JPH049808A - Coupling structure between optical waveguide and optical fiber and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a coupling structure between an optical waveguide and an optical fiber formed on a substrate, and a method for manufacturing the same.

Prior Art FIG. 5 shows a conventional coupling structure between an optical waveguide and an optical fiber. In this figure, an optical waveguide 5 is mounted on a substrate 50.
1 is formed. The optical fiber 52 for introducing light into this optical waveguide 51 or for guiding light from this optical waveguide 51 to the outside has its end surface joined to the end surface of the substrate 50 at the end position of the optical waveguide 50. There is. Such a coupling structure is assembled by precisely adjusting the positions of the end face of the optical fiber 52 and the end face of the optical waveguide 51 and bonding them together. Therefore, it takes time to adjust one position and the joint is unstable. Particularly when connecting multiple optical fibers, the work becomes extremely troublesome.

OBJECTS OF THE INVENTION An object of the present invention is to provide a structure that allows easy coupling of an optical waveguide and an optical fiber, and a method for manufacturing the structure.

Structure 2 of the invention Functions and effects The coupling structure between an optical waveguide and an optical fiber according to this invention is as follows:
An optical waveguide is formed on the substrate using a liquid material that hardens by energy irradiation, and a recess for holding an optical fiber is formed at the end of the optical waveguide.

The method for manufacturing a coupling structure between an optical waveguide and an optical fiber according to the present invention includes an inverted shape corresponding to the shape of the optical waveguide, and a convex portion or a concave portion corresponding to the concave portion for holding the optical fiber at the end position of the optical waveguide. A pre-formed stamper is prepared, a liquid material that is hardened by energy irradiation is injected between the stun hole and the substrate, the liquid material is hardened by irradiating energy, and then the stamper is removed. Features.

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.

A cladding layer may be formed on the optical waveguide using a material whose refractive index is smaller than that of the optical waveguide. Further, a buffer layer may be provided between the optical waveguide and the substrate using a material having a smaller refractive index than the optical waveguide.

According to this invention, since the optical waveguide is formed using a liquid material that hardens by energy irradiation, it can be manufactured using a stamper, and is easy to manufacture and has excellent mass production and reproducibility. At the same time, the manufacturing time can be shortened, and the product can be provided at a low cost.

Furthermore, since a recess for holding an optical fiber is integrally formed using the stamper when producing an optical waveguide, coupling between the optical waveguide and the optical fiber can be achieved by fitting the end of the optical fiber into this recess. . It is possible to attach the optical fiber easily and quickly, and the attachment part is stable. Furthermore, it is not necessary to align the optical axes of the optical fiber and the optical waveguide, and the coupling structure can be easily manufactured. Even if there are a plurality of optical fibers, it is possible to easily attach them by forming the same number of recesses.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments in which the present invention is applied to a rib-shaped optical waveguide will be described in detail.

Figures 1a to 1e show a method of manufacturing the coupling structure between an optical waveguide and an optical fiber in this embodiment.
The figure shows the final bonded structure.

In FIG. 1e, the rib-shaped optical waveguide is composed of a substrate 1 and a core layer 2 formed thereon. Core layer 2
has a rib portion 3 in its center that projects upward and extends in one direction. The rib portion 3 is formed integrally with the core layer 2. Approximately semicircular optical fiber holding recesses 4 are formed in the core layer 2 in portions located at both ends of the rib portion 3 . The ends of the optical fibers 8 and 9 are respectively fitted into the recess 4 and fixed by the material forming the core layer 2, as will be described later.

The light beam propagates within the core layer 2 directly below the rib portion 3 . The light beam 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 within the core layer 2 directly below the rib portion 3. Because its effective refractive index is higher than that of its surrounding area, it is confined to a position directly below the rib portion 3. Therefore, the size and depth of the recess 4 are determined so that the optical axes of the core portion at the center of the optical fibers 8 and 9 and the optical beam propagation path directly below the rib portion 3 are aligned, and the inside of the recess 4 is The optical fibers 8 and 9 will be positioned.

For example, a Sio2 glass substrate is used as the substrate 1, and its refractive index is 1.46. Core layer 2 is.

As will be described in detail later, it can be formed using an ultraviolet (UV) curing resin, and the refractive index of the core layer 2 at this time can be set to, for example, 1.47. In this way, the core layer 2 having a slightly higher refractive index than the substrate 1 can be formed.

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 Zr0z, 'r
Those containing to2, AR20x, SiO2, etc. are suitable.

The cross-sectional shape of the rib portion 3 is arbitrary, and in addition to the rectangular shape shown in Fig. 1e, it may be semicircular, triangular, entirely rectangular with rounded corners, or entirely rectangular with a central part. Examples include those in which small grooves are formed, and those that are rectangular as a whole with a small protrusion formed in the center.

Next, a method for manufacturing this bonded structure will be explained.

First, a master disk for the optical waveguide is fabricated using an electron beam lithography method. An electron beam resist is applied onto a glass substrate, and a rib pattern is drawn on the resist using an electron beam, followed by one phenomenon.

A master having a residual film resist 13 serving as a rib portion is produced on a glass substrate IO. In this master, both ends of the residual film resist 13 that will become the rib portions are cut off, and a piece 14 with a semicircular cross section, which is an optical fiber cut short and cut approximately in half in the axial direction, is glued thereto (see Fig. 1a). ).

Next, nickel (Ni)2OA is applied onto this master by electroforming.
is deposited (FIG. 1b) and the master is released to obtain a nickel stamper 20 (FIG. 1c).

This stamper 20 is formed with a concave portion corresponding to the rib portion and four portions 24 corresponding to the optical fiber holding concave portions located at both ends of the concave portion.

Next, UV curing resin 2A, which is the material of the core layer, is placed on the substrate 1.
Pour in. At this time, the ends of the optical fibers 8 and 9 are fitted into the four parts 24 of the stamper 2o. And board 1
Pressure is applied between the substrate 1 and the stamper 20, and if necessary, vibration is applied so that the distance between the substrate 1 and the nickel stamper 2o becomes a predetermined value (FIG. 1d).

Ultraviolet rays are irradiated from the back side of the substrate 1 to cure the UV curing resin.

After the UV curing resin has hardened, the stamper 20 is peeled off (
Figure 1e). As a result, a core layer 2 having a rib portion 3 made of UV curing resin is formed on the substrate 1, and optical fibers 8.9 are integrally coupled to both ends of the rib portion 3.

Figures 2a to 2f show other embodiments. Second
As can be seen by comparing Figure f with Figure 1e, the final structure obtained in this embodiment is the same.

Before or after forming a residual film resist 33 that will become a rib part on the substrate 30 by an electron beam lithography method or the like, semicircular recesses 34 are formed at both ends of the residual film resist 33 by dry etching from the direction of the end surface of the substrate 30. Form (
Figure 2a).

Nickel 4, OA is formed by electroforming using such a master disc.
is deposited (Figure 2b) to form a nickel stamper 40 (Figure 2C). The nickel stamper 40 has a concave portion corresponding to the rib portion and a convex portion 44 corresponding to the optical fiber holding concave portion.

A UV curing resin 2A is injected between the nickel stamper 40 and the substrate 1 (Fig. 2d), the resin is cured by irradiation with ultraviolet rays, and then the stamper 40 is removed to form the rib portion 3 on the substrate 1. While the core layer 2 is formed,
An optical fiber holding recess 4 is formed in this core layer 2 (
Figure 2e).

Finally, the end of the optical fiber 8.9 is fitted into the recess 4,
And it is adhered with an adhesive or the like (Fig. 2f).

The stamper 20 shown in FIG. 1c is placed on the thing shown in FIG. 2r.
A cladding layer may be formed by a similar process by placing a UV curable resin (having a refractive index smaller than that of the core layer 2) between them. The refractive index of UV-curable resins can be changed by changing the fluorine content.

Further, a buffer layer may be provided between the core layer and the substrate using a material having a smaller refractive index than the core layer. For example, as a substrate, LiNb0. , St.

A GaAs iA plate or the like is used, and a buffer layer is formed thereon by RF sputtering 5i02 glass. By providing a buffer layer in this way, a substrate made of any material can be used.

Since the recess 4 for holding the ends of the optical fibers 8 and 9 is formed, the thickness of the core layer 2 is increased.

Therefore, the optical waveguide of the above embodiment is for multimode use.

In order to obtain a single mode optical waveguide, as shown in FIGS. 3a and 3b, a core layer 2 having a rib portion 3 (this rib portion 3 is not necessarily required) is formed on one substrate 1 by the method described above. (actually becomes a buffer layer) and then on top of that.

By exactly the same method (even using the same stamper).

(You can use a different stamper or either), rib portion 6
It is preferable to form the core layer 5 thinly. It is assumed that the refractive index of the core layer 5 is slightly higher (for example, about 1%) than the refractive index of the core layer 2. The optical fiber holding recess 4 is formed across both core layers 2 and 5. The light beam is in the core layer 5
It propagates directly below the inner rib portion 6.

FIG. 4 shows how a large number of optical fibers are coupled to the optical waveguide on the substrate 1. As described above, according to the present invention, it is possible to easily couple a large number of optical fibers to an optical waveguide.

Optical waveguides formed on substrates are not only linear.

It goes without saying that a Y-branch or any other arbitrary shape may be adopted.

[Brief explanation of the drawing]

1a to 1e are perspective views showing an example of the manufacturing method according to the present invention. 2a to 2f are perspective views showing other examples of the manufacturing method according to the present invention. Fig. 3a is a perspective view showing still another embodiment, and Fig. 3b is a cross-sectional view taken along the line ■--■ of Fig. 3a. FIG. 4 is a perspective view showing still another embodiment. FIG. 5 is a perspective view showing a conventional example. 1... Board. 5... Core layer. 6... Rib part. Recess for holding optical fiber. 9... Fiber end 40... Stamper. that's all

Claims (2)

[Claims] (1) Coupling of an optical waveguide and an optical fiber, in which an optical waveguide is formed on a substrate using a liquid material that hardens by energy irradiation, and a recess for holding the optical fiber is formed at the end of the optical waveguide. structure. (2) Prepare a stamper in which an inverted shape corresponding to the shape of the optical waveguide and a convex part or a concave part corresponding to the concave part for holding the optical fiber are formed in advance at the end position of the optical waveguide, and combine the stamper and the substrate. During the process, a liquid material that hardens by energy irradiation is injected, the liquid material is hardened by irradiating energy, and then,
A method for manufacturing a coupling structure between an optical waveguide and an optical fiber, the method comprising removing the stamper.