JPH0643328A - Multilayered optical waveguide and its production - Google Patents

Abstract

PURPOSE:To enable the power of interlayer propagating light to be controlled and to make size smaller and density higher by providing an optical coupling part where a part of the cores of three-dimensional optical waveguides and a part of the cores of the three-dimensional optical waveguides of the other layer are disposed in proximity to each other via a clad layer held therebetween. CONSTITUTION:A lower clad layer 12a, an interlayer clad layer 12b and an upper clad layer 12c are formed on a substrate 11 and a lower core 13a is formed within the interlayer clad layer 12b on the lower clad layer 12a. An upper core 13b is formed within the upper clad layer 12c on the interlayer clad layer 12b and an interlayer core 13c for optical coupling is formed above the lower layer core 13a in proximity thereto so as to intrude into the interlayer clad layer 12b physically continuously with the upper core 13b. The interlayer clad layer 13c and a part of the lower layer core 13a are in proximity to the extent of allowing optical coupling by holding the interlayer propagation layer 14 which is a part of the interlayer clad layer therebetween, by which the optical coupling part 15 is constituted. Then, the light power propagating in the different layers is controlled by changing the length or thickness of the interlayer propagation layer 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layered optical waveguide in which optical waveguides are laminated to enable propagation between layers, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a thin film optical waveguide composed of a clad layer and a core layer (waveguide layer) made of a thin film, a third-order optical waveguide in which light is confined in the plane direction of the thin film and a specific narrow band-like region along the plane is used as an optical waveguide. A multilayer optical waveguide is known in which a plurality of original optical waveguides are laminated to form a three-dimensional optical waveguide.
Although it is possible to miniaturize such a multilayer optical waveguide, reduce the capacity of an optical component using the optical waveguide, and increase the number of functions, on the other hand, a mechanism for propagating light propagated in an optical waveguide of one layer to another layer, that is, A mechanism for propagation between layers is required.

As an inter-layer propagation mechanism in such a multilayer optical waveguide, for example, RAVI SELVARAJ, HTLIN, and
JFMcDONALD, “Integrated Optical Waveguides
in Polyimide for Wafer Scale Integration, ”
Journal of Lightwave Technology, vol.6, no.6,
There is a mirror type inter-layer propagation mechanism described in pp1034-1044, June 1988. This mechanism will be described with reference to FIG. As shown in FIG. 6, the clad layers 2 a, 2 are formed on the substrate 1.
b, 2c, 2d are sequentially laminated, and the cladding layer 2
cores 3a and 3b extending in the plane direction in b and 2d, respectively.
Are formed. A core 3c, which is an optical waveguide for interlayer propagation, is formed in the clad layer 2c between the clad layers 2b and 2d so as to penetrate the clad layer 2c in the thickness direction and physically connect the cores 3a and 3b. The cores 3a and 3c, and the cores 3c and 3b are optically connected to each other via mirror surfaces 4a and 4b. Therefore, for example, the propagating light incident from the end surface of the core 3a is
The light is totally reflected on the mirror surface 4a and the optical path is bent 90 ° toward the upper layer to enter the core 3c, the core 3c to enter the upper core 3b, the light is totally reflected again on the mirror surface 4b and the optical path is again 90 °. It is bent and propagates through the core 3b.

[0004]

In the above-mentioned multilayer optical waveguide, since the optical waveguide for interlayer propagation that physically connects the core of the lower layer and the core of the upper layer is used, almost 100% of the propagation light power is different from each other. This is effective when it is desired to propagate to the optical waveguide of. However, in such a structure, in addition to the step of manufacturing a three-dimensional optical waveguide having only a single layer, a step of forming a mirror surface, which is relatively difficult to manufacture, and a step of forming a core of an optical waveguide for interlayer propagation are required. However, there is a problem that the manufacturing process becomes complicated. Further, in the interlayer propagation structure using such a mirror, it is possible to propagate almost 100% of the propagation light power, and only a part of the propagation light power is propagated to the optical waveguides of different layers, There is also a problem that another branching structure is required to multi-branch the optical waveguide into a plurality of optical waveguides in different layers.

In view of such circumstances, the present invention provides a multi-layer optical waveguide which can be manufactured by a simple process, can control the power of interlayer propagation light, and can be miniaturized and densified, and a manufacturing method thereof. The purpose is to

[0006]

A multi-layer optical waveguide according to the present invention that achieves the above object is a multi-layer optical waveguide in which a three-dimensional thin film waveguide including a core layer and a clad layer formed of thin films is laminated in multiple layers. And at least one optical coupling part in which a part of the core of the three-dimensional optical waveguide and a part of the core of one or more other three-dimensional optical waveguides are arranged in close proximity to each other with the cladding layer interposed therebetween. It is characterized by having.

On the other hand, a method of manufacturing a multilayer optical waveguide according to the present invention comprises a step of forming a thin film on a substrate to be a first clad layer of the optical waveguide, and a step of forming the first clad layer on the first clad layer.
Forming a first core of the three-dimensional optical waveguide by forming a thin film having a refractive index higher than that of the clad layer and patterning the thin film, and forming a first core on the first core more than the first core. A step of forming a thin film having a low refractive index as a second clad layer, and a step of etching a part of the second clad layer to locally form a processed portion having a reduced thickness, A thin film having a refractive index higher than that of the second clad layer is formed on the second clad layer, is formed on the processed portion, and is disposed close to a part of the first core. It includes a second core of the three-dimensional optical waveguide capable of being optically coupled to a part of the first core and a portion formed on the second cladding layer and physically coupled to at least the second core. Form the third core of the three-dimensional optical waveguide by patterning Characterized in that it comprises a step of at least.

Another method of manufacturing a multi-layered optical waveguide according to the present invention comprises a step of forming a thin film on a substrate to be a first clad layer of the optical waveguide, and a step of forming a thin film on the first clad layer. The first three-dimensional optical waveguide is formed by forming and patterning a thin film having a refractive index higher than that of the first cladding layer.
Forming the core of the first core and the first core on the first core.
Forming a thin film having a refractive index lower than that of the core as a second cladding layer, and forming a thin film having a refractive index higher than that of the second cladding layer on the second cladding layer. The second core of the three-dimensional optical waveguide, which is disposed close to the first core with the second cladding layer interposed therebetween and partially includes a portion capable of being optically coupled to the first core, is used as a pattern. And at least a step of forming by tanning.

[0009]

According to the multi-layered optical waveguide having the above-mentioned structure, the inter-layer propagation is caused by the interference effect of electromagnetic waves through the optical coupling portion in which the core of the three-dimensional optical waveguide and the core of the other layer of the three-dimensional optical waveguide are arranged close to each other. Is done. Further, the optical coupling section can control the power propagated between layers by changing the form of close proximity. Therefore, when multi-branching of propagating light is required between layers, interlayer propagation and branching can be performed at once by simply disposing one optical waveguide and a plurality of optical waveguides vertically adjacent to each other.

[0010]

EXAMPLES The present invention will be described below based on examples.

FIG. 1 conceptually shows a multilayer optical waveguide according to an embodiment. As shown in the figure, a lower clad layer 12a, an interlayer clad layer 12b and an upper clad layer 12c are sequentially formed on a substrate 11, and a lower core 13a is formed in the interlayer clad layer 12b on the lower clad layer 12a. There is. An upper core 13b is formed in the upper clad layer 12c on the interlayer clad layer 12b. The upper core 13b is physically continuous with the upper clad layer 12b and enters the inner clad layer 12b to be close to the lower core 13a. An interlayer core 13c for optical coupling, which is arranged above it, is formed. The interlayer core 13c and a part of the lower core 13a are in close proximity to each other with the interlayer propagation layer 14 which is a part of the interlayer clad layer interposed therebetween so that they can be optically coupled to each other, and form an optical coupling section 15.

In this embodiment, Si (silicon) is used as the substrate 11, and the cladding layers 12a to 12c have a refractive index of 1.4.
6 SiO ₂ thin film, cores 13a to 13c have a refractive index of 1.5
A Corning® glass thin film of 3 was used. Further, the cores 13a to 13c have a width of 1.2 μm and a thickness of 1.2 μm.
m, and the cladding layers 12a to 12c each have a thickness of 4 μm.
m. Further, the interlayer propagation layer 14 in the portion between the lower core 13a and the interlayer core 13c has a thickness of 1.2 μm and a length z of about 170 μm.

In such a multilayer optical waveguide, when a light having a wavelength of 1.3 μm, for example, is incident on the lower core 13a of the lower optical waveguide, this light is transmitted through the interlayer propagation layer 14 of the optical coupling portion 15 due to the interference effect of electromagnetic waves. Interlayer core 13c of the upper layer
Most of the optical power propagates to the
3c is propagated to the upper core 13b that is physically coupled to the upper core 13b. Thereby, inter-layer propagation is performed.

The interlayer propagation mechanism in the multilayer optical waveguide of the present invention as described above is based on the upper core (interlayer core 1) which is vertically adjacent.
3c) and the lower layer core (lower layer 13a) are used for the interference effect of electromagnetic waves, the optical power propagating to different layers can be changed by changing the length or thickness of the interlayer propagation layer 14. It is controllable. In general, the ratio p of the optical power transferred to different layers is represented by the following equation (1) according to the mode coupling theory of the optical waveguide. In the formula (1), Δ≡ (β _a −β _b ) / 2, β _a , and β _b are propagation constants of the upper and lower three-dimensional optical waveguides, κ is a coefficient of the two optical waveguides, and z is a coupling. Is the length of the adjacent three-dimensional optical waveguide relating to, that is, the length of the interlayer propagation layer 14 described in the first embodiment.

[0015]

[Equation 1]

Here, when the upper and lower three-dimensional optical waveguides have the same cross-sectional dimension and refractive index profile as in the first embodiment, the propagation constants of the two optical waveguides are the same, and therefore Δ = It becomes 0. Therefore, the ratio p of the optical powers to be transferred to different layers in the formula (1) is expressed by the following formula (2). p = sin ² (κz) (2) In the first embodiment, the interlayer propagation layer 14 of the upper and lower three-dimensional optical waveguides in which the ratio p of the optical power transferred from the lower layer to the upper layer is almost 100%. Since the length z is about 170 μm, from the formula (2), if the length of the interlayer propagation layer 14 is ½ of the above-mentioned case, the power of almost half of the light propagated to the lower layer core is obtained. It is possible to propagate light between layers to the upper core. Since the optical power propagating between layers can be controlled in this way, an optical bus structure or the like using an optical waveguide can be easily obtained. Further, since the power of light propagated between layers varies depending on the wavelength of light, if the length and thickness of the interlayer propagation layer 14 are optimally designed, light of different wavelengths propagates through the optical waveguide in each layer. An optical waveguide can also be realized.

In the embodiment shown in FIG. 1, one lower core 1
Although one interlayer core 13c is provided in close proximity to 3a via the interlayer propagation layer 14, a plurality of interlayer cores 13c may be provided as shown in FIG. In this case, the propagation light of the lower layer core 13a can be branched to the plurality of interlayer cores 13c and propagated between the layers. Needless to say, at this time, it is not always necessary to arrange the multi-layer core 13c on the lower layer core 13a.

Further, in the above embodiment, a part of the lower core 13a and the interlayer core 13c in the other layer are formed by the interlayer propagation layer 1.
4 are arranged close to each other to form an optical coupling portion 15, and the interlayer core 13c and the upper core 13b of the other layer are physically coupled.
It goes without saying that the upper core 13b and the upper core 13b may be coupled via another optical coupling section.

Next, an example of manufacturing the multilayer optical waveguide shown in FIG. 1 will be described with reference to FIG. (1) A Si wafer is used as the substrate 11 and the Si wafer (1
1) A 4 μm SiO ₂ film is formed on the surface by a thermal oxidation method to form a clad layer 12a (FIG. 3A). (2) A Corning 7059 (registered trademark) glass film was deposited on the SiO ₂ film (12a) by a sputtering method to obtain 1.2.
After forming a core layer of μm, patterning of the core is performed by using photolithography technology and reactive ion etching technology, and the core 13a of the three-dimensional optical waveguide having a width of 1.2 μm is formed.
Are formed (FIG. 3 (B)). (3) A SiO ₂ film is deposited on the core 13a so as to have a thickness of 4 μm on the core 13a by the CVD method to form an interlayer clad layer 14b (FIG. 3).
(C)). (4) Using the photolithography technique and the reactive ion etching technique, the interlayer clad layer 12b is provided at a position overlapping a part of the lower core 13a.
The groove 16 having a length of about 170 μm is accurately etched along the longitudinal direction of the so that the distance between the groove 16 and the lower core 12a is 1.2 μm to form the interlayer propagation layer 14 (FIG. 3).
(D)). (5) On top of this, a Corning 7059 (registered trademark) glass film was deposited again by 1.2 μm by bias sputtering, and the core of the three-dimensional optical waveguide with a width of 1.2 μm was formed by the same patterning method as the lower core 12a. Thirteen
b and 13c are formed (FIG. 3 (E)). (6) A SiO ₂ film having a thickness of 4 μm is deposited on this by a CVD method,
A multilayer optical waveguide was completed by using the clad layer 12c (FIG. 3 (F)).

According to the above manufacturing process, it is not necessary to form a mirror in the three-dimensional optical waveguide as in the conventional case, and the optical waveguide that physically connects the layers can be omitted. A multilayer optical waveguide capable of inter-layer propagation can be formed by a simple process of adding a groove etching process to the above. In order to make the number of layers more, the steps (3) to (5) may be repeated between the steps (5) and (6).

FIG. 4 conceptually shows a multilayer optical waveguide according to the second embodiment. In addition, the same reference numerals are given to the portions having the same operations as those in FIG. 1, and the duplicate description will be omitted.

As shown in the figure, a lower clad layer 12a, an interlayer clad layer 12b 'and an upper clad layer 12c are sequentially formed on a substrate 11, and the lower clad layer 1 is formed.
A lower core 13a is formed in the interlayer clad 12b 'on 2a, and an upper core 13b' is formed in the upper clad 12c on the interlayer clad 12b '. Here, the interlayer clad 12b 'is formed on the lower core 13
When the upper core is formed so as to overlap with a, the core is formed with a thickness such that the cores are optically coupled with each other by using the interlayer clad 12b 'as an interlayer propagation layer. Then, the upper core 13b 'formed on the interlayer clad 12b' is
A portion that overlaps a part of the pattern of the lower core 13a (about 170
(the length of μm) is included, and the lower side of this portion becomes the interlayer propagation layer 14 and constitutes the optical coupling portion 15. In this embodiment, the substrate 11 is made of Si, the cladding layers 12a, 12
b ', 12c are SiO ₂ thin films having a refractive index of 1.46, core 1
3a and 13b 'are Corning (registered trademark) glass thin films having a refractive index of 1.53. The cores 13a and 13b ′ have a width of 1.2 μm and a thickness of 1.2 μm, and the upper and lower clad layers 12a and 12c have a thickness of 4 μm.
The thickness of the interlayer propagation layer 14 of 2b 'was 1.2 μm.

In such a multi-layered optical waveguide, when light having a wavelength of 1.3 μm, for example, is incident on the lower core 13a of the lower optical waveguide, this light is transmitted through the interlayer propagation layer 14 of the optical coupling portion 15 due to the interference effect of electromagnetic waves. , Propagates to the upper core 13b '. This causes interlayer propagation. Since the action and effect of this inter-layer propagation are the same as those of the first embodiment, the description thereof is omitted here.

In the embodiment shown in FIG. 4, one lower core 1
Although one upper-layer core 13b 'is provided in close proximity to 3a via the interlayer propagation layer 14, a plurality of upper-layer cores 13b' may be provided as shown in FIG. In this case, the propagation light of the lower layer core 13a can be branched into a plurality of upper layer cores 13b 'and propagated between the layers. Needless to say, it is not always necessary to arrange the multiple cores 13b 'on the lower core 13a at this time. In addition, the upper core 13
It goes without saying that it is also possible to provide another upper layer core which is arranged in close proximity to a part of this upper layer core 13b 'via the interlayer propagation layer, in a layer further above b'.

Next, a manufacturing example of the multilayer optical waveguide shown in FIG.
Will be described with reference to FIG. (1) A Si wafer is used as the substrate 11 and the Si wafer (1
1) 4 μm SiO 2 on the surface by thermal oxidation method₂Forming a film
To form the cladding layer 12a. (2) This SiO₂Membrane (1
2a) Corning 7059 by sputtering method
(Registered trademark) glass film is deposited to form a 1.2 μm core layer.
After formation, photolithography technology and reactive ion
The patterning of the core is performed using
The core 13a of the three-dimensional optical waveguide of 1.2 μm is formed.
(3) SiO is deposited on this by CVD method. ₂Membrane core 1
Accurately deposit 1.2 μm on top of 3a,
The interlayer clad layer 14b is used. (4) On top of this, buy
Corning 7059 again by the as-sputtering method
(Registered trademark) a glass film of 1.2 μm was deposited, and
3D with the same patterning method as 13a and a width of 1.2 μm
Part of the optical waveguide core 13b 'has a length of about 170 μm
Is formed so as to overlap with the pattern of the lower core 13a. Up
In the portion where the layer core 13b ′ and the lower layer core 13a overlap
Interlayer propagation will occur and the cladding layer between these layers
12b 'becomes the interlayer propagation layer 14. (5) On top of this, C
4μm thick SiO by VD method₂Deposit the film and
A multilayer optical waveguide was completed as the active layer 12c. Above work
According to the procedure, locally through the interlayer clad layer 12b '
Interlayer propagation is possible simply by stacking upper and lower three-dimensional optical waveguides
A multi-layered optical waveguide can be formed. It should be noted that more layers
In order to achieve this, (3)-
The step (4) may be repeated.

The material, manufacturing method and dimensions of the multilayer optical waveguide of the present invention are not limited to the above. For example, although a Si wafer is used as the substrate, a semiconductor substrate may be used or a glass substrate may be used. As the thin film optical waveguide material, Corning 7059 (registered trademark) glass and SiO ₂ were used in the above embodiments, but TiO ₂ , Ta ₂ O were used.
_It may be ₅ or other glass material, semiconductor material or organic waveguiding material. Further, in order to obtain an optical waveguide film having good film quality, high temperature annealing treatment may be performed after depositing the waveguide film. Although the sputtering method or the CVD method is used as the manufacturing method, another deposition method such as a spin coating method may be used. Further, the etching method is not limited to the reactive ion etching method, and may be an ion milling method or a reactive ion beam etching method, or a wet etching method if the etching film thickness control is accurate. Also, in the example,
I used a three-dimensional optical waveguide whose core cross section is almost square,
A three-dimensional optical waveguide by the diffusion method may be used as long as the coupling distance between the upper and lower cores in the interlayer propagation layer can be accurately controlled. Further, in the embodiment, the cores in the upper and lower layers use the same size and the same material core and clad, but cores and clads of different sizes and different materials may be used. Of course, in the multilayer optical waveguide of the present invention, it is necessary to change the manufacturing dimensions of the optical waveguide and the inter-layer propagation mechanism depending on the material of the three-dimensional optical waveguide to be used and the manufacturing method. Needless to say.

[0027]

As described above, in the multilayer optical waveguide having the inter-layer propagation mechanism of the present invention, the inter-layer propagation is performed by the interference action of the electromagnetic wave through the inter-layer propagation layer, so that a special mirror or physical layer for inter-layer propagation is used. Does not require an optical waveguide to connect the layers,
The manufacturing process can be greatly simplified. In addition, the inter-layer propagation of the multilayer optical waveguide having the above-mentioned configuration can control the optical power propagating between the layers, and when the signal light needs to be branched, it is not necessary to form another branching structure.
A high-density multilayer optical waveguide can be realized.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a multilayer optical waveguide according to a first example.

FIG. 2 is a conceptual diagram of a multilayer optical waveguide according to an application example of the first embodiment.

FIG. 3 is a process drawing showing a manufacturing example of the multilayer optical waveguide according to the first embodiment.

FIG. 4 is a conceptual diagram of a multilayer optical waveguide according to a first example.

FIG. 5 is a process drawing showing one manufacturing example of the multilayer optical waveguide according to the second embodiment.

FIG. 6 is a conceptual diagram showing a multilayer optical waveguide having a conventional mirror-type interlayer propagation mechanism.

[Explanation of symbols]

 11 Substrate 12a Lower Clad 12b, 12b 'Interlayer Clad 12c Upper Clad 13a Lower Core 13b, 13b' Upper Core 13c Interlayer Core 14 Interlayer Propagation Layer 15 Optical Coupling 16 Machining Groove

Claims (3)

[Claims] 1. A multi-layer optical waveguide in which a three-dimensional thin film waveguide including a core layer and a clad layer formed of thin films is laminated in multiple layers, and a part of the core of the three-dimensional optical waveguide and one of the other layers are provided.
A multi-layer optical waveguide, characterized in that at least one core of the three-dimensional optical waveguide has one or more optical coupling portions arranged close to each other with a cladding layer interposed therebetween. 2. A step of forming a thin film to be a first cladding layer of an optical waveguide on a substrate, and a thin film having a refractive index higher than that of the first cladding layer is formed on the first cladding layer. Forming a first core of the three-dimensional optical waveguide by filming and patterning, and a thin film having a lower refractive index than the first core on the first core as a second cladding layer A step of forming a film, a step of etching a part of the second cladding layer to locally form a processed portion having a thin thickness, and a step of forming the processed portion on the second cladding layer. A thin film having a refractive index higher than that of the first core is formed on the processed portion, is disposed in proximity to a part of the first core, and can be optically coupled to a part of the first core. Formed on the second core of the three-dimensional optical waveguide and the second cladding layer And a step of forming at least a third core of the three-dimensional optical waveguide including a portion that is physically coupled to the second core, by a patterning method. 3. A step of forming a thin film to be a first cladding layer of an optical waveguide on a substrate, and a thin film having a refractive index higher than that of the first cladding layer is formed on the first cladding layer. Forming a first core of the three-dimensional optical waveguide by filming and patterning, and a thin film having a lower refractive index than the first core on the first core as a second cladding layer The step of forming a film, and forming a thin film having a refractive index higher than that of the second clad layer on the second clad layer and sandwiching the second clad layer in the vicinity of the first core. Forming at least a second core of the three-dimensional optical waveguide, which is partially arranged to be optically coupled to the first core, by patterning, the multilayer optical waveguide. Manufacturing method.