JP2003015082A - Isolator with lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that miniaturization is restricted where the occupancy area of a polarization depending type polarizer is limited by a light spot diameter based on the spread angle of a laser and a distance between lenses. SOLUTION: The isolator with a lens is equipped with the lens and constituted by attaching a first polarizer whose light transmission surface is coated with antireflection coating, and a compound element obtained by optically adjusting and bonding a Faraday rotator and a second polarizer whose transmission surfaces are respectively coated with the antireflection coating on the same base plate respectively. The first and/or the second polarizer is formed by laminating a thin film having a low refractive index and a thin film having a high refractive index on the stripe groove part of the base plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a polarization-dependent optical isolator used for the purpose of preventing reflected return light generated due to the structural cause of a laser module used for transmission such as optical communication. The present invention relates to a lens-equipped isolator for achieving required reflection characteristics, downsizing, and compounding with a lens.

[0002]

2. Description of the Related Art Conventionally, an isolator used for optical communication or the like has a polarizer and a Faraday rotator attached to metal fittings by soldering or low melting point glass, which is attached by fusion while adjusting the rotation with a YAG laser. It is completed. When this was used, it was attached after the lens to form a collimating system or a non-collimating system, and it was used by being attached at an appropriate position.

Since such a structure is adopted, the distance between the laser diode and the lens is designed in consideration of the size of the lens and the size of the metal fitting for mounting the lens. The mode field diameter is inevitably large, which increases the size of the polarizer and Faraday rotator used in the isolator, which is one of the cost factors of the isolator.
It was one. Further, it is required to make optical adjustments one by one, which further increases the processing cost.

As one of the solutions, there has been adopted a method of constructing a non-collimating optical system between the laser and the pigtail and attaching a laminate isolator to the front surface of the pigtail, but this method uses the pigtail itself and the directivity. Therefore, when it is attached to the actual module, it is necessary to adjust the rotation to match the polarization plane of the laser.

Further, even if the non-collimating optical system is used, the plate thickness of the Faraday rotator and the polarizer cannot be made thin, so that the size thereof is limited by the beam shape on the surface of the front polarizer. Further, since the laminate isolator has the polarizer and the Faraday rotator fixed by an adhesive, the reliability anxiety cannot be fully resolved in the future where the laser emission intensity will increase. .

A configuration example of a conventional isolator having such a problem will be described with reference to the drawings. FIG. 8 shows a configuration example of a conventional general isolator.

As shown in the figure, the polarizer 4 is attached to the metal fitting 11 by using the low melting point glass 12. Further, the Faraday rotator 3 is similarly attached to the metal fitting 11 ′ using the low melting point glass 12. After these two elements are rotationally adjusted, they are fixed by fusion with a YAG laser.

Another polarizer 4 is attached to the metal fitting 11 "using the low melting point glass 12. After that, the metal fitting 11 'is attached.
And 11 "are rotationally adjusted so that the two polarizers 4 are at 90 ° to each other, and fused and fixed with a YAG laser.
An element having a function of transmitting incident laser light but absorbing reflected light is completed.

This isolator is usually used in a collimating system. Therefore, the spot diameter of the light passing through the isolator is determined by the divergence angle of the laser and the focal length of the lens placed in front of the isolator. The focal length of the lens is determined by its mounting method, numerical aperture and the like.

The spread angle of the LD is typically 30 °.
Is well known. Since 0.8 mm is often adopted as the focal length of the lens, the spot diameter of the light obtained from that is 1 mm, and therefore, the effective range of the isolator is required to be at least 1 mm □.

FIG. 9 shows a structure adopted for the purpose of reducing the area occupied by the isolator. A laminate isolator 16 is attached to the pigtail 15.

As shown in the figure, first, the plates of the two polarizers 4 and the Faraday rotator 3 are rotationally optically adjusted and attached with an adhesive. Therefore, in this case, the number of processing steps is reduced because the elements are not attached one by one. The laminate isolator 16 is obtained by cutting this into desired dimensions.

On the other hand, the pigtail 15 is created as follows. The ferrule 17 and the metal fitting 11 are attached by press fitting, and the fiber 12 with the sheath 13 removed is the ferrule 1
Then, the whole coating is fixed with an adhesive. After that, the tip of the ferrule 17 is angle-polished, and the laminate isolator is attached to the tip of the ferrule 17 with an adhesive.

At this point, an isolator having the magnetic body 5 attached to the pigtail is completed.

Although this isolator is optically adjusted, when it is attached to a module, since the laser has polarization dependence, it is necessary to match the directionality with this laser. In the case of mounting, it is required to mount again while adjusting the rotation optical.

FIG. 10 is shown in Japanese Unexamined Patent Publication No. 9-90282, in which a lens 2 is attached to a first polarizer 1, a Faraday rotator 3 and a second polarizer 4 are attached.
Has a structure in which the magnetic substance 5 is attached thereto, and the emitted light beam 22 of the laser 20 is connected to the fiber 26. In the case of such a structure, the purpose of reducing the area occupied by the isolator has been achieved, but it has various weak points as described below.

[0017]

In the conventional collimator type isolator, the isolator shown in FIG. 8 is placed after the lens, and in the case of the collimator system, the laser is placed at the focal length of the lens and the distance can be attached to the lens. Therefore, if the isolator and lens are configured separately, a mounting structure is required for each, and as a result, the spot diameter of the light becomes large, and the polarization of the isolator is therefore a component. There was a problem that the child and the Faraday rotator could not be made smaller.

In order to reduce the size of the isolator,
As shown in the figure, there is a means of adopting a non-collimator system and attaching an isolator immediately before the pigtail. However, even in this case, the thickness required for the polarizer and Faraday rotator (polarizer 0.2 to 0.5 m
m, Faraday rotator 0.5 mm), so naturally there is a limit in size.

Further, in the above structure, as can be seen from FIG. 9, when the metal fitting 11 is used for welding by YAG, the metal fitting 11 does not have an accurate mark indicating the direction or the isolator is accurately attached to the mark. Since it is not designed, the structure does not show the direction. For this reason,
Again, optical adjustments are needed and a dedicated device for mounting is required.

Further, the structure shown in FIG. 10 is effective in reducing the area occupied by the isolator, but has a structure which realizes a measure against the return light and simplification of the assembly after the measure against the return light. I haven't mentioned it. For example, although the isolator is tilted to prevent the return light, when the isolator is downsized and the distance between the laser 20 and the isolator becomes extremely short, a structure for providing an easy attachment structure is not presented.

[0021]

In view of the above, the present invention provides:
A first polarizer having a lens and having a light-transmitting surface coated with antireflection, a composite element in which a Faraday rotator having a light-transmitting surface coated with antireflection and a second polarizer are optically adjusted and joined. By mounting each on the same substrate, and by further attaching a magnetic material to this substrate to form an isolator with a lens, a structure in which the lens and the isolator are integrally attached is provided, and the distance between the laser and the lens is shortened, and It can be easily installed.

Further, the first and / or the second polarizer are formed by alternately laminating thin films having a low refractive index and thin films having a high refractive index on the striped groove portion of the substrate. Is characterized by.

Further, an inorganic thin film is formed on one surface of the Faraday rotator, and the thin film is etched to form a striped groove portion, and a thin film having a low refractive index and a thin film having a high refractive index are alternately formed thereon. It is laminated to form a composite of the Faraday rotator and the second polarizer.

Further, the striped groove portion is formed on one surface of the Faraday rotator, and thin films having a low refractive index and thin films having a high refractive index are alternately laminated on the striped groove portion, so that the Faraday rotator and the second thin film are formed. It is a composite of polarizers.

The requirement for the substrate of such a polarizer is that it has a transmission wavelength characteristic as long as it is a material that transmits the wavelength used, and glass, Pyrex (registered trademark), quartz, garnet or the like may be selected. Therefore, as described above, the formation of the first polarizer including the lens or the formation of the second polarizer including the Faraday rotator by 1
It has the function of being formed as one part, and the optical adjustment of each of the first and second polarizers can be replaced by photoengraving technology. Further, the bonding is replaced by film formation, which has a great effect that such an operation is omitted.

As a further application of the above technique, a striped groove is formed on one side of the Faraday rotator in alignment with the optical axis of the Faraday rotator, and a striped groove is formed on the back side thereof so as to be inclined at 45 ° with respect to the optical axis. It is also possible to form a thin film having a low refractive index and a thin film having a high refractive index, respectively, to form a composite with the first polarizer, the Faraday rotator, and the second polarizer.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an isolator of the present invention. The lens 2 is formed in front of the first polarizer 1, and the rear end surface 1a thereof is an inclined surface. Both surfaces of these elements are antireflection coated, a metal layer 6a is formed on the lower surface thereof, and they are attached to a substrate 7 having a metal layer 6b.

Further, the Faraday rotator 3 is mounted on the same substrate 7.
The second polarizer 4 is fixed, and the Faraday rotator 3 tilts the plane of polarization of the incident light by 45 °, and the second polarizer 4 transmits the incident light. After these are optically adjusted, the metal layer 6c formed on the Faraday rotator 3 and the second layer 6c
And the metal layer 6d formed on the polarizer 4 to form a composite element. A metal layer 6a is formed on the lower surface of this composite element, and is attached to the substrate 7 having the metal layer 6b.
Further, a magnetic body 5 for applying a magnetic field to the Faraday rotator 3 is attached to the substrate 7 to form an optical isolator.

As described above, the lens 2 is formed on the first polarizer 1.
By forming the lens 2 having a short focal length and a large numerical aperture, the lens 2 and the isolator can be placed in the immediate vicinity of the laser. As a result, the spot diameter of the laser emission light can be suppressed to a small value, and High coupling efficiency can be obtained.

As a result of calculation, it has been confirmed that the coupling efficiency between the return light and the laser due to the reflection characteristic from the lens does not pose a problem. The reflection at the interface between the lens 2 and the first polarizer 1 does not occur if the refractive index is the same. In the case of attaching by adhesion or the like, in the collimating system, the returning light is directly coupled with the laser, so that it is necessary to make the joint surface oblique. In the case of the collimating system, the reflection from the rear end face 1a of the first polarizer 1 is almost 100% coupled with the laser. Therefore, in the present invention, the end face 1a is provided with a predetermined angle and antireflection coating is applied to reduce the coupling efficiency between the returning light and the laser.

Next, another embodiment of the present invention is shown in FIG. As shown in FIG. 3, in the first polarizer 1 made of this photonic crystal, a striped groove portion 28 is formed on a large substrate having a lens 2, and a thin film 2 having a low refractive index is formed on the substrate.
6 and a thin film 27 having a high refractive index are formed in a laminated structure, whereby the thin film 27 serves as a polarizer.

In FIG. 2, an oxide film is formed on the Faraday rotator 3 by CVD, and the oxide film is photoengraved to form striped convex portions 29 as shown in FIG. An isolator is formed by forming a thin film 26 having a low refractive index and a thin film 27 having a high refractive index in a laminated form, and using this as a second polarizer 4 to form a composite. Alternatively, a striped groove portion 28 is formed on the Faraday rotator 3 itself, and the thin film 26 having a low refractive index is formed on the groove portion 28.
It is also possible to form a thin film 27 having a high refractive index by lamination to form a composite.

The polarizer is constructed by laminating thin films 26 and 27 having different refractive indexes on the striped groove portion 28 or the striped convex portion 29 formed on the substrate in this way.

What is important in the present invention is that the distance from the main axis of the lens 2 to the bottom surface of the substrate 7 falls within a desired value. In order to realize this purpose, the position of the lens 2 formed on the large substrate for cutting out the first polarizer 1 is formed at a precisely controlled position. Furthermore, it is cut to the correct size by a dicer. Further, the substrate 7 is required to have an accurate flatness and an accurate thickness. Therefore, glass is the most suitable material. However, this does not mean that other materials cannot be used.

The effect that can be realized by adopting the above structure is that the lens 2 is attached to the first polarizer 1,
By using a short focal length of the lens 2 and a high numerical aperture, it is possible to bring the isolator close enough to the laser, and as a result, the effective area of the isolator can be reduced, thus reducing the cost. You can do it.

Since a large number of lenses can be formed on one polarizer substrate by combining the lens and the polarizer, the cost of one lens can be reduced and the lens can be attached. Metal fittings and man-hours can be reduced.

Further, since the optical adjustment of the Faraday rotator 3 and the second polarizer 4 can be performed for each large substrate, or in the example of FIG. 2, it can be prepared by photolithography, so that the assembly is simplified. Can be realized, leading to cost reduction. A method of cutting this substrate obliquely is currently established with a dicer.

The metal layer 6a is attached to the substrate 7. This method is easy to control the thickness of the joint surface,
In addition, by adopting the substrate 7 having an accurate thickness, the lens 2
It is possible to easily control the distance between the optical axis and the bottom surface of the substrate 7. When this invention is installed by controlling this value,
The degree of freedom of mounting can be made one-dimensional, and easy mounting is realized.

Next, the production of each optical element shown in FIG. 2 will be described in detail.

The substrate for separating the first polarizer 1 has the structure shown in FIG. A striped groove portion 28 is formed on one surface of a large substrate including a large number of lenses 2, and a thin film 26 having a low refractive index and a thin film 27 having a high refractive index are laminated on the groove portion, so that the first Forming a polarizer. The period Lx of the striped groove portion 28 of the first polarizer 1
The range is preferably Lx = 0.39 to 0.43λ, for example, Lx = 0.4λ = 0.62 μm. The period Lz of the two thin film layers 26 and 27 is, for example, Lz = 0.
8 · Lx = 0.656 μm is set, and the thickness and period ratio of each film are balanced so that the polarization effect can be confirmed. The material of the thin films 26 and 27 is, for example, the thin film 26.
As employs Si as SiO _2, a thin film 27.

A plurality of elements are cut out from one substrate formed under the above conditions. The cutting angle is accurately measured, and after selectively removing thin film is coated on both sides,
It will be cut out from the dotted line portion 8 in FIG. 3 by the dicer. The metal layer 6a is formed on a part of the cut surface of the cut element.
Is formed and the selectively removable thin film is removed, whereby the first polarizer 1 is produced.

As a method of forming the lens 2, a crystal material of the lens 2 having a low melting point is selected, and a method of forming a molded lens is used. Created as a substrate.

The composite of the second polarizer 4 and the Faraday rotator 3 is prepared as follows. In FIG. 4, a SiO ₂ thin film of about 0.5 μm is formed on the Faraday rotator 3 by CVD, and a stripe-shaped convex portion 28 having a period of 0.62 μm is formed on the thin film by resist coating, photoengraving and etching. Similarly to the lens 2, the two thin films 26 and 27 are laminated to form the second polarizer 4 to form a composite. In forming the striped convex portion 29, the directionality of the substrate of the Faraday rotator 3 coated with the resist is measured, a hole is made in the resist by a laser beam, and photolithography is performed using the hole as a mark. The directions of the two polarizers are matched.

FIG. 5 shows an example of another embodiment of the above composite, in which the striped groove portion 28 is directly formed on the Faraday rotator 3, and two thin films 26 and 27 are formed on the striped groove portion 28. It was formed.

As another embodiment, it is possible to form the first polarizer 1 and the second polarizer 4 on both sides of the Faraday rotator 3. A mark is made according to the optical rotation axis of the Faraday rotator 3, a striped groove portion 28 is formed according to this mark, and the first polarizer 1 is formed on this. next,
On the other side of the Faraday rotator 3
The striped groove portion 28 is formed according to the direction inclined by 5 °, and the second
To form the polarizer 4. As a result, an isolator is formed.

The influence on the characteristics of the Faraday rotator 3 is the wavelength dependence of the isolation, but this point is not a problem for the following reason. That is, the rotation angle of the Faraday rotator 3 depends on its film thickness, and the film thickness at λ = 1.55 μm is 450 μm, and therefore the rotation angle per 1 μm is 0.1 °. Therefore, since the thickness difference due to the formation of the second polarizer 4 is 0.23 μm, the influence of the characteristic is 0.02 °, which is not a problem at all.

The effect of forming a polarizer by the photonic crystal may be obtained by forming a polarizer on the lens substrate 2 or the Faraday rotator 3 by stacking, for example, the directionality of the first polarizer 1 is striped. Since the direction is determined by the groove portion 28, for example, if a pattern showing directionality is simultaneously provided by photolithography, the directionality can be accurately obtained by cutting along the pattern. For example, 5
Even if the cutting is performed in inches, the error is about ± 15 μm, so the angular error obtained by the cutting is 0.
It has a very high accuracy of 0001 °.

When the second polarizer 4 is formed on the Faraday rotator 3, first, a resist is applied to the substrate of the Faraday rotator 3, and the rotation angle is measured in this state.
After irradiating the substrate of the Faraday rotator 3 with several spots formed by a laser diode to cure the resist, the resist is removed, and the resist of the mark is left, and the striped groove portion 28 or the striped convex portion is used as a reference. By forming 29, it becomes possible to perform higher alignment than the lens portion.

As described above, since the optical adjustment work can be returned to the photolithography, the operability is greatly improved. Further, since the connection work is omitted due to the film formation, the first polarizer 1 and the second polarizer 4 are formed.
The formation of is greatly reduced.

The above substrate is provided with a thin film which can be selectively removed on both sides, and is then cut along the dotted oblique cutting portion 10,
Arrange the mounted parts of the cut elements on top, and here,
By forming the metal layer 6a and then removing the selectively removable thin film, a composite of the polarizer 4 and the Faraday rotator 3 is formed.

The first polarizer 1, the composite of the Faraday rotator 3 and the second polarizer 4 are precisely assembled on the substrate 7 having high accuracy of thickness and flatness, and then the magnetic material. 5 is attached to complete the isolator. The reason why the substrate 7 and the metal layers 6a and 6b are required to have high precision is to reduce the degree of freedom of attachment to one dimension, as described later. As a result, an easy assembling method can be realized.

Next, the metal layer will be described. Metal layer 6
Each of a, 6b, 6c, and 6d is composed of a base, an intermediate layer, an uppermost layer, and a solder layer thereon. The metal layers 6a to 6d are required to have a good adhesion of the underlayer to the glass, an intermediate layer serving as a buffer layer for the underlayer and solder, and an uppermost layer for preventing oxidation of the intermediate layer. In addition, it is a layer that ensures the wettability of the solder layer. Generally, Cr / Au, Cr / Ni
/ Au, Ti / Pt / Au, Ti / W / Au, etc. are suitable. As the solder layer, an Au / Sn alloy layer or a laminated layer is suitable.

As the above-mentioned step of joining the isolator, the joining of the Faraday rotator 3 and the second polarizer 4, the first polarizer 1, the composite of the Faraday rotator 3 and the second polarizer 4, and the substrate 7 are performed. It is the solder layer that joins with. The former requires a high melting point because it must be joined first. The following method is possible as a method for realizing this.

One is a metal layer 6 for joining the composites.
In this method, Au / Sn is used for c and 6d, and Ag / Sn solder is used for the metal layers 6a and 6b for joining to the substrate 7. Another method is to change the weight ratio of Au / Sn. At a weight ratio of 7: 3, this material has a minimum melting point of about 290 ° C. By changing the material cost of the alloy or changing the thickness of Au of the metal layer so that the weight ratio becomes 8: 2, etc., the junction temperature between the Faraday rotator 3 and the second polarizer 4 is changed. Can be raised.

A resist or polyimide is one of the selectively removable thin films used for separating each element. These are removed by the developer. Also,
There is a nitride film as the hard coat. These can be selectively removed by plasma etching. In addition, in some cases, a metal that can be removed by a developer that does not attack the metal layer used and the solder layer 6a can be used.

Next, an application example of the present invention is shown in FIG. The laser diode 20 is attached to the Si platform 23 by the bump 21. The substrate 7 forming the isolator of the present invention is fixed on the Si platform 23, and
Cutting part 2 by the dicer formed on the platform
4 sets the distance from the laser diode 20.
Since the cutting accuracy of the current dicer has been improved, it is possible to mount the laser diode 20 within the accuracy of 5 μm including the mounting accuracy.

The mounting position of the isolator is S
Although it depends on the height of the groove 25 formed on the i platform 23, this accuracy can be ± 1 μm. If the center deviation of the lens 2 is ± 1 μm, the positioning error during cutting is ± 1 μm, and the control error of the metal layers 6a and 6b is ± 0.5 μm, the total error is ± 1.8.
.mu.m, therefore, sufficient and highly accurate mounting is possible.

With this mounting method, the lens 2
And the alignment of the laser diode 20 and the lens 2 with respect to the height direction of the optical axis are uniquely determined.
It is possible to provide an isolator in which only the lateral direction remains as an adjusting element.

In FIG. 6, the isolator substrate 7 is S
Although fixed on the i platform 23, each element can be fixed directly on the Si platform 23 itself to form the isolator of the present invention.

The shape of the lens 2 forming the first polarizer 1 is shown in FIG. In FIG. 7, (a) shows a normal lens, (b) shows the lens 2 not projected on the plane portion, and (c) shows a diffraction grating lens.

All of these shapes can be created by selecting a mold.

[0062]

EXAMPLE An isolator shown in FIG. 2 was produced as an example according to the present invention. As shown in FIG. 3, the period of the lens 2 is 270μ.
A large substrate having a hemispherical ball lens of 120 μmφ with an interval of m was prepared. After that, an antireflection coating is applied to the surface of the lens 2, and the above-mentioned substrate is covered with the photosensitive polyimide. Then, the first polarizer 1 of 240 μm □ is cut out using a blade of 30 μm, and Cr / Ni /
Au base, middle layer, top layer (500Å / 2000Å /
2000 Å) and an Au / Sn solder layer of 2 μm were formed, a metal layer 6a was formed, and finally the polyimide was removed to form the first polarizer 1.

The dimensions of the ball lens were numerically calculated based on the following considerations. The divergence angle of the laser diode 20 is generally 30 ° in the vertical direction and 25 ° C in the horizontal direction. Assuming a spherical lens and assuming that the distance to the main surface of the lens 2 is 100 μm, the spot diameter of the collimated light is 1
It becomes 15 μφ. The diameter of the lens with a focus of 100 μm is f
= From _{n 2 R / 2 (n 2} -n 1), the refractive index of the lens 1.5
Then, it can be easily obtained and becomes 66 μm. Of course, since there is a problem of aberration, such a lens design is not simply performed as it is, and it is premised that an aspherical lens is actually used. Further, since the beam is tilted due to the deviation of the optical axes of the laser diode 20 and the lens 2, it is necessary to consider the effect in the effective area of the isolator.

The thickness of the Faraday rotator 3 is 0.5 mm,
If the thickness of the second polarizer 4 is 0.01 mm and the mounting space for both is 0.1 mm, a total thickness of 0.61 mm is required, and if the emission angle of the beam is allowed to vary up to ± 3 °, The increase in the effective area is 64μ
m.

To this, a damage layer by the dicer was added to 30
Considering μm, the total is 115 μm + 64 μm + 6
At 0 μm, 239 μm is the required size as the effective area of the isolator.

This is the required area of the polarizer and Faraday rotator used in the conventional isolator, 1.2 mm.
This corresponds to about 1/18 of x 1.2 mm, and when the cutting area of the dicer is taken into consideration, the area can be greatly reduced to 1/20.

At this time, the distance between the laser diode 20 and the lens 2 is 34 μm, and a sufficient mountable distance is secured.

Next, conditions for producing a polarizer made of a photonic crystal will be shown. As a material for the thin film 26 having a low refractive index, SiO ₂ is generally used. The material of the thin film 27 having a high refractive index is Si, TiO ₂ , Ta ₂
O ₅ etc. can be raised. These are the materials used for the AR coat, and their stability has been sufficiently confirmed.

In order to obtain the polarizer effect with the photonic crystal, the relationship between the wavelength λ and the period Lx of the striped groove portion 28 is Lx.
/Λ=0.4, so λ = 1.55 μm
Is substituted, Lx = 0.62 μm is obtained. The relationship between the period Lz of the thin films 26 and 27 and the period Lx of the groove is Lz /
Since Lx = 0.8, the period L of the thin films 26 and 27 is L.
z is 0.5 μm. Optimum values are obtained by making samples with various ratios of the high refractive index material and the low refractive index material.

The relationship between the depth F of the striped groove portion 28 and the thin film period Lz is set to F = 0.45Lz = 0.23 μm. A polarizer was formed under these conditions.

The Faraday rotator 3 is provided with a striped groove 28.
23 μm in thickness, antireflection coating is applied on one side, and 10 layers of the thin film 26 having a low refractive index and the thin film 27 having a high refractive index are laminated on the striped groove portion 28 to form a second polarizer 4
And formed a complex with. After forming a photosensitive polyimide on this substrate, it was cut into a size of 240 × 243 μm with a dicer. When cutting, one side is vertical, one side is angled at 8 °, and when the angled part is attached, 240 ×
The size was set to 240 μm. Next, the metal layer 6a was formed and the composite body was completed.

Finally, after forming the metal layer 6b on the substrate 7 and cutting it to a desired size, the first polarizer 1 and the composite body were attached by soldering to complete the isolator.

When this isolator was used and evaluated on an optical bench, a coupling efficiency of about 35% was obtained. In addition, a reflectance of 35 dB or more is obtained. Of course, the insertion loss and isolation characteristics, which are the basic characteristics of the isolator, are 0.2 dB or less and 40 at the peak wavelength, respectively.
A value of dB or less is obtained.

In this result, the coupling efficiency is 35% because of the influence of the aberration due to the use of the spherical lens, and if the aspherical lens can be used, the coupling efficiency of 60 to 70% can be obtained. I think I can do it.

Further, in this prototype, the manufacturing was performed without considering the sufficient alignment accuracy, but it is considered that the accuracy can be ± 2 μm if it is manufactured while sufficiently suppressing each dimension.

[0076]

As described above, according to the present invention, a first lens provided with a lens and having a light-transmissive surface formed by laminating an antireflection-coated thin film having a low refractive index and a thin film having a high refractive index is provided. A polarizer and a composite element formed of a second polarizer formed by laminating a Faraday rotator whose light transmitting surface is antireflection coated, a thin film having a low refractive index, and a thin film having a high refractive index, respectively. It is an isolator with a lens that is mounted on the same substrate, and the required area of the polarizer and the Faraday rotator can be sufficiently reduced compared to the conventional area. Substituting for plate making, and since there is no adhesive on the optical axis, high reliability is ensured.In production, lens substrates are made, polarizers are formed, and substrates for Faraday rotator substrate optical axis measurement are used. Significant reduction in production steps for batch processing is possible is possible. Therefore, it is possible to supply the isolator at a lower cost than in the past, and it will promote further development of the optical communication market, which will be increasingly popular in the future.

[Brief description of drawings]

FIG. 1 is a sectional view showing an isolator with a lens of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the lens-equipped isolator of the present invention.

FIG. 3 is a cross-sectional view showing a method of manufacturing a first polarizer that constitutes the lensed isolator of the present invention.

FIG. 4 is a diagram showing a method for producing a composite body of a second polarizer and a Faraday rotator that form the lens-equipped isolator of the present invention.

FIG. 5 is a cross-sectional view showing a method for manufacturing a composite of a second polarizer and a Faraday rotator, which is another embodiment of the lensed isolator of the present invention.

FIG. 6 is a cross-sectional view showing an application example of the lens-equipped isolator of the present invention.

7A to 7C are cross-sectional views of a lens used in the lens-equipped isolator of the present invention.

FIG. 8 is a sectional view showing a conventional general polarization-dependent isolator.

FIG. 9 is a sectional view showing a conventional laminated isolator mounted on a pigtail.

FIG. 10 is a cross-sectional view of a conventional lens-equipped isolator.

[Explanation of symbols]

1 first polarizer 1a end face 2 lenses 3 Faraday rotator 3a end face 4 Second polarizer 4a end face 5 magnetic material 6a to 6d metal layer 7 substrate 8 cutting part 9 Diagonal grinding section 10 cutting part 11 metal fittings 1 11 'metal fitting 2 11 "metal fitting 3 12 Low melting glass 13 Fiber coating 14 Adhesive 15 Pigtail 16 Laminate Isolator 17 ferrules 18 light spots 20 laser diode 21 bump 22 Outgoing rays 23 Si platform 24 cutting part 25 groove 26 thin film 27 thin film 28 Striped groove 29 Striped convex 30 Optical axis adjustment direction 31 Optical axis adjustment direction

Claims (4)

[Claims] 1. A first polarizer having a lens and having a light-transmitting surface coated with antireflection, a Faraday rotator having a light-transmitting surface coated with antireflection, and a second polarizer are optically adjusted and joined. Is a lens-equipped isolator, wherein the first and / or second polarizer is a thin film having a low refractive index and a high refractive index on the striped groove of the substrate. An isolator with a lens, characterized in that it is formed by laminating thin films of high refractive index. 2. An inorganic thin film is formed on one side of the Faraday rotator, and the thin film is etched to form a striped groove portion, and a thin film having a low refractive index and a thin film having a high refractive index are alternately formed thereon. The lens-equipped isolator according to claim 1, wherein the isolators are laminated to form a composite of a Faraday rotator and a second polarizer. 3. A Faraday rotator and a second polarized light are formed by forming a striped groove on one surface of the Faraday rotator, and alternately laminating thin films having a low refractive index and thin films having a high refractive index on the groove. 2. The lens-equipped isolator according to claim 1, which is a composite of a child. 4. A composite of a first polarizer, a Faraday rotator, and a second polarizer, with stripe grooves formed on both sides of the Faraday rotator in alignment with the rotation axis of the Faraday rotator. The isolator with a lens according to claim 1, wherein