JPH05273421A - Integrated optical coupler and optical transmitter/ receiver and optical communication system using the same - Google Patents

Abstract

PURPOSE:To obtain the integrated optical coupler which facilitates processes, has superior reliability and reproducibility, and also facilitates control over its demultiplexing and multiplexing ratios and the devices using it. CONSTITUTION:Coupler parts 10a and 10b, and 11a and 11b which multiplex and demultiplex light waves are constituted in the intersections of plural channel waveguides 12-14 formed on a semiconductor substrate. The coupler parts are formed not symmetrically about the center line in the horizontal plane of crossing channel waveguide structures. Further, the coupler parts consist of machined parts which are at least two mirror surfaces having different reflection factors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device, particularly an integrated optical coupler, used in an optoelectronic integrated circuit including a transmitter or receiver, which is required in the field of optical communication. And an optical communication system.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 47, in a waveguide type branch coupler, a light wave is branched between a main waveguide 894 and at least two sub-waveguides 892 and 893 connected to the main waveguide 894. In order to perform the coupling, it has been proposed to provide a V-shaped groove 891 at the cross-shaped waveguide crossing portion to form a coupler portion that suppresses transmission / reflection of light waves. As an example of the prototype, an integrated optical node in which a transmitter and a receiver are connected to a main waveguide serving as a bus line via a coupler is reported.

Further, as an optical coupler, an I.D. H. A. F
attah et al. "Semiconductor
r interferometric laser "A
ppl. Phys. Lett. 41 , 2, pp. 112
-114 (Jully 1982) describes an interference laser including a Y-branch optical coupler as shown in FIG. Furthermore, J. Salzman et al. "C
loss coupled cavities semic
onductorlaser "Appl.Phys.L
ett. 52 , 10, pp. 767-769 (Marc
h 1988) describes an interference laser including X-branch optical couplers 910a and 910b as shown in FIGS. 49 (a) and 49 (b). Here, R1 to R4 are resonance planes,
L1 to L4 represent resonator lengths, respectively.

[0004]

However, the structure shown in FIG. 47 has the following problems. First
In addition, the positional accuracy required for the coupler 891 and the process accuracy such as depth control are high, and the yield and reproducibility are poor. That is, since the mode of branching and merging is determined depending on how the coupler section 891 is formed with respect to the field distribution of the light wave propagating through the optical waveguide, strict process accuracy is required.

Further, in the structure as shown in FIG. 47, light waves are coupled at the same intensity ratio in both directions of the main waveguide 894 forming the bus line from the sub-waveguides 892 and 893 to which the transmitting / receiving section is connected. Things are possible, but the main waveguide 894
To the sub-waveguides 892 and 893 differ from each other. That is, the branching ratio to the upper part (open side) of the V-shape is lower than the branching ratio to the lower part (closed side) of the V-shape, and it is difficult to branch with the same strength. It is difficult to control the ratio.

In the conventional example shown in FIG. 48, Y
In an optoelectronic integrated circuit including a plurality of transmitters or receivers using, for example, two branch couplers, a single Y branch coupler cannot provide a large branch angle and the element length is 1 mm or more. The size is too large as compared with, and integration is difficult. Further, in the case of the example including the X-branching type optical coupler shown in FIG. 49, there are problems such as high process accuracy such as position accuracy and depth accuracy required for the X-branching portions 910a and 910b, and poor yield and reproducibility. was there. That is, since the manner of branching and merging is determined depending on how the X-branching portion is formed with respect to the field distribution of the light wave propagating through the optical waveguide, the process accuracy is required to be strict. is there.

Therefore, in view of the above problems, an object of the present invention is to provide an integrated optical coupler suitable for a semiconductor optoelectronic integrated circuit, etc., which is easy to process, has excellent reliability and reproducibility, and can easily control a branching ratio. It is to provide an optical transceiver and a communication system using the.

[0008]

In an integrated optical coupler according to one aspect of the present invention that achieves the above object, in a channel waveguide structure formed on a semiconductor substrate, the optical waveguide is guided in both directions of the main waveguide. The coupler section for branching / coupling the oscillating light wave and the light wave guided to the two or more sub-waveguides connected to the main waveguide is provided with the main waveguide and the sub-guide. The coupler section is formed at the intersection of the waveguides, and the coupler section is formed in one of the channel waveguides so as to perform wavefront division of the waveguide field distribution of the light wave guided in the main waveguide and the sub-waveguide. Is formed by forming a processed portion which is two mirror surfaces (reflection surfaces) having different reflectances, and the shape of the coupler portion is composed of two angled portions, and the axis of symmetry in the horizontal plane of the coupler portion is The sub-waveguide is shifted with respect to the central axis in the horizontal plane. The features.

Further, in an integrated optical coupler according to another embodiment of the present invention which achieves the above object, a light wave propagating in both directions of a main waveguide and the main wave are formed in a channel waveguide structure formed on a semiconductor substrate. At least two sets of coupler sections having two different reflecting surfaces for branching or coupling with a light wave propagating in a sub-waveguide connected to the waveguide are provided, and reflected by the two reflecting surfaces of the coupler section. By varying the intensity of the generated light wave, the light waves propagating in both directions of the main waveguide are coupled to the sub-waveguide at different intensity ratios.

Further, in the integrated optical coupler according to another embodiment of the present invention which achieves the above object, a plurality of channel waveguide structures are formed on a semiconductor substrate, and light waves are coupled at intersections of the channel waveguides. A coupler portion for the coupler portion is configured, and the coupler portion is formed from a processed portion having a different reflectance in a part of the channel waveguide so as to perform wavefront division of a guided light field distribution propagating in the channel waveguide, The processed portion is formed with two sets of micro mirror surfaces, which are respectively arranged at opposite corners of the intersecting portion, and the cut directions of the micro mirror surfaces are orthogonal to each other. ..

Further, in the integrated optical coupler according to another embodiment of the present invention which achieves the above-mentioned object, a branching / coupling of an optical wave is performed in an intersecting portion of a plurality of channel waveguide structures formed on a semiconductor substrate. A coupler portion is configured, and the coupler portion is characterized by forming a processed portion processed into a polygon having at least one total reflection mirror reflection surface.

Further, in the integrated optical coupler according to another embodiment of the present invention which achieves the above object, a branching / coupling of a light wave is performed in an intersecting portion of a plurality of channel waveguide structures formed on a semiconductor substrate. A coupler portion is formed, and the coupler portion is formed so as not to be symmetrical with respect to a center line in a horizontal plane of the intersecting channel waveguide structure,
It is characterized in that it is composed of at least two processed parts which are mirror surfaces having different reflectances.

An integrated optical coupler according to another aspect of the present invention which achieves the above object is a channel waveguide structure formed on a semiconductor substrate, in which a light wave propagating in both directions of a main waveguide and the main wave are formed. At least two sets of couplers having two different reflecting surfaces for branching or coupling with a light wave propagating in a sub-waveguide connected to the waveguide are provided and reflected by the two reflecting surfaces of the coupler. It is characterized in that light waves propagating in both directions of the main waveguide are coupled to the sub-waveguide at different intensity ratios by changing the intensity of the light wave.

More specifically, the channel waveguide structure may include an active layer, the channel optical waveguide structure may be a ridge structure, or a plurality of channel waveguide structures may be formed to have an intersection and an optical path may be formed in the intersection. The coupler part is configured to branch and couple light waves, the crossing part of the channel waveguide structure is X-shaped, T-shaped, etc., and the compound resonance is caused by the coupling between the channel waveguide structures by the optical coupler part. Is formed, the optical coupler portion includes a plurality of portions having different reflectances so as to branch and couple the light waves in a plurality of directions, and the optical coupler portion has a part of the portion where the optical waveguide structure is branched and coupled ( Total reflection mirror (45)
(O) A polygonal etching groove having at least one reflecting surface serving as a mirror is formed.

[0015]

According to the present invention having the above-mentioned structure, in the coupler section,
The at least two different reflecting surfaces branch or couple the light wave propagating in both directions of the main waveguide and the light wave propagating in the sub-waveguide connected to the main waveguide. At that time, the intensities of the light waves reflected by the reflecting surface are changed, and the light waves propagating in both directions of the main waveguide are coupled to the sub-waveguide at different intensity ratios. For example, by adjusting the intensity of the reflected light wave, the light wave can be branched into two light waves of the same intensity, and the light wave from the sub-waveguide can be coupled in both directions of the main waveguide with the same intensity. Therefore, the control accuracy of the branching / coupling of the light waves does not depend on the manufacturing accuracy of the coupler.

[0016]

1 is a top view of an integrated optical coupler according to a first embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA 'of FIG.
FIG. 3 is a sectional view taken along line BB ′ of FIG. In FIG. 1, 1
0a, 10b, 11a and 11b are slit grooves serving as couplers, 12 is a sub-waveguide for light detection, 13 is a sub-waveguide for transmission, 14 is a main waveguide, 15a, 15b, 15
Reference numerals c and 15d are antireflection films formed on the end faces.

First, the process procedure of the first embodiment will be described. On the n ⁺ GaAs substrate 1, the molecular beam growth method (M
N-type AlGaAs to be the first clad layer by BE)
Layer 2, GaAs layer 3 serving as an active layer, p-type AlGaAs layer 4 serving as a second cladding layer, p ⁺ -type Ga serving as a cap layer
An epitaxial film made of As layer 5 is grown in order.
A buffer layer made of GaAs may be formed on the interface with the substrate 1 if necessary. The film thickness of the first and second cladding layers 2 and 4 was 1 μm, and the film thickness of the active layer 3 was about 0.1 μm. Next, a width of 3 is formed on the upper portion by photolithography.
Form the desired pattern of μm and through this mask,
Reactive ion beam etching using chlorine gas (RI
A ridge portion (see FIG. 3) is formed by BE) to form a stripe structure for lateral confinement (FIGS. 2 and 3).
reference).

Further, from the center of the intersection of the ridge waveguides 12, 13, 14 which is the branching / combining portion (the intersection of the center lines extending in the horizontal direction of each waveguide), φ = in the waveguide direction of the light wave. While forming slit grooves 10b and 11a having an end face reaching the lower part of the active layer 3 at an angle of 45 °,
The same length and angle as this slit groove (slit groove 10b,
11a forms 90 °), has a depth, and is displaced from the center of the intersecting portion from the main waveguide 14 to the sub-waveguide 1
Slit grooves 10 (a) for controlling the coupling efficiency to the second and the third waveguides and the coupling efficiency from the sub-waveguides 12 and 13 to the main waveguide 14;
11 (b) was formed by RIBE to form a 45 ° mirror, that is, a total reflection mirror.

The operation of the first embodiment will be described. The light wave 17 incident from the sub-waveguide 13 is coupled to the coupler 1
The main waveguide 14 is bidirectionally branched by 1a and 11b (light waves 17a and 17b). The light wave 17b is emitted from the main waveguide 14 with the same intensity, but the light wave 17a is emitted after a loss (-6 dB in the configuration of FIG. 1) due to transmission through the couplers 10a and 10b. Therefore,
Coupling efficiency of light wave from sub-waveguide 13 to main waveguide 14 by coupler 11a (coupling efficiency of light wave 17 and light wave 17b)
However, the coupling efficiency of the light wave 17 and the light wave 17a and the coupler 10
By setting the horizontal position of the coupler 11b (deviation from the center of the intersecting portion) so that it is equal to the product of the loss generated when passing through a and 10b (-12 dB in the configuration of FIG. 1), A light wave can be guided with the same intensity in both directions of the waveguide 14. At this time, since a part of the light wave 17 is transmitted without being reflected by the couplers 11a and 11b, it is necessary to configure the end of the waveguide 19 so that a part of the transmitted light does not enter the sub-waveguide 13 again. .. Alternatively, an isolator may be inserted in the waveguide 13 (not shown).

The light waves 16a and 16b which are incident on the main waveguide 14 in both directions are branched to the sub-waveguide 12 by the couplers 10a and 10b. At this time, when the light wave 16b is transmitted through the couplers 11a and 11b, it is -6d as described above.
Since the loss of B is received, the coupling efficiency of the light wave from the main waveguide 14 to the sub-waveguide 12 by the coupler 10b (light wave 16b
By setting the position of the coupler 10a in the horizontal direction so that the coupling efficiency of the optical wave 18 and the optical wave 18) becomes −12 dB, the optical wave guided in both directions of the main waveguide 14 is guided to the sub-waveguide 12 with the same intensity. Can wave. In addition, the main waveguide 14
Can be branched to the sub-waveguides 12 and 13 with the same strength.

In the branching / merging element according to the present embodiment, the coupler portion is formed as a wavefront splitting type branch coupler in the horizontal direction (extending direction of the substrate 1 on which the channel waveguide structure is formed). 10a, 10b, 1
The processing depth of the end faces of 1a and 11b may be any depth as long as etching is performed beyond the active layer 3, and strict precision depth control is unnecessary. Furthermore, the coupling efficiency of the light wave between the main waveguide and the sub waveguide can be easily set to an arbitrary value simply by changing the horizontal position of the coupler. In addition, a light wave incident from the sub-waveguide 13 is guided in both directions of the main waveguide 14, and a light wave guided in both directions of the main waveguide 14 is reflected in the sub-waveguide 1.
2 has a configuration capable of guiding waves with the same intensity.

In this embodiment, the ridge type waveguide is described as the channel waveguide, but a refractive index type waveguide can be used as well.

Further, in this embodiment, the slit grooves 10a, 10a
Although the RIBE method has been described as a method for manufacturing b, 11a, and 11b, the same effect can be obtained by using a focused ion beam etching (FIBE) method using ions such as Ga ⁺ and Au ⁺ .

FIG. 4 shows a second embodiment of the present invention. In this embodiment, the coupler portions 20a, 20b, 21a, 21b are formed by etching in a wide area. The formation positions of the couplers 20b and 21a and the formation positions of the couplers 20a and 21b are the same as those of the couplers 10b, 11a and 10a, 11b of the first embodiment, respectively. The way of branching and merging light waves between the main waveguide 24 and the sub-waveguides 22 and 23 is substantially the same as that of the first embodiment.

FIG. 5 shows a third embodiment of the present invention. In this embodiment, the slit grooves 30a, 30b and 31a, 31b are used.
Is a modified example of the first embodiment in which the points are continuously formed at the apex. The way in which the light waves are branched and merged between the main waveguide 34 and the sub-waveguides 32 and 33 is substantially the same as in the first embodiment.

FIG. 6 shows a fourth embodiment. 7 and 8 are an AA ′ sectional view and a BB ′ sectional view of FIG. 6. This embodiment is an application example of an optical node using the integrated coupler of the first embodiment.

First, the process procedure of this embodiment will be described. As can be seen from FIGS. 7 and 8, the n-type GaAs substrate 10
1 on top of the n layer as a buffer layer by the MBE method.
Type GaAs 102 with a thickness of 1 μm and n as a clad layer
A type Al _0.4 Ga _{0.6 As} 103 was formed with a thickness of 1.5 μm. Next, non-doped GaAs (100 Å thickness), Al
_0.2 Ga _0.8 As (30 Å thickness) is repeatedly laminated four times, and finally GaAs is laminated to 100 Å thickness to form an active layer 104 having a multiple quantum well structure, and p as a cladding layer is formed thereon.
A type Al _0.4 Ga _{0.6 As} 105 was formed with a thickness of 1.5 μm, and GaAs 106 as a cap layer was formed with a thickness of 0.5 μm.

Next, a desired mask pattern (waveguide pattern) having a width of 3 μm is formed on this semiconductor laser wafer by a photolithography process, and the front side of the active layer 104 is cut through the mask by RIBE in a chlorine gas atmosphere. Etching to 2 μm to form a ridge,
A stripe structure was adopted to confine in the lateral direction.

Subsequently, an insulating film 109 (thickness 1200) made of Si _X N _Y is formed on the laser wafer on which the ridge is formed.
Å) was formed by a plasma CVD method, and a resist was spin-coated on the SiN insulating film 109 by about 1.0 μm.
Then, the coated resist alone is removed by RIE (reactive ion etching) in an O ₂ atmosphere of ₄ Pa to expose the SiN insulating film 109 at the top of the ridge, and RIE in a CF ₄ gas atmosphere of ₄ Pa. Method was performed to selectively etch the exposed SiN insulating film at the top of the ridge. After that, the remaining resist is 4P
It was removed by the RIE method in the O ₂ atmosphere of a.

Next, the surface oxide film formed on the top of the ridge is wet-etched with hydrochloric acid to form a current injection window, and then a Cr-Au ohmic electrode 107 is formed as an upper electrode by vacuum vapor deposition to form a GaAs substrate. 41 was lapped to a thickness of 100 μm, and then an AuGe—Au electrode was vapor-deposited as an n-type ohmic electrode 108. Then, heat treatment for making ohmic contact with the p-type and n-type electrodes was performed to obtain a ridge-type semiconductor element.

Further, slit grooves 61a, 61b, 62a and 62b to be couplers are formed in FIG. 6 by etching by FIB method using Ge ⁺ ions with an acceleration voltage of 40 keV.
Was formed in the manner shown in FIG. The slit groove was inclined as described above, the depth was 1 μm deeper than the active layer 104, and the inclination angle of the groove in the vertical direction was 85 ° or more (see FIG. 7).

Finally, the resonance surface is formed by cleavage, and E
Al ₂ O ₃ + Zr by B (electron beam) vapor deposition
AR coating 71a, 71b, 71c, 71 by vapor deposition of O ₂
The electrodes 107 and 108 were taken out by wire bonding.

Next, the operation of the fourth embodiment will be described. The light wave incident through the optical fiber 91a and the AR coat 71a enters the integrated couplers 61a and 61b as an incident wave amplified by the amplification unit 65a, and the light wave enters the waveguide 70 to the upper reception unit and the right side. Of the light wave entering the amplification section 65b of A signal is detected in the light wave entering the receiving unit through the waveguide 70 and the fiber 91c, and the light wave entering the amplifying unit 65b is amplified there to form the AR coat 71.
It is output to the fiber 91b via b. At this time,
The waveguide 6 to the transmitter is reflected by the coupler 62b.
The light wave entering 8 is blocked by an isolator (not shown) before entering the fiber 91d for frequency stabilization on the transmitter side. The same applies to the light wave incident from the opposite side (via the AR coat 71b).

The light waves that enter the couplers 62a and 62b from the transmitting portion via the fiber 91d and the waveguide 68 are amplified by the amplifying portion 65b and output to the fiber 91b via the AR coat 71b. To be done. The light wave branched by the coupler 62b is branched into a light wave to the amplification section 65a and a light wave to enter the waveguide 70 to the reception section. The signal component of the light wave entering the receiving unit via the waveguide 70 and the fiber 91c is monitored here, and the light wave entering the amplifying unit 65a is amplified and output to the fiber 91a. In this embodiment, as in the case of the first embodiment, the light waves incident on the waveguide 66 from the fibers 91a and 91b have the same intensity as the receiver side waveguide 70, and the waveguide 6 from the transmitter.
The light waves incident on the waveguide 8 have the same intensity in both directions of the waveguide 66, and are integrated couplers 61a, 61b, 62a, 62b, respectively.
Is guided by.

FIG. 9 shows a fifth embodiment. 10 and 11
9A is a cross section taken along the line AA ′ and a cross section taken along the line BB ′ of FIG. 9. The present embodiment is an example in which the second embodiment of the present invention is applied to an optical amplifier incorporating a transmitter.

In FIG. 9, 121a, 121b, 12
2a and 122b are optical couplers having the same structure as in the second embodiment, 125a and 125b are optical amplifiers by current injection,
Reference numeral 123 is a transmission unit configured by a laser having a DFB structure, 124 is a reception unit having a photodetector that operates by applying a reverse bias voltage, and 126 is a main waveguide forming a bus line. Furthermore, 131a, 1
Reference numeral 31b is an AR coating formed by depositing Al ₂ O ₃ + ZrO ₂ on the end face by electron beam (EB) vapor deposition.

Also, as in the fourth embodiment, FIGS.
In the figure, 101 is an n ⁺ type GaAs layer serving as a substrate, 10
Reference numeral 2 is an n-type GaAs layer serving as a buffer layer, 103 is an AlGaAs layer serving as a first cladding layer, 104 is an active layer, 10
5 is a p-type AlGaAs layer serving as the second cladding layer, 106
Is a p ⁺ -type GaAs layer serving as a cap layer, 109 is a SiN layer serving as an insulating film, and 107 is a p-type ohmic electrode A
u-Cr electrode, 108 is an n-type ohmic electrode Au
It is a Ge-Au electrode.

Next, the operation of the fifth embodiment will be described. The light wave 127 sent from the transmitter 123 is the coupler 1
22a and 122b branch the light waves 127a and 127b. The light wave 127b is coupled to the couplers 121a and 121.
Light wave 1 is caused by a loss of -6 dB that occurs when transmitting b.
The intensity becomes -12 dB of 27, is amplified by the optical amplifier 125a, and is emitted through the AR coating 131a. On the other hand, the coupler 122a causes the light wave 127
The light wave 127a branched with the intensity of 2 dB is amplified by the light amplification section 125b having the same amplification factor as the light amplification section 125a, and is transmitted through the AR coating 131b.
Emitted with the same intensity as b. Since a part of the light wave 127b is guided to the receiver 124 by the coupler 121b,
It is also possible to monitor the signal components.

The light wave 129a incident from the left end of the main waveguide 126 through the AR coating 131a is
The coupler 12 after being amplified by the optical amplifier 125a
Reach 1a. Here, a part of the light wave 129a is incident on the receiving unit 124 by the coupler 121a with an intensity of −12 dB of the light wave 129a, and a signal component is detected. In addition, the light transmitted through the coupler 121a is
After passing through 2b, and after being amplified by the optical amplifier 125b, AR
It is emitted through the coating 131b. On the other hand, the light wave 129b incident from the right end of the main waveguide 126 through the AR coating 131b is amplified by the optical amplification unit 125b and reaches the coupler 122a. At this time, the transmitted wave receives a loss of -6 dB in the couplers 122a and 122b, and then is branched to the receiving unit 124 in the coupler 121b, and has the same intensity ratio as that of the light wave 129a (-12 dB of the light wave 129a).
Then, the light wave 129b becomes a light wave 130 of −12 dB, enters the receiving unit 124, and is detected here. Further, the light transmitted through the coupler 121b is amplified by the optical amplification section 125a and then emitted through the AR coating 131a.

In the case of this embodiment, the light waves 129a, 129b
Since a part of the signal is guided to the transmitter 123 by the couplers 122b and 122a, it is necessary to insert an isolator for stabilizing the frequency of the transmitter 123 (not shown).

The optical amplifiers 125a and 125 are used to compensate for the loss in the couplers 121a and 121b or 122a and 122b, the facet coupling loss, and the waveguide loss.
If the amplification factor of b is set, this embodiment functions as a transmission / reception optical node with virtually no loss, and multistage connection is possible.

In the fifth embodiment, an example in which the resonance surface of the laser is formed by the DFB structure is shown.
Method, a reactive ion etching method, a focused ion beam etching method, or the like, or an etching end surface formed by etching or a cleavage plane may be used.

In the above-mentioned first to fifth embodiments, an example is shown in which the input / output surface to the fiber and the input / output surface of the light are formed by cleavage, but RIBE method, dry etching such as reactive ion etching, etc. An etching end face formed by etching may be used. Further, although the active region is formed with a double hetero (DH) structure, the present invention is not limited to this, and a single quantum well (SQ) is used.
It may be a W) structure, a multiple quantum well (MQW) structure, or the like.

Further, in the first to fourth embodiments, the example in which the channel waveguide is formed by the ridge wave structure is shown, but the buried hetero stripe (BH) structure, the channel substrate planar stripe (CPS) structure, and the constriction of the current light are shown. It is also effective for a refractive index guided laser having a structure in which an absorption layer for this purpose is provided near the active layer. It is also effective for gain-guided lasers such as stripe electrode type and proton bombard type. Further, as a semiconductor material, in addition to GaAs / AlGaAs, InP / InG
It may be formed of aAsP-based or AlGaInP-based material.

FIG. 12 is a plan view of a sixth embodiment of an optical semiconductor branching / merging device to which the present invention is applied, FIG. 13 is a sectional view taken along line AA 'in FIG. 12, and FIG. 14 is a sectional view taken along line BB' in FIG. Is. In the figure, 150a, 150b, 151
a, 151b are etching grooves serving as couplers, 152 is a sub-waveguide for detecting light, 153 is a sub-waveguide for transmitting,
Reference numeral 154 is a main waveguide.

First, the thin film forming process of this embodiment will be described. As shown, n ⁺ GaAs substrate 141
On top, by molecular beam epitaxy (MBE),
The n-type AlGaAs layer 142 serving as the first cladding layer, the GaAs layer 143 serving as the active layer, the p-type AlGaAs layer 144 serving as the second cladding layer, and the p ^{+ -type} Ga serving as the cap layer.
An epitaxial film of the As layer 145 is grown and laminated in order.

A buffer layer made of GaAs may be formed between the substrate 141 and the interface if necessary. In this embodiment, the first and second cladding layers 142 and 1444 have a thickness of 1 μm, and the active layer 143 has a thickness of 0.1 μm.

Subsequently, a desired pattern having a width of 3 μm is formed on the upper part of the laminated thin film by the photolithography method, and reactive ion beam etching (RIBE) is performed thereon.
To form a ridge portion (shown in FIG. 13) to form a stripe structure for confining in the lateral direction.

Further, an etching groove 150b having an end face reaching the lower part of the active layer 143 at an angle of φ = 45 ° from the center of the branching / merging portion of the ridge waveguide in the waveguide direction of the light wave,
151b and the grooves 150b and 151b have the same angle and depth, and by shortening the length in the horizontal direction (the extending direction of the substrate 141 in which the channel waveguide is formed in the figure), the main waveguide 154 is separated from the sub-waveguide. Etching grooves 150a with reduced coupling efficiency of light waves to 152 and 153,
And 151a were formed by the RIBE method. This is 4
A 5 degree total reflection mirror was made.

The operation of the branch coupling element of the sixth embodiment will be described here. Light wave 1 incident from the sub-waveguide 153
57 is branched into two directions of the main waveguide 154 by the couplers 151a and 151b (indicated by arrows 158a and 158b in FIG. 12). One branch light wave 158a
Is branched with the same intensity and emitted from the main waveguide 154 to the outside (right side in the figure). The other branched light wave 15
8b causes optical loss (for example, -6 dB) when passing through the couplers 150a and 150b, attenuates the light, and is branched. Therefore, it is necessary to adjust so that the branched light waves can be guided in both directions of the main waveguide 154 with the same intensity. Specifically, the coupling efficiency of the light wave from the sub-waveguide 153 to the main waveguide 154 by the coupler 158a, that is, the coupling efficiency of the light wave 157 and the branch light wave 158a is determined by the light wave 157 and the branch light wave 15
It is adjusted by setting the horizontal length of the coupler 151a to be equal to the product (-12 dB) of the coupling efficiency of 8b and the optical loss (-6 dB) due to the couplers 150b and 150a.

It should be noted that part of the light wave 157 is due to the coupler 151.
Since the light is transmitted without being reflected by a and 151b, it is necessary to form the end of the waveguide 160 so that even a part of the transmitted light is not re-incident on the sub-waveguide 153. Alternatively, an isolator may be inserted in the waveguide 153 to prevent re-incident light.

On the other hand, the light wave 156a directly incident on the main waveguide 154 and the light wave 156b from the direction opposite to the light wave 156a are branched toward the sub-waveguide 152 by the couplers 150a and 150b. The light wave 156b is accompanied by an optical loss when passing through the couplers 151a and 151b (as in the case where the light wave 157 passes through the couplers 150a and 150b, a loss of -6 dB). Therefore, coupler 1
The coupler 150a so that the coupling efficiency of the light wave from the main waveguide 14 to the sub-waveguide 12 by the 50a, that is, the coupling efficiency of the light wave 156a and the light wave 159 is, for example, −12 dB.
By setting the horizontal length of the sub-waveguide 152 with the same intensity, the light wave guided in both directions of the main waveguide 154 is set.
The main waveguide 154 and the sub-waveguides 152 and 153 can be branched with the same intensity.

As described above, in the sixth embodiment, the optical semiconductor branching and merging element forms the horizontal wavefront splitting type branch coupler in the coupler portion, so that the etching grooves 150a, 150b, 151a, 151b are formed. The processing depth of the end face of is not limited as long as etching is performed beyond the active layer 143, and strict precision depth control is unnecessary.

Further, the couplers 150a, 150b, 15
By simply changing the horizontal lengths and positions of 1a and 151b, the light wave coupling efficiency between the main waveguide 154 and the sub-waveguide 152 and between the main waveguide 154 and the sub-waveguide 153 can be set to arbitrary values. Can be easily set. Therefore, the optical wave 157 incident from the sub-waveguide 153 is bidirectionally in the main waveguide 154 with the same intensity, and the optical waves 156a and 156b guided in the bidirectionally the main waveguide 154 are in the sub-waveguide 152 with the same intensity. Each can be guided.

In this embodiment, the ridge type waveguide is used as the channel waveguide, but a refractive index type waveguide may be used instead. Also, the couplers 150a, 150
b, 151a, is adopted RIBE method as method of producing the etching groove forming the 151b, focused ion beam etching method using an ion such as Ga ⁺ and Au ⁺ In addition (F
IBE) may be used.

Next, a seventh embodiment of the present invention will be described. FIG. 15 is a plan view of an optical semiconductor branching / merging device.

As shown, the couplers 170a, 17a
1a passes through the center of the branch / merge portion of the ridge waveguide. The lengths in the horizontal direction (extension direction of the substrate on which the channel waveguide is formed in the figure) are such that the coupling efficiency between the light waves 176b and 179 and the coupling efficiency between the light waves 177 and 178a are −12 dB. It is set.
The intensity distribution of the light wave in the ridge waveguide is strongest at the center of the waveguide. Therefore, the couplers 170a, 17
The horizontal length of 1a can be shorter than that in the sixth embodiment.

The center of the branching / merging portion of the ridge waveguide corresponds to the transmitting portion of the sixth embodiment, and the coupling efficiency is adjusted in the same manner as in the sixth embodiment. In FIG. 15, FIG.
12, the reference numbers in FIG. 12 are added to indicate the corresponding parts.

An eighth embodiment of the present invention will be described. FIG. 16 is a plan view of an eighth embodiment of the optical semiconductor branching / merging device.

As shown in the figure, in this embodiment, the width of the main waveguide 184 between the couplers 180a and 180b is wide, and the center of the waveguide is arranged to coincide with the center of the waveguides 184 on both sides. ing. At the center of the waveguide,
The highest light intensity. With this configuration, it is possible to further reduce the optical loss that occurs when the light is transmitted through the couplers 180a and 180b, and it is possible to reduce the insertion loss of the branching and joining element. For example, the optical loss can be made smaller than -6 dB.

The main waveguide between the couplers 180a and 180b is set so that it can be guided in a single mode. In FIG. 16, reference numerals of FIG. 12 are added with 30 to show corresponding portions of FIG. 12.

Next, a ninth embodiment of the present invention will be described. 17 is a plan view of an optical amplifier including a transmitter and a receiver, and FIG. 18 is a sectional view taken along the line AA ′ in FIG.
9 is a sectional view taken along the line BB 'in FIG.

In FIG. 17, 191a, 191b and 1
Reference numerals 92a and 192b are optical couplers having the same structure as the coupler of the sixth embodiment, 195a and 195b are optical amplifiers by current injection, and 193 is a transmission unit having a DFB laser.
Reference numeral 94 is a receiver having a photodetector that operates when a reverse bias voltage is applied, 196 is a main waveguide forming a bus line, and 201a and 201b are ZrO ₂ films formed on the end faces by electron beam (EB) vapor deposition. Made of A
R coating.

In FIGS. 18 and 19, reference numeral 211 is a substrate n
⁺ GaAs layer, 212 is n-type GaAs to be a buffer layer
Layers, 213 are AlGaAs layers to be the first cladding layer, 2
14 is an active layer, and 215 is p-type Al to be the second cladding layer.
GaAs layers, 216 are p ^{+ type} GaAs to be cap layers
A layer 217 is a SiN layer serving as an insulating film, 218 is an Au-Cr electrode serving as a p-type ohmic electrode, and 219 is an AuGe-Au electrode serving as an n-type ohmic electrode.

In this embodiment, light waves 199a and 199 are used.
Since a part of b is guided to the transmission unit 193 by the coupler 191b, an isolator (not shown) for stabilizing the frequency of the transmission unit 193 is inserted.

On the optical amplifier 195b side, the transmitter 1
The light waves 197 sent from the 93 are couplers 192a, 1
92b splits into light waves 198a and 198b. One of the branched light waves 192b is a coupler 191a,
Due to the optical loss (-6 dB) that occurs when the light passes through 191b, the intensity of the light wave 197 becomes -12 dB, and the optical amplifier 1
The light is amplified by 95a and emitted through the AR coating 201a. On the other hand, a light wave 197 is generated by the coupler 192a.
-12a of the branched light wave with an intensity of −12 dB
Is an optical amplification unit 19 having the same amplification factor as the optical amplification unit 195a.
It is amplified by 5b and emitted through the AR coating 201b. The intensity of the emitted light wave is the same as that of the light wave 198b. A part of the light wave 198b is a coupler 191b.
Since it is guided to the receiving unit 194 by the, the signal component can also be monitored.

Further, the main waveguide 19 is provided through the AR coating 201a (located at the left end of the substrate 211 in the figure).
The light wave 199a incident on the light source 6 reaches the coupler 191a after being amplified by the optical amplification unit 195a. Then, a part of the light wave 199a is incident on the receiving unit 194 with the intensity of −12 dB of the light wave 199a by the coupler 191a, and the signal component of the light wave 200 is detected. The light transmitted through the coupler 191a passes through the coupler 192b and the optical amplification section 195b, and then the AR coating 201b.
Is emitted via.

On the other hand, the main waveguide 1 is formed through the AR coating 201b (located at the right end of the substrate 211 in the figure).
The light wave 199b incident on 96 reaches the couplers 191a and 191b after being amplified by the optical amplification unit 195b. When passing through the couplers 192a and 192b, the light wave 199b loses the intensity of −6 dB and the coupler 19
After passing through 1a and 191b, they are branched and incident on the receiving unit 194 with the same intensity as the light wave 199a, and the signal component thereof is detected.

In this embodiment, the coupler 191
a, 191b, 192a, 192b, the optical amplifier 195 so as to compensate the optical loss, the end face coupling loss, and the waveguide loss.
When the amplification factors of a and 195b are set, it functions as a transmission / reception optical node that apparently has no loss. Therefore, multistage connection is possible.

Also in the sixth to ninth embodiments described above,
Although the active region is formed with a double hetero (DH) structure, a single quantum well (SQW) structure or a multiple quantum well (M
You may form by QW) structure. Although the channel waveguide is formed in a ridge structure, a buried hetero stripe (BH) structure, a channel substrate planar stripe (CPS) structure, and an absorption layer for narrowing current light are provided near the active layer. It is also effective for a refractive index guided laser having a different structure, a gain guided laser such as a stripe electrode and a proton bombard type. Alternatively, in addition to GaAs / AlGaA based semiconductor materials, InP / InGaA
Good for sP-based and AlGaInP-based materials
FIG. 21 is a top view of an optical coupler which is a tenth embodiment of the present invention, FIG. 21 is a sectional view taken along the line AA ′ of FIG. 20, and FIG.
23 is a sectional view taken along the line CC ′ of FIG. 23. The tenth embodiment will be described below.

An epitaxial film composed of the first cladding layer 222, the active layer 223, the second cladding layer 224, and the cap layer 225 is sequentially grown on the substrate 221 by the molecular beam growth method (MBE). A buffer layer made of GaAs may be formed on the interface with the substrate 221 if necessary. Next, a desired pattern was formed on the upper portion by photolithography, and a ridge portion was formed by reactive ion beam etching to form a stripe structure for confining in the lateral direction.

Next, by the FIBE method (focused ion beam etching method), the fine slits 226 and 227 to be the couplers shown in FIGS. 21 and 22 were formed. 21, FIG.
As shown in FIG. 2, the processing tips of the slits 226 and 227 are located near the center of the field distribution 228 in the layer direction (that is, up to the active layer 223 portion where the center of the field distribution 228 is located), and wavefront division in the stacking direction is performed. ing. The operation of this embodiment will be apparent from the following description of the embodiment.

FIG. 24 shows an eleventh embodiment of the present invention. 25 and 26 are sectional views taken along the lines AA 'and BB' of FIG. 24, and FIG. 27 is a sectional view taken along the line CC 'of FIG.

In this embodiment, the fine slits 246 and 24 are
The processing tip of No. 7 is the first
In Example 0, the processing depth of the slit was set at the center of the field distribution in order to divide the field distribution in the layer direction into wavefronts.
A field distribution 228 in the layer direction for performing horizontal wavefront division
It is deeper until it reaches the bottom of. The same reference numerals as those in the tenth embodiment denote the same functions.

FIG. 28 shows a twelfth embodiment of an optical semiconductor device using the coupler of the eleventh embodiment of the present invention. 29 and 30 are AA ′ sectional views and BB ′ sectional views of FIG. 28. The manufacturing process of this column will be described.

First, on the n-type GaAs substrate 231, n-type GaAs of 1 μm and the cladding layer 233 are sequentially formed as the buffer layer 232 by the molecular beam epitaxy method (MBE method).
As a result, n-type Al _0.4 Ga _0.6 As having a thickness of 1.5 μm was formed. As the active layer 234, non-doped GaAs (thickness 1
00Å) and Al _0.2 Ga _0.8 As (thickness 30 Å) were repeated 4 times, and finally GaAs (thickness 100 Å) was laminated to form a multi quantum well structure (MQW). Next, as the clad layer 235, p-type Al _0.4 Ga _0.6 As is added to 1.5.
.mu.m and GaAs of 0.5 .mu.m is formed as the cap layer 236.

Next, a desired cross-shaped mask pattern having a width of 3 μm is formed on the semiconductor laser wafer by a photolithography process, and the active layer 234 is formed in front of the active layer 234 through the mask by a reactive ion beam etching method in a chlorine gas atmosphere. The stripe structure was formed by etching to 0.2 μm to form a ridge portion and confining in the lateral direction. Subsequently, an insulating film 237 (thickness 120) made of Si _X N _Y is formed on the laser wafer on which the ridge is formed.
0 Å) was formed by the plasma CVD method. Next, Si
A resist was spin-coated on the N insulating film by about 1.0 μm. Then, only the formed resist is removed by a reactive ion etching method in an O ₂ atmosphere of 4 Pa,
The SiN insulating film on the top of the ridge is exposed, and 4P
The reactive ion etching method in the CF ₄ gas atmosphere of a was performed to selectively etch the exposed SiN insulating film at the top of the ridge. Then, the remaining resist was removed by reactive ion etching in an O ₂ atmosphere of 4 Pa.

Next, the surface oxide film formed on the top of the ridge was wet-etched with hydrochloric acid to form a current injection window.

Then, a Cr-Au ohmic electrode 238 is formed as an upper electrode by a vacuum vapor deposition method, and a GaAs substrate is lapped to a thickness of 100 μm.
An AuGe / Au electrode was vapor-deposited as a mold ohmic electrode 239. Next, heat treatment was performed to obtain ohmic contact between the p-type and n-type electrodes, to obtain a ridge-type semiconductor element.

Further, by etching by FIB (Focused Ion Beam) method using Au ⁺ ions with an accelerating voltage of 40 keV, 45 ° with respect to each longitudinal direction of the cross-shaped waveguide.
The inclined slit grooves 256 and 257 are formed at two positions of opposite angles (one slit is orthogonal to the other slit and do not intersect), and the depth is about 1 μm deeper than the active layer 234. And the vertical tilt angle is 85 °
I made it so.

Further, after forming the resonance surface by cleavage,
Al on the resonance surface by EB (electron beam) vapor deposition
AR coatings 253a, 253b, 253c, and 253d were formed by depositing ₂ O ₃ + ZrO ₂ .
Then, the electrode was taken out by wire bonding.

In this embodiment, the optical amplifiers 250a and 250b arranged in the bus line direction are formed, and the branching waveguides 252 and 253 to the receiving and transmitting sections intersect the waveguides in the bus line direction. There is. Branch coupler 256, 257
Performs branch coupling by forming two grooves located at opposite angles at the intersection. The ratio of branch bonds is
It can be adjusted by controlling the photoelectric field distribution of the waveguide and the length of the groove (including position control).

Further, when light is incident from the open side of the branch couplers 256 and 257 (right side of FIG. 28), reflection exists, so it is necessary to insert an isolator for frequency stabilization on the transmitter side. (Not shown).

In FIG. 28, 253a is an AR coat with which the end face of the fiber 261 is in contact, 253b is an AR coat with which the end face of the fiber 262 is in contact, 253c is an AR coat with which the fiber 264 on the receiver side is in contact, 253d.
Is an AR coat with which the fiber 265 on the transmitter side abuts.

Next, the operation of the twelfth embodiment will be described. The light wave incident through the optical fiber 261 and the AR coat 253a enters the integrated coupler unit 258 as an incident wave amplified by the amplification unit 250a, and is transmitted / reflected by the slit groove 2.
56, 257 and the non-grooved portion amplifies the lightwave into a lightwave entering the waveguide 252 to the left receiver and a lightwave entering the waveguide 253 to the right transmitter (which is blocked by the isolator). The light wave entering the portion 250b is branched.
A signal is detected in the light wave entering the receiving unit through the waveguide 252 and the fiber 264, and the light wave entering the amplifying unit 250b is further amplified therein and output to the fiber 262. The same applies to the light wave incident from the opposite side (via the AR coat 253b).

From the transmitter to the fiber 265 and the waveguide 253.
The light wave entering the coupler section 258 via
The reflecting slit grooves 256 and 257 and the non-groove portion allow the waveguides 252 and 253 (light waves reflected by the waveguide 253 to be blocked by the isolator) and the amplifying section 250.
It is split into light waves that enter a and 250b. Waveguide 252
The signal component of the light wave that enters the receiving unit via the optical fiber 264 and the fiber 264 is monitored there, and the light wave that enters the amplifying units 250a and 250b is amplified there, respectively.
It is output to 262.

FIG. 31 is a thirteenth embodiment in which the eleventh embodiment of the present invention is applied to an optical amplifier having a built-in transceiver. 32 and 33 are cross-sectional views taken along the lines AA 'and BB' of FIG. In FIG. 31, 270a and 270b are optical amplifiers by current injection, 271 is a transmitter including a laser having a DFB structure, and 272 is a receiver having a photodetector that operates by applying a reverse bias voltage, 274. Is an optical waveguide forming a bus line. Further, 273a and 273b are AR coatings formed by depositing Al ₂ O ₃ + ZrO ₂ on the end faces by EB (electron beam) vapor deposition.
32 and 33, the same reference numerals as those in FIG. 29 denote the same parts as those in FIG.

Next, the operation of the 13th embodiment will be described. The light waves 280 sent from the transmission unit 271 are light waves 281 a, 281 b, 28 by the couplers 276, 277.
It is demultiplexed to 1c. The optical wave 281b demultiplexed by the coupler 276 is amplified by the optical amplification unit 270a and emitted through the AR coating 273a.

Similarly, the optical wave 281a demultiplexed by the coupler 277 is amplified by the optical amplification section 270b, and AR
It is emitted through the coating 273b. The light wave 281c, which is the transmitted light, can be monitored by the receiving unit 272 for a signal component.

The optical wave 282a incident from the left end of the waveguide 274 through the AR coating 273a is amplified by the optical amplifying section 270a, and then a part of the optical wave 282a is incident on the receiving section 272 by the coupler 277 and the signal is transmitted. The component is detected. Further, the light transmitted through the couplers 276 and 277 is amplified by the optical amplification section 270b and then emitted through the AR coating 273b. On the other hand, from the right end of the waveguide 274, the AR coating 273b
The light wave 282b incident via the
Is amplified by the coupler 276, enters the receiver 272 by the coupler 276, and is detected there.

In the case of this embodiment, the light waves 282a and 282b are used.
A part of the transmission part 271 by the couplers 276 and 277.
It is necessary to insert an isolator for stabilizing the frequency of the transmission unit 271 (not shown) since the light is guided to the.

Further, if the amplification factors of the optical amplifiers 270a and 270b are set so as to compensate for the losses in the couplers 276 and 277, the end face coupling loss, and the waveguide loss, it functions as a transmission / reception optical node having no apparent loss. However, multi-stage connection is possible.

As described above, in the tenth to thirteenth embodiments,
As the manufacturing method of the slit groove serving for the optical coupler has been described FIBE method using Au ⁺ ions, Ga ⁺ a F
Similar effects can be obtained by using IBE or RIBE. Further, although an example in which the resonance surface of the laser is formed by cleavage and an example of the DFB structure are shown, an etching end face formed by etching such as dry etching such as reactive ion beam etching or reactive ion etching may be used. A DBR structure may be used. In addition, the active region is MQW (multiple quantum well structure)
However, the present invention is not limited to this and may have a DH structure, an SQW structure, or the like.

Further, the ridge wave type structure using a GaAs system has been described as an example, but the BH structure, the CSP structure,
This is also effective for a refractive index guided laser having a structure in which an absorption layer for constricting current light is provided near the active layer. Further, it is also effective for a gain waveguide type laser such as a stripe electrode type or a proton bombard type. In addition, the materials for the semiconductor laser are GaAs / AlGaAs, I
Materials such as nP / InGaAsP type and AlGaInP type can also be used.

FIG. 34 shows an optical semiconductor device including a T-branch coupler which is a fourteenth embodiment of the present invention. FIG. 34 (a) is a schematic top view, and FIG. 34 (b) is A of FIG. 34 (a). 34A is a sectional view taken along the line BB ′ of FIG. 34A, and FIG. 35B is an enlarged view of a main portion of FIG. 34A. First, the process procedure of the fourteenth embodiment will be described.

On the substrate 291, the molecular beam growth method (MBE) is used.
Thus, an epitaxial film including the first cladding layer 292, the active layer 293, the second cladding layer 294, and the cap layer 295 is sequentially grown. A buffer layer made of GaAs may be formed on the interface with the substrate 291 if necessary. The film thickness of the first and second cladding layers 292 and 294 was 1 μm, and the film thickness of the active layer 293 was about 0.1 μm. next,
A desired pattern (T-shaped pattern in the illustrated example) having a width of 3 μm is formed on the upper portion thereof by a photolithography method, and a ridge portion (see FIG. 34B) is formed by reactive ion beam etching (RIBE). A stripe structure for confining in the direction is adopted (see FIGS. 34 (a) and 34 (b)).

Furthermore, focused ion beam etching (FI
By the BE method, the end surface processing down to the lower part of the active layer 293 is processed to form the etching groove 300 as shown in FIG. The etching groove 300 has an end face inclination angle θ of 85 degrees or more by FIBE (see FIG. 35 (a)), and φ from the center of the branch / merge portion of the ridge waveguide in the light wave guiding direction.
= 45 ° (see FIG. 35B) to form a 45 ° mirror, that is, a total reflection mirror. Then, the light is incident by cleaving the end face of this element,
I made it possible to emit.

The active layer 293 is formed by this total reflection mirror.
Of the light wave 301 incident in the direction B → B ′ of FIG.
Is a light wave 302 (reflection) and a light wave 303 at the branching / merging portion.
(Transmission) is branched at almost the same ratio. At this time, the light wave 302 is totally reflected by the etching groove 300 in the central portion of the branching / merging portion shown in FIG. 35B, and the light wave 303 is generated by passing through the portion other than the central portion of the branching / merging portion as it is. ..

The branching / merging portion, that is, the optical coupler in this embodiment forms a wavefront splitting type branch coupler in the horizontal direction (extending direction of the substrate 291 on which the channel waveguide structure is formed). The processing depth of the end face of 300 may be any depth as long as it can be etched beyond the active layer 293 (the waveguide layer that is the center of the channel waveguide structure), and strict precision depth control is unnecessary. Then, by controlling the position of the 45 ° mirror, the transmission / reflection ratio of the light wave can be set to a desired value. In this embodiment, the ridge waveguide is described as the channel waveguide structure, but a refractive index type waveguide can be used as well.

FIGS. 36 (a) and 36 (b) show a fifteenth embodiment. In the T-type coupler of FIG. 36, the etching groove 310 has a trench shape of a right triangle, and the direction B ′ → B in FIG. 36 (a). Even if the light wave 311 is incident from the above, the light waves are branched and combined as light waves 312 and 313.

FIG. 37 shows a sixteenth embodiment of a Y-shaped coupler in which an etching groove 315 is formed in a triangular shape at a position as shown in the drawing, and light waves are branched / merged as shown by solid and broken arrows in FIG. To be done.

FIG. 38 shows a seventeenth embodiment. The seventeenth embodiment is an example in which the fifteenth embodiment of the present invention is applied to an optical node provided with a transmitter and a receiver. 39 and 40 are sectional views taken along the lines AA 'and BB' of FIG. 38, respectively. This embodiment is an example in which the processed end face of the fifteenth embodiment is used for an integrated coupler.

In FIG. 38, reference numeral 329 denotes a right-angled triangular etching groove having two total reflection mirrors (45 ° mirrors) formed by FIB, and 330a and 330b are optical amplifiers (not shown) having a gain by current injection. The amplification regions 331a and 331b provided with are photodetection regions provided with photodetectors that operate by applying a reverse bias. 33
8a and 338b are AR coats formed on the end faces,
Al ₂ O ₃ + ZrO ₂ is deposited by electron beam (EB) evaporation. Reference numeral 339 is a waveguide. The waveguide 339 is formed in a cross shape on the upper surface, and the waveguide portions in the vertical direction from the center thereof are amplification regions 330a and 330b.
The left and right directions are detection areas 331a and 331b. The longitudinal direction of the etching groove 329 is 45 ° with respect to each longitudinal direction of the cross-shaped waveguide 339 described above.
The waveguide 339 is provided at a substantially central portion so as to be inclined and extend from the left and right lower ends to the central portion. As a result, the central portion of the waveguide 339 becomes the integrated coupler section 332 indicated by the broken line.

Next, the process procedure of the 17th embodiment will be described. First, as can be seen from FIGS. 39 and 40, n-type Ga
On the As substrate 341, n-type GaAs 342 as a buffer layer having a thickness of 1 μm and n-type Al _0.4 Ga _{0.6 As} 343 as a clad layer having a thickness of 1.5 μm are sequentially formed by MBE.
Formed thick. Next, undoped GaAs (100 Å
Thickness) and Al _0.2 Ga _0.8 As (30 Å thickness) are repeatedly laminated four times, and finally GaAs is laminated to 100 Å thickness to form an active layer 344 having a multi-quantum well structure, and p-type Al as a clad layer is formed thereon. _0.4 Ga _{0.6 As} 345 was formed with a thickness of 1.5 μm, and GaAs 346 as a cap layer was formed with a thickness of 0.5 μm.

Next, a desired cross-shaped mask pattern (pattern of the waveguide 339) having a width of 3 μm is formed on this semiconductor laser wafer by a photolithography process, and an active layer is formed through the mask by RIBE method in a chlorine gas atmosphere. Etching to 0.2 μm before 344,
A ridge portion was formed to form a stripe structure for confining in the lateral direction.

Subsequently, an insulating film 347 (thickness 1200) made of SiN is formed on the laser wafer on which the ridge is formed.
Å) was formed by a plasma CVD method, and a resist was spin-coated on the SiN insulating film 347 by about 1.0 μm.
Then, only the film-formed resist was removed by RIE in an O ₂ atmosphere of 4 Pa, and Si on the top of the ridge was removed.
The N insulating film 347 was exposed, and RIE was further performed in a CF ₄ gas atmosphere of ₄ Pa to selectively etch the exposed SiN insulating film at the top of the ridge. After that, the remaining resist was removed by the RIE method in an O ₂ atmosphere of 4 Pa.

Next, the surface oxide film formed on the top of the ridge is wet-etched with hydrochloric acid to form a current injection window, and then a Cr-Au ohmic electrode 348 is formed as an upper electrode by a vacuum vapor deposition method, and a GaAs substrate is formed. 341
Was lapped to a thickness of 100 μm, and then an AuGe—Au electrode was deposited as an n-type ohmic electrode 349. Then, a heat treatment for making ohmic contact with the p-type and n-type electrodes was performed to obtain a ridge-type semiconductor element.

Further, an etching groove 329 of the coupler portion 332 was formed in the mode shown in FIG. 40 by etching by the FIB method using Ga ⁺ ions with an acceleration voltage of 40 keV. The etching groove 329 is inclined as described above, the depth is 1 μm deeper than the active layer 344, and the inclination angle of the groove is 8 μm.
The angle was set to 5 ° or more (see FIG. 40). Finally, the resonance surface is formed by cleavage and EB (electron beam)
AR coating 3 by vapor deposition of Al ₂ O ₃ + ZrO ₂
38a and 338b, separated by scribing, and the electrodes were taken out by wire bonding.

Next, the operation will be described. The incident light wave 333 is the incident wave 3 amplified in the amplification region 330a.
The incident wave 34 is incident on the integrated coupler 332, and as described in the fifteenth embodiment, the transmitted wave 336 and the reflected waves 335 a and 335.
It is separated into b. The reflected wave 335a is photoelectrically converted in the light detection area 331a of the incident wave 333, and the signal component in the light wave 333 is monitored. At the same time, reflected wave 3
35b, the signal component in the light wave 333 is monitored in the light detection area 331b. On the other hand, the transmitted wave 336 is the amplified region 3
It is further amplified by 30b and output as outgoing light 337.

If the optical amplification factor (gain) is set so as to compensate for the loss of the coupler 332 and the coupling loss on the end face, it apparently functions as a light receiving optical node without loss, and multistage connection is possible. In the above description, it is described that only reception is performed, but an optical node capable of transmission and reception can be realized by providing a transmission unit and a reception unit side by side.

FIG. 41 shows the eighteenth embodiment of the present invention, and FIGS. 42 and 43 show AA 'and B- of the coupler section of FIG.
It is a B'sectional view. This embodiment is an example applied to a bidirectional optical node. In this embodiment, the optical amplification units 380a and 380b arranged in the bus line direction are formed, and the branch waveguides 382 and 383 to the reception unit / transmission unit intersect the waveguides in the bus line direction. The branch coupler 388 is
Four square total reflection mirrors (45 ° mirrors) at the intersection
Branching is performed by forming an etching groove 381 having The branch coupling ratio can be adjusted by controlling (position control) the photoelectric field distribution of the waveguide and the vertical and horizontal lengths of the square groove 381. For forming such a square groove 381, a fine processing technique such as etching with a Ga focused ion beam (FIB) or etching with a reactive ion beam (RIBE) can be used. The parts other than the branch coupler part 388 can be realized by the same structure as that of the seventeenth embodiment.

41, 383a is an AR coat with which the end face of the fiber 391 is in contact, 383b is an AR coat with which the end face of the fiber 392 is in contact, 383c is an AR coat with which the fiber 394 on the receiving side is in contact, 383d.
Is an AR coat with which the fiber 395 on the transmitter side abuts. In FIGS. 42 and 43, the same reference numerals as those in FIG. 40 denote the same parts as those in FIG.

The operation of the eighteenth embodiment will be described. The light wave incident through the optical fiber 391 and the AR coat 383a enters the integrated coupler 388 as an incident wave amplified by the amplification unit 380a, and is reflected by the square etching 3 groove 81 and the non-grooved portion. Is an optical wave entering the waveguide 382 to the left receiver and an optical wave entering the waveguide 383 to the right transmitter (this is blocked by an isolator (not shown) to stabilize the frequency on the transmitter side) and amplified. Part 38
The light wave entering 0b is branched. A signal is detected in the light wave entering the receiving unit via the waveguide 382 and the fiber 394, and the light wave entering the amplifying unit 380b is further amplified therein and output to the fiber 392. The same applies to the light wave incident from the opposite side (via the AR coat 383b). A light wave entering the coupler 388 from the transmitter via the fiber 395 and the waveguide 383 is a light wave entering the waveguide 382 and the amplifying units 380a and 380b by the square etching groove 381 and the non-groove portion which are also reflected and transmitted. Branched to. The signal components of the light waves entering the receiving unit via the waveguide 382 and the fiber 394 are monitored there, and the light waves entering the amplifying units 380a and 380b are respectively
There, it is amplified and output to the fibers 391 and 392.

In the above fourteenth to eighteenth embodiments, an example in which the resonance surface of the laser is formed by cleavage is shown. However, the etching end face formed by etching such as RIBE method and dry etching such as reactive ion etching. May be used. Further, although the active region is formed by the MQW (multiple quantum well structure), it is not limited to this and may be a DH (double hetero) structure, an SQW (single quantum well) structure, or the like. Also, the ridge wave type structure using GaAs has been described as an example.
It is also effective for a refractive index guided laser having a (buried hetero stripe) structure, a CPS structure (channel substrate planar stripe) structure, or a structure in which an absorption layer for confining current light is provided near the active layer. It is also effective for gain-guided lasers such as stripe electrode type and proton bombard type. In addition, the material of the semiconductor laser is GaAs.A
InGaAs / InGaAsP, AlG
It goes without saying that the same applies to materials such as aInP.

Finally, a bus type optical local area network using the waveguide type branch coupling element of the above embodiment (hereinafter, referred to as
The optical LAN will be briefly described). FIG. 44 shows light L
FIG. 45 is a block diagram of the AN, and FIG. 45 is a block diagram of the optical transceiver. In FIG. 44, 391 is a waveguide type branch coupling element provided on an optical fiber, 392 is an optical transceiver, 39
3 is a terminal device, 394 is a semiconductor optical amplifier, and 395 is an optical fiber. When the embodiment of the optical coupler 391 including an amplifier is used, the semiconductor optical amplifier 394 may be installed if necessary. Then, in FIG.
Is a control circuit, 402 is a semiconductor laser, 404 is a semiconductor optical amplifier, 405 is a waveguide type branch coupling element provided in the optical transceiver, and 406 is a photodetector. When the optical coupler 405 of the embodiment in which the optical amplifier and the photodetector are integrated is used, the optical amplifier 404 and the detector 406 may be provided as needed.

The part of the bus type optical LAN is, for example, CSM.
Although the A / CD communication system is used, it goes without saying that another token bus, TDMA, or other communication system may be used. The communication request from the terminal device 393 is sent to the optical transceiver 392, and the control circuit 401 in the optical transceiver 392 controls the optical LA.
The semiconductor laser 402 is driven according to the N communication method to transmit an optical pulse signal (digital signal). The transmitted optical signal is APC-amplified by the semiconductor optical amplifier 404 and sent to the waveguide branch coupling element 405, and further, the optical coupler 39.
1 to be sent to the bus line. Since the semiconductor optical amplifier 394 is provided at an appropriate position on the bus line, the optical signal is amplified and relayed here.

On the other hand, in the case of receiving an optical signal, the optical signal transmitted on the bus line is a waveguide type branch coupling element 391.
And is received by the optical transceiver 392. In the optical transceiver 392, the optical signal is branched by the waveguide type branch coupling element 405, and then the semiconductor optical amplifier 404.
After being APC-amplified by, it is input to the photodetector 406.
The optical signal is converted into an electric signal by the photodetector 406, and the electric signal is subjected to waveform shaping, reproduction, etc. by the control circuit 401 and sent to the terminal device 393. In this embodiment, the waveguide-type branch coupling element 405 operates in the same manner as the appropriate waveguide-type branch coupling element of the above-mentioned embodiments to transmit the optical signal transmitted from the optical transceiver to both directions of the bus line with the same intensity. I am trying to send it in. As a result, in the optical LAN, the optical signal transmitted from the optical transceiver 392 can be transmitted in both directions of the bus line with the same intensity, and the optical signal transmitted in both directions on the bus line is transmitted with the same intensity. It can be received by the transceiver 392.

FIG. 46 shows a case where a non-bidirectional optical coupler 601 having a semiconductor optical amplification function is installed in place of the optical coupler 391 on the bus line of the embodiment shown in FIG. In FIG. 46, 605 is an optical transceiver and 606 is a terminal device. Since the transmission method is the same as that of the embodiment shown in FIG. 44, it is omitted here. Further, in this embodiment, the semiconductor optical amplifier 60 is provided between the optical couplers 601 on the bus line.
2 may be installed as needed.

The waveguide type branch coupling element according to the present invention is not limited to the bus type optical LAN, but can be used in other optical communication networks including loop type and star type optical LANs.

[0120]

As described above, according to the present invention, integration is easier than in the conventional example, the process is easier than in the conventional example, the reliability and reproducibility are excellent, and the yield is high. improves. Further, it has become possible to realize an optoelectronic integrated device having an optical coupler. More specifically, according to one aspect of the present invention, a bidirectional branching or coupling type that couples light waves guided in both directions of the main waveguide to the sub-waveguide with different coupling efficiencies. If it is a coupler and at least two couplers are configured, both a light wave guided in both directions of the main waveguide and at least two waveguides connected to the main waveguide It is possible to couple light waves that are guided in the opposite direction with an arbitrary coupling efficiency, that is, to branch / couple with an arbitrary intensity ratio. In addition, since the wavefront division is performed at least in the horizontal direction, the manufacturing accuracy in the depth direction is reduced, and it is possible to manufacture only with the horizontal position accuracy, and the process is easy and the reliability and reproducibility are high. Excellent and yield is improved.

Further, by changing the intensity of the light waves reflected by the different reflecting surfaces of the coupler at the respective reflecting surfaces, the light waves propagating in both directions of the main waveguide are transmitted to the sub-waveguide at different intensity ratios. Since they are coupled, the light waves propagating in both directions of the main waveguide can be branched to the sub-waveguide with the same intensity without depending on the precision of manufacturing the coupler.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA ′ of FIG.

FIG. 3 is a sectional view taken along line BB ′ of FIG.

FIG. 4 is a plan view showing a second embodiment of the present invention.

FIG. 5 is a plan view showing a third embodiment of the present invention.

FIG. 6 is a plan view showing a fourth embodiment of the present invention.

7 is a cross-sectional view taken along the line AA ′ of FIG.

8 is a sectional view taken along line BB ′ of FIG.

FIG. 9 is a plan view showing a fifth embodiment of the present invention.

10 is a cross-sectional view taken along the line AA ′ of FIG.

11 is a cross-sectional view taken along the line BB ′ of FIG.

FIG. 12 is a plan view of a sixth embodiment of the present invention.

13 is a cross-sectional view taken along the line AA ′ of FIG.

14 is a cross-sectional view taken along the line BB ′ of FIG.

FIG. 15 is a plan view of a seventh embodiment of the present invention.

FIG. 16 is a plan view of an eighth embodiment of the present invention.

FIG. 17 is a plan view of the ninth embodiment of the present invention.

18 is a cross-sectional view taken along the line AA ′ of FIG.

19 is a cross-sectional view taken along the line BB ′ of FIG.

FIG. 20 is a plan view of a tenth embodiment of the present invention.

21 is a cross-sectional view taken along the line AA ′ of FIG.

22 is a cross-sectional view taken along the line BB ′ of FIG.

23 is a cross-sectional view taken along the line CC ′ of FIG.

FIG. 24 is a plan view of the eleventh embodiment of the present invention.

25 is a cross-sectional view taken along the line AA ′ of FIG.

26 is a cross-sectional view taken along the line BB ′ of FIG.

27 is a cross-sectional view taken along the line CC ′ of FIG.

FIG. 28 is a perspective view of a twelfth embodiment of the present invention.

29 is a cross-sectional view taken along the line AA ′ of FIG.

30 is a cross-sectional view taken along the line BB ′ of FIG.

FIG. 31 is a plan view of a thirteenth embodiment of the present invention.

32 is a cross-sectional view taken along the line AA ′ of FIG.

FIG. 33 is a sectional view taken along the line BB ′ of FIG. 31.

FIG. 34 (a) is a top view of the fourteenth embodiment of the present invention,
34B is a sectional view taken along the line AA ′ in FIG.

35 (a) is a cross-sectional view taken along the line BB ′ of FIG. 34 (a),
FIG. 34B is a partially enlarged view of FIG.

36 (a) is a top view of the fifteenth embodiment, and FIG. 36 (b) is a partially enlarged view of FIG. 36 (a).

FIG. 37 is a plan view of the sixteenth embodiment of the present invention.

FIG. 38 is a plan view of the seventeenth embodiment of the present invention.

39 is a cross-sectional view taken along the line AA ′ in FIG. 38.

40 is a cross-sectional view taken along the line BB ′ of FIG. 38.

FIG. 41 is a perspective view of an eighteenth embodiment of the present invention.

42 is a cross-sectional view taken along the line AA ′ in FIG. 41.

43 is a cross-sectional view taken along the line BB ′ of FIG. 41.

FIG. 44 is a block diagram illustrating an optical LAN using the optical coupler of the present invention.

45 is a configuration diagram of the optical transceiver in FIG. 44.

FIG. 46 is a block diagram illustrating another optical LAN using the optical coupler of the present invention.

FIG. 47 is a view showing a conventional example.

FIG. 48 is a view showing a conventional example.

FIG. 49 is a view showing a conventional example.

[Explanation of symbols]

1, 101, 141, 211, 221, 231, 29
1,341 Substrate 2,4,103,105,142,144,213,2
15,222,224,233,235,292,29
4,343,345 Cladding layer 3,104,143,214,223,234,29
3,344 Active layer 5,106,145,216,225,236,25
5,346 Cap layers 10a, 10b, 11a, 11b, 20a, 20b, 2
1a, 21b, 30a, 30b, 31a, 31b, 61
a, 61b, 62a, 62b, 121a, 121b, 1
22a, 122b, 150a, 150b, 151a, 1
51b, 170a, 170b, 171a, 171b, 1
80a, 180b, 191a, 191b, 192a, 1
92b, 226, 227, 246, 247, 256, 2
76,277,300,310,315,329,38
1 Coupler (slit groove) 12, 13, 14, 22, 23, 24, 66, 68, 7
0,126,152,153,154,160,17
2,173,174,182,183,184,19
6,382,383 Waveguides 65a, 65b, 195a, 195b, 250a, 25
0b, 270a, 270b, 380a, 380b Optical amplification section 102, 232 Buffer layer 107, 108, 218, 219, 238, 239, 3
48,349 electrodes 109,217,237,347 insulating films 193,271 transmitters 194,272 receivers 201a, 201b, 253a, 253b, 253c,
253d, 273a, 273b, 383a, 383b,
383c, 383d AR coating 388 Coupler section 391, 392, 394, 395, 604 Optical fiber 392, 605 Optical transceiver 393, 606 Terminal device 394, 602 Semiconductor optical amplifier device 401 Control circuit 402 Semiconductor laser 404 Semiconductor optical amplifier 405, 601 optical Coupler 406 Photodetector

Claims (22)

[Claims] 1. In a channel waveguide structure formed on a semiconductor substrate, an optical wave guided bidirectionally in a main waveguide and two or more sub-waveguides connected to the main waveguide. A coupler portion for branching / coupling the light waves guided to the optical waveguide is formed at the intersection of the main waveguide and the sub-waveguide, and the coupler portion is connected to the main waveguide. The channel waveguide is constituted by forming processed portions which are two mirror surfaces having different reflectances so as to perform wavefront division of the waveguide field distribution of the light wave guided through the sub-waveguide. The shape of the coupler is composed of two angled parts, and the axis of symmetry in the horizontal plane of the coupler is shifted with respect to the central axis in the horizontal plane of the sub-waveguide. .. 2. A channel waveguide structure formed on a semiconductor substrate, in which a light wave propagating in both directions of the main waveguide and a light wave propagating in a sub-waveguide connected to the main waveguide are branched or At least two sets of coupler sections having two different reflecting surfaces for performing coupling are provided, and the intensity of the light wave reflected by the two reflecting surfaces of the coupler section is changed to propagate in both directions of the main waveguide. A waveguide-type branch coupler, characterized in that the optical waves being coupled are coupled to the sub-waveguide at different intensity ratios. 3. A plurality of channel waveguide structures are formed on a semiconductor substrate, and a coupler portion for coupling an optical wave is formed at an intersection of the channel waveguides, and the coupler portion is the channel waveguide. To form a wavefront division of the guided light field distribution that propagates through the channel waveguide is formed from a processed portion having a different reflectance in the channel waveguide, and the processed portion is formed with two sets of micromirror surfaces. 1. An integrated optical coupler, wherein the integrated optical couplers are arranged at opposite corners, and the cut directions of the micromirror surfaces are orthogonal to each other. 4. A coupler section for branching / coupling a light wave is formed in an intersecting portion of a plurality of channel waveguide structures formed on a semiconductor substrate, and the coupler section is at least one total reflection mirror. An integrated optical coupler characterized in that it is formed by forming a polygonal processed portion having a reflective surface that becomes 5. A coupler portion for branching / coupling light waves is formed in an intersecting portion of a plurality of channel waveguide structures formed on a semiconductor substrate, and the coupler portion comprises:
An integrated optical coupler comprising: a processed portion which is at least two mirror surfaces having different reflectances and formed so as not to be symmetrical with respect to a center line in a horizontal plane of the channel waveguide structure which intersects. 6. The integrated optical coupler according to claim 1, wherein the coupler portion is V-shaped or C-shaped. 7. The integrated optical coupler according to claim 1, wherein the channel waveguide structure includes an active layer. 8. The integrated optical coupler according to claim 1, wherein said coupler section is configured to perform guided light field distribution wavefront division in at least a horizontal direction. 9. The coupler according to claim 1, wherein the coupler is provided at an intersection of a main waveguide of the channel waveguide structure and a sub-waveguide connected to the main waveguide. Integrated optical coupler. 10. The integrated optical coupler according to claim 9, wherein the intersecting portion is one of T type, Y type and X type. 11. The integrated optical coupler according to claim 7, wherein the coupler portion includes a processed portion processed beyond the active layer. 12. The integrated optical coupler according to claim 9, wherein the coupler section couples light waves from the sub-waveguide to the main waveguide in both directions of the main waveguide. 13. The integrated optical coupler according to claim 9, wherein in the coupler section, the coupling efficiency of the light wave from the sub-waveguide to the main waveguide differs depending on the waveguide direction of the main waveguide. 14. A plurality of the channel waveguide structures are formed to include a crossing portion forming a coupler portion, one of which is formed.
One set serves as an optical amplification region, and the other set is configured to be connected to at least one of a transmission unit and a reception unit.
An optical node having an amplification function, which constitutes an optical node.
The integrated optical coupler according to 3, 4, or 5. 15. The optical amplifier, wherein a plurality of the channel waveguide structures are formed to include a crossing portion forming a coupler portion, and which has a built-in transmission or reception function.
2. The integrated optical coupler described in 2, 3, 4 or 5. 16. The coupler section changes the intensity of a light wave reflected by the reflecting surface by changing the lengths of two different reflecting surfaces forming the coupler section. The integrated optical coupler described. 17. The integrated optical coupler according to claim 2, wherein the main waveguide changes the structure of the waveguide between the coupler sections. 18. The optical coupler section is configured to perform wavefront division of a light field distribution in a layer direction.
The integrated optical coupler according to 3, 4, or 5. 19. The integrated optical coupler according to claim 1, wherein the minute mirror surface or the reflecting surface of the coupler portion is processed into a slit shape. 20. A control unit having a function of driving a light emitting device based on a signal from a terminal device to output an optical signal and a function of reproducing and relaying an electrical signal from a photodetector unit and sending the electrical signal to the terminal device. A semiconductor optical amplifier that amplifies an optical signal output from the light emitting device that generates an optical signal according to an electrical signal, and a semiconductor optical amplifier that amplifies the optical signal input to the photodetection unit that converts the optical signal into an electrical signal. Claims 1, 2,
An optical transceiver comprising the integrated optical coupler described in 3, 4, or 5. 21. An optical LAN comprising at least one integrated optical coupler according to claim 1, 2, 3, 4 or 5. 22. An optical LAN comprising at least one optical transceiver according to claim 20.