JP2005091996A - Optical component packaging module and optical communication module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical component packaging module in which no deformation occurs for a transparent substrate such as optical glass and stable optical characteristics are obtained, and also to provide an optical component module using the optical component packaging module. <P>SOLUTION: A WDM three terminal filter module 100 which is an optical communication module is provided with: a two core ferrule 10 into which a first optical fiber 11 for incident light beams and a second optical fiber 12 for reflected light beams are respectively inserted; a single core ferrule 20 into which a third optical fiber 21 for transmissive light beams is inserted; two collimating lenses 30 and 40 which respectively convert light beams from the optical fibers into parallel light beams or converged light beams; and a WDM thin film filter element 50 which is arranged between these lenses 30 and 40 and is the optical component packaging module that separates or passes light beams having a prescribed wavelength. The WDM thin film filter element 50 is made by placing the respective multilayered film sides of a first portion element 51, on which a dielectric multilayered film is formed on a first optical substrate, and a second portion element 52, on which a dielectric multilayered film is formed on a second optical substrate, in an opposing manner. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an optical component mounting module and the like, and more particularly, to an optical component mounting module capable of obtaining stable optical characteristics and an optical communication module using the same.

  Data communication using an optical fiber can transmit and receive a large amount of information at high speed. In recent years, with the advent of Wave Division Multiplexing (WDM), data communication using optical fibers can be further increased in speed and capacity. In this WDM data communication, light of several tens to 100 or more multiplexed at an interval of about 1 nm is passed through one optical fiber, and has a predetermined wavelength from the multiplexed light. The light is separated (see, for example, Patent Document 1). As an optical element for separating light having a predetermined wavelength, a WDM thin film filter element having a multilayer film in which a plurality of dielectric thin films are stacked is used. A thin film filter element for WDM needs to separate light multiplexed at an interval of about 1 nm with an insertion loss of 0.5 dB or less. For this reason, the film pressure of a dielectric thin film is ± 0 of the wavelength of light. .Controlled with accuracy within 1%.

JP-A-6-237242

By the way, an optical element used for optical communication such as a WDM thin film filter element is a dielectric multilayer such as SiO ₂ or Ta ₂ O ₅ formed on a transparent substrate such as optical glass by a vacuum film forming process. There are many devices having a film. Such a dielectric multilayer film usually has a structure in which 50 or more dielectric layers are laminated, and the film thickness of the entire multilayer film often exceeds 10 μm. When the dielectric multilayer film has such a thickness, the stress contained in the laminated dielectric layer reaches 100 to 1000 MPa as a typical value. For this reason, a transparent substrate such as optical glass is set to several μm. If it is large, it may be deformed by several tens of μm.

  FIG. 7 is a view for explaining the deformation of the glass substrate by such a dielectric multilayer film. 7 includes a glass substrate 74 having a size of 1.4 mm × 1.4 mm × 1 mm (thickness), and a dielectric multilayer film 75 having a thickness of 50 to 100 μm stacked on the glass substrate 74. An optical element 70 is shown. In addition, a light beam 73 having a predetermined wavelength is transmitted through the center of the optical element 70. As shown in FIG. 7, in the case of the dielectric multilayer film 75 having a thickness of 50 to 100 μm, the glass substrate 74 is deformed by the contained stress, and the deformation amount reaches about 20 to 30 μm.

  As the glass substrate 74 is deformed in this manner, the incident angle of the light beam 73 has a constant angle with respect to the optical axis at the outer edge portion of the optical element 70. This corresponds to a change in the optical path length, which is equivalent to an effective non-uniform film thickness. Further, due to such deformation of the glass substrate 74, the optical characteristics such as the refractive index and optical anisotropy of the dielectric multilayer film 75 itself change. As a result, there arises a problem that the performance as the optical element 70 is lowered.

  Usually, when a multilayer film is formed using a vacuum film-forming method such as a sputtering method or a vacuum deposition method, the tensile stress or compressive stress of the multilayer film acts on the transparent substrate, so that the optical element is deformed, The physical characteristics will change. Such a stress control method is usually performed by controlling film forming process parameters such as input power at the time of film formation, atmospheric gas pressure, or substrate temperature. However, since optical elements used for optical communications and the like require extremely precisely controlled optical characteristics, it is very difficult to find conditions for a film forming process in which each optical characteristic and low stress are compatible. In many cases.

  The present invention has been made to solve the problems which have been raised in developing an optical element having such a dielectric multilayer film. That is, an object of the present invention is to provide an optical component mounting module in which deformation generated in a transparent substrate such as optical glass is small and stable optical characteristics can be obtained, and an optical communication module using the same.

  In order to solve this problem, the present invention employs a configuration in which two subelements laminated with thin films are combined with the thin film sides facing each other. That is, an optical component mounting module to which the present invention is applied includes at least a first partial element in which a thin film is formed on a first optical substrate and a second partial element in which a thin film is formed on a second optical substrate. And the thin film side of the first partial element and the thin film side of the second partial element are configured to face each other.

  Since the optical component mounting module to which the present invention is applied has a structure in which two partial elements are combined, the position of the partial elements, the angle with respect to the optical axis, and the like can be independently adjusted. Compared with this, the degree of freedom of adjustment can be increased. It is also possible to combine the two subelements so as to form a predetermined angle as a result of optimization of their position and angle.

Here, the optical mirror is characterized in that the thin film formed on the first optical substrate and the thin film formed on the second optical substrate are laminates having at least two layers having different refractive indexes. , Antireflection film, various optical filters (for example, band pass filter for DWDM, broadband filter for CWDM, gain equalization filter, edge filter), dispersion compensator, optical attenuator, interleaver, etc. An optical component mounting module applicable to the above can be provided.

  Next, from another viewpoint, the optical component mounting module to which the present invention is applied is provided between two optical substrates facing each other and at least two having different refractive indexes. And a thin film in which various types of layers are stacked.

  Here, if the thin film provided between the two optical substrates facing each other is separated into a predetermined thickness and fixed to each optical substrate, the thin film is formed on the optical substrate. The stress of the thin film is reduced, and the distortion and deformation of the optical substrate are reduced. As a result, the change in the optical constant as the optical element is reduced, and in particular, the angle of incident light with respect to the thin film of the optical element can be made uniform.

  Next, the present invention includes an optical fiber held by an optical fiber holding member, a lens for converting light from the optical fiber into parallel light or focused light, and a thin film filter element on which light transmitted through the lens is incident. The thin film filter element includes a first partial element in which a thin film is formed on a first optical substrate and a second partial element in which a thin film is formed on a second optical substrate, with the respective thin film sides facing each other. It can be understood as an optical communication module that is characterized by the above.

  Here, the thin film filter element provides an optical communication module useful as a WDM three-terminal filter module if it is characterized by separating or transmitting light of a predetermined wavelength from light transmitted through a lens. be able to.

  Here, the thin film of the thin film filter element is a dielectric multilayer film having a high refractive index layer formed from a dielectric material having a high refractive index and a low refractive index layer formed from a dielectric material having a low refractive index. For example, such a thin film filter is useful as a thin film filter element for WDM, and an optical communication module including such a thin film filter is useful as a three-terminal filter module for WDM.

  ADVANTAGE OF THE INVENTION According to this invention, the deformation | transformation which arises in transparent substrates, such as optical glass, is small, and the optical component mounting module which can obtain the stable optical characteristic, and an optical communication module using the same are obtained.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment of the present invention) will be described below with reference to the accompanying drawings.
(Embodiment 1)
FIG. 1 is a diagram showing a WDM (Wavelength Division Multiplexing) three-terminal filter module which is a type of optical communication module used in wavelength division multiplexing optical communication equipment and the like. In the WDM three-terminal filter module 100 shown in FIG. 1, the WDM thin film filter element 50 of the first embodiment is used. A WDM three-terminal filter module 100 shown in FIG. 1 includes a two-fiber ferrule 10 as an optical fiber holding member through which a first optical fiber 11 for incident light and a second optical fiber 12 for reflected light are disposed, And an end face of the two-core ferrule 10 through which the ends of the first optical fiber 11 and the second optical fiber 12 are exposed. 10a and the end surface 20a of the single-core ferrule 20 where the end portion of the third optical fiber 21 is exposed are arranged to face each other. Further, between the two-core ferrule 10 and the single-core ferrule 20, a first collimator lens 30 is disposed opposite to the two-core ferrule 10, and a second collimator lens 40 is opposed to the single-core ferrule 20, respectively. Between the first collimating lens 30 and the second collimating lens 40, a WDM thin film filter element 50 composed of a first partial element 51 and a second partial element 52, which are two optical components, is disposed. The two-core ferrule 10, the single-core ferrule 20, the first collimator lens 30, the second collimator lens 40, and the WDM thin film filter element 50 are formed on a rectangular substrate (not shown) made of, for example, silicon. Has been implemented. For the substrate, hard materials such as ceramics, glass, and plastic can be used in addition to silicon.

  As the first optical fiber 11, the second optical fiber 12, and the third optical fiber 21, single-mode fibers having a diameter (core diameter) of 125 μm are used. The single-core ferrule 20 and the two-core ferrule 10 have a substantially cylindrical shape, and the diameter is 1.5 mm and the length is 10 mm. The single-core ferrule 20 and the two-core ferrule 10 are made of quartz glass. As a material constituting the single-core ferrule 20 and the two-core ferrule 10, in addition to quartz glass, ceramics having crystal particles mainly composed of quartz, zirconia, alumina, silicon nitride aluminum nitride, cordierite, mullite, etc., crystallization Glass, metal, or plastic is suitable, and the material can be appropriately selected according to the use and required accuracy. A through-hole having a diameter of 126 μm for inserting the third optical fiber 21 is formed in the single-core ferrule 20. The diameter of the third optical fiber 21 is slightly larger than the diameter (125 μm), and the third optical fiber 21 can be inserted. The two-core ferrule 10 is formed with two through-holes having a diameter of 126 μm so that the first optical fiber 11 and the second optical fiber 12 can be inserted.

  Furthermore, as the first collimating lens 30 and the second collimating lens 40, so-called aspherical lenses having different curvatures at the central portion and the peripheral portion of the lens are used. The diameters of the first collimating lens 30 and the second collimating lens 40 were set to 1.5 mm, which is the same as that of the single-core ferrule 20 (and the two-core ferrule 10). The first collimating lens 30 and the second collimating lens 40 were obtained by heating the optical glass BK-7 and press-molding it with a mold.

  FIG. 2 is a diagram for explaining the first embodiment of the WDM thin film filter element 50. A WDM thin film filter element 50 shown in FIG. 2 is a first optical substrate 511 made of a light-transmitting material such as glass, and a thin film in which a dielectric layer is laminated on the first optical substrate 511 as will be described later. A first partial element 51 made of a certain dielectric multilayer film 512, a second optical substrate 521 having a structure similar to this, and a second partial element 52 made of a dielectric multilayer film 522 which is a thin film are included. As shown in FIG. 2, the subelements (51, 52), which are two optical components, are assembled with their dielectric multilayer films (512, 522) facing each other.

  3A and 3B are diagrams for explaining two disassembled subelements of the WDM thin film filter element 50. FIG. 3A shows the first subelement 51, and FIG. 3B shows the second subelement 52. FIG. It is. As described above, the first partial element 51 and the second partial element 52 are both stacked on the first optical substrate 511 (second optical substrate 521) and the first optical substrate 511 (second optical substrate 521). A dielectric multilayer film 512 (dielectric multilayer film 522) which is a thin film. The first optical substrate 511 or the second optical substrate 521 is formed of a light-transmitting material, such as an acrylic resin, a methacrylic resin, a polycarbonate resin, a polyolefin resin (particularly amorphous polyolefin), or a polyester resin. , Polystyrene resin, epoxy resin, glass and the like. Among these, a glass substrate is preferable. The thickness of the first optical substrate 511 or the second optical substrate 521 is preferably 0.3 mm to 3 mm.

  As will be described later, the dielectric multilayer film 512 (dielectric multilayer film 522) formed on the first optical substrate 511 (second optical substrate 521) has a low refractive index layer and an optical path length of λ / 4. Two cavities 512a and cavities 512b (cavities 522a and 522b) having a structure in which a plurality of mirror layers paired with a refractive index layer are stacked are laminated via a coupling layer 513 (coupling layer 523), and An antireflection film 514 (antireflection film 524) is laminated thereon. The thickness of the dielectric multilayer film 512 or the dielectric multilayer film 522 is not particularly limited, but is usually 10 μm or more.

  FIG. 4 is a diagram for explaining the structure of the cavity 512a constituting the dielectric multilayer film 512 of the first partial element 51, which is one of the components of the WDM thin film filter element 50. FIG. The other cavities 512b, 522a, and 522b have the same structure and will not be described. The cavity 512a shown in FIG. 4 has a thickness of λ / 4 optical path length symmetrically with respect to the spacer layer 515 having a thickness that is an integral multiple of λ / 2 of the optical path length. A plurality of mirror layers each having a pair of high refractive index layer H and low refractive index layer L are stacked in series. In general, about 14 to 16 mirror layers (a combination of the high refractive index layer H and the low refractive index layer L) in the cavity 512a are laminated. Further, in the WDM thin film filter element 50 having a structure in which the first partial element 51 and the second partial element 52 are combined, the total number of cavities may be at least 2, preferably 4 or more. Therefore, the total number of mirror layers of the WDM thin film filter element 50 as a whole exceeds at least 50 layers.

The material for forming the dielectric multilayer film 512 or the cavity 512a of the dielectric multilayer film 522 is not particularly limited, but examples of the material for forming the high refractive index layer H include TaO _x , TiO _x , ZnS, ZnSn, and GaP. , InP, Si, Ge, SiGe _x , SiN _x , SiC _x , ZrO _x , NbO _x , YO _x and mixtures thereof. Examples of the material for forming the low refractive index layer L include SiO _x , MgF ₂ , AlO _x , SiO _x C _y , SiO _x N _y , MgO _x , or a mixture thereof. Here, x is a numerical value representing the stoichiometric composition ratio or a numerical value adjusted for controlling the optical characteristics based on the numerical value representing the stoichiometric composition ratio. Specifically, as the high refractive index layer H, TiO ₂ , Ta ₂ O ₅ , ZrO ₂ , CeO ₂ , ZnS, ThO ₂ , HfO ₂ , Nb ₂ O ₅ , Pr ₆ O _11, etc. And mixtures thereof. Among these, Ta ₂ O ₅ is preferable. Similarly, what is used as the low refractive index layer L includes MgF ₂ , SiO ₂ , Na ₅ Al ₃ F ₁₄ , Na ₃ AlF ₆ , CaF _{3 and the} like, and mixtures thereof. Among these, SiO ₂ is preferable. In addition, examples of the material used as the intermediate refractive index layer include Y ₂ O ₃ , PbF ₂ , MgO, Al ₂ O ₃ , CeF ₃ , La ₂ O ₃ , WO ₃ , MoO ₃ , and the like. Mixtures may be used as appropriate.

  Note that examples of the material for forming the spacer layer 515, the bonding layer 513, the bonding layer 523, the antireflection film 514, and the antireflection film 524 include the same materials as those for forming the cavity 512a and the like.

  The dielectric multilayer film 512 or the dielectric multilayer film 522 is formed on the first optical substrate 511 or the second optical substrate 521, respectively, by the vacuum film forming method using the dielectric material described above. As the vacuum film formation method, for example, various film formation methods such as a vacuum deposition method, a sputtering method, a chemical vapor deposition method, and a laser ablation method can be used. When using the vacuum deposition method, ion deposition is performed by ionizing a part of the vapor deposition vapor flow and applying a bias to the substrate side in order to improve the film quality, cluster ion beam method, and ion irradiation using another ion gun. It is effective to use the assisted vapor deposition method. Examples of the sputtering method include a DC reactive sputtering method, an RF sputtering method, and an ion beam sputtering method. Examples of the chemical vapor phase method include a plasma polymerization method, a light-assisted vapor phase method, a thermal decomposition method, and a metal organic chemical vapor phase method.

  As described above, in the WDM thin film filter element 50 to which the present embodiment is applied, the first partial element 51 and the second partial element 52 which are two optical components are formed on the respective optical substrates. The dielectric multilayer film 512, which is a thin film, and the dielectric multilayer film 522 are assembled to face each other. The first partial element 51 and the second partial element 52 are designed by separating the multilayer film portion of the target optical element into two predetermined structures and laminating them on separate substrates. After processing into these forms, the optical elements can be constructed by assembling them with the multilayer film surfaces facing each other.

  The WDM thin film filter element 50 adopts such a structure in which two optical components are combined, so that the number of dielectric thin films stacked in each partial element can be reduced, and the total number of multilayer film portions can be reduced. The film thickness can be reduced. As a result, the stress applied to the first optical substrate 511 or the second optical substrate 521 in each partial element becomes smaller than that in the case where all the dielectric thin films are stacked on a single substrate, thereby It is possible to reduce deformation and change in optical characteristics due to stress in the partial element. Furthermore, when the optical component mounting module such as the optical communication module is configured by combining the two optical components as described above, the characteristics of the entire module can be ensured with higher accuracy.

  Furthermore, by combining two subelements each having a thin film laminated dielectric multilayer film face to face, it is possible to select a combination that takes advantage of the advantages of each subelement. For example, one subelement A has good stopband characteristics on the short wavelength side, but insufficient characteristics on the long wavelength side, and the other subelement B has good stopband characteristics on the long wavelength side. If the characteristics on the short wavelength side are insufficient, by combining these, it becomes possible to configure an optical element that satisfies the good performances of both. Further, when the partial element A is manufactured, the performance thereof is examined, and the partial element B is manufactured by designing to compensate for the insufficient performance of the partial element A, so that an improvement in productivity can be expected.

  The thin film filter element 50 for WDM to which the present embodiment is applied has a structure in which two partial elements are combined, so that the position of the partial elements, the angle with respect to the optical axis, and the like can be adjusted independently. Compared with the conventional method, the degree of freedom of adjustment increases. For example, two subelements can be configured with an offset. It is also possible to combine the two subelements so as to form a predetermined angle as a result of optimization of their position and angle. In the WDM thin film filter element 50 to which the present embodiment is applied, an example in which the dielectric multilayer films 512 and 522 having the same laminated structure are used for the first partial element 51 and the second partial element 52 is used. Although shown, the dielectric multilayer films having different structures may be configured and used in each of the partial elements. From the viewpoint of optical characteristics, each partial element can be configured by appropriately combining elements having arbitrary characteristics.

Here, the operation of the WDM three-terminal filter module 100 will be described.
A plurality of lights having different wavelengths are multiplexed and transmitted through the first optical fiber 11 (in this description, the first wavelength included in the light is λ1 and the second wavelength is λ2). The light emitted from the first optical fiber 11 enters the first collimating lens 30, is converted into parallel light, and is emitted from the first collimating lens 30. The light emitted from the first collimating lens 30 enters the WDM thin film filter element 50. Here, the WDM thin film filter element 50 has a characteristic that light of a specific wavelength (for example, wavelength λ1) is transmitted and light of another specific wavelength (for example, λ2) is reflected. As a result, the light of wavelength λ1 is transmitted through the WDM thin film filter element 50 and incident on the second collimating lens 40, converted into focused light, and emitted from the second collimating lens 40. Then, the light having the wavelength λ1 emitted from the second collimating lens 40 enters the third optical fiber 21 in a condensed state, and is transmitted through the third optical fiber 21. On the other hand, the light of wavelength λ 2 is reflected from the WDM thin film filter element 50, enters the first collimator lens 30 from the opposite direction, is converted into focused light, and is emitted from the first collimator lens 30. Then, the light of wavelength λ2 emitted from the first collimating lens 30 enters the second optical fiber 12 in a condensed state and is transmitted through the second optical fiber 12. By adopting such a configuration, the multiplexed light can be separated into light of wavelength λ1 and light of wavelength λ2.

(Embodiment 2)
FIG. 5 is a diagram for explaining a WDM three-terminal filter module using the WDM thin film filter element of the second embodiment. The WDM thin film filter element 60 used in the WDM three-terminal filter module 200 shown in FIG. 5 is configured by offsetting two partial elements (a first partial element 61 and a second partial element 62). That is, the first partial element 61 and the second partial element 62 which are the two partial elements constituting the WDM thin film filter element 60 are, for example, blocked when the respective dielectric multilayer surfaces are assembled to face each other. The opposing positions of the dielectric multilayer film surfaces are combined so as to exhibit the good performance of each partial element in the band characteristics. As described above, the two subelements (the first subelement 61 and the second subelement 62) are offset to form an optical element having the good characteristics of each subelement. it can. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

(Embodiment 3)
FIG. 6 is a diagram for explaining a WDM three-terminal filter module using the WDM thin film filter element of the third embodiment. The WDM thin film filter element 70 used in the WDM three-terminal filter module 300 shown in FIG. 6 has two partial elements (first partial element 71 and second partial element 72), and their positions and angles are optimized. As a result of adjusting the above, they are configured to be combined at a predetermined angle. That is, the first partial element 71 and the second partial element 72 which are the two partial elements constituting the thin film filter element for WDM 70 are assembled to each other when the respective dielectric multilayer film surfaces are assembled to face each other. The dielectric multilayer film surfaces are combined so as to form a predetermined angle so as to exhibit the good performance of the element.

  In the WDM thin film filter element 50, the WDM thin film filter element 60, and the WDM thin film filter element 70 described in the first embodiment, the second embodiment, and the third embodiment, each WDM is used. Dielectrics in which partial elements (first partial element 51 and second partial element 52, first partial element 61 and second partial element 62, first partial element 71 and second partial element 72) constituting the thin film filter element for use are opposed to each other The gap between the body multilayer films may be filled with a liquid or a fluid material having the same refractive index as each optical substrate. It is also possible to fill a liquid or fluid material having the same refractive index as the low refractive index layer. In this case, for example, the antireflection film 514 provided on the uppermost layer of the dielectric multilayer film 512 in the first embodiment is unnecessary. Further, the dielectric multilayer films facing each of the partial elements may be in close contact with each other, or may be in a form substantially separated via air. Alternatively, an adhesive layer adjusted to a predetermined refractive index value may be filled between them.

  In the present embodiment, the WDM thin film filter element 50 as an optical component mounting module and the WDM three-terminal filter module 100 as an optical communication module including the WDM thin film filter element 50 have been described. The optical component mounting module is not limited, and includes, for example, a laser mirror, an antireflection film, various optical filters (for example, a band pass filter for DWDM, a broadband filter for CWDM, a gain equalization filter, an edge filter), The present invention can be applied to a dispersion compensator, an optical attenuator, an interleaver, and the like, and can be applied to all optical component mounting modules configured using an optical component mounting module made of a dielectric multilayer film.

  Hereinafter, the present embodiment will be specifically described in Examples. The present embodiment is not limited to the examples.

(Measurement of optical properties)
In the WDM three-terminal filter module 100 shown in FIG. 1, the center wavelength is 1550.12 nm (34th of the WDM transmission channel grid set by the ITU), the transmission bandwidth is 0.8 nm or more, and the stop bandwidth is 2.5 nm or less. The transmittance spectrum of the designed 200 GHz WDM thin film filter element was measured using a tunable laser and a power meter, and optical characteristics (insertion loss, transmission band ripple, transmission bandwidth, stop bandwidth) were obtained. The center wavelength error is the difference between the center value of the wavelength bandwidth that is within −25 dB from the maximum value of the transmittance spectrum and the design value (1550.12 nm), and the transmission bandwidth is the maximum value of the transmittance spectrum. The stop bandwidth is a wavelength bandwidth that is within -25 dB from the maximum value of the transmittance spectrum.

(Preparation of thin film filter element for WDM)
A dielectric multilayer film is formed by ion beam sputtering on a glass (BK-7) substrate having a thickness of 3 mm using Ta ₂ O _{5 as} a high refractive index layer material and SiO ₂ as a low refractive index layer material. A thin film filter element for WDM was prepared. The configuration of the dielectric multilayer film is expressed as follows. That is, assuming that the film thickness at the optical path length λ / 4 in the high refractive index layer is H and the film thickness at the optical path length λ / 4 in the low refractive index layer is L, the structure of the dielectric multilayer film is as follows: Indicate.
(Notation example) Substrate / (HL) ^ 7 6H (LH) ^ 7

  In the notation example, first, a high refractive index layer and a low refractive index layer are alternately laminated on the glass substrate seven times with film thicknesses of H and L, respectively. Next, a high refractive index layer having a thickness of 6 times the film thickness H is laminated thereon, and further, a low refractive index layer and a high refractive index layer are alternately formed 7 times with L and H film thicknesses thereon. The laminated structure is shown in FIG.

The high refractive index layer and the low refractive index layer of the dielectric multilayer film were formed by sputtering a Ta target and a Si target, respectively, in a mixed gas of Ar and oxygen. The film formation procedure was as follows. The glass substrate was attached to a sputtering apparatus and evacuated. When the degree of vacuum reached 1 × 10 ⁻⁵ Pa, the glass substrate was heated to 200 ° C. using an infrared heater and degassed. Next, the glass substrate surface was reverse sputtered with a mixed gas of Ar and oxygen to clean the glass substrate surface. After cleaning, the temperature of the glass substrate was set to 100 ° C. to form a dielectric multilayer film. The refractive index of the Ta ₂ O ₅ film was 2.07 at a wavelength of 1550 nm, and the refractive index of the SiO ₂ film was 1.47 at a wavelength of 1550 nm.

(Example 1)
A WDM having a total of four cavities is formed on a glass substrate by forming a partial element having a dielectric multilayer film composed of two cavities having the structure described below, and facing each dielectric multilayer film surface. A thin film filter element was prepared. In addition, in the notation, the range enclosed by <<>> is each cavity.

First partial element substrate / << (HL) ^ 7 6H (LH) ^ 7 >> L << (HL) ^ 7 14H (LH) ^ 7 >>
Second partial element substrate / << (HL) ^ 7 6H (LH) ^ 7 >> L << (HL) ^ 7 14H (LH) ^ 7 >>

(Example 2)
On the glass substrate, as described below, the first partial element and the second partial element are designed to have independent laminated structures, and have a center wavelength of 1550.12 nm, a transmission bandwidth of 0.8 nm, and a stop bandwidth of 2 The optical characteristics of the bandpass filter designed to 5 nm were measured in the same manner as in Example 1. The results are shown in Table 1.

First partial element substrate / << (HL) ^ 7 6H (LH) ^ 7 >> L << (HL) ^ 7 14H (LH) ^ 7 >>
Second partial element substrate / << (HL) ^ 7 H8LH (LH) ^ 6 >> L << (HL) ^ 7 14H (LH) ^ 7 >>

  In addition, after forming an antireflection film having a structure of 0.36H 1.32L on the cavities of the respective partial elements, each of them has a predetermined size (1.4 mm × 1.4 mm × 1.0 mm in thickness). After processing, two subelements were assembled. The thin film filter element for WDM composed of the two partial elements thus prepared was fixed between the two collimating lenses of the WDM three-terminal filter module 100 shown in FIG. 1, and the optical characteristics were measured. The results are shown in Table 1.

(Comparative example)
On the glass substrate, a dielectric multilayer film in which four cavities having the structure described below were integrally formed was formed. In addition, the range enclosed in << in the description is each cavity.
Substrate / << (HL) ^ 7 6H (LH) ^ 7 >> L << (HL) ^ 7 14H (LH) ^ 7 >> L) ^ 2 << (HL) ^ 7 4H (LH) ^ 7 >>

  Next, an antireflection film having a structure of (0.36H 1.32L) is formed on the laminate of the cavities, and then the predetermined size (1.4 mm × 1.4 mm × thickness 1.0 mm) is formed. The thin film filter element for WDM was prepared. The WDM thin film filter element thus prepared was fixed between the two collimating lenses of the WDM three-terminal filter module in the same manner as in the example, and the optical characteristics were measured. The results are shown in Table 1.

  From the results shown in Table 1, the thin film filter element for WDM (Example) in which the dielectric multilayer films of two subelements each having a dielectric multilayer film composed of two cavities are combined face to face is a glass substrate. It can be seen that by reducing the stress of the dielectric multilayer film formed thereon, distortion and deformation of the glass substrate are reduced, and as a result, changes in the optical constant as an optical element are reduced. In particular, the distortion of the glass substrate due to the stress of the dielectric multilayer film is reduced, the angle of incident light with respect to the dielectric multilayer film surface of the optical element is made uniform, and the stop bandwidth and insertion loss are improved. I understand. On the other hand, it can be seen that the WDM thin film filter element (comparative example) having a conventional structure has particularly large insertion loss, transmission band ripple and stop band width, and unstable optical characteristics.

  The thin film filter element for WDM to which the present invention is applied includes, for example, an optical mirror, an antireflection film, various optical filters (for example, a band pass filter for DWDM, a broadband filter for CWDM, a gain equalization filter, an edge filter), a dispersion The present invention can be applied to many uses of optical elements such as a compensator, an optical attenuator, and an interleaver.

It is a figure explaining the 3 terminal filter module for WDM which is a kind of optical communication module to which this Embodiment is applied. It is a figure explaining 1st Embodiment of the thin film filter element for WDM. It is a figure explaining two partial optical component mounting modules of the thin film filter element for WDM. It is a figure for demonstrating the structure of the cavity which comprises the dielectric material multilayer film of the thin film filter element for WDM. It is a figure explaining 2nd Embodiment of the thin film filter element for WDM. It is a figure explaining 3rd Embodiment of the thin film filter element for WDM. It is a figure explaining the deformation | transformation of the glass substrate by the conventional dielectric multilayer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... 2 core ferrule, 20 ... Single core ferrule, 30 ... 1st collimating lens, 40 ... 2nd collimating lens, 50, 60, 70 ... Thin film filter element for WDM, 51, 61, 71 ... 1st partial element, 52 , 62, 72 ... second partial element, 73 ... light beam, 74 ... glass substrate, 75 ... dielectric multilayer film, 100, 200, 300, 400 ... three-terminal filter module for WDM, 512, 522 ... dielectric multilayer film

Claims (7)

A first partial element having a thin film formed on at least the first optical substrate;
A second partial element having a thin film formed on the second optical substrate,
An optical component mounting module, wherein the thin film side of the first partial element and the thin film side of the second partial element face each other.   2. The thin film formed on the first optical substrate and the thin film formed on the second optical substrate are laminates having at least two types of layers having different refractive indexes. The optical component mounting module described. Two optical substrates facing each other;
A thin film provided between the two optical substrates, in which at least two types of layers having different refractive indexes are laminated;
An optical component mounting module comprising:   The optical component mounting module according to claim 3, wherein the thin film is separated and fixed to a predetermined thickness. An optical fiber held by an optical fiber holding member;
A lens that converts light from the optical fiber into parallel or focused light;
A thin film filter element on which light transmitted through the lens is incident,
The thin film filter element includes a first partial element in which a thin film is formed on a first optical substrate and a second partial element in which a thin film is formed on a second optical substrate, with the respective thin film sides facing each other. An optical communication module.   6. The optical communication module according to claim 5, wherein the thin film filter element separates or transmits light having a predetermined wavelength from light transmitted through the lens.   The thin film is a dielectric multilayer film having a high refractive index layer formed of a dielectric material having a high refractive index and a low refractive index layer formed of a dielectric material having a low refractive index. The optical communication module described.

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