JPS63156382A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To isolate currents for generating laser light and for tuning the light and to make it possible to couple the light between active layers for generating and tuning the laser light, by arranging the first and second stripe-shaped active layers in close proximity, and tuning the oscillating wavelength of the laser light generated in the first active layer at the DBR region of the second active layer. CONSTITUTION:A mesa shaped stripe is formed, and completely isolated two active layers 12 and 13 are arranged in close proximity. A diffraction grating 25 is formed beneath the active layer 13, i.e., on the side of a substrate 20 through a guide layer 24. Therefore currents can be made to flow through the active layers 12 and 13 in completely isolated mode. The light, which is generated in the active layer 12, is coupled to the active layer 13 during the propagation in the direction of the stripe. The light undergoes feedback in a DBR region 13A. The Bragg wavelength is controlled depending on the current, which is made to flow through the DBR region 13A, i.e., the active layer 13. Thus the oscillating wavelength can be tuned. Said optical coupling can be readily obtained by selecting the width of the active layers 12 and 13 or the interval between the layers 12 and 13.

Description

Detailed Description of the Invention [1 Already Required] The present invention provides a semiconductor light emitting device having a structure in which a first striped active layer and a second striped active layer having a DBR region are arranged close to each other, and By making it possible to tune the oscillation wavelength of the laser beam generated in the first active layer in the DBR region of the second active layer, the current and oscillation wavelength tuning for generating the laser beam can be adjusted. It is possible to completely separate the electric current for laser beam generation, and to achieve highly efficient optical coupling between the active layer for generating laser light and the active layer for tuning the oscillation wavelength. It is something.

[Industrial application field]

The present invention is based on DBR (distributed Bragg).
ref 1ector) area and tuner pull DFB (distributedfeedback)
The present invention relates to a semiconductor light emitting device called a type semiconductor laser.

[Conventional technology]

In recent years, so-called tunable DFB type semiconductor lasers, whose oscillation wavelength can be tuned, have been actively developed for use in coherent communications.

FIG. 3 shows a cutaway view (jl, 11) of the main part of a conventional tuner-pull DFB type semiconductor laser.

In the figure, 1 is an n-type 1nP substrate, 2 is GaInAsP
active layer, 3 is a DBR region consisting of a diffraction grating, 4 is a p-type G
a1nAsP guide layer, 5 is p-type InP cladding layer, 6
and 7 is an electrode for the DBR region, 8 is an electrode for the active layer, and 9 is a p
Each side electrode is shown.

In this semiconductor laser, the light generated in the active layer 2 is DB
By repeating the process of being reflected by the R region 3 and returning, the laser beam oscillates and finally emits a laser beam as shown by the arrow.

In this case, the current supplied from electrode 8 generates light in the active layer 2, and the current supplied from electrodes 6 and 7 causes D
By increasing the number of electrons in BR region 3, the refractive index is changed, creating a state equivalent to changing the pitch of a diffraction grating, controlling the Bragg wavelength and tuning the oscillation wavelength. .

[Problem that the invention seeks to solve]

In the semiconductor laser shown in FIG. 3, as can be seen from its structure, when a current is supplied from the electrode 8, the current does not necessarily all flow to the active layer 2, but flows sideways to the DBR region. Similarly, the electrode 6
Alternatively, not all of the current supplied from 7 flows to the DBR region 3, but may flow to the active layer 2, making control for normal operation extremely difficult.

In order to clearly separate each current supplied from these electrodes 6.7.8, attempts have been made to form grooves between these electrodes, but the grooves are deep enough to separate the currents. This will affect the light emission characteristics.

Furthermore, a further problem is that due to manufacturing reasons, the active layer 2
and DBR? Since it is difficult to align the iJr region 3 at the junction, it is not possible to efficiently couple light at that part.

The present invention provides a tunable DFB semiconductor laser having an active layer and a DBR region.
To completely separate a current flowing through a BR region and to realize optical coupling therebetween with high efficiency, thereby making it possible to have a wide wavelength tuning range.

[Means for solving problems]

The semiconductor light emitting device according to the present invention includes a first striped active layer (for example, a first striped Ga1nAsP active layer 12) that generates laser light when a current is passed therethrough; D B has a diffraction grating (for example, diffraction grating 25) that is arranged in parallel and close to the active layer to enable coupling of the laser beam, and that controls the Bragg wavelength by passing a current through both ends.
A second striped active layer (e.g., a second striped GaI layer) in which an R region (e.g., DBR region 13A) is formed.
The structure includes an nAsP active layer 13).

[Effect]

By adopting the above means, the current for generating laser light and the current for tuning the oscillation wavelength are completely separated, and therefore the oscillation wavelength tuning can be controlled well. The coupling of light between the active layer for generating laser light and the active layer for tuning the oscillation wavelength depends on the coupling between two parallel waveguides, and the length of the coupling part is By optimizing it, optical coupling between the two can be performed with high efficiency.

〔Example〕

FIG. 1 shows a plan view of essential parts of an embodiment of the present invention.

In the figure, 11 is a laser chip, 12 is a first striped GaInAsP active layer, 13 is a second striped GaInAsP active layer, and 13A is a D having a diffraction grating formed above or below the active layer 13. B R area, 1
Reference numeral 4 indicates an electrode corresponding to the active layer 12, 15 indicates an electrode corresponding to the active layer 13, and arrows indicate light propagation paths.

FIG. 2 is a cutaway front view of essential parts for explaining the structure of the various-hand conductor layers in one embodiment of the present invention, and is a front view showing the line A shown in FIG. 1.
-A corresponds to the cut state, and the same symbols as those used in FIG. 1 indicate the same parts or have the same meanings.

In the figure, 20 is an n-type 1nP substrate, 21 is a p-type InP cladding layer; 22 is a p-type 1nP current blocking layer; 23 is an n-type 1nP current blocking layer; 24 is an InGaAsP guide layer; 25 is a diffraction grating are shown respectively.

As is clear from the figure, in this example, two active layers 1 are completely separated by forming mesa-like stripes.
2 and 13 are arranged close to each other, and a diffraction grating 25 is formed under the active layer 13, that is, on the substrate 20 side, with a guide layer 24 in between.

With this configuration, it is possible to flow current through the active layers 12 and 13 completely separately from each other.

In addition, the light generated in the active layer 12 is coupled to the active layer 13 while propagating in the stripe direction, and is coupled to the DBR region 13A.
DB
Since the Bragg wavelength is controlled depending on the current flowing through the R region 13A1, the oscillation wavelength can be tuned accordingly. The above-described coupling of light can be easily achieved by appropriately selecting the widths of the active layers 12 and 13 or the spacing between them.

The outline of manufacturing this example is as follows.

(A diffraction grating 25 is formed on the Al substrate 20 by applying an interference exposure method or the like.

(bl) The portion of the diffraction grating 25 corresponding to the active layer 12 is removed by etching or the like.

(C) Guide layer 24 (of a composition such that the energy band gap takes a value between the active layer 12 or 13 and InP), the active layer (which will become the active layers 12 and 13), and the cladding Ji 21. Make it grow.

(Two mesas are formed through a d+ mask process and an etching process.

(el　Grow the buried layers 22 and 23.

([1p-side electrodes 14 and 15 and n-side electrode 17 are formed.

〔Effect of the invention〕

In the semiconductor light emitting device of the present invention, the first stripe-like active layer and the second stripe-like active layer having the DBR6i region are arranged close to each other, and D when the laser beam is applied to the second active layer
This is so that the oscillation wavelength can be tuned in the BR region.

By adopting this configuration, the current for generating laser light and the current for tuning the oscillation wavelength are completely separated, and therefore the oscillation wavelength tuning can be controlled well. Since there is no structure that would cause mismatch between the active layer for generating laser light and the active layer for tuning the oscillation wavelength, optical coupling between the two can be performed with high efficiency. be able to.・

[Brief explanation of the drawing]

FIG. 1 is a plan view of a main part of an embodiment of the present invention, FIG. 2 is a cutaway front view of a main part of an embodiment of the invention, and FIG. 3 is a cutaway side view of a main part of a conventional example. In the figure, 11 is the laser chip, 12 is the first striped Ga1nAsP active layer, 13 is the second striped Ga1nAsP active layer, and 13A is the lower part of the active layer 13 (
14 is the active N1
2, 15 indicates an electrode corresponding to the active layer 13, and arrows indicate light propagation paths. Patent Applicant Fujitsu Ltd. Representative Patent Attorney Shoji Aitani Representative Patent Attorney Hiroshi Watanabe - Plan view of essential parts of the embodiment Figure 1 Cutaway front view of essential parts of the embodiment Figure 2

Claims (1)

[Scope of Claims] A first stripe-shaped active layer that generates laser light when an electric current is passed therethrough; and a first stripe-shaped active layer that is adjacent to and parallel to the first stripe-shaped active layer so as to enable coupling of the laser light. A DBR that controls the Bragg wavelength by having a current flowing through both ends of the DBR.
1. A semiconductor light emitting device comprising: a second stripe-shaped active layer in which regions are formed.