JP2000199825A - Optical circuit element and optical integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact wavelength selective filter element suited to high integration. SOLUTION: This filter element is constituted of first waveguide lines 8 constituted so that a beam is multiple reflected between two reflection surfaces 3, 4 to be propagated and second waveguide lines 91, 92,..., 9(n-1), 9n connected to the reflection surface 4. By using a waveguide length difference by repeating multiple reflection, an array output beam that a phase difference is controlled is obtained. Thus, an optical circuit element of a compact array waveguide diffraction grating, etc., is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength selective filter element for demultiplexing an arbitrary wavelength in wavelength multiplexed optical fiber communication, and more particularly to a wavelength selective filter element (optical circuit element) using an array waveguide element. The present invention relates to an optical integrated circuit equipped with this wavelength selection filter element.

[0002]

2. Description of the Related Art In recent years, demands for higher capacity in optical fiber communication have been increasing. For this reason, the introduction of a wavelength division multiplexing communication system using a plurality of wavelengths for a carrier is being promoted sequentially. The wavelength division multiplexing communication system has a great effect not only on increasing the capacity but also on the expandability and flexibility of the system for expanding the network of the required capacity at the required place. In order to cope with advanced networking in the future, it is indispensable to further increase the density of multiplexed wavelengths, but in order to realize such a high-density wavelength division multiplexing communication system, a high-performance narrowband wavelength selective filter is extremely important. . As a conventional example for realizing this, an arrayed waveguide type grating (AWG) element using a plurality of arrayed waveguides having different lengths each having a substantially constant length as shown in FIG. 14 has attracted attention. In this AWG element, input light from one input waveguide, for example, input waveguide 221 is diffused by an input-side slab-type star coupler 201, and array waveguides 231 and 23 arranged in front are provided.
, 23 (n-1), 23n. The array waveguides 231, 232,..., 23 (n-1), 23n have different waveguide lengths by a fixed length ΔL, respectively.
Each output end is given a delay due to the waveguide length difference. And array waveguides 231, 232,.
By combining the output terminals of (n-1) and 23n again with another output-side star coupler 202, they interfere with each other on the basis of the phase difference caused by the delay, and the output wavelength dependence of the output terminal of the output-side star coupler. Property, that is, dispersion characteristic d
x / dλ. Based on this linear dispersion, an output of a desired wavelength can be obtained from desired output waveguides 241, 242,... The AWG element can increase the linear dispersion because the diffraction order m can be increased in proportion to the waveguide length difference ΔL, and therefore can operate with low crosstalk even in the n × n multi-channel wavelength separation operation. It has the feature that it is.

[0003]

The wavelength characteristics such as the wavelength selectivity of the AWG element depend on the array waveguide length difference ΔL, the number of waveguides, the length of the star coupler, and the like. Up to now, it has been reported that a glass waveguide is used as an AWG element for multiplexing / demultiplexing 32 channels at sub-nanometer (nm) channel intervals, the waveguide length difference is about 60 μm, and the number of waveguides is 120. The overall chip size is as large as 40 mm square. This increase in overall chip size is a necessary result of the structure shown in FIG. That is, in the structure as shown in FIG. 14, as many as 100 array waveguides must be loosely arranged on the substrate surface to avoid excessive loss. In an optical integrated circuit for which higher integration is desired in the future, it is a serious problem in practical use that the array waveguide requires such a large area.

The present invention has been made to solve the above-mentioned problems of the prior art, and provides a wavelength-selective filter element (optical circuit element) using an array waveguide element which is compact and suitable for high integration. The purpose is to:

Another object of the present invention is to provide a compact and highly integrated optical integrated circuit equipped with a wavelength selective filter element (optical circuit element) using an array waveguide element.

[0006]

In order to achieve the above object, a first feature of the present invention is to provide a first waveguide array configured to propagate light with multiple reflections between two reflecting surfaces. And a second waveguide row or an output light row coupled to the waveguide row from the end of each reflection surface or between the reflection surfaces. Specifically, the first waveguide row may be configured to bend continuously between two reflecting surfaces in a zigzag manner, and a further bent portion or curved portion may be formed in this zigzag shape. "Coupled from the end of each reflection surface" means to couple with output light transmitted from a reflection surface such as a cleavage surface, and "coupled to a waveguide array between reflection surfaces".
A second waveguide array is arranged adjacent to the left and right or upper and lower sides of the first waveguide array, and output light is extracted to the second waveguide array by coupling between the two waveguides. The “second waveguide row or output light row” may mean that a second waveguide row is arranged adjacent to the first waveguide row, and the output light may be extracted to the second waveguide row. The light is extracted as light without using the second waveguide row, and the subsequent processing is not limited. That is, the output light may then be extracted to an optical fiber,
It may be taken out to various semiconductor waveguides or the like.

In the first aspect of the present invention, a light is reflected obliquely between two reflecting surfaces to give a constant optical path length difference to an optical signal output from each reflecting surface, thereby generating a phase difference. Let me. Therefore, according to the first aspect of the present invention, array output light with a controlled phase difference can be obtained with a simple structure. By using multiple reflections in this way, the longitudinal direction basically corresponds to the dimension of the order of the waveguide width multiplied by the number of waveguides, and the lateral direction corresponds to the phase difference required for device characteristics. Since the length of the waveguide is sufficient, an extremely compact array waveguide can be realized.

A second feature of the present invention is that a first array of waveguides is arranged so that light propagates by multiple reflection between two reflecting surfaces, and a waveguide array from each reflecting end or between the reflecting surfaces. , An optical circuit element including a second waveguide row coupled to the second waveguide row, a multiplexer coupled to the second waveguide row, and a third waveguide row coupled to the multiplexer. As the multiplexer, a star coupler or the like can be typically used.

According to the second aspect of the present invention, similarly to the first aspect, the array output light whose phase difference is controlled is obliquely multiple-reflected between the two reflecting surfaces, thereby providing an optical path length difference. Is obtained with a simple structure. Therefore, the longitudinal direction is basically a dimension of the order of the waveguide width multiplied by the number of waveguides, and the lateral direction is the waveguide length dimension corresponding to the phase difference required for device characteristics. An extremely compact array waveguide can be realized. For this reason, even if a multiplexer such as a star coupler is included, the size can be extremely reduced. Therefore, it can be easily applied to a semiconductor waveguide because of its compactness, and a semiconductor AWG multiplexing / demultiplexing device using an array waveguide and other optical functional devices can be easily realized.

In the first and second aspects of the present invention, a mechanism for independently controlling the phase or amplitude of light propagating through each of the waveguides forming the first or second waveguide row is added. Then, a high-performance optical filter such as an optical transversal filter can be realized. In order to control the phase and amplitude of the waveguide, a large refractive index change and an optical amplification function unique to the semiconductor may be used.

A third feature of the present invention is that a first array of waveguides configured to propagate light by multiple reflection between two reflecting surfaces and a guide from the end of each reflecting surface or between the reflecting surfaces. An optical circuit element comprising a second waveguide row coupled to the waveguide row;
Integrated circuit in which at least one of a light emitting element coupled to an input waveguide connected to an input end of a waveguide array and a light receiving element coupled to an output side of a second waveguide array are formed on the same substrate It is to be.

In the third aspect of the present invention, a phase difference is generated in an optical signal output by obliquely multiple reflection between two reflecting surfaces, so that light having a desired wavelength can be selected. To use multiple reflections, the longitudinal direction is the dimension of the order of the waveguide width multiplied by the number of waveguides, and the lateral direction is the waveguide length corresponding to the phase difference required for the characteristics of the optical integrated circuit. The dimensions of Therefore, an extremely compact optical integrated circuit can be realized.

A fourth feature of the present invention is that a first waveguide array configured to propagate light by multiple reflection between two reflecting surfaces, and a waveguide from each reflecting end or between the reflecting surfaces. An optical circuit element including a second waveguide row coupled to the row, a multiplexer coupled to the second waveguide row, and a third waveguide row coupled to the multiplexer; An optical integrated circuit in which at least one of the light emitting element coupled to the input end of the waveguide array and the light receiving element coupled to the output side of the third waveguide array is formed on the same substrate.

In the fourth aspect of the present invention, a phase difference is generated in an optical signal output by obliquely multiple reflection between two reflecting surfaces, so that light having a desired wavelength can be selected. Since multiple reflections are used, the length in the longitudinal direction is the dimension of the waveguide width multiplied by the number of waveguides, and the lateral direction is the waveguide length corresponding to the phase difference required for the characteristics of the optical integrated circuit. The dimensions of Therefore, an extremely miniaturized optical integrated circuit equipped with a multiplexer such as a star coupler can be realized. Further, because of its compactness, integration on a semiconductor substrate is easy, and a semiconductor A using an array waveguide is used.
WG multiplexing / demultiplexing elements and other optical functional elements can be integrated easily and with high density.

The optical integrated circuits according to the third and fourth aspects of the present invention need not necessarily be monolithically integrated on a semiconductor substrate. A hybrid integrated circuit in which an optical circuit element and at least one of a light emitting element and a light receiving element are mounted on an insulating substrate may be used. Further, various other semiconductor chip circuit elements may be mounted. Since “at least one is formed on the same substrate”, both the light-emitting element and the light-receiving element may be mounted on the same substrate, or one of them may be omitted.
That is, it may be divided into a transmission optical integrated circuit in which a light emitting element and an optical circuit element are integrated, and a reception optical integrated circuit in which a light receiving element and an optical circuit element are integrated. Also,
A compact optical integrated circuit can be provided by controlling the phase and amplitude of the waveguide using a large refractive index change and an optical amplification function inherent to the semiconductor.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic diagram showing a basic structure of a wavelength selective filter element (optical circuit element) using a multiple reflection array waveguide according to a first embodiment of the present invention. FIG. Here, InGaAs is used as a material.
An example using sP / InP will be described. As shown in FIG. 1, the optical circuit device according to the first embodiment of the present invention includes:
A first waveguide array 8 configured to propagate light by multiple reflection between the two reflecting surfaces 3 and 4 and a second waveguide array coupled to the end of each reflecting surface 3 and 4 (output Waveguide arrays) 91, 92,
..., 9 (n−1) and 9n. The first waveguide array 8 having a zigzag shape is made of InG having a width of about 2 μm.
a multiple reflection array waveguide composed of aAsP waveguide,
The input end is connected to an external waveguide (input waveguide) 5 such as InGaAsP or an optical fiber. First
The waveguide array (multiple reflection array waveguide) 8 is made of InGaAs.
It is arranged in an array waveguide region 2 composed of an sP or InP cladding region. Both sides of the array waveguide region 2 are InGaAsP or InP outer cladding regions (or air) 6,7.

The operation principle of the present invention is as follows. You
That is, the outside connected to the left end of the multiple reflection array waveguide 8
Strength from the partial waveguide 5_iInput light
Input light from the left waveguide of the multiple reflection array waveguide 8
Multiple reflection between the reflecting surfaces 3 and 4 sequentially and jig to the right
Propagate to Zag. At this time, the reflection surface 3 of each array waveguide 8
Incident angle θ to, for example, about 15 ° and the critical angle of total reflection (about
17.6 °), so that
Constant transmission output light P based on transmittance_0,1, P _0,2,
…, P_{0, n-1}, P_{0, n}, Can be obtained. This
In this case, these output lights are transmitted to the reciprocating waveguide between the reflecting surfaces 3 and 4.
A phase difference based on length can be provided. That is, anti
The distance between the launch surfaces is 1 and the incidence on the reflective surface of the array waveguide
If the angle is constant θ, the length of one round-trip waveguide is L₀= 2l / cos θ (1), the transmitted waves having a phase difference of φ = 2πn0L0 / λ (2) are output from the output waveguides 91, 92,
..., 9 (n−1), 9n are output. Where λ
Is the wavelength of light, and n0 is the equivalent refractive index of the array waveguide.
The lights having the same phase difference are combined in the slab waveguide.
Then, only discrete wavelengths satisfying the diffraction condition of nsd sin θ + n0ΔL = mλ are diffracted in the direction of θ.
Is done. Here, ns is the transmission refractive index of the slab waveguide, and d is
The output waveguide spacing, m, is an integer. Also, the diffraction angle and
The linear dispersion characteristic is given by dx / dλ = fm / (nsd) (4) from the focal length f of the waveguide. Where x is the lateral position of the output waveguide
is there.

Here, numerical examples are shown to show advantageous effects of the present invention. First, consider the dimensions required to realize the conventional array waveguide shown in FIG. An InP-based semiconductor array waveguide is taken as a material, and the wavelength is λ = 1.55 μm and the refractive index n _{s is} 3.3. Assuming that the output waveguide spacing is d = 10 μm and the channel spacing is δλ = 0.8 nm, the linear dispersion is d
x / dλ = d / δλ = 12,500, and the focal length is f
= 250 μm, the diffraction order is m = 1650. In order to realize such a large diffraction order,
From equation (3), the difference in waveguide length between the array waveguides is ΔL = 77.
5 μm is required. The number of array waveguides is usually 3
Since about 0 pieces are required, a few millimeters can be roughly estimated.
It can be seen that a degree of array waveguide area is required. On the other hand, in the array waveguide according to the present invention, since the waveguide length difference is obtained by multiple reflection of each waveguide between the two reflecting surfaces, the length 1 is approximately 380 μm, which is approximately half of ΔL.
Further, the width w can be realized with a very compact dimension of about 600 μm due to the angle of incidence on the reflecting surface, the required number of waveguides, and the introduction of the bent waveguide 8.

Various structures can be employed for the reflecting surfaces 3 and 4. For example, reflection can be obtained when the waveguide structure changes. FIG. 2 shows an example of one of the reflection portions. This structure is an example using a so-called ridge structure as a waveguide structure. The ridge structure (ridge waveguide) 8 is formed on an InP substrate 10 by forming a 0.5 μm thick
GaAsP first waveguide layer 11, 0.2 μm thick InP
It is configured based on a multilayer structure in which an intermediate layer 12, an InGaAsP second waveguide layer 13 having a thickness of 0.2 μm, and an InP cladding layer 14 having a thickness of 1.0 μm are sequentially laminated. This multilayer structure is formed into a ridge waveguide having a zigzag top pattern as shown in FIG.
Is composed. The reflection surface in the structure shown in FIG. 2 is the interface 15 between the ridge waveguide 8 and air and the discontinuous surface 16 of the second waveguide layer 13 forming the ridge waveguide. A ridge structure output waveguide (ridge waveguide) 91 having a width of 3 μm is coupled to the reflection surface formed of the discontinuous surface 16.

Normally, the reflection surface 15 is a total reflection. On the reflection surface 16, reflection having a reflectivity determined by a difference in structure between the array waveguide 8 and the output waveguide 91 is caused. The structure is transmitted through the wave path 91. The reflection due to the difference in structure of the ridge waveguide is not so large at most about 10% even if the incident angle is increased, so that the number of output waveguide rows is limited to a device that functions with only a few lines.

The element structure of the wavelength selection filter element (optical circuit element) shown in FIG. 2 can be created by the following manufacturing process.

(A) First, reduced pressure metalorganic vapor phase epitaxy
Growth method (decompression MOVPE method), molecular beam epitaxy
Growth method (MBE method), chemical beam epitaxial growth
Method (CBE method) or liquid phase epitaxial growth method
(LPE) using InGaAs on the InP substrate 10
P first waveguide layer 11, InP intermediate layer 12, InGaAs
P second waveguide layer 13 and InP cladding layer 14 are sequentially formed
I do. For example, when growing by the reduced pressure MOVPE method, the pressure 1
At a substrate temperature of 600 ° C.
Limethyl indium), TEG (triethyl gallium)
M), AsH₃(Arsine) and PH₃(Phosphine)
Is introduced to grow the InGaAsP first waveguide layer 11,
TMIn and PH₃To further form the InP intermediate layer 12.
TMIn, TEG, AsH₃And PH₃With InG
aAsP second waveguide layer 13 is grown, and finally TMIn and
PH₃The InP cladding layer 14 may be formed by
No. AsH ₃Instead of TBA (tertiary butyl)
・ Arsine ((C₄H₉) AsH₂) May be used.

(B) Next, a first etching mask pattern for forming a ridge structure is formed on the wafer with a photoresist. Using this mask pattern, In
P cladding layer 14, InGaAsP second waveguide layer 13,
The InP intermediate layer 12 is etched by dry etching such as RIE or ECR ion etching,
A ridge structure as shown in FIG. 2 is formed. In this first etching, the discontinuous surface 16 is not yet formed,
The same multilayer structure is formed continuously from the portion where the discontinuous surface 16 is to be formed to the upper portion of the portion where the ridge structure output waveguide 91 is to be formed. In addition to dry etching, wet chemical etching can also be employed. In this case, the etching can be stopped at the InP intermediate layer 12 by making full use of the hydrochloric acid-based / sulfuric acid-based selective etching.

(C) Next, the first etching mask pattern is removed, and a second etching mask pattern for forming the ridge structure output waveguide 91 is formed of photoresist. This second etching mask pattern is a mask pattern having a window only above the portion where the ridge structure output waveguide 91 is to be formed. Then, the InP cladding layer 14 and the InGaAsP second waveguide layer 13 are selectively formed by performing dry etching or wet chemical etching such as RIE or ECR ion etching using the second etching mask pattern. Then, the discontinuous surface 16 and the ridge structure output waveguide 91 as shown in FIG. 2 are completed.

FIG. 3 shows a wavelength selective filter element (optical circuit element) according to a modification of the first embodiment of the present invention. This wavelength selection filter element (optical circuit element) has a structure in which a bent waveguide is introduced. Here, the radius of curvature of the bent waveguide 8 depends on the refractive index difference between the bent waveguide 8 and the cladding region, but can be made substantially non-radiative loss by setting it to about 300 to 400 μm. Further, the radiation loss can be extremely reduced not only in the continuous bending waveguide but also in the continuous bending waveguide.

(Second Embodiment) First Embodiment of the Present Invention
In the form, the wavelength selection filter element (optical circuit element) of the present invention is used.
The description has been given based on the basic configuration of For explanation in it
FIGS. 1 and 3 show the reflection surfaces 3 and 4 of the first waveguide row 8.
When the angle of incidence on the light is a constant value θ, that is, when the reflectance is constant,
It is shown. In the present invention, the first waveguide row
8 from each output light train P_0,1, P_0,2, ..., P
_{0, n-1}, P_{0, n}Is output dependently, so the reflection
At a constant rate, the output light decreases in geometric progression as it goes to the later stage.
Will be. However, each output light P
_0,1, P_0,2, ..., P_{0, n-1}, P_{0, n}The constant
Need to be In that case, the reflectivity depends on the angle of incidence.
The lower the angle of incidence, the more downstream
Just do it. That is, as shown in FIG.
Angle of incidence with respect to surface 3 is θ₁> Θ₂> Θ₃…> Θ_n-1When
By making it smaller in the later stages according to certain rules, each
Outgoing light P_0,1, P_0,2, ..., P _{0, n-1}, P
_{0, n}Can be kept constant. By the way, like this
If the incident angle becomes smaller as it goes to the later stage,
In a structure in which the distance l between the launch surfaces 3 and 4 is constant, the distance between the reflecting surfaces is
The phase difference of each output light is
This is inconvenient if the difference is desired to be constant. Therefore, in FIG.
Means that the phase difference in the waveguide between the reflecting surfaces 3 and 4 is constant, that is,
In order to keep the waveguide length difference constant, the distance between the reflecting surfaces must be 1
₁<1₂<1₃… <1_n-1<1_nAnd the waves that got longer
3 shows a long selection filter element (optical circuit element). Concrete
As a typical numerical example, the difference between θ at each reflection point is about 0.5 °
And the waveguide length difference between the reflection surfaces is about 3 μm.

FIG. 4 shows a structure in which the distance between the reflecting surfaces is gradually changed. The same effect can be achieved also in a structure in which the distance between the reflecting surfaces 3 and 4 is continuously increased as shown in FIG. Is done.

(Third Embodiment) FIG. 6 shows a structure in which a relatively small angle of incidence from the array waveguide to the output waveguide, a large reflectivity can be obtained, and the structure can be precisely controlled. FIG. 13 is a plan view of a wavelength selection filter element (optical circuit element) according to a third embodiment. FIG. 7 is a perspective view of one portion of the reflection section.

As shown in FIG. 6, the optical circuit device according to the third embodiment of the present invention has a first optical circuit element in which light is propagated by multiple reflection between two reflecting surfaces 4 and 16. Waveguide array 8
, 9 (n−1), 9n, second waveguide arrays (output waveguide arrays) 91, 92,.
It is composed of The first waveguide array 8 having a zigzag shape is a multiple reflection array waveguide composed of an InGaAsP waveguide having a width of about 2 μm, and its input end is connected to the input waveguide 5.
It is connected to the. The first waveguide array (multiple reflection array waveguide) 8 is arranged in the array waveguide region 2. Both sides of the array waveguide region 2 are InGaAsP or InP outer cladding regions (or air) 6,7.

As shown in FIG. 7, in the third embodiment of the present invention, between the array waveguide region 2 and the output waveguide 91, a substrate of, for example, about 1 μm or less, which is coupled by evanescent light, is dug. A groove 17 of very small width, or
A groove 17 in which the first waveguide layer 11 is partially removed is formed. By adjusting the width and depth of the groove 17, the reflectance on the reflection surface 16 can be precisely controlled. For example, when the film thickness of the first waveguide 11 is 0.5 μm, the groove 17 is formed by etching to a depth of about 0.3 μm or more and a width of about 0.5 μm or less, so that the reflection surface 16 is formed. The incident light is basically totally reflected, but a part of the light is coupled to the output waveguide 91 as evanescent light. This degree of coupling depends on the width and depth of the groove 17 and the groove 17.
It can be adjusted by filling a silicon-based or organic-based dielectric medium into the substrate, so that a desired reflectance can be accurately set. The dimensions and manufacturing method such as the thickness and width of the waveguide are the same as those in the first embodiment of the present invention.

(Fourth Embodiment) Precise control of the transmission efficiency from the array waveguide to each output waveguide can also be achieved by using a coupling waveguide. FIG. 8 shows a structure of a wavelength selective filter element (optical circuit element) using an array waveguide according to a fourth embodiment of the present invention using a parallel coupling waveguide as a coupling method. Also, a ridge structure is shown as a waveguide structure.

As shown in FIG. 8, in the optical circuit device according to the third embodiment of the present invention, light is reflected by two reflecting surfaces 15;
,..., 17n, and each reflecting surface 15; 171,
..., 19 coupled to the waveguide 8 between 17n and the second waveguide row (output waveguide row) 191,.
n. The first waveguide array 8 having a zigzag shape is a ridge-type multiple reflection array waveguide having a width of about 2 μm. This ridge structure is based on a multilayer structure in which an InGaAsP first waveguide layer 11 having a thickness of 0.5 μm and an InP cladding layer 14 having a thickness of 1.0 μm are sequentially laminated on an InP substrate 10. This multilayer structure is formed on a ridge having a zigzag top surface pattern as shown in FIG. FIG.
Is the interface between the ridge waveguide 8 and the air as shown in the first embodiment, while the other reflecting surface is an etching mirror surface 171,...
.., 17n are employed.

As described above, the structure of the reflective array waveguide according to the fourth embodiment of the present invention is substantially the same as the structure shown in the first embodiment. In the fourth embodiment, the output waveguides 191,.
9n, a coupling waveguide 19 coupled to the array waveguide 8
,..., 19n are different. The desired output light P _0,1 ,... From the output waveguides 191,.
, P _{0, n} are adjusted so that the coupling efficiency of the coupling portion in each array waveguide 8, that is, the coupling portion length l _{c , n}
Alternatively, control can be easily performed with high precision by changing the distance d between the waveguides for each waveguide. At the same time, unlike the above-described embodiment, since it is not necessary to control the end face reflectance to obtain output light of a predetermined intensity, it is possible to make the end face reflectance of the reflective array waveguide be total reflection. Since the angle of incidence on the reflecting surface may simply be equal to or larger than the total reflection angle, the manufacturing conditions are extremely relaxed. 8, one is a cleavage reflection surface 15 as the total reflection surface, and the other is an etching mirror surface 171,...
.., 17n were used. The groove for forming the etching mirror surface has a width of 10 to 20 by wet or dry etching so that total reflection can be obtained on the etching mirror surface.
What is necessary is that the waveguide layer 11 is formed in a thickness of about μm so as to be in contact with air. Although the fourth embodiment of the present invention has shown the parallel coupling waveguide type as the coupling waveguide, the coupling waveguide can be realized not only by the parallel coupling waveguide but also by the laminated coupling waveguide. A similar function can be achieved by a structure such as a mold that can obtain coupling between waveguides.

(Fifth Embodiment) FIG. 9 shows a fifth embodiment of the present invention.
FIG. 3 is a bird's-eye view of the optical transversal filter according to the embodiment. As shown in FIG. 9, the optical transversal filter according to the fifth embodiment of the present invention has two reflection surfaces 4; 171, 172, 173,...
1) and 17n, and a second waveguide array 191 coupled to the waveguide array 8 between the reflection surfaces, and a second waveguide array 191, 192,... ..., 19 (n-
1), 19n and the second waveguide row 191, 192,
..., A multiplexer (output-side star coupler) 202 coupled to 19 (n−1), 19n, and a third waveguide row 21 coupled to the multiplexer (output-side star coupler) 202
, 21 (n-1), 21n. Further, in the optical transversal filter according to the fifth embodiment of the present invention, each of the waveguides 191, 192,..., 19 (n−
1), mechanism (phase adjuster) 19 for controlling the phase of light propagating through 19n and mechanism (amplitude adjuster) 1 for controlling amplitude
8

The operation principle of the optical transversal filter according to the fifth embodiment of the present invention is as follows. Although the optical transversal filter is required to incident light enters a desired amount of light in each waveguide for phase adjustment, the incident light P _i is a first wavelength-multiplexed signal light from the reflection type arrayed waveguide 8 according to the present invention, Each output waveguide 191, 192, 19
3,..., 19 (n-1), 19n are output at appropriate intensities. And each output waveguide 191, 192, 193,
..., 19 (n-1) , the 19n, amplitude _a 1 by the amplitude adjuster _{18, a 2, a 3,} ..., a n-1, in _{a n, 1} phase φ by further phase adjuster 19, φ ₂ , φ ₃ ,
, Φ _n−1 , φ _n, are combined by the output-side star coupler 202, and separated according to the interference. The wavelengths are respectively output to the final output waveguides 211, 212,.
(N-1) and 21n. That is, the optical transversal filter according to the fifth embodiment of the present invention functions as a coherent transversal filter,
An arbitrary wavelength λi is set to an arbitrary output waveguide 211, 212,
, 21 (n-1), 21n. Here, a semiconductor optical amplifier or an electro-absorption type optical modulator can be used as the amplitude adjuster 18. Further, the function of the phase adjuster 19 can be achieved by utilizing a change in the refractive index of the semiconductor due to current injection or electric field application. FIG. 9 shows the reflection surfaces 171, 172, 173,..., 17 of the reflection type array waveguide 1 according to the present invention.
(N-1), the incident angle to 17n is constant as θ, that is, since the reflectance is constant, the output waveguides 191, 192, 19
As the number n of 3,..., 19 (n−1), 19n advances, the amount of transmitted light decreases geometrically. Therefore, each output waveguide 191, 192, 193,..., 19 (n−
1), 19n and the length l _{C, n} of the coupling portion between the array waveguide (first waveguide row) 8 and the transmittance (amplification) of the amplitude adjuster 18 in consideration of this if it is constant. Rate). The length of each of the amplitude adjuster 18 and the phase adjuster 19 may be about several hundred μm, and the current injection amount may be several tens of μm.
The desired effect can be obtained with mA.

FIG. 10 is a plan view of an optical transversal filter according to a modification of the fifth embodiment of the present invention.
As shown in FIG. 10, an optical transversal filter according to a modification of the fifth embodiment of the present invention is configured such that light is propagated by multiple reflection between two reflecting surfaces 3 and 4. One waveguide array 8 and second waveguide arrays 91, 92, 93,..., 9 coupled to the respective reflection ends 3 of the first waveguide array 8.
(N-1), 9n and second waveguide rows 91, 92, 9
,..., 9 (n−1), 9n coupled multiplexer (output star coupler) 202 and third waveguide array coupled to the multiplexer (output star coupler) 211, 21
, 21 (n-1), 21n. Further, the optical transversal filter according to the modification of the fifth embodiment of the present invention has a mechanism (phase adjuster) for controlling the phase of light propagating through each waveguide constituting the first waveguide array 8. 19 and mechanism for controlling amplitude (amplitude adjuster)
18

Even if the amplitude adjuster 18 and the phase adjuster 19 are arranged in the reflection type array waveguide 8 as shown in FIG.
Functions similar to those in FIG. 9 can be achieved. In this case, since the amplitude and phase adjustment conditions at the first stage also affect the second stage,
It is necessary to set the parameters of the adjusters 18 and 19 in consideration of the amount.

(Sixth Embodiment) FIG. 11 is a plan view of an optical integrated circuit according to a sixth embodiment of the present invention. The optical integrated circuit according to the sixth embodiment of the present invention includes the first waveguide array 8 described in the first embodiment on the same substrate (semiconductor chip) 600 as shown in FIG. , And light emitting elements 301, 302,... Coupled to an input waveguide 411 connected to an input end of the first waveguide row 8.
.., 30 (n−1), 30n and second waveguide rows 91, 92, 93,..., 9 constituting the optical circuit element
(N-1), light receiving element 50 coupled to the output side of 9n
1,502,503, ..., 50 (n-1), 50n
It is composed of Here, the optical circuit element is composed of a first waveguide array 8 configured to propagate multiple reflections between the two reflecting surfaces 3 and 4, and a second waveguide array 8 coupled to the ends of the respective reflecting surfaces 3 and 4. , Waveguide arrays (output waveguide arrays) 91, 92, 93,...
, 9 (n-1) and 9n. For example, the zigzag first waveguide array 8 is formed of an I
What is necessary is just to comprise an nGaAsP waveguide. Light emitting element 30
, 30 (n-1), 30n may be composed of, for example, an InGaAsP / InP laser diode. Light receiving elements 501, 502, 503,...
The light emitting elements 301, 302,.
, 30 (n-1), 30n, it is possible to detect light with high efficiency by using an InGaAsP / InP photodiode having the same or smaller forbidden band width as that of the InGaAsP / InP photodiode. Light emitting elements 301, 302, ..., 30 (n-
1) A multiplexing circuit 4 is provided between 30n and the input waveguide 411.
01, and light emitting elements 301, 302,.
The input lights having different wavelengths from 0 (n-1) and 30n respectively correspond to waveguides 311, 312,..., 31 (n-
1), guided to the multiplexing circuit 401 via 31n, and multiplexed.

The wavelength-multiplexed optical signal from the multiplexing circuit 401 is obliquely multiple-reflected between the two reflecting surfaces 3 and 4, so that the optical signal output from each reflecting surface has an optical path length according to a certain rule. An array output light with a given difference and a controlled phase difference becomes light receiving elements 501, 502, 503,..., 50
(N-1), 50n. By using multiple reflections in this way, the longitudinal direction basically corresponds to the dimension of the order of the waveguide width multiplied by the number of waveguides, and the lateral direction corresponds to the phase difference required for device characteristics. Since only the waveguide length is required, an extremely compact array waveguide is realized, and as a result, an extremely compact optical integrated circuit can be realized.

The multiplexing circuit 401 shown in FIG. 11 may not only function as a multiplexing device but also be a more sophisticated multiplexing circuit capable of performing an optical logic operation. Further, the multiplexing circuit 401 shown in FIG. 11 may be a multiplexing circuit having an optical amplification function or the like. Further, the multiplexing circuit 401 and the first
Another optical circuit element or optical function element may be inserted between the input end of the waveguide array 8 and the input end. Similarly, the second waveguide arrays 91, 92, 93,..., 9 (n−1), 9n and the light receiving elements 501, 502, 503,.
Other optical circuit elements or optical functional elements may be inserted between 1) and 50n.

FIG. 12 is a plan view of an optical integrated circuit according to a modification of the sixth embodiment of the present invention. An optical integrated circuit according to a modification of the sixth embodiment of the present invention includes an optical circuit element having a first waveguide array 8 on the same substrate (semiconductor chip) 600 as shown in FIG. .., 30 (n−1), 30n coupled to the input waveguide 411 connected to the input end of the first waveguide row 8
, 9 (n-1), 9n connected to the respective reflection ends 3 of the first waveguide row 8
, 9 (n
-1), 9n and a third waveguide array 211, 212, 213,... Coupled to the multiplexer (output side star coupler) 202 coupled to the multiplexer (output side star coupler).
, 21 (n−1), 21n and the third waveguide row 21
1, 212, 213,..., 21 (n-1), 21n
Receiving elements 501, 502, 50 coupled to the output side of
.., 50 (n-1), 50n. The zigzag first waveguide array 8 may be composed of, for example, an InGaAsP waveguide having a width of about 2 μm. Further, the optical integrated circuit according to the modified example of the sixth embodiment of the present invention has a mechanism (phase adjuster) 19 for controlling the phase of light propagating through each waveguide constituting the first waveguide array 8. And a mechanism (amplitude adjuster) 18 for controlling the amplitude. Light emitting element 3
, 30 (n-1), 30n may be composed of, for example, an InGaAsP / InP laser diode or the like. Also, the light receiving elements 501, 502, 50
3,..., 50 (n−1), 50n are also light emitting elements 30
, 30 (n-1), 30n and the same structure of InGaAs having the same or smaller bandgap.
High efficiency photodetection is possible by using a P / InP photodiode. Light emitting elements 301, 302, ..., 3
A multiplexing circuit 401 is arranged between the input waveguides 411 and 0 (n-1), 30n, and the light emitting elements 301, 302,.
,..., 30 (n−1), input light having different wavelengths from the waveguides 30n
The signal is guided to the multiplexing circuit 401 via (n−1) and 31n and multiplexed.

The wavelength multiplexed light from the multiplexing circuit 401
The signal is obliquely multiple reflected between the two reflecting surfaces 3 and 4.
The optical signal output from each reflecting surface
Array output light given optical path length difference and controlled phase difference
, 50, 502, 503,..., 50
(N-1), 50n. Furthermore, the sixth aspect of the present invention
In the optical integrated circuit according to the modified example of the embodiment,
In each waveguide constituting one waveguide array 8, amplitude adjustment is performed.
The amplitude is a₁, A₂, A₃, ..., a _n-1,
a_nAnd the phase is adjusted by the phase adjuster 19 to φ₁,
φ₂, Φ₃,…, Φ _n-1, Φ_nOutput side
The light is multiplexed by the tercoupler 202. Output starker
The wavelengths separated by the interference at the puller 202 are
, 21 (n−
1), 21n, and the light receiving elements 501, 502,
..., 50 (n-1), 50n
You. That is, according to a modification of the sixth embodiment of the present invention.
Optical integrated circuits are coherent transversal filters and
A waveguide having the function of
Arbitrary light receiving elements 501, 502, 503,..., 50
(N-1), 50n. Of the present invention
In an optical integrated circuit according to a modification of the sixth embodiment,
Uses multiple reflections, so the longitudinal direction is basically
The order of the waveguide width multiplied by the number of waveguides
Dimensions and the transverse direction are the phase required for device characteristics.
Since the waveguide length dimension corresponding to the difference is sufficient,
A compact optical integrated circuit can be realized.

The multiplexing circuit 401 shown in FIG. 11 may not only function as a multiplexing device but also be a multiplexing circuit capable of performing an optical logic operation. The multiplexing circuit 40
, 9 (n−1), 9n and the multiplexer (output side star) between the first waveguide row 8 and the input end of the first waveguide row 8. Coupler) 202, or
Multiplexer (output side star coupler) 202 and light receiving element 50
1,502,503, ..., 50 (n-1), 50n
Another optical circuit element or an optical functional element may be inserted between them.

(Other Embodiments) As described above, the present invention has been described with reference to the first to sixth embodiments.
The discussion and drawings that form part of this disclosure should not be understood as limiting the invention. From this disclosure, various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art.

For example, in the above-described first to sixth embodiments, a structure using an InGaAsP semiconductor has been described. However, the present invention is not limited to this, and a waveguide such as a SiO ₂ glass planar waveguide or a buried waveguide made of another material may be used. It goes without saying that various structures such as various variable waveguides and coupling variable branching devices such as a Mach-Zehnder interference type as an amplitude adjuster and a heating type as a phase adjuster can be used. In the first to sixth embodiments, the output waveguide arrays 91, 92, 93, ..., 9 (n-1), 19 are provided only on one side.
n, the second output waveguide arrays 291, 292, 293,..., 2 are also provided on the other side as shown in FIG.
If 9 (n-1) and 29n are arranged, two filter functions can be simultaneously achieved by one array waveguide.

In the sixth embodiment, an optical integrated circuit monolithically integrated on a semiconductor chip has been described as an example. However, various semiconductor chips, light emitting elements, light receiving elements, and other circuits can be formed on an insulating substrate. It goes without saying that a hybrid integrated circuit on which elements are mounted may be used.

Further, in the sixth embodiment, the case where both the light emitting element and the light receiving element are mounted on the substrate has been described, but either one may be omitted. That is, a transmission optical integrated circuit in which a light emitting element and the optical circuit element described in the first to fifth embodiments are integrated, and a light receiving element and the optical circuit described in the first to fifth embodiments. The element may be divided into a receiving optical integrated circuit in which the elements are integrated.

As described above, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the matters specifying the invention described in the claims that are reasonable from this disclosure.

[0050]

As described above in detail, according to the present invention, a compact optical circuit device such as an arrayed waveguide grating can be realized.

Further, according to the present invention, an optical circuit element such as an optical transversal filter or a high-performance optical filter can be realized by using the array waveguide diffraction grating.

According to the present invention, a compact and high-performance optical integrated circuit can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view of a wavelength selection filter element (optical circuit element) using a reflective array waveguide according to a first embodiment of the present invention.

FIG. 2 is a bird's-eye view showing a configuration of a reflection surface of the wavelength selection filter element (optical circuit element) shown in FIG.

FIG. 3 is a plan view of a wavelength selection filter element (optical circuit element) using a reflective array waveguide according to a modification of the first embodiment of the present invention.

FIG. 4 is a plan view of a wavelength selection filter element (optical circuit element) using a reflective array waveguide according to a second embodiment of the present invention.

FIG. 5 is a plan view of a wavelength selection filter element (optical circuit element) using a reflective array waveguide according to a modification of the second embodiment of the present invention.

FIG. 6 is a plan view of a wavelength selection filter element (optical circuit element) using a reflective array waveguide according to a third embodiment of the present invention.

FIG. 7 is a bird's-eye view showing a part of a reflection surface of the wavelength selection filter element (optical circuit element) shown in FIG. 6;

FIG. 8 is a bird's-eye view of a wavelength selection filter element (optical circuit element) using a reflective array waveguide according to a fourth embodiment of the present invention.

FIG. 9 is a bird's-eye view of an optical transversal filter according to a fifth embodiment of the present invention.

FIG. 10 is a plan view of an optical transversal filter according to a modification of the fifth embodiment of the present invention.

FIG. 11 is a schematic plan view showing an optical integrated circuit according to a sixth embodiment of the present invention.

FIG. 12 is a schematic plan view showing an optical integrated circuit according to a modification of the sixth embodiment of the present invention.

FIG. 13 is a plan view of a wavelength selection filter element (optical circuit element) using a reflective array waveguide according to another embodiment of the present invention.

FIG. 14 shows a conventional wavelength selection filter element (optical circuit element).
FIG.

[Explanation of symbols]

2 InGaAsP or InP array cladding region 3, 4 Reflecting surface 5 External waveguide such as InGaAsP or optical fiber 6, 7 InGaAsP or InP external cladding region or air 8 Multiple waveguides 91, 92, ..., 9 (n-1), 9n, 191, 19
2, ..., 19 (n-1), 19n, 291,292,
, 29 (n-1), 29n Output waveguide 10 InP substrate 11 InGaAsP first waveguide layer 12 InP intermediate layer 13 InGaAsP second waveguide layer 14 InP clad layer 15 Reflective surface composed of ridge waveguide and air interface 16 In the ridge waveguide, the reflection surface 17 having discontinuity of the second waveguide layer 17 The groove for the reflection surface 18 The amplitude adjuster 19 The phase adjuster 171, 172, 173, ..., 17 (n-1), 17n
Etching mirror surface 201 Input side star coupler 202 Output side star coupler 221, 222,..., 22 (n−1), 22 n Input waveguides 231, 232,..., 23 (n−1), 23 n Array waveguides 241, 242 , ..., 24 (n-1), 24n output waveguides 301, 302, ..., 30 (n-1), 30n light emitting element 401 multiplexing circuit 411 waveguides 501, 502, ..., 50 (n-1), 50n light receiving element 600 semiconductor chip

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinsuke Tanaka 2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside K.D.D. Co., Ltd. (72) Inventor Masakatsu Hotta 2-2-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Kay Didi Co., Ltd. (72) Inventor Yuichi Matsushima 2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-diy Co., Ltd. F-term (reference) 2H047 KA06 KA12 LA18 MA07 PA05 PA21 PA24 QA02

Claims (5)

[Claims] 1. A first waveguide array configured to propagate light by multiple reflection between two reflecting surfaces, and a second waveguide coupled to a waveguide array from each reflecting surface end or between the reflecting surfaces. An optical circuit element comprising: a waveguide row or an output optical row. 2. A first array of waveguides configured to propagate light with multiple reflections between two reflective surfaces, and a second array of light coupled from each reflective end or between the reflective surfaces. An optical circuit device comprising: a waveguide array; a multiplexer coupled to the second waveguide array; and a third waveguide array coupled to the multiplexer. 3. A system according to claim 1, further comprising a mechanism for independently controlling the phase or amplitude of light propagating through each of the waveguides constituting the first waveguide row or the second waveguide row. Or the optical circuit element according to claim 2. 4. A first waveguide array configured to propagate light by multiple reflection between two reflecting surfaces, and a second waveguide coupled to the waveguide array from each reflecting surface end or between the reflecting surfaces. The same optical circuit element as the optical waveguide element, and at least one of the light emitting element coupled to the input end of the first waveguide row and the light receiving element coupled to the output side of the second waveguide row An optical integrated circuit formed on a substrate. 5. A first array of waveguides configured to propagate light with multiple reflections between two reflecting surfaces, and a second array coupled to the waveguide array from each reflecting end or between the reflecting surfaces. An optical circuit element including a waveguide array, a multiplexer coupled to the second waveguide array, and a third waveguide array coupled to the multiplexer, and an input to the first waveguide array An optical integrated circuit, wherein at least one of a light emitting element coupled to an end and a light receiving element coupled to an output side of the third waveguide row is formed on the same substrate.