JP2009058780A - Optical filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical filter capable of reducing the stress, acting in the direction of warping a dielectric multilayer film, when removing a substrate from the dielectric multilayer film. <P>SOLUTION: This optical filter 1 has the first dielectric multilayer film 2 and the second dielectric multilayer film 4, alternately layered with a low-refractive index layer 8 and a high-refractive index layer 10 of an dielectric, and a resin layer 6 for bonding the first dielectric multilayer film 2 and the second dielectric multilayer film 4 along a layered direction A. The resin layer 6 has a refractive index which is substantially the same as that of the low-refractive index layer 8 or the high-refractive index layer 10, so as to constitute the optical filter 1 which is integrated with the first dielectric multilayer film 2, the resin layer 6 and the second dielectric multilayer film 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical filter, and more particularly to an optical filter including a dielectric multilayer film.

  In the optical communication field, when an optical filter is used to select and transmit light in a predetermined wavelength range, the optical filter is generally arranged in space. FIG. 5 is a schematic diagram illustrating an example of an optical system including an optical filter disposed in a space. As shown in FIG. 5, the diffused light 52 emitted from the first optical fiber 51 is converted into parallel light 54 through the first lens 53, and when the parallel light 54 passes through the optical filter 55, a predetermined wavelength range is obtained. The parallel light 54 passes through the optical filter 55, and the transmitted parallel light 54 is converted into convergent light 57 by the second lens 56 and is incident on the second optical fiber 58.

  When the optical filter 55 functions as an optical filter for a CWDM (Coarse Wavelength Division Multiplexing) system that performs optical wavelength division multiplexing at a wavelength interval of 20 nm, the optical filter 55 emits light in a wavelength range other than the 20 nm bandwidth. It is a bandpass filter that can block at -40 dB or less.

  In recent years, in order to enable high-density optical wavelength division multiplexing in the wavelength range of 1530 to 1565 nm, a DWDM (Dense Wavelength Division Multiplexing) system that performs optical wavelength division multiplexing at a wavelength interval of 0.8 nm has attracted attention. An optical filter that functions as an optical filter for a DWDM system is a band-pass filter that can block light outside a wavelength range of a bandwidth of 0.8 nm at −20 to −40 dB or less.

  When the optical filter 55 is formed of the dielectric multilayer film 59, a light-transmitting substrate 60 such as glass is prepared, and a film made of a large number of dielectrics is sequentially laminated thereon by a vacuum deposition method or the like. In the case of an optical filter for a CWDM system, about 60 to 70 layers of dielectric films are laminated, and the thickness of the dielectric multilayer film is about 20 to 40 μm. In the case of an optical filter for a DWDM system, since the bandwidth is very narrow, it is necessary to stack a larger number of dielectric films than for an optical filter for a CWDM system. As a result, the thickness of the dielectric multilayer film is about 40 to 80 μm.

  When the optical filter 55 is actually used, in the optical filter for the CWDM system, the substrate 60 is removed from the dielectric multilayer film 59, and only the dielectric multilayer film 59 is used. On the other hand, in the case of an optical filter for a DWDM system, it is used in a state where a substrate 60 is attached to a dielectric multilayer film 59 (see FIG. 5). The reason is that in the optical filter 55 for the DWDM system, since the number of layers of the dielectric film is large, the total stress acting between the layers increases, and when the substrate is removed from the dielectric multilayer film, the dielectric This is because the multilayer film is warped. Therefore, the thickness of the optical filter 55 for the DWDM system is a total thickness of the substrate 60 and the dielectric multilayer film 59, that is, about 0.5 to 1.0 mm.

  The above-described optical filter is not only spatially arranged, but may also be mounted on a substrate type optical multiplexer / demultiplexer using a resin substrate or a quartz substrate (for an optical filter for a DWDM system, for example, a patent Reference 1).

Japanese Patent Laying-Open No. 2006-98897 (FIG. 6)

  When the optical filter 55 for the DWDM system in a state where the substrate 60 such as glass is attached to the dielectric multilayer film 59 is spatially disposed, the light propagating through the optical filter 55 is parallel light. The insertion loss of light propagating through the substrate 60 is small.

  On the other hand, when the optical filter 55 for the DWDM system is mounted on the substrate type optical multiplexer / demultiplexer, the insertion loss of the propagating light increases. Specifically, when single-mode light is incident on the substrate 60, it is not parallel light, and is diffused and emitted at the interface of the substrate 60. If the substrate 60 is removed from the dielectric multilayer film 59, the insertion loss is reduced. However, as described above, the dielectric multilayer film 59 warps and cannot be used as the optical filter 55.

  Accordingly, an object of the present invention is to provide an optical filter capable of reducing stress acting in a direction in which the dielectric multilayer film is warped when the substrate is removed from the dielectric multilayer film.

  In order to solve the above-described problems, an optical filter according to the present invention includes a first dielectric multilayer film and a second dielectric multilayer film in which dielectric low-refractive index layers and high-refractive index layers are alternately stacked. And a resin layer for adhering the first dielectric multilayer film and the second dielectric multilayer film in the laminating direction. The resin layer includes the first dielectric multilayer film, the resin layer, and the second dielectric layer film. The dielectric multilayer film has substantially the same refractive index as that of the low refractive index layer or the high refractive index layer so as to constitute an integrated optical filter.

  According to the optical filter configured as described above, since the resin layer has substantially the same refractive index as that of the low refractive index layer or the high refractive index layer, the first dielectric multilayer film, the resin layer, and the first The two dielectric multilayer films can function as an integral optical filter. In addition, by interposing a resin layer between the first dielectric multilayer film and the second dielectric multilayer film, the stress generated in the first dielectric multilayer film and the second dielectric multilayer film is made resin. It is possible to reduce the stress acting in the direction of warping the dielectric multilayer film in the integrated optical filter.

  In an embodiment of the optical filter according to the invention, preferably the optical filter functions as an optical filter for a DWDM system.

  The optical filter functioning as an optical filter for the DWDM system has a larger number of dielectric films than the number of dielectric films of the optical filter for the CWDM system, and when the substrate is removed from the dielectric multilayer film, The dielectric multilayer film is warped. However, according to the configuration of the above-described embodiment, even if the number of dielectric films of the optical filter for the CWDM system is larger than the number of dielectric films, the stress generated between the dielectric films is relaxed by the resin layer. The stress acting in the direction of warping the multilayer film can be reduced.

  In this embodiment, more preferably, the first dielectric multilayer film functions as an optical filter for a CWDM system that transmits light in the first wavelength range, and the second dielectric multilayer film is the first dielectric multilayer film. An integrated optical filter that functions as an optical filter for a CWDM system that transmits light in a second wavelength range shifted to a wavelength lower than the wavelength range, and overlaps the first wavelength range and the second wavelength range Functions as an optical filter for the DWDM system.

  According to the optical filter configured as described above, the first dielectric multilayer film and the second dielectric multilayer film themselves are made of conventional optical filters for the CWDM system. Therefore, the first dielectric multilayer film and the second dielectric multilayer film can be manufactured by using a conventional film forming technique for an optical filter for a CWDM system. Furthermore, it is possible to obtain a first dielectric multilayer film and a second dielectric multilayer film that are free from warping and have excellent blocking characteristics. By matching the wavelength range between the lower limit wavelength of the first wavelength range and the upper limit wavelength of the second wavelength range to the wavelength range for the DWDM system, the first dielectric multilayer film, the resin layer, and the second wavelength range The optical filter formed by the dielectric multilayer film can function as an optical filter for the DWDM system.

  In the embodiment of the optical filter according to the present invention, the substrate used when laminating the dielectric is preferably removed.

  According to the optical filter configured as described above, since the substrate is removed from the dielectric multilayer film, there is no interface for diffusing single mode light, and the single mode propagating through the optical filter for the DWDM system is eliminated. Light insertion loss can be reduced.

  In an embodiment of the optical filter according to the invention, preferably the optical filter has 120 to 150 layers of dielectric.

  When a dielectric multilayer film is formed by continuously laminating 120 to 150 dielectric layers, the dielectric multilayer film warps when the substrate is removed from the dielectric multilayer film. However, in the configuration of the above embodiment, even if the dielectric has 120 to 150 layers, the dielectric is formed by the resin layer interposed between the first dielectric multilayer film and the second dielectric multilayer film. The stress acting in the direction of warping the multilayer film can be reduced.

  As described above, the optical filter according to the present invention can reduce the stress acting in the direction of warping the dielectric multilayer film when the substrate is removed from the dielectric multilayer film.

  First, a first embodiment of an optical device according to the present invention will be described with reference to FIG. FIG. 1 is a schematic view of an optical filter according to the present invention.

As shown in FIG. 1, the optical filter 1 includes a first dielectric multilayer film 2, a second dielectric multilayer film 4, a first dielectric multilayer film 2, and a second dielectric multilayer film 4. And a resin layer 6 that adheres in the laminating direction A. Each of the first dielectric multilayer film 2 and the second dielectric multilayer film 4 is formed by alternately laminating dielectric low refractive index layers 8 and high refractive index layers 10. The low refractive index layer 8 is made of, for example, a SiO ₂ dielectric, and in this case, the refractive index is 1.46. The high refractive index layer 10 is made of, for example, a TiO ₂ dielectric, and in this case, the refractive index is 2.40. In the embodiment shown in FIG. 1, the layer of the first dielectric multilayer film 2 and the layer of the second dielectric multilayer film 4 adjacent to the resin layer 6 are formed of the high refractive index layer 10, and the resin layer 6 is The low refractive index layer 8 is made of a material having substantially the same refractive index. As a result, the high refractive index layer and the low refractive index layer are alternately continued over the first dielectric multilayer film 2, the resin layer 6 and the second dielectric multilayer film 4. Forming. The refractive index of the resin layer 6 is preferably within a range of ± 0.020 with respect to the refractive index of the low refractive index layer 8 or the high refractive index layer 10, and may be within a range of ± 0.010. Further preferred. The resin layer 6 is formed of, for example, a silicone adhesive WR8962H manufactured by Kyoritsu Chemical Co., Ltd. In this case, the refractive index is 1.455.

  In an example of a method for forming the optical filter 1, first, a dielectric low refractive index layer 8 and a high refractive index layer 10 are alternately stacked on a substrate 12 to form a first dielectric multilayer film 2. . Further, the dielectric low refractive index layer 8 and the high refractive index layer 10 are alternately laminated on another substrate (not shown) to form the second dielectric multilayer film 4. Next, the first dielectric multilayer film 2 and the second dielectric multilayer film 4 are bonded with the resin layer 6. It is preferable to remove the substrate 12 used when laminating the dielectric from the first dielectric multilayer film 2 and the second dielectric multilayer film 4.

  The first dielectric multilayer film and the second dielectric multilayer film 4 preferably have a number of layers and a thickness that do not cause a single warp, for example, 50 to 80 layers, and more preferably 60 to 60 layers. 70 layers. Further, the total number of layers of the first dielectric multilayer film 2 and the number of layers of the second dielectric multilayer film 4 is the number of layers in which the resin layer 6 is directly laminated without interposing the warp. For example, 120 to 150 layers.

  In the optical filter 1 of this embodiment, since the resin layer 6 is interposed between the first dielectric multilayer film 2 and the second dielectric multilayer film 4, the stress in the first dielectric multilayer film 2 is The stress in the second dielectric multilayer film 4 is relaxed by the resin layer 6, and the optical filter 1 is prevented from warping even when the substrate 12 is removed.

  Further, the elastic modulus of the resin layer 6 is preferably 0.001 to 0.1 MPa, and more preferably 0.001 to 0.01 MPa. If the elastic modulus is greater than 0.1 MPa, the stress cannot be sufficiently relaxed, and warping may occur when the substrate is removed. In order to facilitate handling of the optical filter, the elastic modulus is preferably 0.001 MPa or more.

  The integral optical filter preferably functions as an optical filter for the DWDM system. Thereby, in the conventional optical filter for the DWDM system, it was necessary to leave the substrate 12 attached to the dielectric multilayer film in order to prevent warpage, but in the optical filter 1 according to the present embodiment, The substrate 12 can be removed. As a result, the thickness of the optical filter 1 can be reduced, and the substrate that diffuses the light is eliminated, so that the insertion loss of the optical filter 1 can be reduced.

  In general, a film forming technique for forming an optical filter for a DWDM system by a method of continuously laminating dielectrics without interposing a resin layer 6 is an optical filter for a CWDM system formed by a similar method. It is necessary to carry out with higher accuracy than the film forming technique. However, with the optical filter according to the present invention, the optical filter for the DWDM system can be easily formed by the conventional film forming technique for the optical filter for the CWDM system.

  The first form of the optical filter for the DWDM system is a conventional one, that is, one of the dielectric films of the optical filter for DWDM in which the dielectric is continuously laminated without interposing the resin layer 6. And a resin layer 6 having substantially the same refractive index.

  FIG. 2 is a diagram illustrating characteristics of a specific example of the first embodiment. In the specific example of the first mode shown in FIG. 2, the optical filter 1 is not warped even when the substrate is removed, the thickness is 50 μm, and light outside the wavelength range of 1552 ± 0.4 nm is −30 dB or less. I was able to shut off.

  In the second form of the optical filter for the DWDM system, the first dielectric multilayer film 2 functions as an optical filter for the CWDM system that transmits light in the first wavelength range, and the second dielectric multilayer film 4 Functions as an optical filter for a CWDM system that transmits light in the second wavelength range shifted to a wavelength lower than the first wavelength range, and by superimposing the first wavelength range and the second wavelength range The integrated optical filter 1 functions as an optical filter for the DWDM system.

  FIG. 3 is a diagram illustrating characteristics of a specific example of the second embodiment. The first dielectric multilayer film 2 is not warped even when the substrate is removed, and has a thickness of 30 μm. As shown in FIG. 3A, 1552.82 to 1572.82 nm (bandwidth of 20 nm) It was possible to block light outside the wavelength range of −30 dB or less. The second dielectric multilayer film 4 is not warped even when the substrate is removed, and has a thickness of 30 μm. As shown in FIG. 3B, the second dielectric multilayer film 4 has a band of 1533.6 to 1553.6 nm (band of 20 nm). Light outside the wavelength range of (width) could be blocked at -30 dB or less. The first dielectric multilayer film 2 and the second dielectric multilayer film 4 are formed by using a conventional optical filter forming technique for CWDM. The optical filter 1 obtained by bonding the first dielectric multilayer film 2 and the second dielectric multilayer film 4 with the adhesive layer 6 made of Kyoritsu Chemical's silicone adhesive WR8962H has no warpage, The thickness was 60 μm, and as shown in FIG. 3C, light in the wavelength range of 1558.68 to 1559.28 nm (band width of 0.8 nm) could be blocked at −30 dB or less. The obtained optical filter 1 was sufficiently usable in a DWDM system.

  FIG. 4 is a diagram in which the optical filter of the second embodiment described above is mounted on a substrate type optical waveguide. The optical filter 1 has a wavelength band of 1558.98 ± 0.3 nm from an input port drawn from a utility pole or the like to a video port out of light emitted from a single mode optical fiber or a single mode optical waveguide (not shown). Only light (video signal) is transmitted, and light (Internet protocol signal) having a wavelength of 1490 nm that needs to propagate only from an input port to an IP port connecting a personal computer or the like is reflected by the optical filter 1.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims. Needless to say, these are also included within the scope of the present invention.

  In the above embodiment, the low refractive index layer 8 and the high refractive index layer 10 are alternately arranged for each layer. However, by using an optical filter, a plurality of low refractive index layers 8 or high refractive indexes are used. Even if the layers 10 are adjacent to each other, the low refractive index layers 8 and the high refractive index layers 10 may be alternately arranged as a whole. Therefore, for example, the resin layer 6 having substantially the same refractive index as that of the low refractive index layer 8 is disposed adjacent to the low refractive index layer 8 of the first dielectric multilayer film 2 or the second dielectric multilayer film 4. May be. The resin layer 6 may have a refractive index substantially the same as that of the high refractive index layer 10.

  In the above embodiment, one kind of low refractive index layer 8 and one kind of high refractive index layer 10 are used for one optical filter 1, but a plurality of kinds of low refractive index layers 8 and high refractive indices are used. Layers may be used.

  In the above embodiment, the two dielectric multilayer films 2 and 4 are bonded with the resin layer 6. However, the three or more dielectric multilayer films have the same refractive index as that of the low refractive index layer 8 or the high refractive index layer 10, respectively. You may adhere by the resin layer which has.

It is the schematic of the optical filter by this invention. It is a figure which shows the characteristic of the 1st form of the optical filter for DWDM systems. It is a figure which shows the characteristic of the 2nd form of the optical filter for DWDM systems. It is the figure which mounted the optical filter for DWDM systems of the 2nd form in the substrate type optical multiplexer / demultiplexer. It is the schematic which shows an example of the optical system containing the optical filter arrange | positioned in space.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical filter 2 1st dielectric multilayer film 4 2nd dielectric multilayer film 6 Resin layer 8 Low refractive index layer 10 High refractive index layer 12 Board | substrate A Lamination direction

Claims (5)

A first dielectric multilayer film and a second dielectric multilayer film in which a low refractive index layer and a high refractive index layer of dielectric are alternately laminated;
A resin layer for adhering the first dielectric multilayer film and the second dielectric multilayer film in the stacking direction;
The resin layer is substantially the same as the low refractive index layer or the high refractive index layer so that the first dielectric multilayer film, the resin layer, and the second dielectric multilayer film constitute an integrated optical filter. An optical filter having the same refractive index.   The optical filter according to claim 1, wherein the integrated optical filter functions as an optical filter for a DWDM system. The first dielectric multilayer film functions as an optical filter for a CWDM system that transmits light in the first wavelength range;
The second dielectric multilayer film functions as an optical filter for a CWDM system that transmits light in a second wavelength range shifted to a wavelength lower than the first wavelength range,
The optical filter according to claim 2, wherein the integrated optical filter functions as an optical filter for a DWDM system by superimposing the first wavelength range and the second wavelength range.   The optical filter according to any one of claims 1 to 3, wherein a substrate used for laminating the dielectric is removed.   5. The optical filter according to claim 1, wherein the integral optical filter has 120 to 150 layers of dielectrics.

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