JP2975725B2 - Surface-emitting type semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-emitting type semiconductor laser device, and more particularly, to a surface-emitting type semiconductor laser device which is required to have a constant polarization direction, such as a magneto-optical disk field and a coherent optical communication field. Related to a surface emitting semiconductor laser device.

[0002]

2. Description of the Related Art A surface-emitting type semiconductor laser device having a structure in which an active layer is embedded is disclosed in "Preliminary Collection of the 38th Joint Lecture on Applied Physics""31a-D-3","Polarization of embedded DBR surface-emitting laser." As shown in “Characteristics”, the polarization direction of the surface emitting semiconductor laser is linearly polarized in the [011] direction, linearly polarized in the [0-11] direction, or the polarization direction depending on the element. It is divided into three types, which are unstable.

[0003]

Such a surface-emitting type semiconductor laser device in which the polarization direction is not constant is used in a field requiring a constant polarization direction, such as a magneto-optical disk field or a coherent optical communication field. Was not applicable.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to make a polarization direction of a surface emitting semiconductor laser constant irrespective of an element.

[0005]

According to a first aspect of the present invention, there is provided a surface emitting semiconductor laser device having a buried active layer formed on a [100] crystal plane of a GaAs semiconductor substrate. In the apparatus, the crystal orientation [0
It is characterized in that a loss-adding layer that blocks the polarized light component in the [10] direction or the [001] direction is provided.

The surface emitting type semiconductor laser device according to a second aspect of the present invention has a refractive index n that does not absorb laser light is provided inside the resonator including the active region or outside the resonator of the light-emitting side reflector. _One layer, a layer having a refractive index of n _{2, and} a layer having a refractive index of n ₁ are successively provided, and two boundary surfaces formed of the three layers are formed in parallel planes, and a method of the boundary surface is used. The angle θ ₁ between the line and the laser optical axis is θ ₁ = tan ⁻¹ (n ₂ /
n ₁ ).

[0007]

According to the first aspect of the present invention, the surface emitting laser receives a loss in either the [010] direction or the [001] polarization component and does not oscillate in that direction. Therefore, laser light linearly polarized in the other direction can be extracted.

In the second invention, light polarized in the x direction does not suffer loss, whereas light polarized in the y direction suffers loss due to reflection at two interfaces. Therefore, polarized light existing on a plane determined by the laser optical axis and the normal to the boundary surface oscillates most.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

First, the first invention will be described with reference to FIGS.

In FIG. 1, reference numeral 1 denotes an n-type GaAs substrate having a [100] crystal plane. On this substrate 1, a reflecting mirror 2 and an n-type cladding layer 3 made of an n-type semiconductor multilayer film are provided.

Reference numeral 4 denotes an active layer made of GaAs, and reference numeral 5 denotes a p-type cladding layer.
It is buried in a [100] crystal plane of the substrate 1 in a circular shape.

6 is a p-type current blocking layer, and 7 is an n-type current blocking layer. 8 is a high refractive index layer made of Ga _0.9 Al _0.1 As, 9 is a low refractive index layer made of Ga _0.5 Al _0.5 As, and the high refractive index layer 8 and the low refractive index layer 9 constitute a loss adding layer A. Be composed. An inclined surface is formed inside the resonator by the high refractive index layer 8 and the low refractive index layer 9, and in this embodiment, the inclined surface causes a confusion loss with respect to the polarization in the [010] direction. I have.

Reference numeral 10 denotes a p-type contact layer, 11 denotes a light-emitting-side reflecting mirror, 12 denotes a p-side electrode, and 13 denotes an n-side electrode.

By the way, the shape of the active region of the circular buried surface-emitting type semiconductor laser device formed on the GaAs (100) surface using the LPE selective melt-back method is as shown in FIG. The ellipse has a long axis in the [0-11] direction and a short axis in the [011] direction. The roundness at this time is about 1.3.

In such a case, as described above, the polarization characteristics are classified into three types: [011] linear polarization, [0-11] linear polarization, and the polarization direction is unstable. On the other hand, in all of these three types of elements, the polarization beam splitter was used to calculate the IL of the polarization components in the [010] and [001] directions.
The characteristics are linear and stable, as shown in FIG.
FIG. 3A shows the IL characteristic of [010], and FIG. 3B shows the IL characteristic of [001]. That is, [010]
If the polarization component in either the direction or the [001] direction is blocked, light linearly polarized in the other direction can be extracted.

Therefore, [011]
Loss occurs in the polarized light component in either the [0] direction or the [001] direction, and laser light that is linearly polarized in the other direction can be extracted if oscillation is not performed in that direction. Therefore, in the present invention, the loss adding layer A is provided so as not to oscillate in one direction.

That is, in the embodiment shown in FIG. 1, the light generated in the active layer 4 is reflected between the reflecting mirrors 2 and 11, and
Laser oscillation occurs above the threshold. However, the high-refractive-index layer 8 and the low-refractive-index layer 9 form an inclined surface inside the resonator, and this inclined surface causes confusion loss with respect to polarization in the [010] direction. Therefore, in this embodiment, [010]
Polarization in the direction does not oscillate, but becomes linearly polarized in the [001] direction.

By rotating this inclined surface by 90 °, it is possible to reduce the confusion loss with respect to the polarization in the [001] direction. In this case, the laser is linearly polarized in the [001] direction.

Although the loss adding layer A is provided between the p-type cladding layer 5 and the n-type current block layers 7 and 10 in this embodiment, the current confinement effect (cladding-active layer-cladding) of the laser is impaired. The present embodiment is not limited to the location of this embodiment as long as it is inside the resonator.

Further, the loss adding layer A is provided with a reflecting mirror 11 on the light emitting side.
May be provided on the outside.

Further, the material of the active layer 4 is not limited to GaAs. When the active layer 4 is made of a material other than GaAs, the high refractive index layer 8,
The low refractive index layer 9 may be set so as not to cause absorption loss with respect to the light of the active layer 4.

In the present embodiment, the same applies even if the p-type and the n-type are inverted. The present invention is not limited to the present embodiment as long as the loss is provided for the polarization component in either the [010] direction or the [001] direction, such as the one providing an absorption loss.

Next, a second embodiment of the present invention will be described with reference to FIG.
And FIG.

In FIG. 4, reference numeral 21 denotes an n-type GaAs substrate having a [100] crystal plane. On this substrate 21, a reflecting mirror 22 and an n-type cladding layer 23 made of an n-type semiconductor multilayer film are provided.

Reference numeral 24 denotes an active layer made of GaAs, and 25 denotes a p-type cladding layer, which is buried in a circular shape on the [100] crystal plane of the substrate 21 by the LPE selective melt back method.

26 is a p-type current block layer, and 27 is an n-type current block layer.
It is a type current block layer.

Reference numeral 28 denotes a p-type Ga _0.5 Al _0.5 having a refractive index of n _1.
The first refractive index layer 29 made of As has a refractive index of p ₂ having a refractive index of n ₂ .
A second refractive index layer 30 of Ga _0.9 Al _0.1 As, and a third refractive index layer 30 of p-type Ga _0.5 Al _0.5 As having a refractive index of n ₁ , and the refractive index layers 28, 29 and 30. Constitutes the loss adding layer A.

Reference numeral 31 denotes a p-type contact layer, 32 denotes a light-emitting side reflecting mirror, 33 denotes a p-side electrode, and 34 denotes an n-side electrode.

FIG. 5 is a schematic diagram showing the configuration and route of the present invention. The second invention will be further described with reference to FIG.

In FIG. 5, M₁Represents the reflecting mirror 22 and M represents_TwoIs
The reflecting mirror 32 is shown. P₁, P_TwoIs the first to third refractive index 2
8, 29, 30, 3 layers
, P ₁Are the first refractive index layer 28 and the second refractive index layer 2
9, the interface with P_TwoIs the second refractive index layer 28 and the third refractive index layer.
This is a boundary surface with the folding layer 30. θ1 is the boundary plane P₁And normal
And the angle between them. E is a reflector M₁From the boundary surface P₁Enter
The electric field of the emitted light, E 'is the reflection component at the boundary of the electric field E,
E ″ is a refraction component in the electric field E. θ2 is a boundary of the electric field E
Plane P₁Is the refraction angle at. a and b are optical axes, B is laser light
Axis. The electric field E of light is represented by an x component and a y component shown in FIG.
Axis extending vertically upward from the

[0032] In FIG. 5, the electric field E that is incident from the reflection mirror M ₁ to the boundary surface P ₁ is, E = (Ex, Ey) and the reflection component E at the boundary surface P ₁ 'is E' = (Ex ', Ey '). The refraction component E ″ at the boundary plane P ₁ is E ″ = (Ex ″, E
y ″). In this case, E ′ and E ″ can be expressed as follows using E.

[0033]

(Equation 1)

Here, if θ ₁ = tan ⁻¹ (n ₂ / n ₁ ), Ex ′ = 0, whereas Ey ′ ≠ 0.
The refractive ingredients, after the boundary plane P _1, but reach the boundary surface P _2, even the reflection of similarly x component where 0, reflecting the y component is not zero.

Further, after the light of the boundary surface P _2, just as it returns to the interface P ₂ again by being reflected by the reflecting mirror M ₂ described above, the reflection of the x component is 0, the y component The reflection is not zero.

Therefore, in the configuration of the present invention, light polarized in the x direction does not suffer loss, whereas light polarized in the y direction is reflected at the _two boundary surfaces P ₁ and P ₂ . Suffer loss due to Therefore, in the configuration of the present invention, polarized light existing on a plane determined by the laser optical axis and the normal to the boundary surface is most likely to oscillate.

Here, the optical axes a and b become parallel by continuously forming the three refractive index layers 28, 29 and 30 having the refractive indices n ₁ , n ₂ and n ₁ . Accordingly, the optical axes a and b are perpendicular to the parallel reflecting mirrors M ₁ and M ₂ , respectively.
There is no decrease in reflectance.

In the embodiment shown in FIG.
Is reflected by the reflection mirrors 22 and 32 and oscillates in a laser. In this embodiment, the light generated by [0−
11] The polarization component in the direction receives a loss. Therefore, in this embodiment, the polarized light in the [011] direction is most likely to oscillate.

In this embodiment, a p-type G
a _0.5 Al _0.5 As layer (refractive index n)
₁ 3.26), refractive layer 29 (refractive index n ₂ 3.52 of p-type Ga _0.9 Al _0.1 As layer), a p-type Ga _0.5 Al _0.5 A
A refraction layer 30 (refractive index n ₁ 3.26) composed of an s layer is used. At this time, θ ₁ in FIG. 4 is 47.2 °.

In this embodiment, a loss is provided in the [0-11] direction to make it easy to oscillate the polarized light in the [011] direction, but it exists in the plane (c) whose normal line is the laser optical axis B. The loss may be provided in any direction as long as it is the same. In this case, a direction perpendicular to the direction in which the loss is provided and existing in the plane (c) is likely to oscillate.

In this embodiment, the loss addition layer A is provided between the p-type cladding layer and the p-type contact layer. However, as long as the current confinement structure (cladding-active layer-cladding) of the active region is maintained, resonance occurs. It may be provided anywhere in the vessel. Further, it may be provided outside the resonator of the reflecting mirror on the light emitting side.

As in the first invention, the p-type and the n-type of this embodiment may be inverted. In the embodiment of the second invention, GaAl
Although an As system is shown, other material systems are also effective.

In this embodiment, a surface emitting semiconductor laser on a (100) crystal plane is described, but the present invention is not limited to this.

[0044]

According to the first aspect, the polarization direction of the surface emitting laser can be specified to either [001] or [010].

Further, according to the second aspect, the polarization direction of the surface emitting laser can be made constant in an arbitrary direction within a plane whose normal line is the laser optical axis, regardless of the element.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the first invention of the present invention.

FIG. 2 is a schematic view of an active layer having a buried structure as viewed from a wafer surface.

FIG. 3 is an IL characteristic diagram when each component is extracted using a polarizing beam splitter, and (a) is [010].
(B) [001] direction component.

FIG. 4 is a structural diagram showing an example of an embodiment of the second invention of the present invention.

FIG. 5 is a schematic diagram illustrating the operation of the second invention of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 n-type GaAs (100) substrate 2 reflector 3 n-type cladding layer 4 active layer 5 p-type cladding layer 6 p-type current blocking layer 7 n-type current blocking layer A loss adding layer 8 high refractive index layer 9 low refractive index layer REFERENCE SIGNS LIST 10 p-type contact layer 11 light-emitting side reflector 12 p-side electrode 13 n-side electrode 21 GaAs substrate 22 reflector 23 n-type clad layer 24 GaAs active layer 25 p-type clad layer 26 p-type current block layer 27 n-type current block Layer 28 First refractive index layer 29 Second refractive index layer 30 Third refractive index layer 31 P-type contact layer 32 Light-emitting-side reflecting mirror 33 P electrode 34 N electrode

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Teruaki Miyake 2-18 Keihanhondori, Moriguchi City Sanyo Electric Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) H01S 3/18

Claims (2)

(57) [Claims] 1. A surface emitting semiconductor laser device in which a buried active layer is formed on a [100] crystal plane of a GaAs semiconductor substrate, wherein the crystal orientation is [010] or [0].
[01] A surface-emitting type semiconductor laser device comprising a loss-adding layer that blocks polarization components in the [01] direction. _2. A layer having a refractive index of n _1, a layer having a refractive index of n ₂ which does not absorb laser light, and a layer having a refractive index of n ₂ are provided inside the resonator including the active region or outside the resonator of the reflector on the light emitting side. n ₁ layers are continuously provided, and two boundary surfaces formed of the three layers are formed as parallel planes, and an angle θ ₁ between a normal line of the boundary surface and the laser optical axis is θ ₁ = tan. ^-1 (n ₂ / n ₁₎ the surface-emitting type semiconductor laser device, characterized by satisfying the.