JPH04373193A - Integrated light emitting device - Google Patents

Abstract

PURPOSE:To obtain an integrated light emitting device which can be miniaturized and has a wide wavelength changing width. CONSTITUTION:This integrated light emitting device is composed of a plurality of light emitting elements 2, 3, and 4 formed on the same substrate 1 and a common light waveguide 5 arranged in parallel with and closely to the light waveguides of the light emitting elements. The light waveguides 5 of the elements and the common waveguide 5 are brought nearer to each other at a distance at which the electric field distribution of each guided light can overlap upon another and the rays of light emitted from the elements 2, 3, and 4 are optically coupled with and emitted from the common waveguide 5. The resonator lengths of the elements 2, 3, and 4 are shorter than the length of the common waveguide 5 and the rays of light emitted from the elements 2, 3, and 4 are not emitted from other parts than the common waveguide 5.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to optical recording, optical information processing,
The present invention relates to a device that serves as a light source in fields such as optical measurement and optical communication, and particularly relates to an integrated light emitting device that is an element that can be used when light sources of a plurality of different wavelengths are required.

0002

[Prior Art] Conventionally, in fields that require a plurality of light sources of different wavelengths, light obtained from independent light emitting elements that generate light of different wavelengths is irradiated onto a target location using optical components, or It uses an element with a wavelength tunable structure.

For example, when independent elements are assigned to each wavelength, a configuration as shown in FIG. 7 is common. In FIG. 7, the light emitted from the semiconductor lasers LD1 and LD2 is focused by lenses L1 and L2 and is incident on a target location (in the case of FIG. 7, the end face of the optical fiber F).

[0004] Furthermore, it is possible to use a plurality of wavelengths by using a wavelength tunable light source. As a typical example of a wavelength tunable light source, the configuration of a wavelength tunable distributed reflection semiconductor laser is shown in FIG. In order to help understand the configuration, FIG. 8 is partially cut away to show a cross section. In FIG. 8, 201 is n-Ga
As substrate, 202 is n-Al0.5Ga0.5As layer,
203 is an i-GaAs active layer, 204 is an i-Al0.5
Ga0.5As layer, 205 is i-Al0.2Ga0.8
As light guide layer, 206 is p-Al0.5Ga0.5A
s layer, 207 is a p-GaAs cap layer, 208 is n-
Al0.5Ga0.5As buried layer, 209 is an insulating layer, 101, 102, 103, 104 are ohmic electrodes,
211 is a grating.

The configuration shown in FIG. 8 is divided into three regions. The lower part of the electrode 101 is an active region, the lower part of the electrode 102 is a phase control region, and the lower part of the electrode 103 is a wavelength control region. When a voltage is applied between the electrodes 101 and 104 and a current is injected into the active layer 203, a resonator is formed by the cleaved end face and the grating 211 carved in the optical waveguide layer, and the period Λ of the diffraction grating and the optical waveguide layer are The reflectance of the grating 211 becomes maximum at the Bragg wavelength λB determined by the equivalent refractive index neq, and laser oscillation occurs. The relationship between these parameters is expressed by the following equation. λB=neq×Λ At that time, when a voltage is applied between the electrodes 103 and 104 and a current is injected into the wavelength control region, the equivalent refractive index ne of the optical waveguide layer
As q changes, the wavelength at which the grating 211 has a maximum reflectance changes, and the oscillation wavelength of the laser changes. In this example, since the oscillation wavelength can be changed by changing the value of the current injected into the wavelength control region, it is used when different wavelengths are required in the same optical system.

[0006]

However, the conventional configuration has the following problems. first,
When assigning independent light emitting elements for each wavelength as in the example of FIG. 7, the number of required optical components (lenses, etc.) and the effort for alignment increase in proportion to the increase in the number of light emitting elements. In addition, it is difficult to miniaturize the entire structure including the light emitting element and optical components.

Further, in the wavelength tunable laser device as shown in FIG. 8, the current injected into the wavelength control region and the phase control region must be controlled in order to control the oscillation wavelength, and the control method is complicated. One problem is that the wavelength tuning width is narrow, a few nanometers.

Therefore, an object of the present invention is to overcome the above-mentioned problems and provide an integrated light emitting device that can be downsized and can have a wide wavelength tuning range.

[0009]

[Means for Solving the Problems] A light emitting device of the present invention that achieves the above object includes one or more light emitting elements formed on the same substrate and arranged in parallel and close to an optical waveguide of the light emitting elements. The optical waveguide of the light emitting element and the common optical waveguide are close to each other at such a distance that the electric field distribution of the guided light overlaps, and the light emitted by the light emitting element is optically coupled to the common optical waveguide, and the common optical waveguide is It is characterized by being emitted from an optical waveguide.

More specifically, the light-emitting element is a distributed feedback semiconductor laser, the resonator length of the light-emitting element is shorter than the common optical waveguide length, and the light generated by the light-emitting element is not emitted outside the common optical waveguide. The light emitting element is a distributed reflection type semiconductor laser, the resonator length of the light emitting element is shorter than the common optical waveguide length, and the light generated by the light emitting element is not emitted from outside the common optical waveguide. In other words, the common optical waveguide has a semiconductor active layer that can inject current,
The semiconductor active layer is characterized in that it generates optical gain by current injection, and the end face of the common optical waveguide is coated with a non-reflective coating.

According to the present invention, it is possible to integrate a plurality of light emitting elements, and since the light emitted by the plurality of light emitting elements is finally emitted through the same optical waveguide, peripheral optical components, etc. simplification is possible. Furthermore, since the structure has multiple light emitting elements, each element can be designed independently, increasing the degree of freedom in wavelength setting.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a drawing showing the configuration of an embodiment of the present invention. In FIG. 1, (a) shows the overall configuration of this embodiment, and (b) shows a cross-sectional view taken along line A-A' in (a),
(c) shows a sectional view taken along line BB' in (a). This example uses two distributed feedback semiconductor lasers (DFB-LD).
) and one optical waveguide located between them. In the same figure, 1 is an n-GaAs substrate, 2 is an n-Al0
．． 5 Ga0.5As layer, 3 i-GaAs active layer, 4 i-Al0.5Ga0.5As layer, 5 i-Al0.2
Ga0.8As light guide layer, 6 is p-Al0.5Ga0
．． 5As layer, 7 p-GaAs cap layer, 8 n-A
l0.5Ga0.5As buried layer, 9 is an insulating layer, 10
1, 102, 103, and 104 are ohmic electrodes, 11 is a grating, and 12 is an antireflection coating.

Next, a method for manufacturing this element will be explained using FIG. 2. First, on the n-GaAs substrate 1, an n-A
l0.5Ga0.5As layer 2, active layer 3, i-Al0.
5Ga0.5As layer 4, i-Al0.2Ga0.8As
Semiconductors are stacked in the order of layer 5 (FIG. 2(a)). DFB-
A grating 11 is fabricated on the optical guide layer 5 in a region that will become an LD (FIG. 2(b)). In this example, two DFB-
Although the LDs are integrated, two different wavelengths can be generated by changing the pitch of the gratings 11 in the two LD regions.

Next, p-
The Al0.5Ga0.5As layer 6 and the p-GaAs layer 7 are stacked again. After this, a step of separating each element is performed. SiO213 is further deposited on the top of the stacked semiconductor layers. This SiO213 is formed into a striped pattern (FIG. 2(c)). Using this as a mask, the semiconductor layer is etched to form a ridge (FIG. 3(a)). Thereafter, the ridge side portions are filled with an i-Al0.5Ga0.5As layer 8 and regrown (FIG. 3(b)). S when implanted and regrown
Leave iO213 behind. This results in regrowth only on the sides of the ridge. After filling and regrowth, SiO213 is removed. After that, an insulating layer 9 is applied, and the insulating layer is removed only in the contact areas, and the ohmic electrodes 101 and 10 are
2, 103, and 104 to complete the process (Figure 3(c)). If necessary, a step of polishing the substrate 1 is added during the process. It is also good to apply a non-reflective coating 12 to the end face.

Next, the operation of the integrated light emitting device shown in this embodiment will be explained. When a current is passed between the electrodes 102 and 104, one of the DFB-LDs operates (this will be referred to as laser 1). Furthermore, when a current is passed between the electrodes 103 and 104, another DFB-LD operates (this will be referred to as laser 2).
. In this case, the optical waveguide between the two DFB-LDs is connected to the laser 1 by first passing current only between the electrodes 102 and 104.
Suppose you run . Here, the optical waveguide of the laser 1 and the optical waveguide under the central electrode 101 (this is referred to as the central optical waveguide) are close enough to each other that the electric field distributions of the light propagating through them overlap. In addition, the propagation constant β1 of the optical waveguide of laser 1 and the propagation constant β2 of the central optical waveguide
are almost equal, and the length of the adjacent portion of the optical waveguide and the coupling length L are selected so that L=π/|β1−β2|. At this time, the optical output of the laser 1 is coupled to the central optical waveguide. The combined light is emitted from the end face of the central optical waveguide. The absorption loss of light in the central optical waveguide is large,
When the optical output from the central optical waveguide end face is small, the optical output can be amplified by flowing a current between the electrodes 101 and 104. Here, the length of the optical waveguide of the laser 1 was made shorter than that of the central optical waveguide, and the optical waveguide was buried to prevent the light emitted from the laser 1 from leaking out of the element from a portion other than the central optical waveguide. This structure is illustrated in the cross-sectional views shown in FIGS. 1(b) and 1(c).

Similarly, the light emitted from the operation of the other laser is coupled to the central waveguide and emitted from the end face. In this example, two laser elements are used as light sources.
It is possible to increase the number of lasers arranged on both sides of the central optical waveguide.

FIG. 4 is a drawing showing the configuration of another embodiment of the present invention. In FIG. 4, (a) shows the overall configuration of this embodiment, (b) shows a cross-sectional view taken along line AA' in (a), and (c) shows a cross-sectional view taken along line B-B' in (a). shows. This example uses two distributed reflection semiconductor lasers (DBR-L
D) and one optical waveguide located between them. In the same figure, 1 is an n-GaAs substrate, 2 is an n-Al
0.5Ga0.5As layer, 3 is i-GaAs active layer, 4
is an i-Al0.5Ga0.5As layer, 5 is an i-Al0.5As layer, and 5 is an i-Al0.5Ga0.5As layer.
2Ga0.8As light guide layer, 6 is p-Al0.5Ga
0.5As layer, 7 is a p-GaAs cap layer, 101,
102, 103, and 104 are ohmic electrodes, 11 is a grating, and 12 is an antireflection coating.

Next, a method for manufacturing this element will be explained using FIG. First, on the n-GaAs substrate 1, an n-A
l0.5Ga0.5As layer 2, active layer 3, i-Al0.
5Ga0.5As layer 4, i-Al0.2Ga0.8As
Layer 5, p-Al0.5Ga0.5As Layer 6, p-GaA
Semiconductors are stacked in the order of s-layer 7 (FIG. 5(a)). All three optical waveguides are ridge-shaped. The pattern of the optical waveguide was made with resist 14 (Fig. 5(b)), and the i-Al0.2Ga
A ridge is created by etching up to the top of the 0.8As layer 5 (FIG. 5(c)).

A grating 11 is fabricated on the optical guide layer 5 in a region that will become a DBR-LD (FIG. 6(a)). In this embodiment, two DBR-LDs are integrated, but as in the first embodiment, two different wavelengths can be generated by changing the grating pitch of the two LDs. After that, ohmic electrodes 101, 102, 103,
104 to complete the process (Fig. 6(b)). If necessary,
A step of polishing the substrate 1 is included in the middle. A non-reflective coating 12 may be applied to the end face. Note that the insulating layer is omitted here to make the diagram complicated.

Next, the operation of the integrated light emitting device shown in this example will be explained. When a current is passed between the electrodes 102 and 104, D
One of the BR-LDs operates (this is called laser 1)
. Furthermore, when a current is passed between the electrodes 103 and 104, another DBR-LD operates (this will be referred to as laser 2). In the optical waveguide between the two DBR-LDs, it is assumed here that the laser 1 is operated by first passing current only between the electrodes 102 and 104. Here, the optical waveguide of the laser 1 and the optical waveguide under the central electrode 101 (this is referred to as the central optical waveguide) are close enough to each other to overlap the electric field distributions of the light propagating through them. In addition, the propagation constant β1 of the optical waveguide of the laser 1 and the propagation constant β2 of the central optical waveguide are made to be almost equal, and the length of the adjacent portion of the optical waveguide and the coupling length L are set as L=π/|β1−β2| Choose as you like. At this time, the optical output of the laser 1 is coupled to the central optical waveguide. The combined light is emitted from the end face of the central optical waveguide. The absorption loss of light in the central optical waveguide is large,
When the optical output from the central optical waveguide end face is small, the optical output can be amplified by flowing a current between the electrodes 101 and 104. Here, a grating 1 that makes the optical waveguide length of the laser shorter than the central optical waveguide and also serves as a reflector.
1 was made as long as possible to prevent light from leaking out of the device from areas other than the central optical waveguide at the end face of the laser waveguide. This structure is illustrated in the cross-sectional views shown in FIGS. 4(b) and 4(c).

The other laser operates in the same manner, and the generated light is coupled to the central optical waveguide and exits from the end face. In this embodiment, two laser elements are configured as light sources, but it is possible to increase the number of lasers arranged on both sides of the central optical waveguide.

[0022]

[Effects of the Invention] As is clear from the above description, the integrated light emitting device of the present invention has a plurality of light emitting devices and a common optical waveguide formed on the same substrate, and light emitted from the light emitting devices is coupled to the common optical waveguide. The optical waveguide is configured to emit the light from the end face of the common optical waveguide. In addition, if the optical loss in the common optical waveguide is large, in order to compensate for the loss, an electrode is provided so that current can be injected into the semiconductor active layer of the common optical waveguide, and the semiconductor active layer increases the optical gain by current injection. is configured to occur.

Therefore, by using the integrated light emitting device of the present invention, a light source for irradiating the same area with light of multiple wavelengths can be constructed in a compact size, and each light emitting device can be designed independently, so that the number of wavelengths that can be handled can be reduced. It has the advantage of wide range.

[Brief explanation of the drawing]

1: (a) is a perspective view showing the entire basic configuration of Embodiment 1 of the present invention; (b) is a cross-sectional view taken along line A-A′ in (a); It is a drawing which shows the cross section in the BB' part.

FIG. 2 is a drawing showing the manufacturing process of Example 1 of the present invention.

FIG. 3 is a drawing showing the manufacturing process of Example 1 of the present invention.

4(a) is a perspective view showing the entire basic configuration of Embodiment 2 of the present invention; FIG. 4(b) is a cross-sectional view taken along line A-A' in FIG. It is a drawing which shows the cross section in the BB' part.

FIG. 5 is a drawing showing the manufacturing process of Example 2 of the present invention.

FIG. 6 is a drawing showing the manufacturing process of Example 2 of the present invention.

FIG. 7 is a drawing showing the configuration of a conventional example of an apparatus for irradiating a single area with a multi-wavelength light source composed of independent elements, optical components, and the like.

FIG. 8 is a drawing showing the configuration of a wavelength tunable light source as a conventional example of a multi-wavelength light source.

[Explanation of symbols]

1
n-GaAs substrate 2
n-Al0.5Ga0.5As layer 3
i-GaAs active layer 4
i-Al0.5Ga0.5As layer 5
i-Al0.2Ga0.8As layer 6
p-Al0.5Ga0.5As layer 7
p-GaAs layer 8

n-Al0.5Ga0.5As layer 9
Insulating layers 101, 102, 103,
104 Ohmic electrode 11

Grating 12
Anti-reflective coating

Claims (5)

[Claims] 1. A device comprising one or more light emitting elements formed on the same substrate and a common optical waveguide arranged in parallel and close to the optical waveguide of the light emitting elements, the optical waveguide of the light emitting elements and the common optical waveguide are close to each other at such a distance that the electric field distributions of the guided light overlap each other, and the light emitted by the light emitting element is optically coupled to the common optical waveguide and is emitted from the common optical waveguide. An integrated light emitting device. 2. The light emitting element is a distributed feedback semiconductor laser, the resonator length of the light emitting element is shorter than the common optical waveguide length, and the light generated by the light emitting element is emitted from a source other than the common optical waveguide. The integrated light emitting device according to claim 1, wherein the integrated light emitting device is not. 3. The light emitting element is a distributed reflection type semiconductor laser, the resonator length of the light emitting element is shorter than the length of the common optical waveguide, and the light generated by the light emitting element is emitted from a source other than the common optical waveguide. The integrated light emitting device according to claim 1, wherein the integrated light emitting device is not. 4. The integrated light emitting device according to claim 1, wherein the common optical waveguide has a semiconductor active layer into which current can be injected, and the semiconductor active layer generates optical gain by current injection. 5. The integrated light emitting device according to claim 1, wherein an end face of the common optical waveguide is coated with an anti-reflection coating.