JP2006309190A - Optical isolator and optical module using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical isolator which is miniaturized in a small number of assembly processes and has an excellent optical characteristics, high durability, and high reliability. <P>SOLUTION: The optical isolator includes a Faraday rotator 5 having a pair of principal faces, polarizers 4 and 6 which are arranged in the vicinity of the respective principal faces of the Faraday rotator 5, and a permanent magnet 7 which holds the Faraday rotator 5 and the polarizers 4 and 6. At least a part of the respective side faces of the Faraday rotator 5 and the polarizers 4 and 6 is connected to the permanent magnet 7 via a connecting material 8 so that a gap partially exists between the polarizer 4 and the Faraday rotator 5, and between the Faraday rotator 5 and the polarizer 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical isolator used for removing return light generated when light emitted from a light source is coupled to various optical elements and optical fibers, and an optical module using the optical isolator.

  When light emitted from a light source such as a laser diode (LD) passes through various optical elements or optical fibers, a part of the light may be reflected or scattered by an interface or the like and return to the light source side. In general, an optical isolator is used as an optical component for blocking such return light. A typical optical isolator is configured by arranging a Faraday rotator between two polarizers, and the Faraday rotator is adjusted so that the polarization of light rotates 45 degrees. These three optical elements are arranged and fixed on the mounting surface of the metal base.

  FIG. 7 is a partially broken perspective view showing an example of a conventional optical isolator. This is a so-called laminate chip type described in Patent Document 1 below, and the optical isolator 40 includes a Faraday rotator 42 and a pair of polarizers 41 disposed on both sides of the Faraday rotator 42. Between the Faraday rotator 42 and each polarizer 41, an optical adhesive 45 having a good light transmittance and controlled to an appropriate refractive index is filled, and the optical elements are bonded and fixed. The optical isolator 40 further includes a cylindrical magnet 43 for supplying a magnetic field to the Faraday rotator 42.

Each polarizer 41 has a polarization component in one direction of light passing therethrough in which the elliptical dielectric is oriented in substantially the same direction on the surface layer portions of both main surfaces and coincides with the major axis direction of the dielectric. It has a function of absorbing and transmitting a polarization component orthogonal to the polarization component. Part of the absorbed light is converted to heat. The Faraday rotator 42 has a function of rotating the polarization plane of light of a predetermined wavelength by about 45 degrees at the saturation magnetic field strength. Each polarizer 41 is arranged so that the direction of transmission polarization is shifted by about 45 degrees.
JP-A-4-338916

  However, the laminated chip type isolator as shown in FIG. 7 can be reduced in size by adhesion between optical elements. However, when the optical adhesive 45 is an organic adhesive, the moisture resistance is inferior, particularly under high temperature and high humidity conditions. Use in is limited. Further, when high-power laser light passes or laser light passes for a long time, the optical adhesive 45 may be deteriorated, and the reliability of the optical component is lowered.

  Further, when the thermal expansion coefficients are different between each polarizer 41 and the Faraday rotator 40, a thermal stress is generated under a temperature cycle, a bending moment is generated like a bimetal, or an optical caused by an internal stress variation. Variations in characteristics may occur.

  Further, when the optical isolator 40 is incorporated in the laser module, it is exposed to a high temperature in the brazing process. Therefore, when an organic adhesive is used as the optical adhesive 45, the thermal decomposition of the adhesive may cause generation of bubbles, a decrease in adhesive strength, and the like, and the optical element may fall off. In addition, when outgas is generated from the organic adhesive, the outgas adheres to the surface of surrounding optical components such as a laser chip and a lens and deteriorates optical characteristics.

   An object of the present invention is to provide an optical isolator and an optical module that can be miniaturized with a small number of assembly steps and have excellent optical characteristics, high durability, and high reliability.

  In order to achieve the above object, an optical isolator according to the present invention includes a Faraday rotator having a pair of main surfaces, and a first polarizer and a second polarizer disposed close to each main surface of the Faraday rotator. A Faraday rotator, a holding member for holding the first polarizer and the second polarizer, and a gap is formed between the first polarizer and the Faraday rotator and between the Faraday rotator and the second polarizer. Therefore, at least a part of each side surface of the Faraday rotator, the first polarizer, and the second polarizer is bonded to the holding member via a bonding material.

  In the present invention, it is preferable that an antireflection film is formed on each opposing surface of the first polarizer and the Faraday rotator and on each opposing surface of the Faraday rotator and the second polarizer.

  In the present invention, the bonding material is preferably an inorganic adhesive, low-melting glass or solder.

  In the present invention, the holding member is preferably configured as a magnet for applying a magnetic field to the Faraday rotator.

  Moreover, in this invention, it is preferable to adhere | transmit the translucent member with a larger heat conductivity than air to the light-incidence surface of any one of a 1st polarizer and a 2nd polarizer.

  Moreover, in this invention, it is preferable that a translucent member has large thermal conductivity compared with a 1st polarizer and a 2nd polarizer.

  Moreover, in this invention, it is preferable that a translucent member is a board | substrate which has glass as a main component.

  An optical module according to the present invention includes a light emitting element that makes light incident on the optical isolator, and a light guide that is optically coupled to the optical isolator.

  According to the present invention, since at least a part of each side surface of the Faraday rotator, the first polarizer, and the second polarizer is bonded to the holding member with the bonding material, the bonding material does not exist on the light passing surface. It is possible to prevent deterioration and deterioration of the bonding material due to light.

  Further, by providing a gap between the first polarizer and the Faraday rotator and between the Faraday rotator and the second polarizer, the thermal expansion coefficient is different between each polarizer and the Faraday rotator. In addition, the thermal expansion occurring in each polarizer and the thermal expansion occurring in the Faraday rotator can be separated between elements. As a result, the thermal stress generated under the temperature cycle can be greatly reduced, so that fluctuations in optical characteristics can be suppressed, and an optical isolator having high durability and high reliability can be realized.

  Further, since the Faraday rotator, the first polarizer, and the second polarizer can be bonded to the holding member at the same time using a bonding material, the number of assembling steps can be reduced.

  Further, an antireflection film is formed on each of the opposing surfaces of the first polarizer and the Faraday rotator and on each of the opposing surfaces of the Faraday rotator and the second polarizer, whereby a gap between each polarizer and the Faraday rotator is formed. In the unlikely event that the opposing surfaces partially adhere to each other, the reflectance characteristics of the antireflection film will not change, and stable optical characteristics can be realized.

  In addition, by using an inorganic adhesive, low-melting glass, or solder as the bonding material, as described above, problems inherent to the organic adhesive can be solved. In particular, low melting point glass or solder is more preferable in that no outgas is generated during bonding.

  In addition, since the holding member is configured as a magnet for applying a magnetic field to the Faraday rotator, the number of parts can be reduced by sharing the member, so that man-hours and costs can be reduced.

  In the present invention, each light incident surface of either the first polarizer or the second polarizer is attached to a light transmissive member having a thermal conductivity higher than that of air, thereby absorbing each reflected return light. It becomes possible to diffuse the heat generated from the polarizer to the translucent member. As a result, according to this configuration, deterioration of the extinction ratio characteristic due to heat generation of the polarizer can be prevented, so that stable insertion loss and isolation characteristics can be maintained. And the said translucent member can further promote the spreading | diffusion of the heat which generate | occur | produced in each polarizer, when heat conductivity is large compared with a 1st polarizer and a 2nd polarizer.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a first embodiment of the optical isolator of the present invention. The optical isolator X1 includes a Faraday rotator 5, two polarizers 4 and 6 disposed on both sides of the Faraday rotator 5, a cylindrical permanent magnet 7, and the like.

  The Faraday rotator 5 is made of a material exhibiting a Faraday effect, such as a YIG single crystal or a Bi-substituted garnet crystal, and is formed in a plate shape having a pair of opposed main surfaces.

  The polarizers 4 and 6 have transmission axes that allow linearly polarized light in a specific direction to pass therethrough, and are arranged so as to be close to the respective principal surfaces of the Faraday rotator 5. The transmission axes of the polarizers 4 and 6 are set so as to rotate relatively 45 ° around the optical axis with the Faraday rotator 5 interposed therebetween. The polarizers 4 and 6 are made of, for example, metal particles such as copper or silver on one surface of a substrate (thermal conductivity: 1.005 (W / m · K)) made of a glass material containing silicon, boron, and zirconium. A dielectric layer including it is formed.

  The permanent magnet 7 has a function of applying a magnetic field along the optical axis direction to the Faraday rotator 5. Here, the permanent magnet 7 is also used as a holding member for accommodating the Faraday rotator 5 and the polarizers 4 and 6 inside the cylinder. By doing so, the number of parts, the number of steps, and the cost can be reduced.

  Part or all of the side surfaces of the Faraday rotator 5 and the polarizers 4 and 6 are bonded to the permanent magnet 7 via the bonding material 8. In addition, the polarizer 4 and the Faraday rotator 5 and the Faraday rotator 5 and the polarizer 6 are almost in close contact with each other. The same air layer as the surrounding atmosphere is interposed.

  In the present embodiment, the optical isolator having such a configuration is arranged so as to be optically coupled to the optical fiber 3. The optical fiber 3 is inserted and fixed in the cylindrical metal fitting 2, and the strand of the optical fiber 3 is inserted in the capillary 1, and is positioned so that the end face of the optical fiber 3 is substantially in contact with the polarizer 6.

  The capillary 1 is formed of ceramic or the like and is press-fitted into the metal fitting 2. The outer end face of the capillary 1 is slightly inclined with respect to the longitudinal axis of the optical fiber 3. Since the optical isolator is positioned so as to be in close contact with the inclined surface, the principal surfaces of the Faraday rotator 5 and the polarizers 4 and 6 are similarly inclined with respect to the optical axis. As a result, the reflected light on each main surface deviates from the optical axis, and stray light and noise light can be prevented from returning.

  When fixing the optical isolator to the capillary 1 1) A method of fixing the Faraday rotator 5 and the polarizers 4 and 6 to the permanent magnet 7 to complete a single optical isolator, and then fixing the entire optical isolator to the capillary 1 And 2) a method of fixing the Faraday rotator 5, the polarizers 4, 6 and the permanent magnet 7 to the capillary 1 at the same time.

  In any method, it is preferable to use an inorganic adhesive, low-melting glass, or solder as the bonding material 8. In particular, when sealing together with a light source such as a semiconductor laser element, it is preferable to use low melting glass or solder that does not generate decomposition products or outgas of the bonding material 8 during bonding.

  When solder is used as the bonding material 8, it is preferable that the side surfaces of the polarizers 4 and 6 and the Faraday rotator 5 are metallized and then fixed using solder such as gold-tin alloy solder. The outermost surface of the metallization is preferably gold.

  From the viewpoint of shortening the process, the above-described simultaneous fixing of 2) is desirable, and from the viewpoint of ease of process, the above-described separate fixing of 1) is desirable. In the case of separate fixing, it is desirable to use an alloy or a metal having a melting point lower than that of the alloy previously used for fixing in the subsequent fixing.

(Embodiment 2)
FIG. 2 is a cross-sectional view showing a second embodiment of the optical isolator of the present invention. This optical isolator X2 has the same configuration as that shown in FIG. 1, and includes a Faraday rotator 5, two polarizers 4 and 6 disposed on both sides of the Faraday rotator 5, a cylindrical permanent magnet 7, and the like. Is done.

  In the present embodiment, the optical isolator having such a configuration is disposed so as to be optically coupled to the optical fiber 3 fixed in the center hole of the ferrule 9. The ferrule 9 is made of ceramic or the like and is press-fitted into the cylindrical metal fitting 10. One end face of the optical fiber 3 is positioned so as to substantially contact the polarizer 6, and the other end face is positioned so as to substantially coincide with the end face 11 of the ferrule 9. An optical connection is made when the connector abuts against the end face 11 of the ferrule 9.

  Similarly in this embodiment, 1) after fixing the Faraday rotator 5 and the polarizers 4 and 6 to the permanent magnet 7 to complete a single optical isolator, and then fixing the entire optical isolator to the ferrule 9; 2) A method of fixing the Faraday rotator 5, the polarizers 4, 6 and the permanent magnet 7 to the ferrule 9 at the same time is conceivable.

  In any method, it is preferable to use an inorganic adhesive, low-melting glass, or solder as the bonding material 8. In particular, when sealing together with a light source such as a semiconductor laser element, it is preferable to use low melting glass or solder that does not generate decomposition products or outgas of the bonding material 8 during bonding.

  When solder is used as the bonding material 8, it is preferable that the side surfaces of the polarizers 4 and 6 and the Faraday rotator 5 are metallized and then fixed using solder such as gold-tin alloy solder. The outermost surface of the metallization is preferably gold.

  From the viewpoint of shortening the process, the above-described simultaneous fixing of 2) is desirable, and from the viewpoint of ease of process, the above-described separate fixing of 1) is desirable. In the case of separate fixing, it is desirable to use an alloy or a metal having a melting point lower than that of the alloy previously used for fixing in the subsequent fixing.

  In each of the above-described embodiments, the bonding material 8 exists on the light passage surface by bonding at least a part of each side surface of the Faraday rotator 5 and the polarizers 4 and 6 to the permanent magnet 7 using the bonding material 8. Therefore, it is possible to prevent deterioration and deterioration of the bonding material due to light.

  Further, it is preferable that a very small gap exists between the polarizer 4 and the Faraday rotator 5 and between the Faraday rotator 5 and the polarizer 6. As a result, even if the thermal expansion coefficients are different between the polarizers 4 and 6 and the Faraday rotator 5, the thermal expansion generated by the polarizers 4 and 6 and the thermal expansion generated by the Faraday rotator 5 are changed between the elements. Can be separated. As a result, the thermal stress generated under the temperature cycle can be greatly reduced, so that fluctuations in optical characteristics can be suppressed, and an optical isolator having high durability and high reliability can be realized.

  In addition, it is preferable to form an antireflection film 13 for air having a refractive index n = 1 on each facing surface of the polarizer 4 and the Faraday rotator 5 and each facing surface of the Faraday rotator 5 and the polarizer 6. Similarly, it is preferable to form an antireflection film 13 against air on the outer main surfaces of the polarizers 4 and 6.

  If the polarizers 4 and 6 and the Faraday rotator 5 are in close contact with each other and no air layer is present, the opposing surfaces of the polarizers 4 and 6 and the Faraday rotator 5 are matched to the refractive indexes of the individual optical materials. It is necessary to apply an antireflection film. However, in practice, when there is no transparent adhesive between the elements, an air layer exists in a very small gap, so it is preferable to apply an antireflection film against air on each facing surface of each element. . As a result, the gap between each polarizer and the Faraday rotator changes, and even if the opposing surfaces are partially in close contact with each other, the reflectance characteristics of the antireflection film 13 do not change, so that it is stable. Optical characteristics can be realized.

  The antireflection film 13 is made of, for example, a dielectric multilayer film, and the thickness of each layer is preferably 2 μm or less. The antireflection film 13 can be formed using a known method such as a sputtering method, a vacuum deposition method, a CVD method, or the like. For example, the sputtering method is performed according to the following principle. First, a film material (target) is placed in the vicinity of the sample to be coated in a vacuum processing container, and a voltage is applied between the sample and the target to move electrons and ions at high speed and collide with the target. Let Ions that collide with the target repel target particles. (Sputtering phenomenon) The repelled raw material particles collide and adhere to the sample to form a film. In the vacuum deposition method, a film target is placed in the vicinity of a sample to be coated in a vacuumed processing container, and the target is opposed to the sample to be coated in a vacuumed processing container. Is heated and the evaporated and vaporized raw material collides with the sample to form a film. In the CVD method, a sample is placed in an atmosphere of a gas raw material, and a high-purity thin film is formed on the sample surface by a chemical reaction.

(Embodiment 3)
FIG. 3 is a cross-sectional view showing a third embodiment of the present invention. The optical isolator X3 includes a Faraday rotator 5, two polarizers 4 and 6 disposed on both sides of the Faraday rotator 5, a cylindrical permanent magnet 7, and the like. Although it is the same as that of embodiment (refer FIG. 1), it differs in the point provided with the translucent member 12 adhere | attached on the 2nd polarizer 6. FIG.

  The translucent member 12 has a function of transmitting incident signal light without substantially absorbing it. Since the translucent member 12 is set to have a higher thermal conductivity than air, for example, reflected light from the capillary 1 or the like is absorbed by the polarizer 6, and heat is generated in the polarizer 6 by this light absorption. Even can receive this heat. As a result, according to the third embodiment of the present invention, it is possible to prevent defects of the polarizer 6 caused by heat generation of the polarizer 6, for example, deterioration of the extinction ratio characteristic, and thus it is possible to maintain stable isolation characteristics. In the third embodiment of the present invention, the light transmissive member 12 is attached to the polarizer 6. However, even if the light transmissive member 12 is attached to the polarizer 4, the heat dissipation effect is promoted. In addition, the translucent member 12 may be attached to both the polarizers 4 and 6.

  The translucent member 12 is set to have a thermal conductivity larger than that of the polarizer 6, but the refractive index is substantially equal to that of the core portion of the optical fiber and the polarizer 6, and the thermal expansion coefficient is also the polarizer 6. It is more preferable if it is almost the same. As a material constituting such translucent member 12, for example, glass can be used as a main component, but it is a substrate made of quartz glass (thermal conductivity: 1.38 (W / m · K)). It is desirable. In addition, even if the translucent member 12 is the glass whose main component is the same as the polarizer 6, you may make it thermal conductivity become larger than a polarizer by controlling content of a subcomponent.

  The translucent member 12 preferably has a refractive index substantially equal to that of the core portion of the optical fiber and the polarizer 6 and a thermal expansion coefficient substantially equal to that of the polarizer 6. As a material constituting the translucent member 12, for example, glass can be used as a main component, but in view of the refractive index and the thermal expansion coefficient, it is a substrate made of quartz or borosilicate glass. Is desirable. Thus, if the translucent member 12 is comprised with the board | substrate which has glass as a main component, it can be made to adhere to the polarizers 4 and 6 generally formed in flat form with high precision. Further, such a translucent member 12 is fixed by a bonding material 8 in the same manner as the polarizers 4 and 6 and the Faraday rotator 5. The light incident / exit surface of the translucent member 12 may be provided with the antireflection film 13 disclosed in the second embodiment of the present invention.

(Embodiment 4)
FIG. 4 is a cross-sectional view of the optical module of the present invention. The optical module 60 includes an LD (laser diode) chip 50 that is a light emitting element that generates light, a submount 51 on which the LD chip is mounted, a thermoelectric cooling device TEC (Thermo Electric Cooler) 52 that controls the temperature of the LD chip 50, An optical isolator X3 having an optical fiber 3 that is a light guide optically coupled with the oscillation light from the LD chip 50, a first lens 53 and a second lens for transmitting the oscillation light from the LD chip 50 to the optical isolator X3. 54, a lens holder 56 for holding the second lens 54, a sleeve 57 for optically aligning the optical isolator X3 in the optical axis direction, and a package 55 for mounting the above-described components. As the optical isolator, the optical isolator X3 according to the third embodiment of the present invention is used.

  In such an optical module 60, even high-power reflected return light can be blocked by the optical isolator 58, and fluctuations in oscillation output and fluctuations in wavelength can be suppressed. Can be maintained.

  As described above, in the case of a conventional optical isolator in which the main surfaces of the optical elements are bonded with an adhesive, when high output light from the light source passes through the optical isolator, the adhesive portion deteriorates and the transmittance decreases. However, there is a concern about the deterioration of the insertion loss characteristic of the optical isolator. On the other hand, in the present invention, since no organic substance such as an adhesive is used on the light passage surface of the optical element, an optical isolator excellent in moisture resistance and light resistance can be realized.

  Further, since the principal surfaces of the optical elements are not fixed with an adhesive, stress on the polarizers 4 and 6 and the Faraday rotator 5 having different thermal expansion coefficients is not generated between the element surfaces but fixed to the permanent magnet 7. Therefore, the stress applied to the optical element can be relaxed.

  As an example of the present invention, the optical isolator shown in FIG. 1 was prototyped and the characteristics were evaluated. Each component and configuration will be described below.

  The polarizer is a polar core (product name) manufactured by Corning, and the size is 11 mm square and the thickness is 0.2 mm. After the optical adjustment is performed so that the transmission polarization directions are deviated from each other by 45 °, the polarizer is 1 mm. Cut into corners. A Faraday rotator having a size of 11 mm square and a thickness of 0.45 mm was cut into 1 mm square. The polarization rotation angle in the saturation magnetic field strength of the Faraday rotator was 45.0 °.

  The polarizer and the Faraday rotator are elements that operate with respect to light having a wavelength of 1.55 μm, and antireflection films for air (n = 1) are applied to both main surfaces of the polarizer and the Faraday rotator. Yes. An antireflection film for air is also applied to the end face of the capillary.

  As a result of measuring the characteristics of the optical isolator thus fabricated, it was confirmed that all the optical isolators had good and uniform characteristics with an insertion loss of 0.3 dB or less and an isolation of 40 dB or more.

  With the above trial production, man-hours were reduced and long-term stability was achieved, and a resin-free optical isolator was realized on the optical path.

  Next, the optical isolator was evaluated using experiments and calculations, and it was confirmed that there was no problem in reflection characteristics as follows.

  FIG. 5A shows a measurement system used for evaluating the optical isolator. A fiber 23 was fixed on a ferrule (tip is flat, no inclination) 22, and a polarizer 24 was fixed on the ferrule 22. Antireflection film for air is applied to both main surfaces of the polarizer 24. In this state, the precision reflectometer 21 was operated, and the presence or absence of a reflection peak from the polarizer 24 was measured.

  Next, with the Faraday rotator 25 placed on the polarizer 24, the precision reflectometer 21 was operated to measure the presence or absence of reflection peaks from the polarizer 24 and the Faraday rotator 25. Both main surfaces of the Faraday rotator 25 are provided with antireflection films for air.

FIG.5 (b) is a graph which shows the result of having measured only the polarizer 24, and FIG.5 (c).
These are graphs showing the results of measurement with the Faraday rotator 25 placed on the polarizer 24. 5B and 5C, the vertical axis represents the intensity (dB) of the reflected light, and the horizontal axis represents the wavelength (nm). For convenience of measurement, the curve of FIG. 5C is closer to the left side than that of FIG. 5B, but it can be seen that the peak intensities are substantially equal when the leftmost peaks are compared. . In either case, the reflection peak intensity was about 46 to 49 dB, showing the same level of characteristics as the antireflection film for air, and confirmed that the reflection characteristics were not affected.

  Next, the evaluation result using calculation will be described. In the calculation, the reflectance of the antireflection film was calculated based on the reflection of the multilayer film. FIG. 6A and FIG. 6B show configuration examples of the multilayer film to be calculated.

In FIG. 6 (a), light sequentially passes through the four antireflection films of the TiO ₂ layer 32, the SiO ₂ layer 33, the TiO ₂ layer 32, and the SiO ₂ layer 33 from the upper quartz substrate 31, and It passes through an air layer (not shown) in the gap, and then passes through the four antireflection films of SiO ₂ layer 33, TiO ₂ layer 32, SiO ₂ layer 33, and TiO ₂ layer 32, and the lower quartz substrate A configuration reaching 31 is shown.

  On the other hand, FIG. 6B shows a configuration in which the upper antireflection film and the lower antireflection film are completely adhered, the gap is zero, and no air layer is present.

Specific configuration examples in FIGS. 6A and 6B are shown in the following (Table 1).

  As a result of calculating the total reflectivity, the reflectivity was 0.00% when the air layer was present, and the reflectivity was 0.00% when the air layer was not present. From these results, an antireflection film for air is formed on the opposing surfaces of the polarizer and the Faraday rotator, making it almost ideal for antireflection, regardless of whether an air layer is present or absent. It was confirmed that

    As described above, even when the surfaces of the two optical elements on which the antireflection film for air is applied are brought into close contact with each other and the air layer is eliminated, the same reflectance characteristics as when the air layer is present can be obtained. Actually, it is extremely difficult to completely eliminate the air layer due to the flatness of the optical element and the manufacturing and assembly problems. However, an air layer exists in a certain part. Even in that case, it was confirmed that the characteristics of the antireflection film did not change.

  INDUSTRIAL APPLICATION Since this invention can implement | achieve the optical isolator provided with the outstanding optical characteristic, durability, and reliability, it is very useful industrially.

It is sectional drawing which shows 1st Embodiment of this invention. It is sectional drawing which shows 2nd Embodiment of this invention. It is sectional drawing which shows 3rd Embodiment of this invention. It is sectional drawing which shows 4th Embodiment of this invention. FIG. 5 (a) shows a measurement system used for the evaluation of the optical isolator, FIG. 5 (b) is a graph showing the result of measurement with only the polarizer 24, and FIG. It is a graph which shows the result of having mounted and measured the Faraday rotator 25 on the child 24. FIG. FIG. 6A and FIG. 6B show configuration examples of the multilayer film to be calculated. It is a partially broken perspective view which shows an example of the conventional optical isolator.

Explanation of symbols

X1 to X3: Optical isolator 1: Capillary 2: Metal fitting 3: Optical fiber 4, 6: Polarizer 5: Faraday rotator 7: Magnet 8: Bonding material 9: Ferrule 10: Metal fitting 11: End face 12: Translucent member 13 : Antireflection film 21: Precision reflectometer 22: Ferrule 23: Fiber 31: Quartz substrate 32: SiO ₂ layer 33: TiO ₂ layer 50: LD chip 51: Submount 52: TEC
53: First lens 54: Second lens 55: Package 56: Lens holder 57: Sleeve 60: Optical module

Claims (8)

  Holds a Faraday rotator having a pair of main surfaces, a first polarizer and a second polarizer arranged close to each main surface of the Faraday rotator, and a Faraday rotator, a first polarizer and a second polarizer A Faraday rotator, a first polarizer, and a Faraday rotator, and a Faraday rotator and a second polarizer such that a gap is partially present between the first polarizer and the Faraday rotator and between the Faraday rotator and the second polarizer. An optical isolator, wherein at least a part of each side surface of the second polarizer is bonded to a holding member via a bonding material.   2. The optical isolator according to claim 1, wherein an antireflection film is formed on each of the opposing surfaces of the first polarizer and the Faraday rotator and on each of the opposing surfaces of the Faraday rotator and the second polarizer.   The optical isolator according to claim 1, wherein the bonding material is an inorganic adhesive, low-melting glass, or solder.   The optical isolator according to claim 1, wherein the holding member is configured as a magnet for applying a magnetic field to the Faraday rotator.   5. The translucent member having a thermal conductivity higher than that of air is attached to one of the light incident surfaces of the first polarizer and the second polarizer. 6. The optical isolator according to 1.   The optical isolator according to claim 5, wherein the translucent member has a higher thermal conductivity than the first polarizer and the second polarizer.   The optical isolator according to claim 5, wherein the translucent member is a substrate mainly composed of glass.   An optical module comprising: the optical isolator according to claim 1; a light emitting element that makes light incident on the optical isolator; and a light guide that is optically coupled to the optical isolator.

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