JPH02267988A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To achieve shortening of working time and improvement in yielding rate and contrive the decrease of production cost and improvement in reliability by forming a light modulation element on the surface of a semiconductor and integrating a semiconductor laser and a light modulator monolithicall. CONSTITUTION:This device is composed of: a semiconductor laser LD 91; a light modulation element 90; a higher-order diffraction grating region 6 which performs photocoupling; and an opening 12 through which modulated light is taken out from the light modulation element 90 to the outside. The LD 91 is composed of: an n<-> type InP substrate 1; an InGaAs waveguide layer 2; an InGaAsP active layer 3; a p<-> type InP clad layer 4; a p<-> type InGaAsP cap layer 5; a p<-> side electrode 13; an n<-> side electrode 14; the higher-order diffraction grating region 6 for photocoupling. Subsequently, the light modulation element 90 is composed of: a p<+-> type InGaAsP layer 7; a p<-> type InP layer 8; an InGaAsP layer 9; an n<-> type InP layer 10; and an n<-> side electrode 11. Further, the light modulation element 90 is an electric field absorption type light modulator having the InGaAsP layer 9 as an absorption layer. In this way, the decrease of a manufacturing cost and improvement in reliability are achieved by causing the LD, i.e. a light source, and the light modulation element to be integrated monolithically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical semiconductor device that converts an electrical signal into an optical signal in an optical fiber transmission system or an optical signal processing system.

[Conventional technology]

With the rapid spread of optical fiber transmission in recent years.

Long-distance, large-capacity optical transmission of Gb/S or more, tens of Gb/s or more, is being actively studied. In such long-distance, large-capacity optical fiber transmission, conventional semiconductor lasers (L
In contrast to the direct modulation method that modulates the current injected into the input signal (abbreviated as D), an external modulation method that causes less deterioration in transmission quality due to chirping is attracting attention. That is, this is a method in which an LD is used as a DC light source and the laser light is modulated by an optical modulator.

Promising optical modulators for use in the above external modulation method include Electronics Letters, Volume 23, No. 23;
Pages 1232 to 1234 (1987) (t<
1 electronics Letters, vol.
23.

&23. There are electroabsorption types such as those discussed in pp. 1232-1234 (1987).

When such a device is used in a transmission system, an optical coupling system is required at the optical input/output section of the optical modulator, as shown in the above paper. An example of this is shown in FIG. The optical coupling system here is particularly composed of an optical fiber 93, an optical coupling system for an optical modulator 90, and an optical fiber 94 for a transmission line 97. Light emitted from a light source 91 is inputted to an optical modulator 90 via an optical fiber 93.

At this time, optical coupling between the optical fiber 93 and the optical modulator 90 is performed using a butt joint that does not use any other optical element.
oint) system. A concrete image of optical coupling is shown in Fig. 3. The board 92 sends the human input signal data to the light changer 11iIwI 90 via the bonding wire 95.

The optical modulator 90 superimposes this signal on the human power light and sends it as signal light to the transmission line 97 via the optical fiber 94 in FIG. 2. At this time, optical coupling between the optical modulator 90 and the optical fiber 94 is also performed by the above-mentioned butt joint system.

[Problem to be solved by the invention]

In the prior art shown in FIGS. 2 and 3, in order to improve the performance of the optical transmitter 99, the optical coupling system of the optical input/output section of the optical modulator 90 and the optical output section of the light source 91 must be made highly efficient. Must be. This requires not only precise optical axis positioning technology but also optical axis fixing technology. That is, this is a technique that prevents the optical components from shifting their optical axes due to shrinkage during the curing process of the adhesive of the optical components after constructing a highly efficient optical coupling system for each optical component.

Currently, this type of optical coupling technology has a low speed because the manual adjustment of the [, L) module requires skill.
This is the cause of the production cost island. When using an optical modulator, not only the number of such optical coupling systems increases, but also the optical modulating element itself is not a light emitting element, making it even more difficult to adjust the optical coupling.

An object of the present invention is to provide a method for solving the above-mentioned problems of the prior art.6 [Means for Solving the Problems] The above object is to monolithically integrate an LD as a light source and an optical I & control element. This is achieved by That is, an optical coupling mechanism for extracting laser light toward the surface of LL) is provided at one end in the waveguide direction of Ll), which has a waveguide including an active layer in the semiconductor, and a semiconductor (LL) facing the optical coupling mechanism is provided. t, U) This can be achieved by providing a semiconductor optical modulator in Table 1r+i and further providing an optical coupling mechanism on the surface of the optical modulator for transmitting laser light to the outside.

[Effect]

The optical coupling between LL) and the light modulation element is L
This will be done by an optical coupling device built into the opposite side. Therefore, problems with conventional optical modulators such as increased work time for optical axis alignment adjustment and optical axis misalignment for optical coupling of the predecessor output section, 1, and D optical output section of the optical variable fJs probe, and low yield due to optical axis misalignment. The cost from start to finish is comparable to that of the conventional LL) module. Further improvements can be expected depending on the optical coupling device provided in the light curve adjustment element table [111]. Also, LL)
Since the optical modulation element and the optical modulation element are monolithically integrated, the device can be miniaturized.

Furthermore, according to this method, a similar optical coupling mechanism can be provided at the other end of the remaining waveguide on the LL) side, and an optical modulation element can be provided thereon in the same process. This element has a second luminous intensity, 151. Functionalization can be achieved by using it as an M element to double the transmission range, or as an optical monitor for LL).

〔Example〕

FIG. 1 shows an optical semiconductor device according to an embodiment of the present invention.

The optical semiconductor device of this example is LL)91. Light modulation element 9
0. It is composed of an ^h-order diffraction grating region 6 that performs optical coupling between L[) 91 and the light modulation element 90, and an opening 12 that takes out all the dimming from the light modulation element 90 to the outside. LL)
91 is n-1nP base treatment 1, InGaAs 4-wave layer 2, I
nGaAsF active layer 3, p-1nP cladding layer 4, p-1nGaAsP cap layer 5, p-side electrode 13, n-side electrode 14, high-order diffraction grating region for optical coupling 6, and the light modulation element 90 is composed of p
+-In Ga As P layer 7, p-In1' layer 8, In Ga As P layer 9, n-1nP layer 1
0 and an n-side electrode 11.

Next, the operation of this embodiment will be described.

The resonator of LL) 91 is composed of a high-order diffraction grating 6 and a chip cleavage plane at the other end of the waveguide.

Therefore, when carriers are injected by applying a forward bias to Ll) 91 via the electric current 4413.14, a laser action is realized by the above-mentioned resonator. At this time, the oscillation wavelength λe of the laser and the pitch Δ of the diffraction grating have the following relationship.

m λ8 netl n eta is effective, M refractive index, and m is an integer. m=
When m = 1, it becomes a 1st-order diffraction grating, when m = 2, it becomes a 2nd-order diffraction grating, and as it becomes an integer multiple, it becomes a 3rd-order diffraction grating, a 4th-order diffraction grating, and so on. As the wavelength increases, the amount of light emitted in directions other than the waveguide direction increases. Here I
The peak wavelength of spontaneous emission light of the nGaAsP active layer 3 is set to 1.
When set to 3 μm, the pitch A of the second-order diffraction grating is approximately 48
There will be 00 people. When using the high-order diffraction grating 6 made in this way, the output light (LL) will be 15.17 mm as shown in FIG.
15 is directly introduced into the light modulation element 90 formed on the chip surface (LL).

The optical modulation element 90 is an electro-absorption optical modulator having the lnGaAsP layer 9 as an absorption layer. Therefore, when a reverse bias is applied to the element 90 through the electrodes 11.13, the human-powered light 15 is absorbed by the absorption layer M9, but when the reverse bias is reset, the absorption layer 9 is transmitted through the absorption layer 9, and the aperture 1
2, the light is emitted as emitted light 16. When a binary data signal is applied with a reverse bias to the optical modulation element 90, an optical on/off (ONLOFF) signal 16, which is performed using a conventional semiconductor laser, is output.

This embodiment can be easily formed using conventional semiconductor manufacturing techniques. In other words, an n-1nP substrate is prepared, and a distributed feedback type (1) FB:1) istrib is placed on it.
(Uted-Feedback) Applying the two-beam interference exposure method, etc. in the same way as forming the diffraction grating of a semiconductor laser,
After forming the high-order diffraction grating region 6, the n-InGaAs waveguide layer 2.1 nG is formed using a liquid phase epitaxial method, a metal-organic chemical vapor deposition method, etc. after surface treatment.
a As P active layer 3, p-1nP cladding layer 4,
p −f nQ a A, s P cap layer 5, p+
-i n Ga As P layer'/, p-1nP layer 8
, InGaAsP layer 9, and n-1n)' layer 10 are grown in this order. Thereafter, a silicon dioxide film is formed and buttered to form a protective film covering the photovariable 11Jl element 90. Next, an unnecessary n-1n P layer 10 is etched.
, l n G a A SPPO2p-1nP layer 8,p
+-Remove the InGaAsP layer. After removing the protective film 1, an n-side electrode 11 made of, for example, Au-Ge-Ni,
14. When the n-side electrode 13 made of 'l°i.Pt'Au is formed, the device of this embodiment shown in FIG. 1 is formed.

Here, as can be seen from the above description, in the present invention, the method and procedure for forming the present optical semiconductor device are not essential problems. Applying a multi-η [wind well structure, etc.] to the active layer and absorption layer is a μf function. The key point in manufacturing is the active layer of LL) so that the oscillation wavelength of Ll) matches the absorption wavelength of the optical modulation element.

This involves designing the components of the absorption layer of the light modulation element and the pitch of the diffraction grating.

Since the present invention has various possible applications, some of them will be listed below.

In the embodiment of FIG. 1, p-In is placed on top of the LIJ active layer.
A GaAsP waveguide layer is formed, and instead of the high-order grating 6 in the figure, a high-order diffraction grating region is formed in Il of the waveguide, and by optical coupling, a structure similar to that of the previous example can be obtained.
(It is Noh.

As shown in FIG. 4, the LD structure is
L) with FB type.

In manufacturing, only a first-order diffraction grating formation process for DFB is added to the example shown in FIG.

As shown in the embodiment of FIG. 5, the laser light output can be taken out to the substrate surface 1hJ side by making one end of the laser inclined with respect to the main surface of the semiconductor base (19) instead of the high-order diffraction grating. can.

In the embodiment shown in FIG. 6, the efficiency of focusing light onto the optical fiber at the light output section of the light modulation element is increased. That is, a method is applied in which the light output part is processed into a dome shape 20 in order to increase the light output using a light emitting diode or the like and to increase the optical coupling efficiency with the fiber.

In the embodiment shown in FIG. 7, high-order diffraction grating regions are provided on both end faces of the laser, and the same or separate optical modulation elements are provided on the semiconductor table 1r[1 opposite to the high-order diffraction grating regions.

For example, if two optical modulation elements are provided by the same process, both can be used as optical modulators, but one element can be fixed in a reverse bias state to monitor the laser.
It can be used as a photodiode 23. - The laser 91, the optical modulator 90, and the monitor photodiode 23 can be integrated into one chip by a relatively simple process.

The embodiment shown in FIG. 8 is the same as the embodiment shown in FIG. 7 by providing a groove 24 between the laser section and the optical modulation element section to strengthen the electrical isolation and improve the crystal frequency characteristics.

In the embodiment shown in Fig. 9, the laser section has multiple electrodes (13°25).
This makes the wavelength aJ variable light source 26 applicable to wavelength multiplex transmission and the like. The wavelengths described so far are 1.3 to 1.55 μm, and the semiconductor material is In.
Although mainly P-based, GaA rI As-based semiconductor materials may be used for the wavelength range of 0.7 to 0.9 μm.

〔Effect of the invention〕

According to the present invention, a coupling device for extracting laser light to the semiconductor surface is provided at the terminal end of the semiconductor laser, and an optical modulation element is formed on the semiconductor surface opposite to the coupling device, so that the semiconductor laser and the optical modulator are monolithically integrated. This eliminates the problem of optical coupling between the laser and the optical modulator, which reduces work time and improves yield, making it possible to reduce costs and improve reliability. Furthermore, monolithic integration allows for miniaturization of the device. The same process can also be used to produce monitor photodiodes for lasers, increasing the functionality and reliability of equipment.

[Brief explanation of drawings]

Fig. 1 is a top view of an optical semiconductor device according to an embodiment of the present invention, Fig. 2 is a schematic plan view of an optical transmitter using a conventional optical modulator, and Fig. 3 is a schematic plan view of an optical transmitter using a conventional optical modulator. A perspective view of a modulator light input section and FIGS. 4 to 9 are cross-sectional views of an optical semiconductor device according to another embodiment of the present invention. No. ■ And - 1 person and ・1 Soku ■ Kayoko No. ■ 1-cho 1-ko, 7 noro/D 几-■Rushit D No. D tei] Figure L'F) Somu-zu So v No. 1 ShiD

Claims (1)

[Claims] 1. In a semiconductor laser in which a waveguide including an active layer is provided in a semiconductor, a mechanism for extracting laser light to the surface of the semiconductor at one end in the direction of the waveguide, and a mechanism for extracting the laser light An optical semiconductor device comprising: a semiconductor light modulator that applies optical modulation to the laser light formed on a semiconductor surface facing the semiconductor light modulator; and an optical coupling device that extracts the modulated laser light to the outside on the surface of the semiconductor light modulator. . 2. The optical semiconductor device according to claim 1, wherein the semiconductor laser has a distributed feedback structure. 3. In the optical semiconductor device according to claim 1 or 2,
An optical semiconductor device characterized in that the laser beam extraction mechanism is a high-order diffraction grating formed along the waveguide direction. 4. The optical semiconductor device according to claim 1 or 2,
An optical semiconductor device characterized in that the laser beam extraction mechanism is a mirror that is inclined so that the laser beam is directed toward the semiconductor surface. 5. The optical semiconductor device according to claim 1, wherein the optical coupling device for extracting the modulated laser beam to the outside is an opening provided in an electrode on the surface of the semiconductor optical modulator. 6. In the optical semiconductor device according to claims 1 to 4, the optical coupling device for extracting the modulated laser beam to the outside is an opening formed in the electrode by processing the surface of the semiconductor optical modulator into a lens shape (dome shape). An optical semiconductor device characterized by: 7. In the optical semiconductor device according to claims 1 to 6, a similar laser beam extraction mechanism is provided at the other end of the waveguide, a similar semiconductor optical modulation element is provided on the semiconductor surface facing the extraction mechanism, and a monitor An optical semiconductor device characterized in that it is used as a photodiode or a second optical modulator. 8. The optical semiconductor device according to claim 1, wherein a groove is provided in the semiconductor to electrically isolate the laser section, the optical modulation section, and the monitor photodiode section. 9. The optical semiconductor device according to claim 1, wherein the electrode of the laser section is divided into a plurality of parts to form a wavelength tunable laser.