JPH0414762B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical waveguide formed on a substrate and a light flux within a prism, or a light wave propagating within the optical waveguide, which is used to guide a light beam into a prism. This invention relates to a coupling device.

Conventional configuration and its problems In recent years, with the development of lasers, the development of devices using lasers as light sources has become active. However, the optical components that have been used conventionally are bulk types and have drawbacks such as being heavy and having a large volume. In order to eliminate these drawbacks and make the optical system used in devices more stable, so-called optical ICs are being considered.

As shown in FIG. 1, this is done on a dielectric substrate 1.
The optical waveguide 2 with a higher dielectric constant is formed by vapor deposition, sputtering, ion exchange, diffusion, etc., and the concept is that light undergoes various processing while traveling through this optical waveguide 2. It is something. By allowing light to pass through the optical waveguide 2 in this way, the size and cost of the optical element can be reduced,
It is possible to manufacture optical components that are far superior to conventional bulk-type optical components in terms of improved stability, etc.

However, how to efficiently and stably transmit the light emitted from the laser light source or passed through the fiber to the optical waveguide 2, and how to efficiently and stably transmit the light transmitted within the optical waveguide 2. However, there remained a big problem in how to take it out.

Below is the first part about the conventional triangular prism optical coupler.
Explain using diagrams. 1 is a dielectric substrate, 2 is a transparent dielectric optical waveguide, 3 is a triangular prism, 4 is a tapered gap, 5 is incident light, 6 is a traveling direction of light, 7 is an optical coupling point, 8 is a coupling surface, 9 indicates a contact point. This principle is explained in JOSA, Vol61, No.11,
1971, P1467.

The incident light 5 entering the triangular prism 3 is refracted and then sent to the coupling surface 8 . At this surface 8, the incident light 5 is converted into evanescent light and sent to the optical waveguide 2. Therefore, the surface precision of this bonding surface 8 is very important and is optically polished. Now, the light transmitted to the optical waveguide 2 travels in a traveling direction 6.
On the other hand, a tapered air gap 4 is required between the coupling surface 8 and the optical waveguide 2 in order to increase the coupling efficiency, and the coupling efficiency varies widely depending on this angle.

Therefore, according to this configuration, it is necessary to rotate the triangular prism 3 while bringing the triangular prism 3 into contact with the optical waveguide section 2 at one vertex 9 to form a small tapered air gap 4 of 1/10 milliradian. The surface accuracy of the portion 2, that is, the surface accuracy of the substrate is required. Then, contact point 9 and transmission point 7
Since the distance from the transmitter to the transmitter increases, the accuracy is required to be very high, for example, about 1/10λ (λ: wavelength of transmitted light). Further, since the contact point 9 is a thin part of the prism 3, the prism may be damaged due to pressure applied to this part, and good contact may not be obtained. Furthermore, when fixing the triangular prism 3, adhesive can be used only around the prism except for the optical path of the optical waveguide, but the structure shown in FIG. It has to become a product.

Purpose of the Invention The present invention was made in view of these problems, and can be manufactured at approximately the same cost as a conventional triangular prism column, and the surface accuracy of the substrate is about 1/10 of that of the conventional one, making it highly efficient. The object of the present invention is to obtain an optical coupling device that enables optical coupling and stable fixation.

Structure of the Invention The present invention provides an integrated optical system having a part divided into an optical waveguide prism part and an optical coupling prism part having an obtuse apex angle in one prism (a prism etc. is also possible). A coupling prism is used, and this optical coupling prism is used as an input to an optical waveguide formed on a substrate or as an output from the optical waveguide.

DESCRIPTION OF EMBODIMENTS FIG. 2 is a side view of a coupling device using an optical coupling prism according to a first embodiment of the present invention.

In FIG. 2, 1 is a substrate, 2 is a transparent dielectric optical waveguide, 3a is a triangular prism for light guide, 4 is a tapered air gap, 5 is incident light, 6 is the traveling direction of light, 7 is a light transmission point, 8 9 is an optical coupling surface, 9 is an apex angle (contact point), 10 is an adjustment gap, and 11 is a coupling triangular prism, which is formed integrally with the prism 3a and is brought into contact with the optical waveguide 2 at the contact point 9. There is.

The operation of the optical coupling device having the above configuration will be explained with reference to FIG.

The incident light 5 is sent to the optical waveguide prism section 3a, and after surface refraction, is sent to the optical coupling surface 8. Now, in the case of the present invention, unlike a normal triangular prism, the coupling triangular prism part 11 shown with a dotted line in the figure
exists. An enlarged view of this part is shown in FIG.
Now, in the optical coupling prism according to the present invention, one apex of the triangular prism-shaped optical coupling prism section 11, which is different from the optical waveguide columnar prism section 3a, and which forms an obtuse angle, connects the optical waveguide section 2 and the optical coupling prism section 11. The point of contact is 9. Therefore, the coupling surface 8 is one slope of the triangular prism-shaped coupling prism section 11 , and the incident light 5 is converted into evanescent light by this coupling surface 8 and sent to the optical waveguide section 2 . Therefore, the surface precision of this bonding surface 8 is very important, so it is optically polished. On the other hand, an adjustment gap 1 is provided between the opposite slope of the triangular prism optical coupling prism section 11 and the optical waveguide section 2.
The angle of apex angle 9 is chosen such that 0 exists.

Next, a method for installing an optical coupling prism according to the present invention will be described. The coupling prism according to the present invention has the optical waveguide 2 at the apex 9 by pressure from above.
be brought into contact with. Next, the coupling surface 8 and the optical waveguide 2
The coupling prism rotates slightly about the contact point 9 so that an optimal coupling tapered air gap 5 is obtained between the two. The tapered air gap for connection is usually about 1/10 milliradian. By the above adjustment method, a coupling efficiency of 90% or more has been obtained using the prism of the present invention.

As described above, according to this embodiment, by adding the triangular prism-shaped light coupling prism section 11 having an obtuse vertex angle to the prism section 3a corresponding to a conventional triangular prism, it can be compared with a conventional simple triangular prism coupler. By comparing, the following effects can be obtained.

(1) By changing the position of the apex angle 9, the bonding surface length can be adjusted.
Since L ₁ can be changed arbitrarily, the bonding surface length L ₁ can be changed to the optimum length according to the diameter of the incident light beam and the precision of the substrate surface. Therefore, since the bonding surface length L ₁ can be shorter than the conventional bonding surface length, the requirement for substrate surface accuracy is much lower than that of the conventional triangular prism method. (About λ is possible). (2) Since an adjustment gap 10 is provided on the coupling surface 8 and the reflection side, it is possible to fill this gap 10 with a photocurable adhesive or the like, so that the prism can be It has become possible to bond much stronger than bonding only the periphery. (3) The prisms of FIGS. 2 and 3 cut the conventional triangular prism optical coupler 3 along the dotted line 12 so that the cost of the prism of the present invention can be almost the same as that of the conventional triangular prism coupler. obtained by Since this cut surface has no relation to the coupling of light, surface precision is not required at all. (4) Since the contact point 9 is an obtuse angle,
The wall thickness of the prism at this point is thicker than that of a conventional triangular prism. Therefore, even if strong pressure is applied to the prism in order to obtain the optimum air gap and bring the prism and the optical waveguide into good contact as described above, defects such as chipping are unlikely to occur as in the conventional case. Therefore, a good tapered air gap 4 is formed as a result, and extremely good transmission efficiency is obtained.

As can be understood from the above description, there is no strict limit to the obtuse angle of the one vertex angle of the triangular prism optical coupling prism section 11. However, unless the adjusting gap 10 is made much larger than the coupling gap, there is a possibility that stray light within the prism may be sent from the gap 10 into the optical waveguide 2 as a light wave traveling in the opposite direction to that of the optical waveguide 6. Also, when considering the final flow of adhesive into the gap 10, it is desirable that the taper angle is 10 degrees or more. However, if the taper angle is too large, the angle of the apex 9 will become steep and there is a possibility that the apex 9 will be bent. Therefore, it is preferable that the taper angle is 45 degrees or less. Further, the position of the apex 9 is usually selected so that the bond length is about 1 mm. In the example we are actually using, the adjustment gap angle is 10° and the tapered air gap angle is 0.5mrad, so the apex angle is 170°, the length of the adjustment gap is 2mm, and the connection length is approximately 1.
mm.

In addition, the slope of the prism 3a for normal introduction and the incident light 5
When the angles are at right angles, there is less reflection, and since there is no effect of refraction on slopes, adjustment becomes easier. If we consider the conditions that the refractive index of the substrate 1 is 1.77, the refractive index of the optical waveguide thin film 2 is 2.6, and the refractive index of the coupling prism is 3.3, the slope and the incident light 5 are at right angles and the light is transmitted within the film. The angle of incidence on the thin film must be 51°. Therefore, in this example, the obtuse angle of the apex 9 is preferably 129 degrees or more.

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 5 shows a light coupling prism showing a second embodiment of the present invention. The numbering is the same as in FIG. 2, and in the case of this embodiment, the light introducing prism part 12
a is a quadrangular prism, and a triangular prism 1 constitutes the adjustment air gap 10.
A part of the slope 13 of 1 is also used as a reflective surface. Therefore, the incident light 5 is reflected by the reflecting surface 13 and then sent to the coupling surface 8 and guided to the optical waveguide 2. This embodiment differs from the previous embodiment in that the incident light 5 is sent perpendicularly to the substrate, and also has the features described in the previous embodiments.

In the case of this embodiment, the angle and position of the apex 9 must be designed so that the light beam reflected from the reflecting surface 13 reaches the coupling surface 8. As an example, a substrate,
Assuming that the refractive index of the optical waveguide and the coupling prism are the same as described above, the introducing prism 1 as shown in FIG.
In order for 2a and the incident light 5 to be at right angles, the vertex 9
The obtuse angle of must be 115°.

In addition, although the above-mentioned embodiment described the case where light is made to enter the waveguide, the present invention is also applicable to the case where light is made to exit from the waveguide.

FIG. 6 shows an optical transmission device in which the optical coupling device of FIG. 2 of the present invention is used as both the light input section and the light output section, and 14 is the output light. Figure 7 shows the third
This shows an optical transmission device using the device shown in the figure.

The above explanation has been given for the case where all the bonding surfaces are straight lines, but in reality they do not need to be straight lines. Rather, the paper by R. Ulrich mentioned above states that the optimal bonding surface is not a straight line. Therefore, the gap 4 created between the bonding surface and the substrate is not a linearly tapered air gap, but a tapered air gap corresponding to a certain function. The tapered air gap that has been described so far naturally includes the above meaning.

Effects of the Invention The optical coupling prism of the present invention has a coupling triangular prism part having an obtuse angle with respect to the waveguide prism part, and the coupling surface is one slope of the coupling triangular prism part. Therefore, it can be manufactured at almost the same cost as a conventional triangular prism column, and the surface accuracy of the substrate is about 1/10, making it possible to achieve optical coupling with the same or higher efficiency than conventional prisms. A stable and fixable optical coupling device can be obtained,
Its industrial effects are significant.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical coupling device using a conventional coupling triangular prism, FIG. 2 is a side view of the optical coupling device according to the first embodiment of the present invention, and FIG. 3 is a coupling section of FIG. 2. , FIG. 4 is a side view for explaining processing of the present invention, FIG. 5 is a side view of the optical coupling device according to the second embodiment of the present invention, and FIG. A schematic diagram of an optical transmission device used as an optical input/output section. FIG. 7 is a schematic diagram of an optical transmission device using the device of FIG. 5 of the present invention as an input/output section. 1...Substrate, 2...Transparent dielectric optical waveguide, 3a
...triangular prism for optical waveguide, 4...tapered air gap, 5...incident light flux, 6...progressing direction of light, 7...optical coupling point, 8...coupling surface, 9...contact point, 11... ... Triangular prism part for triangular prism-shaped light coupling, 12 ... Cutting line, 12a ... Quadrilateral prism, 13 ... Reflection surface, 14 ... Outgoing light flux.

Claims (1)

[Scope of Claims] 1. A triangular prism-shaped optical coupling prism part and an optical waveguide prism part each having an obtuse apex angle and an optical coupling surface are installed on an optical waveguide formed on a substrate, and The apex angle having the one apex angle of the optical coupling prism portion is brought into contact with the optical waveguide portion, and the light beams from both prisms are made to enter the optical waveguide portion, or the light beams from the optical waveguide portion are made to be incident on the optical waveguide portion. An optical coupling device characterized by emitting light from both prisms. 2. The optical coupling device according to claim 1, wherein the optical waveguide prism portion is a triangular prism or quadrangular prism. 3. The optical coupling device according to claim 1, wherein one slope connected to the apex of the optical coupling prism section is a reflective surface.