JPH03110505A - Rib-shaped optical waveguide and its manufacture - Google Patents

Abstract

PURPOSE:To easily manufacture the rib-shaped optical waveguide and make it suitable to mass-production by including a substrate and a core layer which has a rib part formed on the substrate and forming the core layer of a liquid material which hardens the core by energy irradiation. CONSTITUTION:The rib-shaped optical wavegude consists of the substrate 1 and the core layer 2 formed thereupon. The core layer 2 has the rib part 2a, which projects upward and extends in one direction, at its center part. For the manufacture, a stamper which has a recessed groove corresponding to the rib part 2a is used and the liquid material which hardens the core by energy irradiation is injected into the gap between the stamper and substrate 1 and irradiated with energy to set. Thus, the core layer 2 is formed then the stamper is removed. Consequently, the manufacture is made easy, and superior mass- productivity and reproducibility is obtained; and the manufacture time can be shortened and the cost is reducible.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rib-shaped optical waveguide and a method of manufacturing the same.

Prior art and its problems A rib-type optical waveguide has a core layer formed on a substrate, and a rib portion is formed integrally with the core layer along the propagation direction of light. In the city perpendicular to the light propagation direction, propagating light is confined in the thickness direction of the core layer by the refractive index difference between the core layer and air and the refractive index difference between the core layer and the substrate. In the width direction of the core layer, confinement is achieved by utilizing the phenomenon that the effective refractive index near the rib portion increases because the rib portion is thicker than other portions of the core layer.

Some conventional rib-shaped optical waveguides are fabricated by ion irradiation enhanced etching. However, this method is expensive because each manufacturing step is complicated, and each manufacturing process is time-consuming and lacks mass productivity and reproducibility. Due to etching, the surface of the guide waveguide becomes rough and the dimensional performance decreases, resulting in a large light propagation loss.The shape of the guide waveguide (rib part) that can be realized by etching is limited to create an optical waveguide pattern. There is a problem with this.

On the other hand, in conventional rib-shaped optical waveguides, the core layer including the rib portions is exposed, so it is easily damaged and is inconvenient to handle.

When considering a single mode rib-shaped optical waveguide.

The smaller the difference in refractive index between the core layer and its surroundings (air and substrate), the easier it is to manufacture because the thickness of the core layer and the width of the rib portion can be increased. However, in conventional rib-shaped optical waveguides, part of the core layer is exposed and in contact with the air.
If the core layer is made of a high refractive index material, its dimensions will be small, making it difficult to manufacture. Furthermore, there is a problem in that the usable substrate material is limited when the difference in refractive index between the core layer and the substrate is taken into account.

SUMMARY OF THE INVENTION OBJECTS OF THE INVENTION An object of the present invention is to provide a rib-shaped optical waveguide that can be easily manufactured and is suitable for mass production, and a method for manufacturing the same.

The invention also aims to protect the core layer.

Furthermore, even when a single-mode optical waveguide is considered, the thickness of the core layer and the width of the rib portion can be increased, 1 manufacturing is easy, and any substrate material can be used. The purpose is to

Structure of the Invention 1 Functions and Effects The rib-shaped optical waveguide according to the present invention includes a substrate and a core layer having a rib portion formed on the substrate, and the core layer is formed using a liquid material that is hardened by energy irradiation. It is characterized by being

A method of manufacturing a rib-shaped optical waveguide according to the present invention is as follows.

Prepare a stand bar with a groove corresponding to the rib part.

A liquid material that is cured by energy irradiation is injected between the standber and the substrate, a core layer is formed by irradiating energy and the liquid material is cured, and then the standbar is removed.

Liquid materials that are cured by energy irradiation include photocurable or thermosetting resins, such as ultraviolet (UV) cured resins. Examples of inorganic materials include coating liquids for forming thermosetting films.

Liquid state also includes gel state.

According to this invention, since the core layer having the rib portion is formed using a liquid material that hardens by energy irradiation,
It can be manufactured using a standber, is easy to manufacture, has excellent ffi productivity and reproducibility, and
Since the manufacturing time can be shortened, the product can be provided at low cost. Furthermore, if the standber is manufactured with high precision, it is possible to manufacture one with a smooth optical waveguide surface, and it is possible to reduce light propagation loss. The standby is manufactured using a rib-shaped optical waveguide master, and this master can be manufactured by various methods, such as electron beam lithography.
It is possible to realize leading waveguides with rib structures of various shapes.

The rib-shaped optical waveguide according to the present invention includes a substrate, a core layer having a rib portion formed on the substrate, and a material having a refractive index smaller than that of the core layer, which is closely adhered to the core layer. A cladding layer formed as shown in FIG.

Both the core layer and the cladding layer are made using a liquid material that hardens upon energy irradiation as described above.

Although this is preferable because the process can be simplified, the core layer and cladding layer may be formed of other materials. For example, a material having a nonlinear optical effect may be used as the material for the core layer.

According to this invention, since the core layer is protected by the cladding layer, the core layer is not damaged and handling becomes easy. In addition, even if the core layer has a large refractive index, 1
By appropriately selecting the refractive index of the cladding layer, it is possible to increase the thickness of the core layer and the width of the rib portion when single mode propagation is to be achieved, which facilitates fabrication.

Since the thickness of the core layer and the width of the rib portion can be increased, there is also the advantage that optical coupling for input/output with an optical fiber or the like is facilitated.

The rib-shaped optical waveguide of the present invention includes a substrate, a core layer having a rib portion formed on the substrate, and a material having a refractive index smaller than that of the core layer. and a buffer layer provided in between. Any material can be used for the core layer and buffer layer.

According to this invention, by combining the material of the core layer and the material of the bath sofa layer with appropriate refractive indexes, the thickness of the core layer and the width of the rib portion are increased and single mode propagation of light is achieved. Not only can this be realized, but also any material can be used for the substrate.

Description of examples FIG. 1 shows a first embodiment of the invention.

The rib-shaped single mode optical waveguide shown in FIG. 1 is composed of a substrate 1 and a core layer 2 formed thereon. The core layer 2 has a rib portion 2a in its center that projects upward and extends in one direction. The rib portion 2a is formed integrally with the core layer 2.

The light beam LB propagates directly under the rib portion 2a within the core layer 2, as shown by the chain line and hatching. The light beam LB is confined within the core layer 2 in the vertical direction due to the refractive index difference between the core layer 2 and air and the refractive index difference between the core layer 2 and the substrate 1, and in the lateral direction, it is confined in the core layer 2 directly below the rib portion 2a. Because the effective refractive index of the portion is higher than that of the surrounding portion, it is confined to a position directly below the rib portion 2a.

For example, a 5in2 glass substrate is used as the substrate 1, and its refractive index is 1.46. The core layer 2 can be formed using an ultraviolet (UV) curing resin, as will be described in detail later.

The refractive index of the core layer 2 at this time can be set to 1.47, for example. In this way, it is possible to form the core layer 2 whose refractive index is slightly higher than that of the substrate 1.
Single mode leading waveguide, thickness of core layer 2, rib portion 2
It becomes possible to increase the width of a.

Other materials, such as thermosetting materials, can also be used for the core layer 2. Examples of thermosetting inorganic materials include coating liquids for forming thermosetting films. There are many types of coating liquids, but as a film-forming product after baking, Z"02,
TlO2, AM203.

Those containing Sio2 etc. are suitable.

The cross-sectional shape of the rib portion 2a is arbitrary, and in addition to the rectangular shape shown in FIG. B) ),
The overall shape is rectangular with rounded corners (see figure (C)
)), one that is rectangular as a whole with a small concave groove formed in the center ((D) in the same figure), and one that is rectangular as a whole and has a small convex groove formed in the center ((E) in the same figure). I can do it.

FIG. 3 shows a second embodiment of the invention.

In the single mode rib type optical waveguide shown in FIG.

A cladding layer 3 is formed on and in close contact with the core layer 2. The cladding layer 3 has a refractive index equal to that of the core layer 2.
The material is selected so that it is slightly smaller than that of . For example, when the core layer 2 is made of a UV-cured resin, the cladding layer 3 can be made of a UV-cured resin having a lower refractive index than the core layer 2. The refractive index of UV-curable resins can be changed by changing the fluorine content. Core layer 2. If both the cladding layers 3 are made of UV-curable resin, the manufacturing method thereof becomes easy, as will be shown later. The substrate 1 is, for example, a 5in2 glass substrate.

As the material for the cladding layer 3, inorganic materials can be used in addition to organic materials such as UV-curable resins.

When using an inorganic material, the cladding layer 3 may be formed by a vapor deposition method or the like.

Further, the core layer 2 is made of the above-mentioned UV curing resin.

In addition to coating liquids for forming thermosetting films, MNA (refractive index 1
．． 8) PTS (polydiacetylene, refractive index 1.88
), KDP (KH2PO4), and other nonlinear organic and inorganic optical materials can be used.

In this way, by providing the buffer layer 3 on the core layer 2, protection of the core layer can be achieved.

FIG. 4 shows a third embodiment of the invention.

In the rib-shaped single mode optical waveguide shown in FIG. 4, a buffer layer 4 is provided between the substrate 1 and the core layer 2. A material having a slightly lower refractive index than the core layer 2 is used for the buffer layer 4 .

For example, as the substrate 1, LiNbO3, Si.

A GaAs substrate or the like is used, and a buffer layer 4 is formed thereon by RF sputtering 5in2 glass. As the core layer 2, it is possible to use the above-mentioned UV curable resin, coating liquid for forming a thermosetting film, nonlinear organic or inorganic optical material, and the like.

By providing the buffer layer in this manner, a substrate made of any material can be used.

FIG. 5 shows a fourth embodiment of the invention, in which the substrate 1
A core layer 2 is formed thereon via a buffer layer 4, and a cladding layer 3 is further provided on the core layer 2.

Also in the second to fourth embodiments, the rib portion 2a of the core layer 2
It goes without saying that the shape of is arbitrary.

FIG. 6 shows an example of the manufacturing process of the rib-shaped single mode optical waveguide shown in FIG. Here, 5 is used as a buffer layer.
In 2, UV curing resin is used as the core layer and the cladding layer, respectively.

A master disk for a single mode optical waveguide is fabricated using the electron beam lithography method. An electron beam resist is applied on a glass substrate, and a rib pattern is drawn on the resist using an electron beam, and then developed, thereby producing a master disk having a residual film resist 12 that will become the ribs on the glass substrate 11. (Figure 6(A)).

Next, 13A nickel (Ni) was applied onto this master by electroforming.
is deposited (FIG. 6(B)), and the master is released to obtain a nickel stand bar 13 (FIG. 6(C)).

On the other hand, a buffer layer 4 is formed by RF sputtering 5in2 glass on the guiding waveguide substrate 1 (see Fig. 6(D).
)).

Next, the UV curing resin 2A, which is the material of the core layer, is dropped onto the buffer layer 4 of the substrate 1, and the nickel stamper 13 is placed on top of it, and the gap between the buffer layer 4 on the substrate 1 and the nickel stamper 13 is The substrate 1
Pressure is applied between the stand bar 13 and the stand bar 13, and vibration is applied if necessary (FIG. 6(E)).

Ultraviolet rays are irradiated from the back surface of the substrate 1 to cure the UV curing resin (FIG. 6(F)).

After the UV curing resin has hardened, the stamper 13 is peeled off (
Figure 6 (G)). As a result, the core layer 2 made of UV-curable resin is formed on the buffer layer 4.

Furthermore, between the molded plate 14 that transmits ultraviolet rays and the core layer 2, a UV curable resin 3A that will become a cladding layer is injected.
Figure (H) ), ultraviolet rays are irradiated from the forming plate 14 side.
The V-curing resin 3A is cured (FIG. 6(1)). This forms the buffer layer 3.

Finally, the molded plate 14 is peeled off (Fig. 6 (J)), and if necessary, a cleavage groove is formed on the back surface of the substrate 1, and the entire rib-shaped optical waveguide is separated along this groove to realize a leading waveguide end face. (Figure 6 (K)). This allows end-face injection into the rib-shaped optical waveguide.

When manufacturing a rib-shaped optical waveguide without a cladding layer as shown in FIG. 4, the steps in FIG. 6()I to (J) may be omitted.

When manufacturing a rib-shaped optical waveguide without a buffer layer as shown in FIG. 3, the step in FIG. 6(D) is omitted.

In the step shown in FIG. 6(E), UV curing resin 2A may be injected between the substrate 1 and the standber 13.

In the case of manufacturing a rib-shaped optical waveguide without the cladding layer and buffer layer shown in FIG. 1, FIG. 6(D) is used.

(Steps 1() to (J) may be omitted.

FIG. 7 shows a process for manufacturing the rib-shaped optical waveguide shown in FIG. 1 using a thermosetting film forming coating liquid as a core material.

The space between the standby bar 13 and the substrate 1 produced as described above is filled with the coating liquid 2B for film formation, and the pressure between the standby bar 13 and the substrate 1 is controlled so that the distance between them becomes a predetermined value. Figure 7 (A)). and.

The coating liquid 2B is baked to harden it (FIG. 7(B)). This forms the core layer 2. Finally, the stand bar 13 is peeled off (FIG. 7(C)).

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention, FIGS. 2(A) to (E) are sectional views showing examples of the shape of the rib portion, and FIG.
This figure is a perspective view showing a second embodiment of the invention, FIG. 4 a third embodiment, and FIG. 5 a fourth embodiment. 6(A) to (K) show an example of the manufacturing process of the rib-shaped optical waveguide shown in FIG.
C) shows an example of the manufacturing process of the rib-shaped optical waveguide shown in FIG. 1... Board. 2... Core layer. 2a...Rib portion. 2 p, , 3 A, UV cured t6 fat. 2B... Coating liquid for forming a thermosetting film. 3...Clad layer. 4...Buffer layer. 13...Stanba. Figure 2 (A) (C) Figure 1'2I

Claims (6)

[Claims] (1) A rib-shaped optical waveguide including a substrate and a core layer having a rib portion formed on the substrate, the core layer being formed using a liquid material that is hardened by energy irradiation. (2) A substrate, a core layer having a rib portion formed on the substrate, and a cladding layer formed in close contact with the core layer using a material having a lower refractive index than the core layer. Contains a rib-shaped optical waveguide. (3) a substrate, a core layer having a rib portion formed on the substrate, and a buffer formed using a material having a lower refractive index than the core layer and provided between the substrate and the core layer; a rib-shaped optical waveguide comprising a layer; (4) Prepare a stamper with a groove corresponding to the rib portion, inject a liquid material that hardens by energy irradiation between the stamper and the substrate, and harden the liquid material by irradiating energy to form a core. A method for manufacturing a rib-shaped optical waveguide, comprising forming a layer and then removing the stamper. (5) After removing the stamper, a cladding layer is formed on and in close contact with the core layer using a material having a lower refractive index than the core layer. Method of manufacturing wave channels. (6) Forming a buffer layer on the substrate using a material with a lower refractive index than the core layer, and then injecting a liquid material that hardens by energy irradiation between the stamper and the buffer layer on the substrate. The method for manufacturing a rib-shaped optical waveguide according to claim 4 or 5, further comprising a step of manufacturing a rib-shaped optical waveguide.