JPS61133906A - Optical confluence circuit - Google Patents

Abstract

PURPOSE:To shorten a circuit length and to permit a large-scale integration by providing plural optical guides for input on a base plate, providing an optical waveguide for output to intersect therewith and providing reflection faces on the intersected parts thereof. CONSTITUTION:The plural optical waveguides 3-1-3-n for input and one optical waveguide 4 for output intersecting therewith are provided on a base plate G. The reflection faces 6-1-6-n which incline at the same angle phi with both of the waveguides 3-1-3, 4 in both directions of the plate G are provided to the side faces in the intersected parts 5 of the waveguides 3-1-3, 4 for the input and output. The light of the reflection mode theta of which the angle with the side faces of the waveguides 3-1-3-n is below the critical angle propagates in the waveguides 3-1-3-n from the total reflecting conditions of the light. The light of the mode theta is made incident at the prescribed angle on the reflection face 6-k and the light inputted to the optical waveguide 3-k for output is outputted to an output port 7. The reflection mode theta is not affected by the reflection faces 6-k+1-6-n and therefore said light propagates in the waveguide 4 without radiation loss. The greater part of the light power is thus outputted to the port 7 and the optical confluence is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to an optical merging circuit having an optical waveguide structure and merging light.

"Prior Art" Conventionally, as shown in FIG. 6, this type of optical circuit gradually changes the direction of light propagating inside the waveguide by very gradual changes in the shape of the waveguide, and connects multiple input optical waveguides. 1-
It was configured so that the input lights P1 to Pn inputted to the channels 1 to ln are taken out from one output optical waveguide 2 as output light P out . In the circuit shown in FIG. 6, most of the light is transferred to the input/output optical waveguide by increasing the width of the output optical waveguide 20 by n times the width of each of the input optical waveguides 1-1 to 1-n. It was known that 1-1 to 1-n and 2 could merge without radiating outward.

``Problem to be solved by the invention'' However, in such a configuration, continuous and gradual shape change is essential, so the circuit length (the entire length of the input/output optical waveguide) is usually about Wl. Therefore, there is a problem in that a large number of circuits cannot be efficiently integrated in a small area compared to semiconductor circuits and the like.

"Means for Solving the Problems" The present invention has been made to solve such problems, and the first invention of the present invention is to provide a plurality of manual optical waveguides on a substrate, An output optical waveguide is provided to intersect with these, and a reflecting surface is provided at the intersection of these to reflect the light in the input optical waveguide into the output optical waveguide. In addition, in this first invention, a low refractive index layer having a lower refractive index than the medium outside the input/output optical waveguide is provided outside the intersection, or the upper surface K of the input/output optical waveguide is It is desirable to provide a waveguide layer with a refractive index higher than ~10.Furthermore, the third aspect of the present invention is to provide input optical waveguides with KiJi numbers on a substrate, and these manual optical waveguides with [intersecting outputs]. A plurality of merging circuits each consisting of optical waveguides are provided, and any input optical waveguide in at least one of these merging circuits is made to intersect with an output optical waveguide of another merging circuit. It is. On this substrate q, a plurality of input optical waveguides 3-1 to 3-n are provided, and one output optical waveguide 4 intersecting these input optical waveguides 3-1 to 3-n is provided. It is being

Intersection 1 of these input and output optical waveguides (hereinafter referred to as input/output optical waveguides) 3-1 to 3-n@4! M
The side surface of 5 is inclined toward the plane of the substrate G at the same angle ψ with respect to both of these input/output optical waveguides.

Oblique reflective surfaces 6-1 to 5-n are provided.

Note that the reference numeral 7 in the figure indicates an output boat.

Leading waveguides 3-1 to 3-n, 4 for input and output of this optical combining circuit
To form this, photolithography technology was applied to a quartz fiber waveguide film. In this example, amorphous 81 is masked,
Also, C, F6 and C! The input/output optical waveguides 3-1 to 3n*4 were formed by a reactive ion etching method using a mixed gas of H4 as an etching gas. Thickness 5μm,
Substrate] The relative refractive index difference with respect to K is a2%, and the sides and upper sides of these input/output optical waveguides 3-1 to 3 ns4 are in contact with air (refractive index /, O). In addition, the refractive index of the input/output optical waveguides 3-1 to 3-n*4 is 111 and the width of the input/output optical waveguides 3-1 to 3-n17) is 10 μm. The width of the optical waveguide 4 increases each time it intersects the input optical waveguides 3-1 to 3-n, and the intersection angle of the input/output optical waveguides is 3θ0, and the reflection surface 6
The inclination angle ψ of -1 to 5-n is set to /&'.

In the optical merging circuit configured as described above, in the manual optical waveguides 3-1 to 3-n, the angle formed with the side surface of the input optical waveguides 3-1 to 3-n is a critical angle 1θc due to the total reflection condition of light.
Light in the reflection mode θ of less than l(θc −9θ−5ia−′ −/, φ6 Kazuhiro 7°) propagates.

For example, as shown in FIG. 2, the light in the reflection mode θ is
The light is incident on the reflecting surface 5-k at an angle θ-ψ or θ+ψ. If the conditions of 1θ−1pl and 1θ+ψ1×θC are satisfied, the propagating light is totally reflected by the reflecting surface 6- and passes through the output optical waveguide 4.
Enter. At that time, the reflection mode θ is equal to the reflection mode in the input optical waveguide 3-k, and the critical angle θC of the output optical waveguide 4 is also equal to the critical angle θ of the input optical waveguide 3-, so the input source is the same as the reflection mode in the input optical waveguide 3-k. It can propagate within the optical waveguide 4.

On the other hand, light that exceeds the range of the inner boundary angle θC of light reflected at one angle 1θ−ψI or 10+ψ1 is not totally reflected. However, according to Fournel's law, a certain amount of optical power is reflected, and in general, in the reflection mode of light propagating in a waveguide, the larger 1θ1 is, the lower the power density is, so the critical angle θ. Since the optical power of light exceeding the range is small, the loss due to radiation is small.
The light Pk input to - is output to the output port door. However, since the reflection mode θ is preserved on the reflection surface 6- without being affected by +1 to 6-n, it can be propagated within the output optical waveguide 4 without radiation loss, and as a result, the magnitude of the input light P1 to F is reduced. Part of the light pipe can be taken out from the output port door, and light merging gutter function can be realized.

By the way, in the fabrication example of the n-1I3 circuit, P.

Reflection surface 6 when p,,p, are output to the output port door
The losses caused by being radiated out of the waveguide without being reflected at -1 to 6-3 are respectively l s dB, knee dB,
It was Yuko dB.

In addition, in this embodiment, it is possible to further increase the reflectance and reduce the above loss by the following method. After manufacturing the circuit shown in FIG. 1, only the reflective surfaces 6-1 to 5-n 5 to 7 The resist material is patterned using an otolithography technique, and then a metal film with high light reflectance, such as a gold or aluminum film, is formed by vapor deposition, and the resist material is removed. That is, the reflective surfaces 6-1 to 6-n
A metal film is provided on the outside of the According to this method, light reflection occurs on the metal film, so even if light exceeding the critical angle is incident on the reflecting surfaces 6-1 to 6-n, this light will not be radiated out of the input/output optical waveguide. It is reflected and enters the output leading waveguide 4, so that loss due to radiation can be reduced.

On the other hand, FIG. 3 shows a second embodiment of the present invention, in which reference numeral 8 denotes a confluence circuit manufactured according to the first embodiment, and reference numeral 9 denotes input/output optical waveguides 3-1 to 3-n, 4 of the confluence circuit. - It is a medium (cladding layer) with a lower refractive index and a lower OI, and a merging circuit 8 is embedded therein. 10 is a merging circuit 80 reflecting surfaces 6-1 to 5
- A groove for exposing n to the air. That is, this groove 10 allows the outside of the intersection 5 (the reflective surfaces 6-1 to 6-1 to
6-n) An air layer (low refractive index layer) 11 having a lower refractive index than the K cladding layer 9 is provided.

In this embodiment, the cladding layer 9 is a quartz glass layer, and the first
Applying the same photophosphorography technique as in the example again,
◎ In this optical merging circuit in which the convenient new groove 10 is formed, the refractive index difference between the input/output optical waveguides 3-1 to 3-n, 4 and the cladding M9 is the inside and outside of the intersection 5, that is, the input/output optical waveguide 3-n. 1~
Since the refractive index difference between 3-n and 4 and the low refractive index layer 11 is smaller, the critical angle θC in the input/output optical waveguide becomes smaller than the critical angle θC/ at the intersection 5. . Therefore, it is possible to widen the range of reflection modes θ that can be reflected by the reflecting surfaces 6-1 to 6-n, and more incident light can be reflected.

Further, Fig. 3 shows the @3 embodiment of the present invention, and the input/output optical waveguide 3-1 manufactured according to the first embodiment shown in Fig. 1 is shown in Fig. 1.
~3-n@ Waveguide layer 1 with a higher refractive index on top of 4
2, and the input end of the waveguide layer 120 is tapered, that is, directed toward the input end, so that the light guided through the input optical waveguides 3-1 to 3-n quickly transfers to the waveguide layer 12. It is an optical merging circuit formed in a shape in which the wall thickness gradually decreases.@In this embodiment, the waveguide layer 12 is Tag 0g + SiO,
It was formed using a sputtered film using a target material. The input/output optical waveguides 3-1 to 3-n and 4 were patterned by the same reactive sputter ion etching method as in the first embodiment after the waveguide layer 12 was formed.

According to this circuit, most of the light input to the input optical waveguides 3-1 to 3-n transfers to the waveguide layer 12 having a higher refractive index. Moreover, the refractive index of the waveguide layer 12 is the same as that of the input/output optical waveguide 3-
Since the total reflection critical angle θC/ at the intersection increases because it is higher than 1 to 3-n e 4, the intersection angle ψ between the input and output optical waveguides can be made larger, and the optical merging circuit becomes more Miniaturized. Also, the outside of the circuit is refracted by lφS
The waveguide end can be cladded with a medium of about 0.00m, which can reduce the propagation loss of the waveguide itself. When connecting fibers, connection loss can be kept small.

FIG. 5 shows the first embodiment of the present invention, in which the first embodiment,
A plurality of merging circuits 13 manufactured according to the fourth embodiment or the third embodiment are arranged in an array on the same substrate G. In this figure, Ll is an input port, and is configured so that light input from the input optical waveguide 14 to the input optical waveguide 14 is output to the output port Oj via one of the output optical waveguides 15. has been done. That is, in each merging circuit 13iC, among the input optical waveguides 14 that intersect with the output optical waveguide 15 in a T-shape, several input angle optical waveguides 14 are extended in the length direction, It crosses the output optical waveguide 15 in an X-shape, and crosses the output optical waveguide 15 of the other merging circuit 13 in a T-shape. In this figure, the reflective surface is provided only at the T-shaped intersection T. Generally, in a party merging circuit, as shown in FIG.
The input lights No. 11 to Iln are often required to be output to another output port Ok, and therefore, the input lights No. 11 to Iln are often required to be output to another output port Ok. As shown by the symbol X in the figure, it is necessary to intersect the input/output optical waveguides 14 and 15 in an X-shape. This has the disadvantage that the crosstalk at the X-shaped intersection becomes large and the performance deteriorates because of the extremely small value. On the other hand, in the optical combining circuit of this embodiment, the input/output optical waveguides 14 and 15 intersect each other at a steep angle, so there is less crosstalk at the X-shaped intersection W6X, and a compact circuit can be realized. By the way, as a result of manufacturing the n-hiro original merging circuit array using the same process as the example shown in Fig. 1, the crosstalk at each X-shaped intersection X was extremely small, less than -30 dB. Effects of the Invention As explained above, according to the present invention, the light merging function is realized by reflection without using continuous shape changes, which shortens the circuit length and enables high integration. Since the input/output optical waveguides intersect at a steep angle, the waveguide intersections necessary for various applications can be realized with less crosstalk, which is an excellent effect.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention;
The figure is a plan view, FIG. 1 is an enlarged view of the main part, FIG. 3 is a perspective view showing the third embodiment of the present invention, FIG. FIG. 2 is a plan view showing the φth embodiment of the present invention. FIG. 6 is a plan view of a conventional optical circuit. 3-1 to 3-n114... Input optical waveguide, 4
゜15...Output optical waveguide 5...Intersection, 6-1 to 6-n...Reflection surface, 7...
・Output port, 8...Merge circuit, 9...
・Medium (cladding layer), 10... Groove, 11...
...Low refractive index layer (air m>, 12... Waveguide layer, 13... Merging circuit, P, ~Pn...
...Input light, Pout ...Output light, III~
Machining tray...Input boat, 0, ~On...
・Output port, T...T-shaped intersection, X...
...X-shaped intersection, G... substrate, θ...
...Reflection mode, θC1θC'...Critical angle, ψ...Inclination angle, Coψ...Intersection angle.

Claims (4)

[Claims] (1) A plurality of input optical waveguides are provided on the substrate, and an output optical waveguide is provided that intersects with these input optical waveguides. An optical convergence circuit that has a reflecting surface that reflects the light into the output optical waveguide. (2) The reflective surface is configured by providing a low refractive index layer having a lower refractive index than a medium outside the input/output optical waveguide on the outside of the intersection. The optical merging circuit according to scope 1. (3) The input optical waveguide and the output optical waveguide are provided with a waveguide layer having a higher refractive index than the input/output optical waveguide on their upper surfaces. optical convergence circuit. (4) A plurality of merging circuits each consisting of a plurality of input optical waveguides and an output optical waveguide that intersects with these input optical waveguides are provided on the substrate, and an arbitrary number of merging circuits in at least one of these merging circuits are provided. The input optical waveguide intersects with the output optical waveguide of another merging circuit, and a reflective surface is provided at the intersection of these input/output optical waveguides to reflect the light in the input optical waveguide into the output optical waveguide. Light convergence circuit.