JPH1130735A - Hybrid optical circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the high-performance, low-cost hybrid optical integrated circuit used for optical communication. SOLUTION: The hybrid optical circuit which includes an optical element having a light input end and a light output end at opposite positions on the substrate, an optical waveguide circuit coupled optically at the light input end and light output end of the optical element, and an element fixation part for fixing the optical element and is provided with positioning marks at corresponding positions of the optical element and element fixation part and then positioned and fixed so that the positioning marks have specific position relation is provided with >=2 positioning marks 21a to 21c for one of the light input end and light output end and >=1 positioning mark 22a for the other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an optical communication system,
The present invention relates to a high-performance and low-cost hybrid optical integrated circuit.

[0002]

2. Description of the Related Art In recent years, hybrid optical circuits in which an active optical element and a passive optical waveguide circuit are combined have been actively developed. By the way, in order to perform optical coupling between an optical element and an optical waveguide circuit, high-precision alignment in units of microns is required. In the production of a conventional optical component, alignment has been performed by actually performing alignment using light to maximize the coupling. However, this alignment work makes it difficult to reduce the cost of the optical component, and also makes it difficult to create a new high-performance hybrid optical circuit. In order to solve this problem, a method of simply performing high-accuracy alignment without using light has been studied.

FIG. 6 shows a first example of a conventional hybrid optical circuit. In this example, a two-channel semiconductor optical amplifier 11 as an optical element, an optical fiber 1 as an optical waveguide,
The configuration is such that the silicon substrate 2 is used as the element fixing section 4. In this conventional example, in order to align the semiconductor optical amplifier 11 and the optical fiber 1, the silicon substrate 2 is used.
Is provided with a highly accurate positioning V-groove 15 formed using anisotropic etching. Simply placing the semiconductor optical amplifier 11 and the optical fiber 1 in the positioning V-groove 15 automatically completes highly accurate positioning.

However, it is generally not always easy to form a structure in which such a highly accurate positioning V-groove 15 is provided. That is, in the case of hybrid optical integration of a planar optical circuit such as a silica-based optical waveguide and an optical element, it is necessary to provide the above structure on a planar optical circuit board. The process is inevitably complicated, and is not suitable for reducing the cost of optical components.

FIG. 7 shows a second conventional example. In this example, a semiconductor laser 10 is used as an optical element and a quartz optical waveguide 3 is used as an optical waveguide circuit. What is different from the first conventional example is that the positioning structure is very simple, instead of a complicated uneven structure.
Is provided on the optical element and the element fixing portion. Alignment can be easily achieved by adjusting the marks 12, 5 so that they have a predetermined positional relationship with each other.
Here, the alignment marks 12 and 5 can be easily formed by embossing the surfaces of the optical element and the element fixing portion, or by using a thin film such as a metal, so that a complicated process is required. do not need. Therefore, the present method is applicable in many cases and is suitable for achieving cost reduction.

However, in the conventional method using the alignment mark, an optical element having an optical input end and an optical output end at opposing positions on a substrate such as a semiconductor optical amplifier,
There has been no example of successful hybrid integration with an optical waveguide circuit.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly accurate and simple optical waveguide circuit having an optical element having an optical input end and an optical output end at opposing positions on a substrate. It is an object of the present invention to provide a low-cost and high-performance hybrid optical circuit which enables accurate alignment.

[0008]

According to the first aspect of the present invention, there is provided an optical element having an optical input end and an optical output end at opposing positions on a substrate, and an optical input end and an optical output end of the optical element. An optical waveguide circuit that performs optical coupling, including an element fixing portion for fixing the optical element, of the optical element and the element fixing portion,
Positioning marks are provided at corresponding positions, and the positioning marks are positioned so as to have a predetermined positional relationship. In a fixed hybrid optical circuit, a light input end or a light Two or more alignment marks are provided on one of the output terminals, and one or more alignment marks are provided on the other output terminal.

[0009]

Embodiments of the present invention will be described below.

Conventionally, an alignment mark is provided only near one of the light input end and the light output end.
The present invention is different from the related art in that positioning marks are provided near both the light input end and the light output end, and positioning marks are provided at three or more points instead of two points.

That is, as described in the section of the prior art, the height of the optical waveguide and the optical element having the optical input end and the optical output end at positions opposing each other on the substrate by using the alignment marks so far. Accurate alignment has not been achieved. The reason for this is that conventionally, it was often considered that it was necessary and sufficient to provide marks at two points in a plane in order to perform alignment in a plane. If a semiconductor laser or the like has only one light input / output end and has a small element size, the positioning can be performed with sufficient accuracy by providing two marks. However, in the case of an optical element having an optical input end and an optical output end at opposing positions on a substrate such as a semiconductor optical amplifier, both of the optical input end and the optical output end are simultaneously positioned at a high precision in the two-point mark. It is difficult to perform the matching. This is because (1) there is an alignment error for each mark in actual alignment, resulting in an angular shift;
(2) There is a parallelism shift between the optical element and the element fixing part at the time of alignment, and (3) Both the optical element and the element fixing part are warped. by. Further, this has a considerable effect on a semiconductor optical amplifier having a large element size. In particular, the first reason, angular displacement, has been a factor that significantly deteriorates the positioning accuracy of a point sufficiently distant from the positioning mark.

According to the present invention, an alignment mark is provided in the vicinity of both the light input end and the light output end, and three marks are used instead of two points.
By providing alignment marks at positions equal to or more than a point, (1) the angular displacement of the optical element is effectively suppressed, and (2)
In addition, even when there is a parallelism shift between the optical element and the element fixing part and each of the optical element and the element fixing part has a warp, a proper alignment can be performed on a substrate such as a semiconductor optical amplifier. In the case of an optical element having a light input end and a light output end at a position opposite to the above, there is an effect that both the light input end and the light output end can be simultaneously and accurately and easily aligned.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention. The present embodiment shows a hybrid integration of the semiconductor optical amplifier 11 and the quartz optical waveguide 3. The element fixing portion is formed by processing a silicon substrate in advance into a convex shape and forming the quartz optical waveguide 3 on the silicon substrate. Was formed by etching.

The alignment mark is a semiconductor optical amplifier 1
Two were provided on one light input end side and one was provided on a light output end side. FIG. 2 shows an example of alignment using these marks. Here, the alignment mark of the present embodiment is formed by two cross-shaped marks 21 a and 21 on the back side of the semiconductor optical amplifier 11.
b is provided on the light input end 13 side, and one cross mark 21c is provided on the light output end 14 side. In addition, two marks 22a and 22b are provided on the light input end 13 side on the surface on the element fixing portion 4 side so as to correspond to these marks 21a to 21c, and one cross mark 22c is formed on the light output end 14 side. It is provided on the side. In the present embodiment, the shapes of the marks 22a to 22c on the surface of the fixing portion 4 are such that squares are arranged at four corners of a square corresponding to the cross-shaped mark provided on the semiconductor optical amplifier 11. However, the present invention is not limited to this. In the present embodiment, first, two corresponding marks 21 on the light input end 13 side are used.
a, 21b, 22a, 22b, and then one corresponding mark 21c, 22 at the light output end.
c was also combined.

As apparent from FIG. 2A, at the time when the alignment is performed using the two marks on the light input end 13 side, two corresponding marks 21a, 21b, 22a,
Since there is an alignment error in each of the semiconductor optical amplifiers 22b, an angle shift occurs in the entire semiconductor optical amplifier. For this reason, although the position is substantially adjusted at the light input end 13 relatively close to the mark, the position shift occurs at the light output end 14 far from the mark. On the other hand, as is clear from FIG. 2B, one corresponding mark 21 on the light output end 14 side.
After the adjustment of c and 22c, it can be seen that the angle shift is suppressed, and both the light input end 13 and the light output end 14 can be aligned at the same time.

(Embodiment 2) FIGS. 3 to 5 show a second embodiment of the present invention. In this embodiment, the hybrid integration of the semiconductor optical amplifier and the silica-based optical waveguide is shown using the same marks as in the first embodiment, but the optical element is not a single element but is connected to a four-channel element. Four marks 21, that is, an array element, a point in which the quartz optical waveguide substrate used is warped, and two alignment marks 21 on each of the optical input end and the optical output end.
The points provided with a to 21d and 22a to 22d are different from the first embodiment. Generally, the optical element 11 and the element fixing part 4 are
As shown in (1), both are not completely flat and often have a small amount of warpage. This warping poses a problem when an optical element having an optical input end and an optical output end at opposing positions on a substrate such as a semiconductor optical amplifier or an element such as an array element is large.

FIGS. 4 and 5 show the state after the two corresponding marks 21a, 21b, 22a and 22b at the light input end are aligned.
Four corresponding marks 21a-21d, 22a-22d
FIG. As shown in FIG. 4, the two marks 21a, 21b, 22a,
The displacement in the direction of the optical axis is increased only by adjusting the distance 22b. Therefore, as shown in FIG. 4, especially in the case of an optical element 11 having an optical input end 13 and an optical output end 14 at opposing positions on a substrate such as a semiconductor optical amplifier, both sides of the optical element are connected to an optical waveguide circuit. Differences occur in the gap, resulting in adverse effects on optical characteristics. In the worst case, the optical element 11 and the optical waveguide 3 come into contact with each other as shown in FIG. On the other hand, as shown in FIG. 5, after all the four marks 21a to 21d and 22a to 22d have been aligned, appropriate alignment has been performed also in the optical axis direction.

In general, when there is a warp, it is not possible to align two or more marks at the same time so as to have an original positional relationship. For this reason, it is necessary to adjust all the set marks so that the shift amounts are all equal. Therefore, by providing a large number of marks, not basically two marks as in the present embodiment, and performing alignment by using these marks at the same time, it is possible to achieve more accurate alignment.

As can be seen from the present embodiment, the present invention
In addition to effectively suppressing the angle shift, even if there is a parallelism shift between the optical element and the element fixing part, or if both the optical element and the element fixing part are warped, an appropriate position This has the effect of enabling matching.

Further, in the present embodiment, one of the marks provided at four points on the optical element has an incorrect shape due to damage. Even in such a case, by providing a large number of marks, alignment can be performed without lowering the accuracy.

Also, the alignment marks 21a-22
1, 22a to 22d may be marks and shapes that can be easily matched by corresponding marks, and are not limited to planar ones. It can be easily formed by processing or by using a thin film of metal or the like, and does not require a complicated process. Therefore, the present method is applicable in many cases and is suitable for achieving cost reduction.

[0023]

As described above, according to the present invention, two or more light input terminals or light output terminals of an optical element having a light input terminal and a light output terminal at opposing positions on a substrate are provided. Providing one or more alignment marks on the other side has the following effects. That is, (1) both the light input end and the light output end can be accurately and simply positioned. (2) High-precision alignment is possible even when there is a parallelism deviation between the optical element and the element fixing part. (3) High-precision positioning is enabled even when the optical element or the element fixing portion is warped. Therefore, the object of the present invention is to enable high-precision and simple alignment between an optical element having an optical input end and an optical output end at opposing positions on a substrate and an optical waveguide circuit, thereby reducing cost and cost. It has become possible to provide a high-performance hybrid optical circuit.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment.

FIG. 2 shows a state of alignment in the first embodiment.

FIG. 3 is a sectional view showing a second embodiment;

FIG. 4 illustrates a state of alignment in the second embodiment.

FIG. 5 illustrates a state of alignment in the second embodiment.

FIG. 6 is a first conventional example.

FIG. 7 is a second conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Si substrate 3 Quartz optical waveguide 4 Element fixing part 5, 22a-22d Positioning mark provided in element fixing part 10 Semiconductor laser 11 Semiconductor optical amplifier 12, 21a-21d Positioning mark provided in optical element Mark 13 Optical input end of optical element 14 Optical output end of optical element 15 V groove

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Fumihiro Ebisawa 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. An optical element having an optical input end and an optical output end at opposing positions on a substrate, an optical waveguide circuit for performing optical coupling at the optical input end and the optical output end of the optical element, and An element fixing portion for fixing, wherein alignment marks are provided at corresponding positions of the optical element and the element fixing portion, and the alignment marks are positioned so as to have a predetermined positional relationship. In a hybrid optical circuit to be aligned and fixed, two or more alignment marks are provided on one of an optical input end and an optical output end of the optical element, and one or more alignment marks are provided on the other one. And a hybrid optical circuit.