JPH03192207A - Waveguide, prism coupler and prism joining method - Google Patents

Abstract

PURPOSE:To provide the joint form of a prism with high accuracy by pressing the reference section of the prism to be joined to a pattern for positioning and joining the prism by an adhesive layer. CONSTITUTION:A gap layer 3 is formed of a material having the refractive index lower than the refractive index of an optical waveguide layer 2 on the optical waveguide layer 2 at a prescribed thickness. The pattern 6 for positioning for regulating the joint form of the prism 4 is formed as a projecting part by photolithography on this gap layer 3. An adhesive having the refractive index higher than the adhesive of the optical waveguide layer 2 is applied thinly on the gap layer 3 formed with the pattern 6 for positioning to form the adhesive layer 5. The reference part of the prism 4 to be joined is then pressed to the pattern 6 for positioning to execute the positioning of the prism. The prism 4 is joined by the adhesive layer 5 with high accuracy to the gap layer 3 in this way and the optical performance of the function element is sufficiently exhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveguide/prism coupler and a prism joining method.

[Prior Art] A waveguide/prism coupler is an optical device that optically couples a light beam from the outside to an optical waveguide HIM via a prism in order to guide the waveguide to an optical waveguide layer formed on a substrate. be.

In order to obtain good optical coupling efficiency with a waveguide/prism coupler, it is necessary to maintain a constant distance between the prism and the optical waveguide layer.

As a method of joining prisms while keeping the distance between the prism and the optical waveguide layer constant, the leading wave HI is placed on the optical waveguide layer.
A gap layer is formed to a predetermined thickness using a material with a refractive index lower than that of NI, and a thin adhesive layer made of an adhesive with a higher refractive index than the optical waveguide layer is provided on top of the gap layer. A method of bonding a prism onto a gap layer is known (IEEE J, Quantum El
electronics QE-6, 557 (1970) F
, Zernike et al., Improve V.
version of the Evanescent
-Wave Coupler).

[Problems to be Solved by the Invention] Functional elements such as mirrors, condensing lenses, light receiving elements, mode separation elements, etc. are generally formed in the optical waveguide layer of the waveguide/prism coupler.

These functional elements themselves are formed with extremely high precision, and in order for the functional elements to exhibit the desired optical performance, the light beam incident position and angle of incidence must be adjusted even for optical coupling using a prism. High precision is required.

Conventionally, in the bonding method of bonding a prism onto the gap layer described above, the bonding state of the prism, that is, the bonding position, bonding direction, etc., have been determined by mechanical alignment. Therefore, the accuracy of the joining position of the prism is rougher than the formation accuracy of the functional element itself, and therefore, the optical performance of the functional element may not be fully exhibited.

The present invention was made in view of the above-mentioned circumstances, and
The purpose of the present invention is to provide a waveguide/prism coupler in which the prism bonding position is adjusted with extremely high precision, and a prism bonding method that can realize a highly accurate bonding position.

[Means for Solving the Problems] Hereinafter, the invention of claim 1 which characterizes the present invention is ``For optically coupling a light beam to an optical waveguide layer formed on a substrate and having a functional element via a gap layer. Method of bonding the prism on the gap layer J
It has the following characteristics.

That is, the gap layer is formed on the optical waveguide layer with a predetermined thickness using a material with a lower refractive index than that of the optical waveguide layer. A pattern is formed as a convex portion by photolithography.

Then, on the gap layer in which the positioning pattern J is formed, a thin layer of adhesive having a higher refractive index than the optical waveguide layer is applied to form an adhesive layer.

Next, the reference portion of the prism to be joined is brought into contact with the "positioning pattern" to align the prism, and the prism is characterized by an adhesive layer.The invention of claim 2 is a "waveguide/prism coupler"; A structural feature is that the prism is joined by the method of claim 1 above.

[Function] In the present invention, the prisms to be joined are aligned by bringing the reference portion into contact with the positioning pattern j.

Since the "positioning pattern" is formed as a convex portion by photolithography, its formation accuracy can be comparable to that of the functional element in the optical waveguide layer.

[Embodiments] Hereinafter, specific embodiments will be described with reference to the drawings.

FIG. 1 is an explanatory diagram showing one embodiment of the waveguide/prism coupler of the present invention as a three-view diagram.

In the figure, numeral 1 is a substrate, numeral 2 is an optical waveguide layer, numeral 3 is a gap layer, numeral 4 is a prism, 5 is an adhesive layer, numeral 6
indicate the positioning patterns, respectively.

In this waveguide/prism coupler, the prism 4 is joined as follows.

The optical waveguide layer 2 is formed on the substrate 1 and has functional elements. The gap layer 3 is formed on the optical waveguide layer 2 to a predetermined thickness. The gap layer 3 has a lower refractive index than the optical waveguide layer 2.

Standards for prism bonding are established on the substrate side.

Now, a layer of an appropriate thickness is formed on the gap layer 3 using a photosensitive thick film resin. Then, known photolithography is performed on this layer of photosensitive thick film resin, leaving a "hook-shaped" positioning pattern as shown in FIG. remove. In this way, the positioning pattern 6 is formed as a convex portion on the gap layer 3. The thickness of this convex portion is the thickness of the photosensitive thick film resin layer formed previously, but it is the thickness necessary to align the prism, for example, several tens of μm.
shall be. Of course, the formation position of the positioning pattern 6 is accurately determined by the above-mentioned criteria for prism bonding.

Next, an adhesive having a higher refractive index than the optical waveguide layer is applied to the entire surface of the gear wheel 3 including the positioning pattern 4. The thickness of the adhesive layer 5 thus formed is made sufficiently thinner than the thickness of the positioning pattern so that the adhesive layer follows the convex portions of the positioning pattern.

Next, use the two sides of the prism 4 as reference parts, and set these two sides as reference parts.
Positioning is performed by bringing the two sides into contact with the sides a-b and b-c of the positioning pattern, and the prism 4 is pressed against the adhesive ffB5 to be adhesively fixed.

Thereafter, by removing the adhesive layer 5 protruding from the bottom surface of the prism, the waveguide/prism coupler shown in FIG. 1 can be obtained.

FIG. 2 shows another embodiment.

The difference from the embodiment shown in FIG. 1 is that the positioning pattern is composed of two patterns 6A and 8B;
, 8B are separated from each other. The process of joining the prism 4 is the same as in the embodiment shown in FIG.

If the pattern is hook-shaped like the positioning pattern 6 in Figure 1, the adhesive tends to accumulate at the corners of the positioning pattern, and the thickness of the adhesive layer tends to increase in these areas. Adhesive must be applied to prevent this from happening, but if it is composed of two separated patterns 6A and 8B like the positioning pattern in Figure 2, the problem of adhesive pooling as described above will occur. Since there is no adhesive layer, it is easy to form an adhesive layer.

The positioning of the prism uses the two sides of the prism as reference parts, and these are the sides a-b and b' of patterns 8A and 6B.
− Do this by touching it to 〇.

In the above example, the adhesive was applied to the entire surface of the gap layer, but the adhesive layer may be formed only on the minimum portion necessary for adhering the prism.

Further, after adhering the prism, the adhesive layer protruding from the bottom of the prism can be removed as necessary, and if it is not necessary to remove it, it can be left as is.Also, the positioning pattern 6 can also be removed after adhering the prism. It can be removed if necessary.

As the photosensitive thick film resin used for forming the positioning pattern in the above explanation, for example, Probimide 348 (
(Product name: Ciba Geigy) etc. can be used.

In addition to the method using the photosensitive thick film resin described above, the positioning pattern can be produced using resin films such as polyimide, SOG films,
Patterning the 5i02 film etc. with photoresist,
This is also possible by etching.

[Effects of the Invention] According to the present invention, a novel waveguide/prism coupler and a novel prism joining method can be provided.

According to the present invention, it is possible to realize a waveguide/prism coupler in which a prism can be bonded to a gap layer with extremely high precision and the optical performance of a five-functional element can be fully exhibited.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining one embodiment of the present invention, and FIG.
The figure is a diagram for explaining another embodiment.

Claims (1)

[Claims] 1. A method of bonding a prism on the gap layer for optically coupling a light beam to an optical waveguide layer formed on a substrate and having a functional element via the gap layer, comprising: A positioning pattern for regulating the bonding position of the prism is formed as a convex portion by photolithography on the gap layer formed on the optical waveguide layer to a predetermined thickness using a material having a refractive index lower than that of the optical waveguide layer. and on the gap layer on which the positioning pattern is formed,
Apply a thin layer of adhesive with a higher refractive index than the optical waveguide layer to form an adhesive layer, align the prism by bringing the reference part of the prism to be joined into contact with the positioning pattern, and then use the adhesive layer to secure the prism. A prism bonding method characterized by bonding. 2. A waveguide/prism coupler formed by joining a prism by the method according to claim 1.