JPS5830754B2 - semiconductor laser - Google Patents

Description

[Detailed description of the invention] The present invention relates to a semiconductor laser.

In general, the method for extracting the output of a semiconductor laser is to make one opposing surface of the semiconductor laser an arm-opening surface, and create a resonator by making this have the same effect as a reflecting mirror. (Fabry-Perot
A wavy boundary surface is provided inside or near the intervening active region (resonator) and the interlayered active region at right angles to the laser beam output direction, thereby forming a periodic structure of optical refractive index and loss (referred to as corrugation). There is a device that generates laser oscillation.

By the way, since the active region of a semiconductor laser having such a structure needs to be continuously oscillated at approximately room temperature, its layer thickness is usually 1. ,, m or less.

Therefore, the half-value angle of laser beam spread in the layer thickness direction of the active region is large, approximately 50 degrees.

In general, in a semiconductor laser, filament oscillation occurs when defects etc. exist in the crystal, so the laser beam extraction direction is made relatively long in order to make the gain uniform, and the width of the laser beam extraction surface is shortened. Overall, the area occupied by the semiconductor laser is kept small.

Therefore, since the width of the active region on the laser beam extraction surface is small, the laser beam within the plane containing the active region is not parallel but has a slight spread half-value angle.

For this reason, in order to easily couple the output to other optical components, conventional lenses are used to make the laser beam into parallel beams, but it is now possible to make laser beams that spread in the vertical and horizontal directions and have different half-value angles into parallel beams. Therefore, a lens with a special shape was required, and its manufacture and installation were extremely difficult.

Furthermore, conventional semiconductor lasers cannot perform modulation with a single element, and must also be equipped with other modulation elements.

Another object of the present invention is to provide a semiconductor laser in which it is easy to manufacture and attach a lens for collimating a laser beam.

Another object of the present invention is to provide a semiconductor laser that can be modulated with a single element.

In order to accomplish this purpose, the present invention provides an active region and a different semiconductor layer (light guide layer) on the top surface of a semiconductor substrate.
A semiconductor layer is formed on the top surface of the active region and the top surface of the optical guide layer, and a periodic structure of optical refractive index and loss is formed inside or near the active region and the optical guide layer. At the same time, the optical guide layer is made to have a predetermined angle other than 0 degrees or 90 degrees in the periodic direction of the periodic structure so that the laser beam is irradiated from the active region to the optical guide layer, and a reverse bias modulation voltage is applied to the optical guide layer. This is how it was done.

Hereinafter, the present invention will be explained in detail using Examples.

FIG. 1 is a partially broken configuration diagram showing an embodiment of a semiconductor laser according to the present invention.

For example, p-type Ga1, which becomes the active region, is grown by epitaxial growth on the upper surface of the substrate consisting of n-type Ga1 and AlxAs layer 1.
As layer 2 is located near one side, and n-type G serves as a light guide layer.
An aAs layer 3 is formed in another region, and the P-type GaAs
A P-type Ga1 and AlyAs layer 4°4' is formed on the upper surface of the layer 2 and the upper surface of the n-type GaAs layer 3 in the vicinity of the opposite side.

The surfaces of the P-type Ga1 and AlyAs layers 4°4' are selectively etched by photolithography using laser interference light to form opposing P-type Ga1 and yAlyA layers.
s 4. Concave and convex surfaces 5. ! l/ is formed.

And P-type Ga1-yAlyAs processed in this way
On the upper surfaces of the layers 4 and 4', a p-type Ga1-2AlzAs layer 6°σ is formed by epitaxial growth, etc., and on this upper surface and the back surface of the n-type Ga1-XAlxAs layer 1, metal is deposited to form the electrodes 7 and 7'. and 8 are formed.

Further, in the semiconductor chip 9 thus formed, both end surfaces 10 and 1σ on the sides where the cross sections of the P-type Gal and AlyAs layers 4 and 4' appear are provided with a bone gap to form a resonator.

Electrodes 7 and 8 of a semiconductor laser having such a configuration
When an excitation current is passed in the forward direction between them, laser oscillation occurs in the active region between the end surfaces 10 and 10', which are the interosseous surfaces, and then P
Type Ga, AlyAs layer 4 and P type Ga1-, Z, A
Due to the influence of the periodic structure (corrugation) of the refractive index and loss of light formed on the uneven surface 5 which is the interface with the lxAs layer 6,
The laser beam is irradiated in a direction perpendicular to the longitudinal direction of the P-type Ga, AlyAs layer 4.

On the other hand, if a reverse bias modulation voltage is applied between the electrodes 7' and 8, a change in dielectric constant occurs due to the Franz-Keldysh effect or the Pockels effect, so that amplitude and phase modulation is added to the laser output.

The relationship between the direction of the corrugations and the irradiation angle of the laser beam is determined by the periodic interval A of the corrugations, as shown in Figure 2.
θ for the laser oscillation wavelength λ: P-type Ga1-yAly
An angle in the periodic direction of corrugation with respect to the longitudinal direction of the As layer 4.

If you choose , the laser beam will be P-type Ga 1-yAlyAs
It has been found that there is a relationship in which the radiation is irradiated at an angle of 2θ with respect to the longitudinal direction of the layer 4.

Therefore, in the case of θ-45 degrees, the laser beam is perpendicular to the longitudinal direction of the P-type Gal yAlyAs layer 4 (2
It can be seen that it is taken out at θ--R).

In this way, if the laser beam is taken out from the end face in the longitudinal direction of the P-type Gal, AlyAs layer 4, the half-value angle of spread becomes extremely small.

For example, when the longitudinal distance of the P-type Ga1 yAlyAs layer 4 is set to d-approximately 300 μm and the laser oscillation wavelength is set to λ0.9 μm, it has been found that the distance becomes about 0.2 degrees, compared to the conventional several to 10 degrees.

Therefore, when extracting the laser beam as parallel light, it is only necessary to consider the spread in the layer thickness direction of the P-type GaAs layer 2, which becomes the active region, so that a cylindrical lens can be used.

Since it is only necessary to determine the curvature of one side of this cylindrical lens, it is easy to manufacture and easy to install.

Further, by adopting such a configuration, laser oscillation and modulation can be performed in one element.

Note that such a configuration has P-type Ga 1- which is related to gain.
The longitudinal distance of the yA IyAs layer 4 is almost the same as that of the conventional one, and the laser beam can be taken out perpendicular to the longitudinal direction of the P-type Ga1-yAlyAs layer 4. As a result, a modulation element is incorporated in this laser beam irradiation direction part. Therefore, the area occupied by the semiconductor chip 9 can be reduced.

In this example, the P-type GaAs layer 2 serving as the active region and the n-type GaAs layer 3 serving as the optical guide layer are made of n-type Ga1-XAI.
As shown in FIG. 3, an n-type GaAs layer 3 is formed over the entire upper surface of the n-type Ga1-XAlxAs layer 1, and the band gap with the P-type GaAlyAs layer 4 is Of course, the effective active region may be formed from the difference -y.

Further, although the semiconductor laser described in this embodiment has a double heterojunction structure, it may have a single heterojunction structure or a homoheterojunction structure, and the semiconductor material is not limited.

Although the corrugation is provided above the active region, the same effect can be obtained even if the corrugation is provided within the active region.

As described above, according to the semiconductor laser according to the present invention, it is possible to easily manufacture and attach a lens for collimating a laser beam, and also to be able to modulate the laser beam using only one element.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway configuration diagram showing an embodiment of the semiconductor laser according to the present invention, FIG. 2 is an explanatory diagram for illustrating the effects of the semiconductor laser, and FIG. 3 is a diagram showing other semiconductor lasers according to the present invention. FIG. 2 is a partially cutaway configuration diagram showing an embodiment of the present invention. 1...--n-type Ga, -xAlxAs layer, 2...
...P-type GaAs layer, 3=-n-type GaAs layer,
4, 4'...-P-type Ga, AlyAs layer,
5, 5'-----uneven surface, 6, 6'...
P-type Ga A1zAs layer, 7, 7', 8...
・Electrical 1-7° pole, 9---- semiconductor chip.

Claims (1)

[Scope of Claims] 1. An active region and a different semiconductor layer (light guide layer) are formed on the upper surface of a semiconductor substrate, an isolated semiconductor layer is formed on the upper surface of the active region and the upper surface of the optical guide layer, and A periodic structure of optical refractive index and loss is formed inside or near the active region and the optical guide layer, and the periodic structure is tilted at 0 degrees or in the periodic direction of the periodic structure so that the laser beam is irradiated from the active region to the optical guide layer. A semiconductor laser having a predetermined angle other than 90 degrees and applying a reverse bias modulation voltage to the light guide layer. 2. A light guide layer is formed over the entire upper surface of the semiconductor substrate, a separated semiconductor layer is formed on the upper surface of the light guide layer, and a periodic structure of optical refractive index and loss is formed inside or near the light guide layer. At the same time, the periodic structure has a predetermined angle other than 0 degrees or 90 degrees to the periodic direction of the periodic structure so that a laser beam can be taken out in the opposite direction of the semiconductor layer, and a reverse bias modulation voltage is applied to the optical guide layer under one of the semiconductor layers. A semiconductor laser characterized in that it is configured to apply voltage.