direct bonding may be performed without using a solution.

[0069]

As described above, according to the present invention,
It is possible to easily join the optical elements to each other with a strong joining strength without using an adhesive. Further, it is possible to inexpensively provide a small-sized and highly reliable optical device having excellent optical characteristics without generation of outgas and deterioration of the joint surface.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing heat treatment conditions in a manufacturing method of the present invention.

FIG. 2 is a diagram schematically showing another heat treatment condition in the manufacturing method of the present invention.

FIG. 3 is a flowchart showing an example of the joining method of the present invention.

FIG. 4 is a schematic diagram showing an example of the configuration of an optical device of the present invention.

FIG. 5 is a schematic diagram of a junction type optical isolator manufactured in an example.

[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.

   ─────────────────────────────────────────────────── ─── 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) 2H049 BA02 BA08 BB03 BB65 BC25                 2H079 AA03 AA12 BA02 CA04 CA06                       DA12 EA13 EA22 JA06 KA05                 2H099 BA02 DA05                 2K009 AA02 CC03

Claims (14)

[Claims] 1. A method for manufacturing an optical device by bonding optical elements to each other without using an adhesive, wherein at least the bonding surface of each of the optical elements is subjected to polishing, washing and hydrophilization treatment, The optical elements are bonded to each other at the bonding surface, and then the temperature is raised to the first temperature T1 (° C.) at the first temperature rising rate V1 (° C./hr), and then the second temperature T2.
Manufacturing of an optical device in which optical elements are bonded to each other by performing a heat treatment in which the temperature is raised to (° C.) at a second temperature raising rate V2 (° C./hr) slower than the first temperature raising rate V1. Method. 2. In the heat treatment, the first temperature T
A third temperature T3 (° C.) is set between 1 and the second temperature T2, and the first temperature increase rate V is set up to the third temperature T3.
The method for manufacturing an optical device according to claim 1, wherein the temperature is raised at a third temperature increase rate V3 (° C./hr) slower than 1 and higher than the second temperature increase rate V2. 3. The heat treatment is performed by holding at least one of the first temperature T1, the second temperature T2, and the third temperature T3 for a certain period of time. The optical device manufacturing method according to claim 1 or 2. 4. The first heating rate V1 is 60 ° C./h
It is r or less, The manufacturing method of the optical device as described in any one of Claim 1 to Claim 3 characterized by the above-mentioned. 5. The first temperature T1 is T1 <150, and the second temperature T2 is 150 ≦ T2 ≦ 400. A method for manufacturing the optical device described. 6. In the heat treatment, a temperature rising rate in a temperature range of less than 150 ° C. is 60 ° C./hr or less,
The method for manufacturing an optical device according to claim 1, wherein a temperature rising rate in a temperature range of not lower than 0 ° C. is not higher than 10 ° C./hr. 7. The method of manufacturing an optical device according to claim 1, wherein the heat treatment is performed in a reduced pressure atmosphere or an atmosphere containing hydrogen. 8. When bonding the optical elements to each other at a bonding surface, the bonding surfaces are bonded directly or through a solution,
After that, the heat treatment is performed to perform the bonding, and the method for manufacturing an optical device according to claim 1, wherein the bonding is performed. 9. The liquid according to claim 8, wherein a liquid containing polar molecules as a main component is used alone or as a mixture when the optical elements are bonded to each other via a solution. Method of manufacturing optical device. 10. The method of manufacturing an optical device according to claim 1, wherein the bonded optical elements are at least a magnetic garnet and a polarizer. 11. The optical element is bonded after the metal oxide film is formed on at least one bonding surface of the optical element to be bonded, according to any one of claims 1 to 10. Method of manufacturing optical device. 12. The metal oxide film formed on the bonding surface of the optical element is formed of Al ₂ O ₃ , Ta ₃ O ₅ , TiO ₂ , and SiO.
_The method for producing an optical device according to claim 11, wherein one or more metal oxide films selected from 2 are formed, and the metal oxide films are laminated in a single layer or a multilayer. 13. An optical device manufactured by the method according to any one of claims 1 to 12. 14. The optical device according to claim 13, wherein the manufactured optical device is an optical isolator.