JPS60189708A - Photocoupler - Google Patents

Abstract

PURPOSE:To obtain an inexpensive photocoupler which is manufactured easily and has high precision and good efficiency by forming a grating, optical waveguide, and buffer layer of an LB film. CONSTITUTION:The LB film 31 having a plane type grating formed is adhered to a substrate 31. An LB film 33 is provided in recesses of the grating part of the LB film 31, and the LB film 31 and LB film 33 are in level with each other, thereby forming a plane type, i.e. phase difference type grating 36. Further, the LB films 31 and 33 have the same surface property. When the surface of the LB film 31 is hydrophilic, the surface of the LB film 33 is also made hydrophilic. When the surface of the LB film 31 is hydrophobic, on the other hand, the surface of the LB film 34 is also made hydrophobic. A reflecting layer 35 is formed by vapor-depositing an Al film. The film thickness of the LB film 34 is so set that light 36-b which is diffracted by the grating and projected directly on the substrate side 32 and light 36-a which is projected on the LB film side 34, reflected by a reflecting layer 35, and projected on the substrate side 32 interfere with and intensify each other. In this case, an LB film 34 functions as a buffer layer. The projection light beams 36-a and 36-b intensity each other when their optical path difference is an integral multiple of the wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical coupler, and more particularly to an optical coupler in which a grating is installed in an optical waveguide.

In recent years, with the development of optical integrated circuits, there has been a demand for highly accurate and efficient optical couplers.

However, in the past, in order to obtain a coupler with desired precision, a high degree of microfabrication technology was required, which resulted in a drawback of low yield and, therefore, high cost.

Here, a conventional grating type optical coupler will be explained. FIG. 1 is a cross-sectional view of a conventional planar grating type optical coupler. In this figure, 2 is a substrate, for example,
glass, plastic or lithium niobate (LiNb)
A transparent substrate such as O3) or an opaque substrate such as silicon or ceramics is used. An optical waveguide l is provided on the surface of the substrate 2. The optical waveguide l has a higher refractive index than the substrate 2. For example, when lithium niobate is used as a substrate, an optical waveguide l having a film thickness of about 0.5 to 5 mm can be obtained by thermally diffusing titanium (Ti) onto its surface. Alternatively, if glass with a refractive index of 1.5 is used as a substrate, a surface with a refractive index of 1.55 (
A glass with a wavelength of 6328A (for example, Corning Co., Ltd. product name C-70511) is sputtered to a film thickness of 0.5A.
A film is formed to a degree of 5 to 5 to obtain a leading wavepath l.

Reference numeral 6 denotes a grating having a pitch of 0.3 to 1 μm and a depth of 0.1 to 0.2 μm. When the incident light 3 enters the optical coupler configured in this way, the light 4 propagates through the waveguide by total reflection, is diffracted by the grating 6, and the emitted light 5 is taken out.

In this case, it is generally difficult to manufacture the grating.

The flat type is more difficult than the relief type. This is because a completely rectangular grating is preferable in order to more effectively exhibit the function of the grating 6, or it is generally not easy to obtain such a completely rectangular grating.

The present invention has been made in view of these points, and it is an object of the present invention to provide an optical coupler that is easy to manufacture and inexpensive.

A further object of the present invention is to provide a highly accurate and efficient optical coupler.

Furthermore, the present invention provides an optical coupler having a planar grating so that other structural elements (buffer layer) that are difficult to construct on the relief grating (described later) can be easily constructed. The purpose is to

The present invention uses the single molecule accumulation method shown below to
The basic idea is to obtain a monomolecular stacked film, and further improvements have been made to enable a grating format.

Hereinafter, the single molecule accumulation method which is the basis of the present invention and the single molecule accumulation film formed thereby will be explained.

The monomolecular accumulation method is a method in which a monomolecular film formed on the water surface is transferred to the substrate surface and layered one by one to create an ultra-thin film.
Langmuir Prodget (LB) named after the inventor
Also called law. Here, the qt molecular film refers to a uniform film with a thickness of one molecule, and a film obtained by accumulating this film is called a cumulative film.

The molecules constituting such a monomolecular film and a composite film must necessarily have at least a hydrophobic part and a hydrophilic part in the same chemical structure. The most typical hydrophobic moiety is a long-chain alkyl group, which generally has 5 to 30 carbon atoms, preferably 10 to 25 carbon atoms. Furthermore, both straight-chain alkyl groups and branched alkyl groups are useful as long as the length of the alkyl chain is appropriate. Examples of groups constituting other hydrophobic moieties include olefinic hydrocarbon groups such as vinylene, vinylidene, and acetylene, condensed polycyclic phenyl groups such as phenyl, naphthyl, and anthranyl, and chain polycyclic groups such as biphenyl and terphenyl. There are phenyl groups, etc., and these may be used alone or in combination, or may be located at the end or in the middle of the alkyl group mentioned above. The most typical hydrophilic moieties include, for example, carboxyl groups and their metal salts and amine salts, sulfonic acid groups and their metal salts and amine salts, sulfonamide groups, amide groups,
Amino group, imino group, hydroxyl group, quaternary amino group,
Examples include 1 oxyamino group and 7 oxyimine groups, diazonium group, guanidine group, hydrazine group, phosphoric acid group, silicate group, aluminate group, and the like. However, it is not always possible to form a monomolecular film or a cumulative film with any combination of hydrophobic and hydrophilic parts. In order to obtain a monomolecular film and a cumulative film by the single molecule accumulation method, the steps in the manufacturing process are as follows:
First, a monomolecular film must be formed on the water surface,
If hydrophilicity is stronger than hydrophobicity, the molecule dissolves in water and becomes an aqueous solution; conversely, if hydrophobicity is stronger, it separates into two phases. A medium molecular film is formed on the water surface when hydrophobicity and phyllophilicity are appropriately balanced. At this time, the molecules as a whole do not float or sink, but instead direct their hydrophilic parts toward the water phase and are adsorbed at the air-water interface, forming a monomolecular film. Therefore, the molecules constituting the monomolecular film and the cumulative film are required to have a proper balance of hydrophobic parts and woody parts.

Next, the LB film manufacturing apparatus and manufacturing method will be explained with reference to FIGS. 2(A) and 2(B). Here, the LB film refers to a monomolecular film and a cumulative film produced by a single-molecule accumulation method. The LB film manufacturing apparatus illustrated in FIGS. 2(A) and 2(B) was devised by Kuhn's research group based on the principle of the aforementioned Rankmuir-Blodgett method (LB method). A frame 15 made of polypropylene is suspended horizontally inside a shallow and wide rectangular water tank 14 to partition a water surface 23. The frame 15 functions as a two-dimensional cylinder as described below. A polypropylene float 16 is floating inside the frame 15. The width of the float 16 is made slightly narrower than the inside of the frame 15 so that it can move smoothly from side to side as a two-dimensional piston. A weight 17 is tied to the float 1G via a slider 18 in order to pull the float 1G to the right. Generally, the repulsive force of a magnet is used to stop the float 16 or push it back to the left. For this purpose, a magnet 19 fixed to the float 16 and a counter magnet 20 that can be moved left and right are provided. That is, when pushing back, the counter magnet 20 is
If it is brought close to , a repulsive force will work and the float 1B will be pushed back.

Instead of such weights and magnets 18, 20, it is also possible to directly move the float 16 from side to side using a rotary motor or pulley. The left and right suction nozzles 22 are connected to a suction pump (not shown) via suction pipes 21, respectively.

In the middle molecule accumulation method, clean pure water is used to prevent impurities from entering the monomolecular film and the cumulative film, but cleaning the water surface 23 and cleaning the monomolecular film that is no longer needed A suction pump and a suction nozzle 22 (not shown) are utilized for quick removal of. In that case, the water surface 23 is purified by quickly sucking it out with the suction nozzle 22 while sweeping away the middle molecular layer and the like that are no longer needed with the float 16. In this way, move the float I6 to the left end of the clean water surface 23 ~ 5X10-3mo
When a few drops of a thin solution of a film constituent material dissolved in a volatile solvent such as Hensen's chloroform at a concentration of 1/1 are dropped on the water surface, a monomolecular film is left on the water surface 231 after the solvent evaporates. This monomolecular film exhibits two-dimensional behavior at the water surface 23-L. When the areal density of molecules is low, it is called a gas film of a second-order gas, and the equation of state of a second-order redundant ideal gas holds between the occupied area per molecule and the surface pressure. The occupied area and surface pressure are automatically and continuously measured by a measuring device (not shown). The occupied area and the amount of change thereof can be determined from the left and right movement of the float 16. The surface pressure measuring device uses a method to measure the surface pressure indirectly from the difference in surface tension between pure water and the water surface covered with a medium molecular film, and a float 16 floating to separate the pure water surface and the monomolecular film surface. There are methods that directly measure the two-dimensional pressure applied to the surface, and each has its own characteristics. From the gas film state, when the float Iθ is gradually moved to the right to gradually reduce the extent of the water surface where the middle molecular film develops and increase the areal density, the minute-1-interphase-ge action becomes stronger, and 2 It passes through a liquid film of dimensional liquid and turns into a solid film of two-dimensional solid. When it comes to the solid film,
The molecular alignment and height are well aligned, resulting in the high degree of order and uniform ultra-thin film properties required for optical materials. Therefore, it becomes possible to transfer the monomolecular film to the surface of a clean substrate 24 (for example, a substrate made of glass, ceramic, plastic, or metal is used) while maintaining the state of the solid film. . It is also possible to accumulate any number of additional monolayers on top of the monolayer deposited on the substrate 24.

In general, the surface pressure of a monolayer suitable for cumulative operation is 15~
It is 30dyne/c11. Outside this range, the arrangement and orientation of molecules may be disturbed and the film may peel off, which is inappropriate. However, in special cases, for example, depending on the chemical structure of the membrane structure material, temperature conditions, etc., the suitable surface pressure value may fall outside the above range.
-The above range is just a guideline. A driving device (not shown) that drives the counter magnet 20 from side to side is controlled by a surface pressure control device (not shown) so that the monomolecular film can always maintain a constant surface pressure selected within the range of conditions suitable for cumulative operation. controlled. For example, during the cumulative operation process, the monolayer is deposited on the substrate 2.
4, the surface pressure will naturally be low, so move the counter magnet 20 and accordingly move the float 16 to compress the area of the developed film and correct the low surface pressure to maintain a constant surface pressure. The maintenance operation is done automatically. There are roughly two types of methods for transferring the monomolecular film 26 (see FIG. 3) from the water surface 23-L to the surface of the substrate 24.

- is the vertical immersion method, and the others are the horizontal attachment method. The vertical immersion method is a monomolecular film formed by dipping the substrate 24 in the direction across the film, that is, in the vertical direction, while applying a constant surface pressure suitable for cumulative operation to the monolayer film 26 on the water surface 23. This is a method of transferring 26. The horizontal adhesion method is a method in which the substrate is held horizontally, brought as close as possible to the water surface 23 from the top, slightly tilted, and the monomolecular film 26 is touched from one end for adhesion.

Each has its pros and cons. In the case of the vertical dipping method, three types of membrane structures can be formed as shown in FIG. 3 depending on the molecules constituting the membrane and the conditions for manufacturing the membrane. Figure 3 (A) shows an X type in which the film adheres only during immersion; Figure 3 (B) shows a Y type in which the film adheres both during immersion and lifting; Figure 3 (C) shows a Y type in which the film adheres during pulling up. There is an X-type, in which only a film is attached.

Therefore, the X type is attached with the hydrophobic portion facing the surface of the substrate 24 and the hydrophilic portion facing outward. The X type is attached with the woodphilic portion Q facing the surface of the substrate 24 and the hydrophobic portion P facing outward. On the other hand, in the case of the horizontal deposition method, only an X-shaped cumulative film can be produced, but it is relatively easier to produce an X-shaped cumulative film with a superior cumulative ratio, which will be described later, than in the vertical dipping method. Moreover, this horizontal pricking method is suitable for producing a protein medium molecule film.

However, in either method, the substrate 24
The surface must be sufficiently clean interfacially. If the surface of the substrate 24 is insufficiently cleaned, the film may peel off,
It becomes difficult to produce a cumulative film.

For example, if a glass substrate is immersed in a chromic acid mixture, washed with distilled water, and then dried in a clean air stream, its surface becomes completely hydrophilic.

For example, if you thoroughly apply molten iron stearate (m) to a cleaned solid surface and rub it thoroughly with a clean cloth such as gauze, then apply stearate with the mother wood group facing the solid surface. A medium molecular film of iron acid (m) is formed and the surface becomes completely hydrophobic.

In order to clarify the accumulation operation more specifically, the operation of producing a Y-shaped accumulation film by the vertical dipping method will be explained according to FIG. The illustrated example (FIG. 4) is a case where a tree-friendly substrate 24 is used. The first layer of the monomolecular film 2B attached to the hydrophilic substrate 24 is attached during the lifting process as shown in FIG. This is the order in which dilute solutions of the constituents are added dropwise. Then, the surface pressure is increased, and after reaching a surface pressure suitable for producing a cumulative film, the substrate 24 is pulled out. A suitable pulling rate for cumulative film production is 0.1 to locm/win. However, suitable conditions may exist outside this range depending on the film constituent materials and film manufacturing conditions.

In the first lifting process, the first layer of heavy molecular film
41, with the hydrophobic portion P facing the surface of the substrate 24 and the hydrophobic portion P on the outside.

In the next immersion (pulling) process (Fig. 4 (B)), the second
The molecular film in the layer is attached with the hydrophobic portion P facing the surface of the substrate 14 and the hydrophilic portion Q facing outward. In addition, the first layer 28
After applying A, it was found that if a second layer of 28b or more was applied after sufficiently drying in the air to remove moisture and other solvents, the cumulative film would not peel off and the cumulative operation would be more successful. 3
For layers 28c and above, repeat the same operation (4th
(see Figure (C)), it is possible to fabricate a cumulative film with a calendar number of d.

[In the odd-numbered layers of the Y-type film in the ΔV example, the hydrophilic portion Q always faces the surface of the substrate 24, and the hydrophobic portion P faces outward.

It has been confirmed through many experiments that the thickness of the cumulative film produced in this manner is equal to the length of the molecule (10 to 80 A) times the cumulative number of times (t@number of layers of the molecular film). Other factors that affect the way the film adheres are:
These include (1) the chemical structure of the membrane constituents, (2) the pH of the aqueous phase and the type and concentration of salts contained, (3) temperature, and (4) the type of substrate.

For example, fatty acid salts form more stable cumulative films than pure straight-chain fatty acids, and salts of calcium, barium, cadmium, etc. are particularly good. In this case, the composition and deposition of the cumulative film differ depending on the pH of the aqueous phase. That is, generally PH4
If the pH is below 8, it will be pure fatty acid; if the pH is 9 or higher, it will be a film of metal salts; if the pH is in the middle, a cumulative film containing these will be obtained. Note that an index called cumulative ratio is used to visually display how the cumulative film is attached. The cumulative ratio refers to the ratio of the area of the film actually transferred from the water surface 23 to a predetermined area on the substrate. Note that the membrane area transferred from the water surface can be determined by measuring the time during which the float 16 moves. For example, a cumulative ratio of 0 means that no film was attached at all.
The cumulative ratio l indicates the case where the membrane is ideally transferred. Generally, the metal salt has a higher cumulative ratio than the free acid.

The substrate 24 used in the present invention may be any suitable substrate, and the dimensions of the substrate are not particularly limited. The thickness of the LB film in the present invention is determined by the repeated accumulation described above.
It is in the range of 0.5-5 pL. A material suitable for the grating type optical coupler of the present invention has appropriate optical properties,
Any material that forms an LB film may be used.

Particularly suitable are, for example, fatty acids, especially straight-chain fatty acids containing 10 to 30 carbon atoms (stearic acid, araxic acid) and their salts (cadmium am), the polymerizable LB membranes described below. The refractive index of these materials is easily controlled by appropriately selecting the length of the CH2 chain or by adding metal ions.

The formed LB film is patterned by known means. Also, other patent applicants of this applicant (applicant number undetermined)
According to the novel patterning method 1, a desired shape is patterned. The patterned LB film functions as a waveguide.

Next, a method for forming a planar grating according to the present invention will be explained with reference to FIG. A photopolymerizable material is used as the LB film material. In this case, the LB film is assumed to be the aforementioned Y-type film.

First, the polymerizable LB film 7 is formed on the substrate 2 of glass, ceramics, plastics, silicon oxide, etc. by the above-mentioned medium molecule accumulation method. Next, in order to obtain the desired shape of the optical coupler, after patterning exposure with light or electrons (Fig. 5 (1)), the LB of the last exposed part is Remove the film (Fig. 5 (1), (2)). This most polymerized portion is not eluted by the developer (FIG. 5(2)).

Next, a polymerizable LB film 1O is formed on 1- of the polymerized LB film 9 by a single molecule accumulation method. The polymerizable LB film IO is preferably of the same type as the polymerizable LB film 7, but may be of a different type as long as it satisfies the optical conditions.

In this case, if the surface of the polymerizable LB H# 9 (the surface in contact with the polymerizable LB film If it is hydrophobic, it is necessary to adjust the thickness of the polymerizable LBIIIO so that the surface of the polymerizable LB film 10 becomes hydrophilic.

As is clear from the single molecule accumulation method described above, L B
The surface of H is necessarily either lignophilic or hydrophobic, and it is extremely easy to control this. LBBO of desired shape
2, so that only the L B Il* layered on the surface remains.
The patterning exposure described above is performed.

In this case, the grating pattern is also exposed simultaneously or one after the other. After developing this, a relief pattern of LBHMIL shown in FIG. 5(4) is obtained. At this time, the four parts of the grating 11 are polymerized L B H'J,
9, and the convex portions are the surfaces of LBII and IO, so when one is a woody surface, the other is a hydrophobic surface. Next, LBBi12 and 1 are applied to the polymerized LB film 11.
3 is formed by the single molecule accumulation method described above. This and S,
Polymerization LBIIj! If the lower surface of the recess in No. 11 is hydrophilic, LBB
The first layer of i12 is attached so that the parent wood base faces the substrate side. Therefore, in the convex part, a hydrophobic group and a hydrophilic group (LBBi1
2 (first layer) will face each other. On the contrary, polymerized LB
If the lower surface of the concave portion of the film 11 is hydrophobic, the first layer of LBBi 12 is deposited with the hydrophobic side facing the substrate side. LBBi1
2. The thickness should be the same as the depth of the brating (that is, the surface of the convex portion 11 and the surface 13 should be on the same plane) (Fig. 5 (4)). The fact that the LBBi12 film thickness is extremely easy to control is clear from the characteristics of the single molecule accumulation method, which takes about the same amount of repeated accumulation of single molecules.

The LBBi 12 and 13 laminated on the polymerized LB film 11-L may or may not be polymerizable, but the refractive index is required to be smaller than that of the polymerized LB film.

Next, when the structure shown in Fig. 5 (4) is attached to an ultrasonic waterproof tank (not shown) and ultrasonic waves are generated under appropriate conditions, the bonding force is weak (@The water curtain and parent tree base face each other). Because I am LBBi
Peeling (removal) occurs at the contact surface of 1212. Since the hydrophilic groups (or hydrophobic groups) face each other at the contact surface between the LB film and 13, the bonding force is relatively strong, and no peeling occurs. Thus, selective exfoliation (removal) The invention will now be described by way of one embodiment with reference to FIG. In this figure, a substrate 32 is provided with LBBa2O on which a planar grating is formed. LB[33 is attached to the concave of the LBBa2O grating part 36, and the LBBa2
The surface with O33 is on the same plane, and an upper type, that is, a phase difference type grating 36 is formed. Also L
BBa2O and 33 have the same surface properties. That is, if the LBBa2O surface is hydrophilic, the LBBa2O surface must also be made hydrophilic.

Conversely, if the LBBa2O surface is hydrophobic, the LBBa2O surface must also be made hydrophobic.

A LBBa2O film is formed on the grating. LB
The condition is that the Ba2O refractive index is lower than the LBBa2O refractive index. LBBa2OLBBa2O are preferably made of the same material or have the same refractive index. Functions as a LBBa2O buffer layer. A reflective layer 35 is attached to the upper surface of the LB film (Hanwha layer) 34. The reflective layer 35 is formed by depositing an AI film.

The LBn film 34 may be uniformly formed on the LB films 3, . At that time, polymerization is 0
In the case of a formed LB film, in the case of a non-polymerized film formed by pattern fog light, another patent application of the present applicant (application number undetermined)
A desired shape is patterned by the patterning method according to the above. The thickness of the LBBa2O film is such that light 36-b is diffracted by the grating and directly emitted to the substrate side 32.
and the light 36-a reflected by the LB film forming 34 side emission reflection layer 35 and emitted to the substrate side 32 due to interference.
They need to be set so that they strengthen each other. In this case L
The B film 34 functions as a buffer layer as described above.

An appropriate LBBa2O film thickness condition under which the emitted light beams 36-a and 36-b strengthen each other due to interference can be easily derived from known optical laws. However, film thickness control below the wavelength of light is required. The emitted light beams 36-a and 36-b have different optical path lengths as shown in FIG. When this optical path difference is an integral multiple of the wavelength, they become stronger.

In this way, the optical coupler of the present invention, which includes a grating constituted by the LB layer shown in FIG. 6, a leading waveguide, and a reflective layer provided with a reflective layer, can utilize the light emitted to the reflective side of the substrate 32, so that the output efficiency can be improved. This has the effect of being able to determine the direction of the Furthermore, the present invention provides an inexpensive optical coupler and provides an optical coupler having a planar grating in which a buffer layer can be easily constructed.

<Example> - Substrate ~ White plate glass, lommX IQmm, 0.
3mm (Si0281%, 820313%, Na2O
4%t' AIz032%)・Grating pitch
200 people depth 0. Thickness of IJL/LB film formation 0.9 well tt IQ // For 0,1/l 12.13 /l O,1 pL ” 14 tt O,2°・Incident light -He-NeLz-The (111328 people) - Semiconductor laser (8300A) - Olefin type (photopolymerizable) - Polymerizes vinyl stearate by exposing it to gamma rays.

・Dissolves in alcohol at the end of exposure.

-w-Trichosenic acid is polymerized by applying an electron beam (10 to 100 KeV).

・Electron beam exposure equipment (JEOL TEBX-2B) ・Diacetylene derivatives are polymerized by ultraviolet light.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional optical coupler, and FIG. 2 (A). (B) is a perspective view and a cross-sectional view of the LB film forming apparatus, Figures 3 (A), (B), and (C) are diagrams explaining three types of LB film configurations; Figure 4 (A), (B), (C) are LB
A diagram explaining the formation of a film, Figure 5 is (+), (2),
(3), (4). (5) is an explanatory diagram of the second step of forming the movable type crating of the present invention, and FIG. 6 is a sectional view of an embodiment of the present invention. 2-m=Substrate 7-- Monomer L film formation 8--1 Exposure 9-m=Polymerized LB film 10-1-Monomer L film formation+1--1 Polymerized LB film 12, 13-- Monomer L film formation 14-- Water tank 15- Frame 16-- Float 19, 20--One magnet 23-m=Water surface 24-m-Substrate 26-- Monomolecular film 31--One Optical waveguide 32--One Substrate 33, 34---- LB film 35-m-Reflection layer Particularly created by Canon Co., Ltd. Figure 1 Figure 6 Figure 2 (a) 1111 2 (1 (b) (A) Figure 3 j$ 4 11!511

Claims (1)

[Claims] An optical waveguide equipped with a grating, a buffer layer,
1. An optical coupler comprising a reflective layer, the grating, the optical waveguide, and a buffer layer or LB film.・