JPS61166190A - Optical integrated circuit - Google Patents

Abstract

PURPOSE:To simplify a manufacturing method by applying a forward voltage to p-n junction on an n-type intermediate layer, driving a semiconductor laser, applying a reverse voltage to a p-type clad layer to drive a photocontroller. CONSTITUTION:After a grating is formed on an n<+> type InP substrate 1, an n<-> type InGaAsP layer 2, a p<+> type InP intermediate layer 10 and charging clad layers 10', 10'', an InGaAsP active layer 4, an n<+> type InP clad layer 11, an n<+> type InGaAsP layer 12 are sequentially epitaxially grown. After a striped Au/Su electrode 8' is formed on the layer 12, the layers 12, 11, 4 are removed by etching. Then, an Au/Zn electrode 7, Au/Zn electrodes 7', 7'' are formed on the exposed p<+> type InP layer, the layers 10, 10', 10'' are partly etched to separate between the elements as the intermediate layer 10 and mounting clads 10', 10'' of a semiconductor laser, Au/Sn electrode 8 is formed on the separating surface of n<+> type InP substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical integrated circuit in which a semiconductor laser and a light control element such as an optical switch or an optical modulator are monolithically integrated.

Conventional Technology Optical integrated circuits that monolithically integrate optical control elements and semiconductor lasers have a wide range of applications.

For example, not only semiconductor lasers with integrated external optical modulators that exhibit stable oscillation characteristics even during high-speed modulation, semiconductor lasers with integrated optical switches that have an optical path switching function, but also oscillation by phase control of DFB lasers and double-cavity lasers. It can also be used for wavelength control, etc.

FIG. 2 shows an example in which a semiconductor laser and a light control element are simply integrated in this manner.

1 is n” = InP substrate, 2 is band gear 1.P wavelength λ
-1,06 μm n--InGaAs P optical waveguide layer, 3
is n' = InP intermediate layer, 4 is I of λq = 1.3 μm
nGaAsP active layer, 5.5' is P"-InP cladding layer, 6 is P+-1nGaAs with λ""1.11 tm
P key 1" bulge layer, 7, 7' are A, u/Zn
The electrodes 8 are Au/Sn electrodes, and 9 is a grating. The region B constitutes an ITG-DFE type semiconductor laser, and the region B constitutes a light control region. Areas A and B are n+-
An InP substrate 1 is connected with an n-InGaAsP optical waveguide layer 2, and an Au/Sn electrode 8-Au/
A forward voltage is applied between the Zn electrodes 7 to drive the semiconductor laser, and the oscillated light waves propagate through the optical waveguide layer 2 to the region B. Here Au/Sn electrode 8-Au/Zn electrode 7
If a reverse voltage is applied between '', light can be controlled by the electro-optic effect. The light control element in the region B can have a variety of structures, such as a directional coupler type or a total reflection type, and can perform optical modulation and optical switching.

Problems to be Solved by the Invention However, in the optical integrated circuit having the structure shown in FIG. 2, the 4-electrode type of the layer of the optical waveguide layer 2+ is different between the region A and the region B, so it is difficult to create this device. , requires epitaxial growth two or more times, and the fabrication process is complicated. Furthermore, since the second epitaxial growth must be performed directly on the optical waveguide layer 2- without meltback, it is difficult to obtain good pn junction characteristics.

It is an object of the present invention to overcome such problems and to provide a 5T optical integrated circuit that exhibits good performance using a simple manufacturing method.

Means for solving the problems In order to solve the above problems, the present invention uses the optical waveguide layer, the two intermediate layers, and the cladding layer as a common layer of the second conductivity type,
-1- of the intermediate layer, an active layer, a cladding layer of a first conductivity type,
It has a structure in which an electrode is arranged to form a part of the semiconductor laser, and an electrode is arranged to a second conductivity type land layer to form a light control part.
A forward voltage is applied to the pn junction on the intermediate layer to drive the semiconductor laser, and a reverse voltage is applied below the cladding layer of the first conductivity type to drive the light control section.

Function: The present invention provides a semiconductor laser with good characteristics that is simple to manufacture and does not impair the characteristics of the single device, such as requiring only a minimum number of epitaxial growths due to the developed structure and driving method.
An optical integrated circuit with an integrated optical control element can be provided.

Embodiment FIG. 1 shows a semiconductor laser with an optical modulator using an InP substrate as a first embodiment of the present invention.

This is an ITG-DFB type semiconductor laser (area A)
This is an optical integrated circuit that integrates a directional coupler (area B) as an external optical modulator. Here, 1 to 9 are conventional techniques (
As shown in Figure 2), 10 is P''-InP
The intermediate layer 10', 10'' is a P''-InP loaded cladding layer, and each layer 10', 10'' is just the same layer separated from each other. Also, 11 is an n''--InP cladding layer, 12 is 2g-1, 1μm n+-InGaAs
P cap layer, 7, 7' are Au/Zn electrodes,
8' is an Au/Sn electrode of FIG.

This element can be manufactured by the following procedure.

1) After forming a grating in the region A of the n+-InP substrate 1''-, 721.058 m of n--InG was formed.
aAs P layer 2, p''-InP intermediate layer 10 and loaded cladding layer 10', 10'', λ9-1.3 μm InG
aAs P active layer 4, n''-InP cladding layer 11, λ
An n+-I nGaAs P layer 12 having a thickness of 1.1 μm is sequentially epitaxially grown. n+-InGaAs P
Striped Au/Sn electrode 8 in area A of layer 12 soil
After forming ', the total -InG area other than this stripe-like area
aAs P layer 12, n''-InP layer 11, InGaAs
The P active layer 3 is removed by etching. In order to unify the transverse mode of the active layer 3, the stripe width is made wider than the other stripes.

Next, an Au/Zn electrode 7 as a lower electrode of the semiconductor laser and Au/Zn electrodes 7' and 7'' as control electrodes of the directional coupler are formed on the exposed p+-InP layer, and then the p+-InP layer is formed. 10. Etching a part of 10', 10'' to isolate the elements and loading the intermediate layer 101 of the semiconductor laser and the directional coupler, F1o', 1
0tt. Furthermore, Au is placed on the outer surface of the n+-InP substrate.
/ By forming the Sn electrode 8, the optical integrated circuit of the present invention can be manufactured.

Au/Zn electrode 7 of semiconductor laser part A of this device
Au/on the n”-I nGaAs P layer.
When a forward voltage is applied to the Sn electrode 8', the semiconductor laser oscillates with a current equal to the threshold value -10. Here, the optical waveguide layer 2 under the n-1-InP-loaded cladding layer 11 of the semiconductor laser part A and the optical waveguide layer 2 under the p+-InP-loaded cladding layer of the directional coupler section contain three-dimensional light. A leading wave path that can be confined is formed, and the oscillated laser beam propagates through this leading wave path and reaches the loaded cladding 10' of the directional coupler B.
It reaches the optical waveguide below. When the element length of the directional coupler is set to the minimum coupling length, the laser beam moves to the adjacent optical waveguide due to the coupling between the two optical waveguides, and the Iff power light becomes p''
-InP is obtained from the optical waveguide layer 2 under the loaded crat 10". Now ground the Au/Sn electrode on the back side and connect the p"-I
When a reverse voltage is applied to either one of the Au/Zn electrodes 7 and 7' of the nP-loaded cladding, the degree of light migration changes due to a change in the refractive index due to the electro-optic effect, resulting in a flickering pressure Vs.
Then, the output light is switched to the optical waveguide on the p+-InP loaded cladding 10' side, and the intensity of the output light can be modulated according to the applied voltage.

By the way, in this case, the loading cladding part is partially cut off due to separation between the semiconductor laser part A and the directional coupler part 8, causing a slight coupling loss of light, but as shown in Figure 4, the semiconductor laser This problem can be solved by connecting the intermediate layer of the directional coupler with the loading cladding of one side of the directional coupler, and applying voltage to the directional coupler with the load of 7 rad on the other side.

As described above, the semiconductor laser with an external modulator according to the first embodiment of the present invention can obtain good optical modulation and optical switching characteristics with a simple manufacturing method using the structure and driving method described above.

Next, FIG. 5 shows a phase-controlled dual cavity laser as a second embodiment of the present invention. The film structure driving method of this device is the same as in the first embodiment, but the light control section B consists of one loaded waveguide, the semiconductor laser part A is connected to the resonator L1, and the light control section B has a double resonator structure of resonator L2.

The details of the principle of this device are described in Japanese Patent Application No. 59-43301, but it is important to apply a reverse voltage to the Au/Zn electrode 7' on the p + -loaded cladding layer 10' of the light control section B. It is possible to control the phase of the guided light in the second resonator, and the optimal phase matching conditions for the two resonators provide stable oscillation characteristics, especially a semiconductor with a minimum shift in the oscillation frequency during high-speed modulation. Laser is what you can get.

By the way, in the embodiment of the present invention, the semiconductor substrate is n+-InP.
However, a semi-insulating substrate may be used as long as electrodes are formed on the light guide or wave layer, and each layer is not limited to this as long as the conditions are met. Furthermore, it goes without saying that it can be applied to other semiconductor materials such as GaAs. Optical integrated circuits can be formed with a minimum of 10 times of epitaxial growth, and their characteristics can be improved through integration without sacrificing the characteristics of a single element. The range of applications is wide, such as semiconductor lasers with integrated optical switches and external phase-controlled double-cavity lasers, and they are extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor laser with an integrated light control section and an integrated optical control section having a conventional structure. figure,
FIG. 3 is a sectional view of FIG. 1, FIG. 4 is a parent diagram of an element with a partially improved structure in FIG. 1, and FIG. 5 is a phase control mechanism according to a second embodiment of the present invention. This is a night diagram of a dual cavity laser. 1...n''-InP substrate, 2--n-In
GaAs P optical waveguide layer, 3...n''-InP
Intermediate layer, 4... InGaAsP active layer, 5
．． 5'...p''-InPn scratched layer, 6...
...p''-InGaAs P cap layer, 7, 7',
7"--Au/Zn electrode, 8, 8'-
-----・Au/Sn electrode, 9...Grating, 1o...p+-InP intermediate layer, 10'...
...p+I nP loaded cladding, 11...
・・n+-InP cranode layer, 12--- n+-I
nGaAs P cap layer. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure ←β→ ←Δ→ Figure 3 Figure 4〃' Figure 5

Claims (2)

[Claims] (1) If necessary, a semiconductor substrate of a first conductivity type or a semi-insulating type is placed on a semiconductor substrate of a first conductivity type or a semi-insulating type through a buffer layer of a first conductivity type. an optical waveguide layer with a low carrier density and a high refractive index, and an intermediate layer of a second conductivity type and a lower refractive index with a higher carrier density than the optical waveguide layer on the optical waveguide layer in the first region; The structure includes an optical waveguide layer, an active layer having a narrower forbidden band width than the intermediate layer, and a cladding layer of a second conductivity type and having a wider forbidden band width than the active layer, and in the second region, on the optical waveguide layer. The intermediate layer has the same cladding layer, the optical waveguide layer is common in the first and second regions, and the intermediate layer in the first region and the second region have the same cladding layer.
An optical integrated circuit characterized by having a common cladding layer in the region. (2) The intermediate layer of the second conductivity type in the first region and the first
A forward voltage is applied between the cladding layer or the contact layer of the conductivity type to drive the semiconductor laser, and the cladding layer of the second conductivity type and the semiconductor substrate or buffer layer or the optical waveguide of the first conductivity type are connected in the second region. 2. The optical integrated circuit according to claim 1, wherein light is controlled by applying a reverse voltage between the layers.