JPH03233501A - Optical multilayered film filter element and production thereof - Google Patents

Abstract

PURPOSE:To obtain the ultra-thin type optical filter element which is free from deformation, such as warpage, and has good moisture resistance by separating multilayered films of highly compacted optical filters from a glass substrate. CONSTITUTION:The optical filter element 1 is formed of the thin films of the optical filters consisting of the multilayered structure alternately laminated with high-refractive layers 3 and low-refractive layers 4 as its constituting element. The high-refractive layers 3 consist of an optical material having a relatively high refractive index, has the dense compsn. having no adsorptivity of moisture, etc., and exhibits a specified compressive internal stress. The low- refractive layers 4 consist of an optical material having a relatively low refrac tive index, has the dense compsn. having no adsorptivity of moisture, etc., and exhibits the compressive internal stress approximately equal to the compressive internal stress of the high-refractive layers. The thin films 2 of the optical filters with which the compressive internal stress between the glass substrate and the multilayered films is of no problem, unlike the conventional filters, and which have a good yield and excellent moisture resistance are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical multilayer filter element and a method for manufacturing the same. In particular, the present invention relates to an ultra-small and ultra-thin optical multiplexing/demultiplexing filter element used in optical communications, etc., and a method for manufacturing the same.

[Conventional technology]

-i, the optical multilayer film filter material utilizes the interference of light by the multilayer film to selectively transmit or reflect only the end of a specific wavelength βn range. Optical multilayer film filter elements have a laminated structure in which nonmetallic optical materials with different refractive indexes are stacked one on top of the other, and have conventionally been formed on a glass substrate using a vacuum vapor tube. By changing the film thickness and refractive index of each layer, a filter with an arbitrary half-value width for an arbitrary center wavelength can be created.
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Such optical multilayer filter elements are widely used as optical multiplexing/demultiplexing filters in optical multiplex communications and the like. That is, the optical multiplexing/demultiplexing filter is inserted at a branch point of an optical waveguide network made up of optical fibers, and separates and combines each wavelength component. For the second reason, the optical multiplexing/demultiplexing filter has an ultra-small size and an ultra-thin size of about several tens of meters to prevent optical loss.

A conventional optical multiplexing/demultiplexing filter has a structure in which optical materials having different refractive indexes are alternately laminated on a glass substrate having a thickness of several tens of μm using a vacuum evaporation method. In order to manufacture such a filter, conventionally, a multilayer film is vacuum-deposited on a glass substrate, and then the glass substrate is polished to a depth of several tens of millimeters, and then cut into pieces of several millimeters square. Alternatively, it has been manufactured by depositing a multilayer film on a glass substrate that has been polished to a depth of several tens of degrees.

[Problem that the invention attempts to solve]

However, since conventional optical multiplexing/demultiplexing filters have a multilayer film structure deposited by vacuum evaporation, the film quality is porous and has a problem of poor weather resistance, particularly moisture resistance. In other words, since the multilayer film is porous, it adsorbs moisture or alcohol, which changes the transmission frequency characteristics of the filter, making it impossible to perform accurate optical multiplexing and demultiplexing, and causing noise to be mixed into multiplex communications. was there. In view of these problems, a first object of the present invention is to provide an ultra-small and ultra-thin optical multilayer filter element that has excellent weather resistance, particularly moisture resistance. In order to achieve the first object, the present invention utilizes an optical multilayer film having a dense composition that does not adsorb moisture or the like.

By the way, as in the conventional case, after a multilayer film having a dense composition is fixed on a glass substrate, glass 2! When an ultra-thin optical filter is manufactured by polishing a temporary layer to a thickness of several tens of pounds, the dense multilayer film exhibits strong compressive internal stress against the glass substrate.
The glass substrate may be damaged during the polishing stage. Even if it were polished without breaking, the glass substrate would be deformed due to the strong compressive internal stress, making it difficult to use. In view of these difficulties, a second object of the present invention is to manufacture an ultra-thin optical filter element made of a dense multilayer film and having excellent weather resistance without being damaged or deformed.

[Means for solving problems]

In order to achieve the first object, the optical filter element according to the present invention has a single optical filter thin film having a multilayer structure in which high refractive layers and low refractive layers are alternately laminated. The high refractive layer is made of an optical material with a relatively high refractive index, has a dense composition that does not adsorb moisture, etc., and exhibits a certain compressive internal stress. The low refractive layer is made of an optical material with a relatively low refractive index, has a dense composition that does not adsorb moisture, etc., and exhibits a compressive internal stress approximately equal to that of the high refractive layer.

In order to achieve the above second object, the method for manufacturing an optical filter thin film according to the present invention includes a preparation step of preparing a carrier soluble in a solvent.

Subsequently, a deposition step is performed in which a high refractive index optical material and a low refractive index optical material are alternately deposited on the soluble carrier to form a laminated optical filter thin film.

Finally, a separation step is performed in which the soluble carrier is dissolved in a solvent and the optical filter thin film is peeled off to obtain a single optical filter thin film.

[For production]

According to the present invention, the ultra-thin optical filter element is composed of a multilayer film having a dense composition that does not adsorb moisture, etc., and has excellent weather resistance, particularly moisture resistance. In addition, since the high refractive index layer and the low refractive index layer constituting the multilayer film exhibit substantially the same compressive internal stress, no internal strain is accumulated between the layers, resulting in stability in their shape and dimensions.

Further, according to the method for manufacturing an optical filter thin film according to the present invention, the optical filter thin film is obtained as a single multilayer film peeled from a carrier. Therefore, it is possible to manufacture an optical filter thin film with a high yield, unlike the conventional method where compressive internal stress between the glass substrate and the multilayer film poses a problem.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a first embodiment of an optical multi-layer filter element. As shown in the figure, the optical filter element 1 is composed of a single multilayer film 2. However, in actual use, it goes without saying that it can be used in combination with other optical members or optical parts. The multilayer film 2 has a multilayer structure in which high refractive layers 3 and low refractive layers 4 are alternately laminated. The high refractive layer 3 is made of an optical material with a relatively high refractive index, has a dense composition that does not adsorb moisture, and exhibits a certain compressive internal stress. Furthermore, the low refractive layer 4 is made of an optical material with a relatively low refractive index, has a dense composition that does not adsorb moisture, and exhibits a compressive internal stress approximately equal to that of the high refractive layer 3.The refractive index of each refractive layer By appropriately setting the thickness and thickness, it is possible to obtain an optical filter multilayer film 2 having desired optical selection frequency characteristics. In order to be used as a wave filter element, it has an area of several angles and a film thickness of about several tens of degrees.For example, by stacking 60 layers of high refractive layer 3 and low refractive layer 4 each having a layer thickness of 0.25 mm, a film can be formed. A multilayer film 2 with a thickness of 1511 nm can be obtained.

For example, Ta 905 can be used as the optical material with a high refractive index constituting the high refractive layer 3, and 5in9 can be used as the optical material with a low refractive index constituting the low refractive layer 4. These optical materials are laminated by a deposition process using accelerated energy particles and have a dense composition that does not adsorb water or solvents such as alcohol. As a deposition process using accelerated energy particles, for example, an ion-assisted vacuum evaporation method is used.

FIG. 2 is a perspective view showing a second embodiment of the optical filter element according to the present invention. As shown in the figure, the optical filter element 10 is composed of a single multilayer film 2 as in the first embodiment. In this embodiment, the multilayer film 2 includes an adjustment layer 5 in addition to the laminated portion of the high refractive layer 3 and the low refractive layer 4. This adjustment layer 5 has a layer thickness adjusted to obtain a desired thickness of the multilayer film 2. That is, the optical filter element T-10 has, in addition to the laminated portion having a filtering function, an adjustment layer having only a function of adjusting the thickness of the multilayer film 2. The adjustment layer 5 is made of the same optical material as the low refractive layer 4, for example, and preferably has a dense composition that does not adsorb moisture, like the laminated portion.

Next, the physical characteristics of the optical filter element according to the present invention will be explained in detail with reference to FIG. FIG. 3 is a graph showing the internal stress of a single layer film formed by depositing various optical substances on a glass substrate by ion-assisted vacuum deposition. The vertical axis indicates the internal stress of the single layer deposited film,
The upper side shows the compressive internal stress and the lower side shows the tensile internal stress based on the 0 level. Compressive internal stress acts in a direction that applies compressive strain to the bonding surface of the glass substrate, and tensile stress conversely acts in a direction that imparts tensile strain to the bonding surface of the glass substrate. The horizontal axis indicates the ion current density of assist ions used in the ion-assisted vacuum evaporation method. The ion-assisted vacuum deposition method irradiates the deposition surface with ions, which are accelerated energy particles, during vacuum deposition to densify the deposited film. Therefore, the higher the ion current density, the more densification progresses. By using such an ion-assisted vacuum deposition method, a refractive layer having a dense composition that does not adsorb moisture can be formed. When an optical oxide is used as the material for the refractive layer, oxygen ions are preferred as the accelerated ion particles. As shown in FIG. 3, when the ion current density is 0, that is, when normal vacuum evaporation is performed, the high refractive index material TlO2 exhibits tensile internal stress, and the low refractive index material S102 exhibits tensile internal stress. They exhibit compressive internal stresses with approximately the same magnitude. Therefore, in the past, optical filter elements were manufactured by laminating TiO and 5IO2 on a glass substrate using a normal vacuum evaporation method. T
The tensile internal stress of lO2 and the compressive internal stress of SiO2 cancel each other out, so that there is virtually no stress on the glass substrate.

However, when a normal vacuum evaporation method is used, the evaporation also densifies the deposited layer, resulting in a porous layer. Therefore, there is a problem in moisture resistance due to the adsorption of water. In contrast, in the present invention, the deposited layer is made denser by using, for example, an ion-assisted vacuum deposition method. As shown in FIG. 3, as densification progresses, all the refractive layers composed of various optical materials come to exhibit compressive internal stress. Therefore, it has been extremely difficult to deposit a refractive layer having such a strong compressive internal stress on a glass substrate as in the past. This is because the compressive internal stress may cause damage or deformation of the glass substrate. Therefore, in the present invention, the optical filter element is constituted by a partially suspended multilayer film separated from the substrate. In particular, by controlling the ion current density under conditions such that the compressive internal stress of the high refractive layer and the compressive internal stress of the low refractive layer are approximately equal, and forming a multilayer film using ion-assisted vacuum evaporation, it is possible to By eliminating distortion, it is possible to obtain a single optical filter multilayer film that is stable in size and shape. For example, T as a high refractive index material
When aQO5 is used and SIO2 is used as a low refractive index material, as is clear from Fig. 3, the compressive internal stress of both is approximately equal over a wide range of ion current density, and the strain is substantially reduced. It is possible to create a single-piece optical filter multilayer film.

Next, a method for manufacturing a single-piece optical filter thin film according to the present invention will be explained in detail. FIG. 4 is a process diagram showing a first embodiment of the manufacturing method according to the present invention.

In the step shown in FIG. 4(A), a carrier 6 soluble in a solvent is prepared. In this embodiment, the carrier 6 is a flat carrier made of a soluble substance. As the soluble substance, a single crystal of common salt which is soluble in water or a metal soluble in acid or alkali such as aluminum can be used.

Alternatively, a metal oxide such as alumina may be used as the carrier material. As the solvent, a predetermined etchant may be used in addition to acids and alkalis. However, the solvent should be selected so as not to affect the substances constituting the filter thin film.

Subsequently, in the step shown in FIG. 4(B), the soluble carrier 6
A high refractive index optical material and a low refractive index optical material are alternately deposited on the optical filter layer 2 to form a laminated optical filter multilayer film 2. As a deposition method, a normal vacuum evaporation method can be used, but in the second case, the multilayer film is porous and has moisture absorption properties. Therefore, in order to deposit the multilayer film 2 having a dense composition that preferably does not adsorb water, it is preferable to use an ion-assisted vacuum deposition method, an ion-blating vacuum deposition method, or a sputtering method.

By utilizing accelerated energy particles, these deposition methods can form a dense refractive layer that does not adsorb moisture. In addition, the ion blasting vacuum evaporation method is a method in which a substance evaporated by electron beam heating is accelerated in plasma and deposited on the surface of a carrier. For example, Ta2O5 can be used as the high refractive index optical material forming the high refractive layer, and SiO2 can be used, for example, as the low refractive index optical material forming the low refractive layer.

In the step shown in FIG. 4(C), the optical filter thin film 2
While still being supported on the soluble carrier 6, it is cut and finely divided into desired dimensions. For this cutting, for example, a wafer scriber used in semiconductor manufacturing can be used. At this time, it is preferable to set the cutting line slightly deeper than the thickness of the multilayer film 2 and cut the surface part of the soluble carrier 6 as shown in the figure. Note that the cooling liquid used during cutting must not dissolve the soluble carrier 6.

Finally, in the step shown in FIG. 4(D), the soluble carrier 6
is immersed in a specific solvent to dissolve it, and the finely divided optical filter multilayer film 2 is peeled off. As a result, the individual subdivided optical filter multilayer film pieces are separated, and a single optical filter element 1 can be obtained. For example, if the soluble carrier 6 is composed of a single crystal plate of common salt, water can be used as the solvent. Furthermore, when an aluminum metal plate is used as the soluble carrier, an acid can be used as the specific solvent.

FIG. 5 is a process diagram showing a second embodiment of the method for manufacturing a single-piece optical filter thin film according to the present invention.

In the step shown in FIG. 5(A), the temporary substrate 7 made of an insoluble substance! f-equipped.

In the step shown in FIG. 5(B), a film carrier 6 made of a soluble substance is formed on the surface of the temporary substrate 7.

This coated carrier 6 can be obtained, for example, by sputtering or vacuum vaporizing metal aluminum.

This soluble wave membrane carrier 6 is soluble in a specific disoting solution.

In the step shown in FIG. 5(C), a high refractive index optical material and a low refractive index optical material are alternately deposited on the film carrier 6 to form a laminated optical filter multilayer film 2. This deposition step is performed in the same manner as in the first embodiment shown in FIG.

In the step shown in FIG. 5CD), the deposited optical filter multilayer film 2 is cut while being supported on the film carrier 6 to be subdivided into desired -j dimensions. This cutting step is also performed in the same manner as in the first embodiment. In this embodiment, it is preferable to cut deeper than the thickness of the multilayer film 2 and to make a cut in the carrier film 6 at the same time.

However, it is not always necessary to make a cut.

Finally, in the step shown in FIG. 5(E), the film carrier is dissolved in a solvent at an angle of 7 to peel off the subdivided optical filter multilayer film 2. At this time, if the coated carrier has a notch and its end face is exposed, the dissolution of the coated carrier is promoted by the effect of side etching. In this manner, the segmented optical filter multilayer film 2 is separated from the temporary substrate 7 to obtain individual single optical filter elements 1.

〔Effect of the invention〕

As described above, according to the present invention, by separating the densified optical filter multilayer film from the glass substrate, the compressive internal stress of the multilayer film against the glass substrate, which has been a problem in the past, is released, and deformation such as warping is prevented. This has the advantage that it is possible to obtain an ultra-thin optical filter element with good weather resistance, particularly moisture resistance. Furthermore, according to the manufacturing method of the present invention, the glass substrate is not damaged during polishing due to the compressive internal stress of the multilayer film, nor is it deformed due to the compressive internal stress, unlike in the past, and the manufacturing yield can be significantly improved. It has the effect of being able to.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the first embodiment of the optical filter element, Fig. 2 is a perspective view showing the second embodiment of the optical filter element, and Fig. 3 is the relationship between the internal stress of the deposited film and the ion current density. FIG. 4 is a graph showing the first method of manufacturing an optical filter element.
FIG. 5 is a process diagram showing a second embodiment of the method for manufacturing an optical filter element. 1... Optical filter element 2... Multilayer film 3...
High refractive layer 4...Low refractive layer 5...Adjusting layer 6...Soluble carrier 7...Insoluble temporary substrate

Claims (1)

[Scope of Claims] 1. A high refractive layer made of an optical material with a relatively high refractive index, which has a dense composition that does not adsorb moisture, etc., and exhibits a certain compressive internal stress; The constituent element is a single optical filter thin film consisting of a multilayer structure in which low refractive layers are alternately laminated with low refractive layers that are made of an optical material and have a non-adsorbent property for moisture, etc., and exhibit approximately the same compressive internal stress. Optical filter element. 2. The optical filter element according to claim 1, wherein the optical filter thin film includes an adjustment layer having a layer thickness adjusted to obtain a desired film thickness. 3. Claim 1 in which the high refractive layer is a densely deposited layer of Ta_2O_5 and the low refractive layer is a densely deposited layer of SiO_2.
The optical filter element described in . 4. A preparation step of preparing a carrier soluble in a solvent, and a deposition step of alternately depositing a high refractive index optical substance and a low refractive index optical substance on the soluble carrier to form a laminated optical filter thin film. A method for producing a single-piece optical filter thin film, which comprises a separation step of dissolving a soluble carrier in a solvent and peeling off the optical filter thin film. 5. The manufacturing method according to claim 4, further comprising the step of cutting the optical filter thin film supported on the soluble carrier to subdivide it into desired dimensions. 6. The manufacturing method according to claim 4, wherein the preparation step is a step of preparing a flat carrier made of a soluble substance. 7. The manufacturing method according to claim 4, wherein the preparation step is a step of forming a coating carrier made of a soluble substance on the surface of a temporary substrate made of an insoluble substance. 8. The manufacturing method according to claim 4, wherein the deposition step is a step of depositing a dense laminated layer that does not adsorb moisture or the like by utilizing accelerated energy particles. 9. The manufacturing method according to claim 8, wherein the deposition step is a step of alternately depositing optical materials with a high refractive index and optical materials with a low refractive index that generate approximately the same compressive internal stress in a dense stack. 10. The manufacturing method according to claim 9, wherein the deposition step is a step of alternately depositing Ta_2O_5 and SiO_2.