JPS6084892A - Optical ic - Google Patents

Abstract

PURPOSE:To obtain the titled device small-sized, light in wt. and capable of being mass-produced and reduced in cost by a method wherein the main light emitting element, reserve light emitting element, a monitoring photo detection element, and an optical waveguide to output the each light emitting element from the same output part are monolithically formed on the same semiconductor substrate. CONSTITUTION:Photo diodes 28 and 30 for photo output monitoring are provided by the coincidence of optical axes via groove 26 by attachment to each of laser diodes 22 and 24. A semiconductor optical waveguide 32 of a Y-branched structure is formed on the opposite side of the diodes 28 and 30 with respect to the diodes 22 and 24. The diodes 28 and 30 have N-InP clad layers 52 formed on an N-InP substrate 40, an InGaAsP active layer 54 being formed on the clad layer, and a P-InP clad layer 56 being then formed on the active layer. The optical waveguide uses an N-InP clad layer 42 formed on the substrate in common, an N-InGaAsP waveguide layer 60 being formed on the clad layer 42, and an N-InP clad layer 62 being then formed on the waveguide layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical integrated circuit that can be used as a light emitting element for use in optical communication transmitters, optical information processing equipment, and the like.

Semiconductor lasers are used as devices that require 31f in optical communication systems, optical information processing systems, etc.However, semiconductor lasers deteriorate quickly in their light emitting characteristics, and if they are replaced, their service life will be shortened. Therefore, in order to ensure system reliability, optical communication systems, optical information processing systems, etc. are equipped with spare semiconductor lasers.

To be more specific, for example, as shown in the ft5t diagram, in addition to the main semiconductor laser 12 provided with a light receiving element 10 for monitoring, there is also a preliminary semiconductor laser I6 provided with a light receiving element 14 for monitoring. A mirror 18 for optical path switching, which is provided separately, is positioned at the first position 18A, and the laser beam from the main semiconductor laser 12 is sent to the optical fiber 19 and monitored by the light receiving element IO. As a result, after the main semiconductor laser 12 has deteriorated, the optical path switching mirror I8 is moved to the second position 18B so that the laser beam from the auxiliary semiconductor laser 16 is sent to the optical fiber 19.

With the configuration as described above, the short life span of the semiconductor laser can be compensated for. However, the above-described apparatus not only requires an optical path switching mechanism, but also requires mechanical assembly of the optical path switching mechanism, a monitoring light receiving element, and a semiconductor laser. Therefore, the device must be relatively large and heavy. Furthermore, the price has to be high not only because of the price of individual parts but also because of the large number of manufacturing steps and the need for high-precision fine adjustment such as alignment of the optical axis.

Furthermore, since the optical path switching mechanism is mechanical, the semiconductor laser cannot be switched instantaneously.

Therefore, in view of the above-mentioned problems, the present invention aims to realize a lightweight and compact device without requiring a mechanical optical path switching mechanism. A photodetector element for monitoring the output light of these light emitting elements, and an optical waveguide 1 for outputting the output light of each light emitting element from the same output part? It is an object of the present invention to provide a light emitting circuit which can be monolithically formed on the same conductor substrate and can be switched to a preliminary light emitting element as required.

In other words, according to the present invention, at least two light emitting elements are formed on one substrate, and the light emitting elements formed on the substrate are guided to output light from the same output section. A 5 degree nolithic optical integrated circuit comprising: an optical waveguide having a branched structure, and a photodetector element provided on the substrate for each light emitting element to detect the optical output of the light emitting element. is provided.

According to the monolithic optical 4JS product circuit as described above,
All the laser light from each light emitting element passes through the optical waveguide and is output from the same output part, so one light emitting element is operated as the main light emitting element, and the light detecting element attached to it is used to detect that light emitting element. On the other hand, other light emitting elements are not used as preliminary light emitting elements, and as a result of monitoring, for example, if the output of the main light emitting element decreases or oscillation stops, the main light emitting element If it is determined that the light-emitting element has deteriorated, another light-emitting element set as a preliminary light-emitting element is operated instead, thereby allowing instantaneous switching.

In the embodiment of the present invention, each of the light emitting elements is a semiconductor laser, such as a DFB type laser diode or a DFB type laser diode.
It is an R-type laser diode. Lid, λ#0.9-1.
In the case of a long wavelength band of 7 μm, InGa with an InP substrate
AsP-based quaternary mixed crystal semiconductor lasers can be used, and λ#0.
In the case of a short wavelength band of 9 μm or less, G
aA IAS-based ternary mixed crystal semiconductor laser can be used.

Further, the photodetecting element can be a photodiode having the same cross-sectional structure as the semiconductor laser. Further, when there are two light emitting elements, the leading waveguide having a branched structure may be of a Y-branch type, and further may be a semiconductor leading waveguide.

Fire difference side.

The present invention will now be described in detail with reference to the accompanying drawings.

Figure 2 shows In(iaAsP/Inl' system 1) B
3 is a schematic perspective view of a monolithic optical integrated circuit according to the invention incorporating an R-type laser diode, and FIG. 3 is a view in the Ili plane along line A-A of FIG. 2; The illustrated monolithic optical integrated circuit includes two
It has two laser diodes 1, 22 and 24. and °ζ to each of those laser diodes 22 and 24]
In order to align the optical axes, photodiodes 28 and 30 for monitoring the optical output are provided through the groove 264'.

A semiconductor optical waveguide 32 having a Y-branch structure is formed on the opposite side of the first diodes 28 and 30 (excluding the laser diodes 22 and 24).

To explain in detail, as shown in FIG. -1nP clad lH42 has JnGaAs
l' active layer 44 is formed, and its l n Ga
A p-1nP cladding old 46 is formed on the Asl' active species 44. Then, on the lower side of the substrate 40,
A side electrode 48 is formed, and a p-1nP clad Ji
A p-side electrode 50 is formed above f46. These electrodes 48 and 50 are made of, for example, 8μGeNi and AuZn, respectively.

On the other hand, photodiodes 28 and 30 have the same cross-sectional structure as laser diodes 22 and 24, as shown in FIG. Of course, the photodiodes 28 and 30 have an n-1nP cladding layer 52 formed on an n-1nP substrate 40;
An InGaAs1' active layer 54 is formed thereon, and a p-1nP clad layer 56 is formed on the InGaAsP active layer 54. A p-side electrode 58 made of, for example, AuZn is formed above the p-1nl' cladding layer 56. Photo 1 - diode 28 and 3
The lower electrode 48 of the substrate 40 is shared as the n-side electrode of 0.

Further, the optical waveguide 32 is formed on the substrate 40.
The nP cladding layer 42 is commonly used, and an n-1nGaAsP waveguide layer 60 is formed on the n-1nP cladding layer 42, and an n-1nP cladding layer is formed on the n-GaAsP waveguide layer 60. 62 is formed.

n1 near the coupling part of the optical waveguide 32 with the laser diode
A portion of the nP cladding 62 is processed with a 4.1 grating to form a Bragg reflection a: 104, and the laser diode is of the DBR type.

Furthermore, the laser diodes 22 and 24, the photodiodes 28 and 30, and the optical waveguide 32, as shown in FIG.
A buried structure is formed by a buried layer consisting of the p-1nP layer 40A and n-1nl=4OB.

The monolithic optical integrated circuit as described above is manufactured, for example, by the procedure shown in FIG. That is, as shown in FIG. 4, n-1nl' groups 4 & 401:
The cladding layer 42 and the InGaAs of the FoI diode
I n G n A s I that also constitutes P-active m54
'/l'i characteristic lH44 and photodiode p-1
nl'craso! The p-1nP cladding IH46, which also constitutes the layer 50, is sequentially grown epitaxially. Next, as shown in FIG. 4B, a mask 6 such as 5i02 is placed over the portions corresponding to the laser diode and photodiode.
6 and photolithography to perform etching for forming a waveguide layer, and then, as shown in FIG.
-1nGaAsP waveguide [60 and n-1nP cladding layer 6
2 and 2 are epitaxially grown in sequence. At this time, in order to guide the laser light, an n-1nGaAsP waveguide layer 6
0 is the same composition ratio as the active layer of the laser diode. Next, as shown in the fourth diagram, a Bragg reflector 64 is formed by grating the n-InP cladding layer 62 near the coupling part with the laser diode by holographic ink exposure method or electron beam exposure method and photolithography. Form. The period of the grating is chosen to be A=λg/2N so that the light wave in the active layer is effectively Bragg-reflected. Here, 2g is the wavelength with respect to the energy gap of the active layer, and N is the effective refractive index (propagation constant β in the waveguide layer and propagation constant k in vacuum).

ratio: N-β/kn).

As shown in FIG. 4E, butterming is performed to form a branch structure of the photodiode section, laser diode section, and optical waveguide.For example, a 5i02 mask 68 is formed, and the mesa is formed to a depth reaching the base 4k40. After etching, as shown in Fig. 4 1s, p-1nl'J*4
0A and n-In1'1i44013 are sequentially epitaxially grown to form a buried structure.

After that, an n-side electrode 48 is formed on the lower side of the substrate 40 by, for example, vapor deposition, and a p-side electrode constituting the layer side 6, p (11I electrodes 5o and 58 of the plnl' cladding layers 46 and 56) is formed.

Furthermore, Ueso]-etching or C, 1, I? l
By dry etching such as E or ion milling, fJ26 having a depth reaching the substrate 4o as shown in FIG. 4G is formed.

As a result, a DBR type laser diode having a mirror crystal plane of the laser, that is, a mirror on one end face and a grating on one end face is formed, and at the same time, the DBR type laser diodes 22 and 24 and the photodiodes 28 and 30 are separated.

As can be seen from the above, since the photodiode and the laser diode have the same 1R structure and the same composition, the epitaxial growth process is simple. Note that the epitaxial multilayer method includes a liquid phase growth method, a vapor phase growth method, an organometallic vapor phase deposition method, and the like.

In the monolithic optical integrated circuit configured as described above, all the laser beams from the laser diodes 22 and 24 pass through the leading waveguide 32 and are output from the same output section, so one laser diode 22 is used as the main light emitting element. The output state is monitored by the attached photodiode 28, and if it is determined that the laser diode 22 has deteriorated as a result of the monitoring, specifically, the laser diode 22 is If the output of the laser diode 24 decreases or the oscillation stops, instantaneous switching can be achieved by operating the laser diode 24 instead.

The above embodiment is a monolithic optical integrated circuit incorporating an InGaAsP/InP DBR laser.
As the semiconductor material for the laser, a ternary or quaternary alloy of the ■-■ group can be used. For example, to take a case where a °ζ GaAlAs/GaAs semiconductor laser is incorporated as an example of a ternary alloy, GaAs is used as the substrate 4o.
Iriharu, Furano FJM42.46.52.56.6
It is also possible to use GaAlAs for the active layer 44, 54 and the waveguide layer 60.

Figure 5 shows InGaAs1'/Inl' system 1) F
FIG. 6 is a schematic perspective view of a monolithic optical integrated circuit according to the present invention incorporating a 13-inch laser diode;
6 is a 1v1 plane view taken along the line B-H in FIG. 5. FIG. This monolithic light converging circuit IIδ is formed on the substrate 7o.
It has two DFB type laser diodes 1, 72 and 74.

Then ζ, those D FB type LED diodes 72 and 74
Photodiodes 78 and 80 for monitoring the optical output are installed through the photodiodes 76 and 76, respectively, with their optical axes aligned.
Being beaten. On the opposite side of the D FB type regulator diodes 72 and 74 from the photodiodes 1s78 and 80,
A leading wave of 1/881 with a Y-branched structure is formed.

To explain in detail, as shown in FIG.
B-type diodes 72 and 74 each have an n-In1' Jfii 82 formed on an n-1nP substrate 70, with an InGaAsP layer 82 formed on the n-1nP layer 82.
An active layer 84 is formed, and p-1nGaAsl'1x8G is formed on the InGaAsP active layer 84. And that p-1nGaAs! A p-InGaAsP layer 88 is formed on the '198G, and a p-1nP layer 92 is further formed thereon with a grating 90 interposed therebetween. Among these layers, p-InGaAsP
The layers 86 to p-1nP Ji 92 are formed by diffusing, for example, Zn into the non-p-type layers all at once. An n-side electrode 94 is formed on the lower side of the substrate 70, and a p-side electrode 96 is formed on the upper center of the p-1nP layer 90. These electrodes are also made of, for example, AuGeNi and ΔuZn, respectively.

On the other hand, photodiodes 78 and 80 have the same cross-sectional structure as DFB type laser diodes 72 and 74, as shown in FIG. The optical waveguide 81 includes DFB type Ray diodes 72 and 7, except that there is no p-side electrode 96.
It has the same cross-sectional structure as the DFB type laser diodes 72 and 74, except that the layer 86 to the layer 92 is not p-type.

Monolithic light with the above configuration! Is Tei circuit also,
The laser beams from each of the laser diodes 72 and 74 pass through the optical waveguide 81 and are output from the same cutting edge, so one of the laser diodes 72 operates as the main light emitting element. =J As a result of monitoring by the photodiode 78 which has deteriorated, it is determined that the laser diode 72 has deteriorated, and AI can instantly replace Li1J by operating the laser diode 74 instead.

When incorporating a GaAlAs/GaAs semiconductor ray instead of the above-mentioned InGaAsP/InP semiconductor ray, GaAs is used as the substrate 70, and InG
A Ga4183 layer can be used instead of the IN and InP layers for a8sl, and a GaAs layer can be used as a layer for lnG+i8s11.

Although an example of an optical integrated circuit according to the present invention incorporating two laser diodes has been described above, it is obvious that an optical integrated circuit according to the present invention incorporating three or more laser diodes can be similarly realized. Probably.

As described above, the optical integrated circuit according to the present invention includes at least two light emitting elements formed on one substrate, and the output light of each light emitting element is guided from the same output section. Output,
The light emitting device is monolithically constructed and includes a leading waveguide having a branched structure formed on the substrate, and a photodetection element provided on the substrate for each light emitting element to detect the optical output of the light emitting element. ζ, it is small and lightweight, and can be mass-produced using conventional semiconductor device manufacturing methods, making it possible to reduce costs.

In addition, since the output light of each light emitting element is guided to the same light output section by the leading waveguide with a branching structure, there is no need for optical axis adjustment, high reliability, and no mechanical device for switching the light source. Not necessary.

Furthermore, since the light emitting element can be switched to the preliminary light emitting element by electrical operation, a deteriorated light emitting element can be instantaneously switched to the preliminary light emitting element, and even if the performance of the system deteriorates, it can be recovered in an extremely short time.

When forming a 'ζ semiconductor laser as a light emitting element, the structure and composition of the semiconductor laser, especially the active layer, can be made common to all semiconductor lasers, and the oscillation wavelength and modulus of the semiconductor laser can be
S can be made the same, and even if the main semiconductor laser C1 breaks down and is switched to the backup semiconductor laser C1, there is no change in the light emission characteristics.

Furthermore, when forming an 11-conductor laser as a light emitting element and forming an -il diode-I as a photodetecting element,
It is possible to make the composition of the active layer of the semiconductor laser and the photodetection layer of the photodiode the same, and since there are many common parts in the 1lIi plane structure, it is possible to make the semiconductor laser, the photodiode', and the leading waveguide of the branch structure the same. Crystal growth process I'
- It can be formed by one process, therefore the manufacturing process is one step.
There are 1 ladders, and it can be manufactured cheaply.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a conventional light generating device having a T-equipment light source, FIG. 2 is a perspective view of a first embodiment of an optical integrated circuit according to the present invention, and FIG. l along the line A-A of
υ1 side view, FIGS. 4 to 4 are diagrams illustrating the manufacturing method of the first embodiment of the optical integrated circuit according to the present invention shown in FIGS. 2 and 3, and FIG. A perspective view of the second embodiment of the integrated circuit, and FIG. 6 is a 11Ji plane view taken along line B--B in FIG. (Main reference numbers) 10, 14... Light receiving element for monitor, 12... Main semiconductor laser, 16... Reserve semiconductor laser, 18...
Optical path switching mirror, 19... optical fiber, 40.70
... Substrate, 22.24.72.74 ... Laser diode, 26.76... Groove, 28.30.78.
80...Photodiode, 32.81...Optical waveguide patent applicant...Sumitomo Electric Industries Co., Ltd. agent...
Patent Attorney Masahiko Arai 1st H 2N 3

Claims (6)

[Claims] (1) at least two light emitting elements formed on one substrate; an optical waveguide having a branch structure formed on the substrate, which guides the output light of each light emitting element and outputs it from the same output section; 1. A monolithic optical integrated circuit comprising a photodetector element provided on the substrate for each light emitting element to detect the optical output of the light emitting element. (2) Each of the light emitting elements is I) F 13 type or DB
The monolithic optical integrated circuit according to claim 1, wherein the monolithic optical integrated circuit is an R-type semiconductor laser. (3) The monolithic optical integrated circuit according to claim 2, wherein the photodetecting element is a photodiode having the same cross-sectional structure as the semiconductor laser. (4) The monolithic optical integrated circuit according to claim 2 or 3, wherein the substrate is an InP substrate, and the semiconductor laser is an InGaAsP quaternary mixed crystal semiconductor laser. (5) The monolithic optical integrated circuit according to claim 2 or 3, wherein the substrate is a GaAs substrate, and the semiconductor laser is a GaAlAs-based ternary mixed crystal semiconductor laser. (6) The monolithic optical integrated circuit according to any one of claims 1 to 5, wherein the optical waveguide is a semiconductor optical waveguide having a Y-branch structure.