JPH06222233A - Manufacture of laminated type garnet crystal optical waveguide - Google Patents

Abstract

PURPOSE:To provide a high quality laminated type garnet crystal optical waveguide by making crystal growth of and working a second waveguide core layer and a second waveguide upper clad layer on the side opposite to a first waveguide core layer of a lower clad layer to facilitate the formation of the second waveguide. CONSTITUTION:With a first optical waveguide core ridge 1, an intermediate clad layer 2, and an upper clad layer on an optical waveguide used as substrate for crystal growth, a second optical waveguide core ridge 4 formed by working a garnet crystal film of which crystal is grown on the intermediate clad layer 2 and an upper clad layer 5 on the second optical waveguide comprising the garnet crystal film are provided. Because the core ridge 4 is formed on the flat clad layer 2, it is not broken and the working form of it is made square easily. Thus the final film thickness of the first clad layer 2 grown on a crystal substrate can be selected arbitrarily, and the first waveguide 1 and second waveguide 4 can be moved closely to each other easily through the intermediate clad layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a garnet crystal optical waveguide used for optical isolators, optical amplifiers and the like.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher functionality in waveguide devices, and it has become indispensable to achieve high-density integration, multi-functionality, and improved controllability of the performance of directional couplers and the like. . For this purpose, after forming the first optical waveguide,
A structure in which the second optical waveguide is formed immediately above and a light signal can be appropriately coupled between the first optical waveguide and the second optical waveguide, that is, a structure in which the optical waveguides are laminated in multiple stages, Proposed. The demands for high-density integration, multi-functionality, and improved controllability of the performance of directional couplers and the like also apply to garnet crystal optical waveguides.

Conventionally, a garnet crystal waveguide used for an optical device or the like has a lower clad layer on a garnet crystal substrate, and subsequently a core layer formed by a liquid phase epitaxial growth method (LP).
E method) and the like, the core layer is two-dimensionally processed by a method such as ion beam etching, and then the upper clad layer is grown by using the LPE method or the like.

[0004]

In order to achieve high-density integration and multi-functionalization of the garnet crystal optical waveguide and to improve the controllability of the performance of the directional coupler and the like by the conventional technique, the garnet crystal optical waveguide is formed on the first optical waveguide. The following problems arise when trying to manufacture a laminated optical waveguide in which the second optical waveguide is arranged. 10 to 16 show an example of a process of manufacturing the first garnet crystal optical waveguide and the second garnet crystal optical waveguide thereon by the conventional technique.

First, as shown in FIG. 10, on a garnet substrate crystal (gadolinium gallium garnet etc.) 6,
A garnet crystal film 2 having a thickness of several μm, which will be the lower clad layer of the first optical waveguide, is formed by a liquid phase epitaxial method (LPE method) using PbO and B ₂ O ₃ as a flux.
Next, as shown in FIG. 11, a garnet crystal film 7 having a film thickness of about 5 μm, which becomes the first optical waveguide core layer, is similarly formed by LPE.
It is formed by the method. Subsequently, as shown in FIG. 12, the core layer ridge 1 having a line width of about 5 μm is two-dimensionally processed by ion beam etching or the like using the mask 8.

Thereafter, as shown in FIG. 13, on the substrate on which the core layer ridge 1 has been formed, an upper clad layer for the first optical waveguide and a lower clad layer for the second optical waveguide are formed. The garnet crystal film 11 having a thickness of several μm, which acts as an intermediate clad layer, is also used as an LP.
It is formed by the E method or the like. At this time, the garnet crystal film 11
In addition, when the film thickness is relatively thin, such as several μm, several kinds of crystal planes appear just above the core ridge, depending on the orientation of the core ridge, in addition to the plane having the same orientation as the substrate crystal plane. If only the above-mentioned first optical waveguide is manufactured, no significant problem occurs.

Further, as shown in FIG. 14, a garnet crystal film 12 having a film thickness of about 5 μm to be a second optical waveguide core layer is similarly formed on the intermediate cladding layer 11 by the LPE method or the like. In the garnet film 12, several types of crystal planes with irregularities appear according to the crystal orientation of the surface of the intermediate cladding layer 11. Subsequently, as shown in FIG. 15, similarly to the first optical waveguide, the second optical waveguide core ridge 13 is processed by a method such as ion beam etching using the mask 14. At this time, in the vicinity of the first optical waveguide core ridge, since the surface of the intermediate cladding layer 11 is not flat, it is inevitable that the core ridge 13 is difficult to be processed into a square shape.

Finally, as shown in FIG. 16, on the second optical waveguide core ridge 13, a few μm which becomes an upper clad layer is formed.
The garnet crystal film 15 having a thickness of m is formed by the LPE method or the like, and after cutting, the end face of the waveguide is polished to complete the production of the laminated garnet crystal optical waveguide. In such a laminated garnet crystal optical waveguide, since the intermediate clad layer 11 is not flat, the processed shape of the second optical waveguide core ridge may become defective, and the second optical waveguide core ridge may be broken. In addition, there is a drawback in that it is unavoidable that a defective coupling condition between the first optical waveguide and the second optical waveguide may occur due to the processed shape of the second optical waveguide core ridge.

In order to prevent the defective shape of the second optical waveguide core ridge and the disconnection thereof, the intermediate cladding layer 11 is used.
Should be flattened. However, as long as a garnet crystal film is used for the intermediate cladding layer 11, a flattening of a film thickness of several tens is required for flattening.
It cannot be realized unless the thickness is more than μm. However, if the intermediate clad layer 11 has a thickness of several tens of μm or more, it is practically impossible to couple optical signals between the first optical waveguide and the second optical waveguide, which means that a laminated optical waveguide is manufactured. Disappears.

Further, the garnet crystal is a material which is difficult to process itself, and even when a method such as ion beam etching is used to form a directional coupler having a two-dimensional structure, the two core ridges of the coupling portion are formed. Interval (usually 2-4μ
It is difficult to process m) accurately and with good reproducibility. Due to such problems, it was practically impossible to manufacture a laminated garnet crystal optical waveguide by using the conventional technique or to improve the controllability of the performance of the directional coupler.

The present invention has been made in view of the above-mentioned prior art, and in forming a laminated garnet crystal optical waveguide having a basic structure in which a first optical waveguide and a second optical waveguide are laminated, It was a problem in the conventional technology,
For the formation of the second optical waveguide, a laminated garnet crystal optical waveguide that can simultaneously and easily achieve flattening of the crystal growth surface and coupling of optical signals with the first optical waveguide The purpose is to provide a manufacturing method.

[0012]

The structure according to claim 1 of the present invention which achieves the above object has a general formula R ₃ B ₅ O ₁₂ (R is yttrium, lanthanum, bismuth and a trivalent valence. Represents one of rare earth elements, B represents one of iron, gallium, aluminum and scandium, and O represents oxygen), or a part of constituent elements other than oxygen of the garnet equivalent to In a garnet crystal optical waveguide using a substitutional garnet crystal in which one or more elements having a valence is replaced, a crystal substrate, a lower clad, a core layer, and an upper clad layer are formed in this order by crystal growth and processing. For the optical waveguide of No. 1, after removing the crystal substrate or processing it sufficiently thin, the second waveguide core is provided on the side of the lower cladding layer opposite to the core layer of the first waveguide. The layer and the upper cladding layer of the second waveguide are formed by crystal growth and processing.

The structure according to claim 2 of the present invention which achieves the above object is defined by the general formula R ₃ B ₅ O ₁₂ (wherein R is yttrium, lanthanum, bismuth and one of rare earth elements having a valence of 3). , B represents any one of iron, gallium, aluminum, and scandium, and O represents oxygen), or a part or more of the constituent elements other than oxygen of the garnet, which have an equivalent valence. In a garnet crystal optical waveguide using a substitutional garnet crystal replaced with an element, a crystal substrate, a lower clad, a core layer and a sufficiently thick upper clad layer are sequentially formed into a first optical waveguide formed by crystal growth and processing. On the other hand, after the upper clad layer is sufficiently thinly mechanically or chemically polished to be planarized, a second conductive layer is formed on the polished clad layer. The waveguide core layer and the upper cladding layer of the second waveguide are formed by crystal growth and processing.

[0014]

The operation of the laminated garnet crystal optical waveguide according to claim 1 of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 1 is a core ridge of a first garnet crystal optical waveguide formed by processing a garnet crystal film. Reference numeral 2 is a clad layer in which crystals are grown on the garnet crystal substrate, and the crystal substrate used for crystal growth has already been removed. Reference numeral 3 is an upper clad layer of the first waveguide formed of a garnet crystal film. 4 is 1 and 2
3 and 3 are substrates for crystal growth, and are core ridges of a second garnet crystal optical waveguide formed by processing a garnet crystal film on which crystal growth is performed. Reference numeral 5 is an upper clad layer of the second waveguide made of a garnet crystal film.

Since the core ridge 4 of the second optical waveguide is formed on the flat clad layer 2, there is no disconnection and it is easy to make the processed shape square. Figure 1
In the above structure, the final film thickness of the first clad layer 2 grown on the crystal substrate can be arbitrarily selected, and the first waveguide 1 is formed through the clad layer 2 acting as the intermediate clad layer. Since it is easy to bring the second waveguide 4 and the second waveguide 4 into close proximity to each other, the thickness of the intermediate cladding layer 2 is set to, for example, 2 to
If the thickness is selected to be about 4 μm, the controllability of the performance of the directional coupler will be greatly improved. The present invention can be applied to a waveguide constituted by a curved line other than the linear optical waveguide shown in FIG.

A method of manufacturing a laminated garnet crystal optical waveguide according to claim 1 of the present invention will be described with reference to FIGS. First, as shown in FIG. 2, a garnet crystal film 2 having a thickness of about 2 to 4 μm to be a lower clad layer of the first and second optical waveguides, that is, an intermediate clad layer is formed on the garnet crystal substrate 6. .

Next, as shown in FIG. 3, on the side opposite to the substrate 6, that is, the garnet crystal film 2 which is an intermediate cladding layer.
A garnet crystal film 7 having a film thickness of about 5 μm to serve as a first waveguide core is formed on the above. Subsequently, as shown in FIG. 4, the core ridge 1 of the first waveguide is processed by ion beam etching or the like using the mask 8. Thereafter, as shown in FIG. 5, a garnet crystal film 3 having a thickness of about 50 to 300 μm and acting as an upper cladding layer of the first waveguide is formed on the substrate on which the core ridge 1 of the first waveguide is formed. Further, as shown in FIG.
Are removed by a method such as mechanical polishing, and the intermediate clad layer 2
A flat lower surface without damage is obtained by a method such as chemical polishing.

Then, as shown in FIG. 7, the upper clad layer 3 of the first waveguide is taken as a substrate, the intermediate clad layer 2 is used as a crystal growth surface, and the garnet crystal film to be the core of the second waveguide is formed. 9 is grown to a thickness of about 5 μm.
After that, as shown in FIG. 8, the core ridge 1 of the second waveguide is processed by ion beam etching or the like using the mask 10. Finally, as shown in FIG. 9, a garnet crystal film 5 acting as an upper clad layer of the second waveguide is formed on the core ridge of the second waveguide. By this step, the second optical waveguide can be formed in exactly the same way as the first optical waveguide, so that the formation of the second optical waveguide, which has been a problem in the conventional technique, is incomparable to the conventional one. It will be easy.

The garnet crystal as the garnet crystal substrate, the clad layer and the core layer constituting the laminated garnet crystal optical waveguide according to claim 1 of the present invention has the general formula R
Garnet represented by ₃ B ₅ O ₁₂ (R represents any one of yttrium, lanthanum, bismuth, and a rare earth element having a trivalent valence, and B represents any one of iron, gallium, aluminum, and scandium) Alternatively, a substitutional garnet crystal in which a part of the constituent elements other than oxygen of the garnet is replaced by one or more elements having an equivalent valence can be used.

Specific examples thereof include gadolinium gallium garnet (GGG) and yttrium aluminum garnet (YAG). As the substitutional garnet, bismuth, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, television, dysprosium, holmium, erbium, thulium, and ytterbium are appropriately mixed in addition to yttrium in the rare earth element of the melt during crystal growth. In addition to gallium or aluminum, a garnet crystal formed using an appropriate mixture of iron or scandium can be used. Of course, in order to create a melt, a platinum crucible is used to dissolve the raw materials in PbO, B ₂ O ₃ and the garnet crystals formed are mixed with those elements as impurities, but garnet crystals containing these impurities are also included. The invention applies.

The operation of the laminated garnet crystal optical waveguide according to claim 2 of the present invention will be described with reference to FIG. In FIG. 17, reference numeral 21 denotes a core ridge of a first garnet crystal optical waveguide formed by processing a garnet crystal film. Reference numeral 22 is a lower clad layer for the first waveguide 21 crystal-grown on the garnet crystal substrate.
In No. 23, the garnet crystal thick film was polished to be sufficiently thin,
It is an upper clad layer for the first waveguide 21 and at the same time a lower clad layer for the second waveguide 24, and is hereinafter referred to as an intermediate clad layer in order to avoid confusion. 24
Is a core ridge of a second garnet crystal optical waveguide formed by processing a garnet crystal film crystal-grown on the intermediate cladding layer 23. Reference numeral 25 is an upper clad layer of the second waveguide 24 made of a garnet crystal film.

Since the core ridge 24 of the second optical waveguide is formed on the flattened intermediate clad layer 23, there is no disconnection and it is easy to make the processed shape square. In the structure of FIG. 17, the film thickness of the intermediate cladding layer 23 to be finally thinned by polishing can be arbitrarily selected, and the first waveguide 21 and the second waveguide 21 can be interposed via this intermediate cladding layer 23. Since it is also possible to easily bring the intermediate clad layer 24 into close proximity,
If it is selected to be about μm, the controllability of the performance of the directional coupler is also greatly improved. As a matter of course, the present invention can be applied to an optical waveguide formed of a curved line other than the linear optical waveguide shown in FIG.

A method of manufacturing a laminated garnet crystal optical waveguide according to claim 2 of the present invention will be described with reference to FIGS. First, as shown in FIG. 18, a garnet crystal film having a thickness of about 2 to 4 μm is formed on the garnet crystal substrate 26 as the lower clad layer 22 of the first optical waveguide.

Next, as shown in FIG. 19, about 5 μm to be the first waveguide core is formed on the lower clad layer 22.
A garnet crystal film 27 having a thickness of m is formed. Subsequently, as shown in FIG. 20, the core ridge 2 of the first waveguide is formed by ion beam etching or the like using the mask 28.
Process 1. After that, as shown in FIG. 21, a garnet crystal thick film 29 to be an intermediate cladding layer is sufficiently thick on the substrate on which the core ridge 21 of the first waveguide is formed.
The thickness is about 50 to 300 μm.

Further, as shown in FIG. 22, the garnet crystal thick film 29 is processed by a method such as mechanical or chemical polishing so as to be thickened from the core ridge 21 of the first waveguide by about 1 to 3 μm. A flat surface without damage is obtained as the intermediate cladding layer 23 by a method such as chemical polishing.
Then, as shown in FIG. 23, the garnet crystal film 30 to be the core of the second waveguide is crystal-grown to a thickness of about 5 μm, using the intermediate cladding layer 23 as a crystal growth surface. Then, as shown in FIG. 24, the core ridge 24 of the second waveguide is processed by ion beam etching or the like using the mask 31.

Finally, as shown in FIG. 25, a garnet crystal thick film 25 is formed as an upper cladding layer of the second waveguide on the core ridge 24 of the second waveguide. By this step, the second optical waveguide 24 can be formed in the same manner as the first optical waveguide 21, so that the formation of the second optical waveguide 24, which has been a problem in the conventional technique, is different from the conventional one. It will be easier than ever. The garnet crystal substrate, the clad layer, and the core layer that form the laminated garnet crystal optical waveguide according to claim 2 of the present invention include garnet crystals of the general formula R ₃ B ₅ O ₁₂ (R is yttrium, lanthanum, bismuth and Represents one of rare earth elements having a valence of 3, B is iron, gallium,
A garnet represented by any one of aluminum and scandium) or a substitutional garnet crystal in which a part of constituent elements other than oxygen of the garnet is replaced with one or more elements having an equivalent valence can be used. .

Specific examples include gadolinium gallium garnet (GGG) and yttrium aluminum garnet (YAG). As the substitutional garnet, bismuth, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, and ytterbium are appropriately mixed in addition to yttrium in the rare earth element of the melt during crystal growth. In addition to gallium or aluminum, a garnet crystal formed using an appropriate mixture of iron or scandium can be used. Of course, in order to create a melt, these elements are mixed as impurities in the garnet crystal formed because the raw material is dissolved in PbO, B ₂ O ₃ using a platinum crucible, but the garnet crystal containing these impurities is also included. The present invention can be applied.

[0029]

EXAMPLES The present invention will be described in detail below with reference to examples. [Embodiment 1] FIGS. 2 to 9 show one embodiment of the method for producing a laminated garnet crystal optical waveguide according to claim 1 of the present invention.
Will be described in detail with reference to. First, the diameter is 2 inches (about 5
cm) with a thickness of about 400 μm gadolinium gallium
Garnet crystal substrate {GGG substrate: mirror-finished in (111) orientation} 6 and a thickness of about 2 μm, which becomes the intermediate clad layer 2 controlled so that the lattice constant matches that of the GGG substrate crystal
Of _{Y 3-x La x Fe 5} -y Ga y O 12 (0 ≦ x ≦ 1,0 ≦ y ≦
2) The garnet crystal film was formed by a liquid phase epitaxial growth method (LPE method) using PbO and B ₂ O ₃ as a flux to obtain about 9
It was formed at a temperature of 00 ° C. (FIG. 2).

Next, the substrate 6 on which the intermediate cladding layer 2 is formed
On the upper side, the lattice constant is the same as that of the intermediate cladding layer 2, which is to be the first optical waveguide core layer, and in order to increase the refractive index slightly, iron of the composition is slightly increased compared to the intermediate cladding layer 2. The garnet crystal film 7 containing a large amount of gallium and a little less gallium was formed to a thickness of about 5 μm by the LPE method similarly to the intermediate cladding layer 2 (FIG. 3). A processing mask 8 having a width of about 5 μm and a height of about 10 μm is formed on the garnet crystal film 7 with a photoresist, and the mask 8 is used to perform ion beam etching using an argon gas (accelerating voltage about 600 V, ion Beam current density about 1mA / cm ² )
To process the first optical waveguide core ridge 1.
A rectangular core ridge 1 was formed (FIG. 4).

Subsequently, an upper clad layer 3 having the same composition as the intermediate clad layer 2 is formed on the substrate having the core ridge 1 of the first optical waveguide formed and processed to a thickness of about 300 μm by LPE.
And a good embedded shape was obtained (FIG. 5).
Further, this time, after the GGG crystal substrate 6 is mechanically polished to a thickness of about 5 μm, the remaining about 5 μm is removed by etching in hot phosphoric acid at 140 ° C.,
A flat crystal plane on the lower side of the intermediate cladding layer 2 could be formed very easily (FIG. 6).

Next, the upper clad layer 3 of the first optical waveguide
Is used as a substrate for handling, and the second optical waveguide core layer 9 is formed on the surface of the intermediate cladding layer 2 opposite to the first optical waveguide core ridge under the same conditions as the first optical waveguide core layer 7. When it was formed, it was confirmed that the composition and crystallinity and other properties were extremely good in terms of properties as a waveguide core similar to the first optical waveguide core layer 7 (FIG. 7).
When the second optical waveguide core ridge 4 was processed by ion beam etching using the mask 10 in the same manner as the processing of the first optical waveguide core ridge, it was possible to process it into a rectangular shape like the first optical waveguide core ridge 1. (Fig. 8).

Finally, a garnet crystal film 5 having the same composition as that of the intermediate clad layer 2 is formed on the second optical waveguide core ridge 4 as an upper clad layer of the second optical waveguide by the LPE method to a thickness of about 10 μm. Then, the laminated garnet crystal optical waveguide according to the present invention can be realized by obtaining a good buried shape (FIG. 9). In the present example, the formation of the second optical waveguide could be performed extremely easily, as with the formation of the first optical waveguide. The optical waveguide had no disconnection, the core ridge had a good shape, and the optical signal was sufficiently coupled between the first optical waveguide and the second optical waveguide.

Example 2 As compared with Example 1, as elements corresponding to all rare earth elements of the melt during crystal growth, in addition to yttrium, bismuth, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium. , Terbium, dysprosium, holmium, erbium, thulium, ytterbium is also appropriately mixed, even in a laminated garnet crystal optical waveguide formed by a garnet crystal formed using a mixture of aluminum or scandium in addition to iron and gallium It was confirmed that there was no disconnection, the shape of the core ridge was good, and the coupling of optical signals between the first optical waveguide and the second optical waveguide was sufficient.

[Embodiment 3] An embodiment of a method of manufacturing a laminated garnet crystal optical waveguide according to claim 2 of the present invention is shown in FIG.
~ It demonstrates in detail with reference to FIG. First, gadolinium with a diameter of 2 inches (about 5 cm) and a thickness of about 400 μm
Gallium garnet crystal substrate {GGG substrate: (11
1) Mirror finish in azimuth} 26 Y _{3 -X} La _x F with a thickness of about 2 μm as the lower clad layer 22 of the first waveguide 21 controlled to have the same lattice constant as the GGG substrate crystal.
_{e 5-y Ga y O 12} (0 ≦ x ≦ 1,0 ≦ y ≦ 2) garnet crystal film of PbO and B ₂ O ₃ liquid phase epitaxial growth method to flux the the (LPE method) of about 900 ° C. Formed at temperature (Figure 18).

Next, on the substrate 26 on which the lower clad layer 22 is formed, in order to make the lattice constant of the lower clad layer coincide with that of the lower clad layer 22 and slightly increase the refractive index, the composition of iron is smaller than that of the lower clad layer 22. The garnet crystal film 27 with a slightly increased amount of gallium and a slightly reduced amount of gallium was formed to a thickness of about 5 μm by the LPE method similarly to the lower clad layer 22 (FIG. 19). Width of about 5 μm on garnet crystal film 27
And a mask 28 for processing having a height of about 10 μm is formed of photoresist, and using this mask 28, ion beam etching using argon gas (acceleration voltage of about 600 V,
Ion beam current density of about 1 mA / cm ² )
The optical waveguide core ridge 21 was processed to form a rectangular core ridge 21 (FIG. 20).

Next, the core ridge 21 of the first optical waveguide.
The lower clad layer 22 is formed on the substrate 26 formed and processed up to
The garnet crystal thick film 29 to be the intermediate clad layer 3 having the same composition as that of LPE is thick enough to have a thickness of about 300 μm.
And a good embedded shape was obtained (FIG. 2).
1). Further, this time, the garnet crystal thick film 29 was mechanically polished down to a thickness of about 12 μm, and then 1
By further removing about 5 μm by etching in hot phosphoric acid at 40 ° C., the intermediate cladding layer 23 having a flat crystal plane could be formed extremely easily (FIG. 22).

Next, a second optical waveguide core layer 30 was formed on the intermediate clad layer 23 under the same conditions as the first optical waveguide core layer 27. It has been confirmed that the waveguide core layer 27 has very good properties as a waveguide core similar to the waveguide core layer 27 (FIG. 2).
3). Then, when the second optical waveguide core ridge 24 was processed by ion beam etching using the mask 31 in the same manner as the processing of the first optical waveguide core ridge 21, a rectangular shape was obtained like the first optical waveguide core ridge 21. Could be processed (Fig. 24).

Finally, a garnet crystal film having the same composition as that of the intermediate cladding layer 23 is formed on the second optical waveguide core ridge 24 as an upper cladding layer 25 of the second optical waveguide.
By the PE method, the laminated garnet crystal optical waveguide according to the present invention could be realized by forming it to a thickness of about 20 μm and obtaining a good embedded shape (FIG. 25). In this embodiment,
The formation of the second optical waveguide 24, like the formation of the first optical waveguide 21, could be performed extremely easily. This optical waveguide has no disconnection and the shape of the core ridge is good, and the coupling of optical signals between the first optical waveguide and the second optical waveguide is sufficient because the vertical distance of the core ridge is only 2 μm. there were.

[Embodiment 4] In comparison with Embodiment 3, as elements corresponding to all rare earth elements of the melt during crystal growth, in addition to yttrium, bismuth, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium. , Terbium, dysprosium, holmium, erbium, thulium, ytterbium is also appropriately mixed, even in a laminated garnet crystal optical waveguide formed by a garnet crystal formed using a mixture of aluminum or scandium in addition to iron and gallium It was confirmed that there was no disconnection, the shape of the core ridge was good, and the coupling of optical signals between the first optical waveguide and the second optical waveguide was sufficient.

[0041]

As described above, in the garnet crystal optical waveguide using the substitutional garnet crystal, the crystal substrate, the lower clad, the core layer, and the upper clad layer are formed in this order by crystal growth and processing. After removing the crystal substrate from the first optical waveguide, the second waveguide core layer and the upper cladding layer of the second waveguide are crystal-grown on the side of the lower cladding layer opposite to the first waveguide core layer. According to the present invention, which is formed by processing, it is easy to form the second optical waveguide, which is extremely difficult in the prior art, and a high-quality laminated garnet crystal optical waveguide can be realized, which is a great industrial advantage. Is. Further, in a garnet crystal optical waveguide using a substitutional garnet crystal, a crystal substrate, a lower clad, a core layer, and an upper clad layer are formed in this order from the bottom to the first optical waveguide formed by crystal growth and processing, and According to the present invention, in which the second waveguide core layer and the upper cladding layer of the second waveguide are formed by crystal growth and processing after the cladding is processed to be flat by polishing, The second optical waveguide can be easily formed, and a high-quality laminated garnet crystal optical waveguide can be realized, which is a great industrial advantage.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a laminated garnet crystal optical waveguide according to the present invention.

FIG. 2 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 3 is a process drawing showing an embodiment of a method of manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 4 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 5 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 6 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 7 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 8 is a process chart showing an embodiment of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 9 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 10 is a process chart showing an example of a method of manufacturing a laminated garnet crystal optical waveguide according to a conventional technique.

FIG. 11 is a process chart showing an example of a method of manufacturing a laminated garnet crystal optical waveguide according to a conventional technique.

FIG. 12 is a process chart showing an example of a method of manufacturing a laminated garnet crystal optical waveguide according to a conventional technique.

FIG. 13 is a process chart showing an example of a method of manufacturing a laminated garnet crystal optical waveguide according to a conventional technique.

FIG. 14 is a process chart showing an example of a method of manufacturing a laminated garnet crystal optical waveguide according to a conventional technique.

FIG. 15 is a process chart showing an example of a method of manufacturing a laminated garnet crystal optical waveguide according to a conventional technique.

FIG. 16 is a process chart showing an example of a method of manufacturing a laminated garnet crystal optical waveguide according to a conventional technique.

FIG. 17 is a schematic perspective view showing an example of a laminated garnet crystal optical waveguide according to the present invention.

FIG. 18 is a process chart showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 19 is a process chart showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 20 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 21 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 22 is a process chart showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 23 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 24 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

FIG. 25 is a process drawing showing an example of a method for manufacturing a laminated garnet crystal optical waveguide according to the present invention.

[Explanation of symbols]

1 First Optical Waveguide Core Ridge 2 Intermediate Cladding Layer 3 Upper Cladding Layer of First Optical Waveguide 4 Core Ridge of Second Optical Waveguide 5 Upper Cladding Layer of Second Optical Waveguide 6 For Forming First Optical Waveguide Crystal substrate 7 First optical waveguide core layer 8 Mask for processing first optical waveguide core ridge 9 Second optical waveguide core layer 10 Mask for processing second optical waveguide core ridge 11 First optical waveguide Upper clad layer of 12 Second optical waveguide core layer 13 Second optical waveguide core ridge 14 Mask for processing second optical waveguide core ridge 15 Upper clad layer of second optical waveguide 21 First optical waveguide core ridge 22 Lower cladding layer 23 Intermediate cladding layer 24 Core ridge of second optical waveguide 25 Upper cladding layer of second optical waveguide 26 Forming first optical waveguide Crystal substrate for use 27 First optical waveguide core layer 28 Mask for processing first optical waveguide core ridge 29 Upper clad crystal thick film of first optical waveguide 30 Second optical waveguide core layer 31 Second Mask for processing optical waveguide core ridge

Claims (2)

[Claims] 1. The general formula R ₃ B ₅ O ₁₂ (R is yttrium,
A garnet represented by lanthanum, bismuth, or a rare earth element having a trivalent valence, B represents any one of iron, gallium, aluminum, and scandium, and O represents oxygen; In a garnet crystal optical waveguide using a substitutional garnet crystal in which a part of constituent elements other than oxygen is replaced by one or more elements having an equivalent valence, a crystal substrate, a lower clad layer, a core layer, an upper part from the bottom. After removing the crystal substrate from the first optical waveguide formed by crystal growth and processing in the order of the clad layer, the second waveguide core layer and the second waveguide core layer are formed on the side of the lower clad layer opposite to the first waveguide core layer. A method for producing a laminated garnet crystal optical waveguide, characterized in that the upper clad layer of the second waveguide is formed by crystal growth and processing. 2. The general formula R ₃ B ₅ O ₁₂ (R is yttrium,
A garnet represented by lanthanum, bismuth, and one of rare earth elements having a trivalent valence, B represents any one of iron, gallium, aluminum, and scandium, and O represents oxygen; In a garnet crystal optical waveguide using a substitutional garnet crystal in which a part of constituent elements other than oxygen is replaced by one or more elements having an equivalent valence, a crystal substrate, a lower clad, a core layer, an upper clad from the bottom. A second waveguide in which the upper clad layer is mechanically or chemically polished with respect to the first optical waveguide formed by crystal growth and processing in the order of layers, and then the polished upper clad layer is used as a lower clad layer. Stacked garnet crystal characterized in that the core layer and the upper clad layer of the second waveguide are formed by crystal growth and processing. Preparation of the waveguide.