JPS62159489A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To perform the adjustment of an emission angle of a laser beam without using a lens by providing a waveguide layer of refractive index distribution type oppositely to an emission plane of a laser element including an edge plane of an active layer which will become an edge plane of a resonator so as to change the refractive index outward in order. CONSTITUTION:On a substrate 11, a lower cladding layer 13, an active layer 15 and an upper cladding layer 17 are laminated to compose a double hetero structure and one edge part of the layers 13-15 is etched by directional chemical etching in vertical direction to the active layer 15 and down to a depth reaching the substrate 11, thereby forming a cavity 31. Next, a refractive index distribution type waveguide layer 33 is arranged in this cavity 31. This waveguide layer 33 is arranged oppositely to an emission plane of a laser element 29 and the refractive index is changed in order from the center 33a of the waveguide layer 33 opposite to the center of an edge plane 35 of a resonator in the emission plane toward the outsides 33b and 33c.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a structure of a semiconductor laser device that allows easy adjustment of the radiation angle of laser light when optically coupling the semiconductor laser device to an optical fiber or the like.

(Prior Art) In recent years, research has been actively conducted on semiconductor laser devices useful as light sources for optical communications, optical information processing, and the like.

FIG. 2 is an overall perspective view showing an example of the configuration of a conventional semiconductor laser device (Reference I: "Applied Physics Lectures").
tters)j 18 [4] (1971-2-15)
(p. 155-157) Hereinafter, an example of the basic structure of a semiconductor laser device will be explained by taking the semiconductor laser device shown in FIG. 2 as an example.

In FIG. 2, 11 is an H-QAAs substrate product,
On this substrate 11, n Gal-x A JLx
AS cladding layer 13, p-Ga AS active layer 1
5, p-Gal-x Aim As cladding layer 17
, p-GaA 5M19, and an oxide film 21 provided to form stripe grooves are sequentially stacked and provided. Further, a p-side electrode 23 is provided on the oxide film 21 and a portion of the p-GaAs layer 19 exposed by the stripe groove, and an n-side electrode 25 is provided on the side opposite to the side on which the p-side electrode 23 is provided. It is provided on the side substrate 11 surface.

The semiconductor laser device (hereinafter also simply referred to as a laser device) 27 configured in this manner has a tuple heterostructure in which the active layer 15 is sandwiched between two heterojunctions.

In such a laser device, the active layer 15 forms a heterojunction with the cladding layer 13 and the cladding layer 17, which have a larger 7-hand gap and a smaller refractive index than the active layer 15, and therefore, the active layer 15 Injected carriers (electrons and holes) and light waves generated within the active layer 15 are confined in the active layer 15. As a result, the light waves are amplified within the active layer 15.

Further, both end faces of the active layer 15 are a pair of mutually parallel optical reflecting surfaces formed by the folds of the crystal.
Therefore, the active layer 15 constitutes a resonator (optical resonator) together with this pair of parallel reflecting surfaces. This optical resonator causes the light waves confined within the active layer 15 to resonate, resulting in laser oscillation. As a result, a laser beam having coherent characteristics is emitted from the end face of the active layer 15.

In this way, the laser light emitted from the thin active layer 15 spreads greatly in the thickness direction of the active layer (direction perpendicular to the active layer) due to the diffraction phenomenon, and as a result, the laser light radiation pattern L becomes elliptical. This elliptical radiation pattern L has an angle of approximately 20″ to 30° in the direction perpendicular to the active layer 15.
with a divergence angle of approximately 10″ in the direction of and perpendicular to this direction (
radiation angle).

For this reason, in semiconductor laser devices with conventional configurations, when the laser beam is guided to the next stage using an optical fiber with a particularly small shaft diameter, the laser beam is focused or parallelized in order to increase the coupling efficiency with this optical fiber. It was necessary to obtain a narrow beam of light with little spread.

(Problems to be Solved by the Invention) However, since a semiconductor laser device with a conventional configuration uses a lens to adjust the radiation angle, an object to be optically coupled to the semiconductor laser device (for example, an optical fiber), a lens and It was necessary to align the optical axes of the three light-emitting surfaces of the active layer. Therefore, there is a problem in that optical axis alignment is not easy but extremely difficult in optical coupling that requires highly accurate optical axis alignment, such as in the case of optical fibers with small shaft diameters.

In conventional semiconductor laser devices, the emission pattern of laser light is elliptical, so a lens, particularly a cylindrical lens, is used. Therefore, a problem frequently arises in that the optical system for adjusting the radiation angle of the laser beam becomes complicated.

, - The purpose of Koryo's attack 1st person: The single-week body of Yoyou Uyosatsu - Eliminate the problems mentioned in Zaboko in general, and easily and freely adjust the radiation angle of laser light without using a lens. It is an object of the present invention to provide a semiconductor laser device that can be used for various purposes.

(Means for Solving the Problem) In order to achieve this object, according to the semiconductor laser device (laser device) of the present invention, the end face of the active layer, which becomes the end face of the resonator (reflecting face of the optical resonator). A gradient index waveguide layer is provided opposite to the light emitting surface of the laser element including the laser element. This waveguide layer has a refractive index distribution that sequentially changes from the center of the waveguide layer facing the reflective surface of the optical resonator in the light emitting surface toward the outside of this center.

The gradient index waveguide layer may be provided apart from the light emitting surface, or may be provided in contact with the light emitting surface.

In addition, the refractive index distribution of the waveguide layer is such that the refractive index is high at the center of the waveguide layer, and the refractive index decreases continuously or stepwise from the center of the waveguide layer outward. is preferable.

(Function) According to such a configuration, since the laser light passes through the gradient index waveguide layer included in the semiconductor laser element, the length of the waveguide layer and/or the distance between the waveguide layer and the light emitting surface is By setting the interval appropriately, the radiation angle of the laser beam can be set.

In other words, when the light emitting surface of the semiconductor laser element and the waveguide layer are provided apart from each other, the emission angle of the laser beam is determined by the refractive index distribution of the waveguide layer, the length of the waveguide layer, and the relationship between the waveguide layer and the light emitting surface. When the waveguide layer is provided in contact with the light emitting surface, it is determined by the refractive index distribution of the waveguide layer and the length of the waveguide layer.

(Embodiment) Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Note that the drawings schematically illustrate each component to the extent that the present invention can be understood, and therefore, the dimensions, shapes, and arrangement relationships of each component are not limited to the illustrated examples. In addition, the same constituent components as those of the conventional constituent components are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

FIGS. 1A and 1C are cross-sectional views for explaining the embodiment, and FIG. 1B is a perspective view for explaining the embodiment.

In the embodiment shown in FIG. 1(A), 29 is a semiconductor laser device, and this laser device 28 is sequentially formed on the substrate 11 by a lower cladding layer (p layer) 13, an active layer 15, and an upper cladding layer (n layer) 17, an upper electrode 30a on the upper cladding layer 17, and a substrate 1.
1, and a gradient index waveguide layer 33 facing the light emitting surface (end surface of the resonator of the laser element) 35 of the double heterojunction structure. It has a structure in which a recess or groove 37 is provided between the light emitting surface 35 and the waveguide layer 33.

The structure of this embodiment will be briefly described in detail with reference to its manufacturing method. First, a double heterojunction structure is formed on an n-GaAs substrate.
As cladding layer 13, GaAs active layer 5 and p-
After sequentially forming n layers of Ga1-2A×As cladding layers 17, one end of the layer is formed in a direction perpendicular to the active layer 15 (direction along the end face of the resonator) and to a depth that reaches the substrate 11. Directional chemical etching (RIE) for 13-15
to form a cavity 31 on the substrate 11 (see Fig. 1).
B) ), the electrodes 30a and 30b are formed on the substrate 1, for example.
This can be done after laminating layers 13, 15, and 17 on top of layer 1, or after forming cavity 31.

Next, a refractive index distribution type waveguide layer 33 is provided in this space 31. In this case, the waveguide fi 33 is provided facing the light emitting surface of the laser element 23, and the end surface 35 of the resonator in the light emitting surface
facing the center of Center of waveguide layer 33 (waveguide layer 33a)
The refractive index is formed so as to change sequentially from the top toward the outside (waveguide layers 33b and 33C).

It is preferable to form this waveguide layer 33 with Gany Alv As, and when forming it, the concentration of A pattern ( The composition ratio) is gradually decreased from the center waveguide layer 33a to the waveguide layer 33 sandwiching the center waveguide layer 33a.
It is preferable to form the waveguide layer 33c so that the concentration of Afl gradually increases up to the waveguide layer 33c on the side opposite to the waveguide layer 33c. By changing the degree of A and C in this way, the refractive index of the waveguide layer 33 can be made high in the waveguide layer 33a at the center and in the waveguide layers 33 on both outer sides.
It can be made to change continuously and become smaller towards b and 33c. In this case, it is best to form the waveguide layer 33 so that the refractive index is symmetrical with respect to the center of the waveguide layer 33 (waveguide layer 33a). The most ideal refractive index distribution is
The refractive index distribution is like a quadratic curve centered on the waveguide layer 33a, and by making the refractive index of the waveguide J133a the highest, the effect of confining light (emitted laser light) in the waveguide layer 33a is expected. I can do it. Therefore, G a +
The refractive index distribution of the waveguide layer 33 is adjusted by changing the composition ratio of the A pattern of the waveguide layer 33 consisting of −vAlyA s, thereby directing the laser light emitted from the active layer 15 to the waveguide layer 33. can effectively guide waves.

The refractive index is high in the waveguide layer 33a, and the refractive index is high in the waveguide layer 33b and 33c.
It may also be configured so that it changes stepwise and becomes smaller toward .

The waveguide layer 33 can be formed, for example, by liquid phase epitaxial growth (
(LPE method) or metal organic chemical vapor deposition method (MOCVD method).

The waveguide layer 33 is preferably provided apart from the light emitting surface of the laser element 29 including the resonator end face 35 (see FIG. 1(A)).
). In particular, if the refractive index of the active layer 15 and the refractive index of the waveguide layer portion at the position corresponding to the active layer 15 are substantially equal or close to each other, a resonator surface cannot be formed. After forming the waveguide layer 33, a groove 37 is formed by RIE to form an etched mirror as an optical reflection surface on the end face 35 of the resonator.

The radiation angle of the laser beam oscillated in the semiconductor laser element 29 configured in this way (in this case, the radiation angle in the direction perpendicular to the active layer 15) is determined by taking the refractive index distribution of the waveguide layer 33 into consideration. Waveguide layer 33 in the laser direction (laser extraction direction)
The length of the waveguide part) hl and the groove in the same direction @h2
(See FIG. 1(A)) can be set by setting and configuring in advance.

FIG. 1(C) is a diagram showing a modification of this embodiment, in which the refractive index of the active layer 15 and the refractive index of the portion of the waveguide layer 33 corresponding to the active layer 15 are substantially different. Therefore, if the laser beam resonates in the resonator without any problem, the waveguide layer 33
may be provided in contact with the light emitting surface of the laser element 29.

Although this embodiment describes a semiconductor laser device using a GaAs substrate, the present invention is not limited thereto, and can also be applied to a semiconductor laser device using an InP substrate as the substrate material, for example.

In this case, the gradient index waveguide layer is In1-7G a
By forming the waveguide layer with z A 5w PI-w and changing the composition by changing the value of W, the refractive index of the waveguide layer is changed. As the number of W increases, the refractive index also increases.

Further, in this embodiment, an example of an edge-emitting type semiconductor laser device has been described, but the present invention can also be applied to a surface-emitting type semiconductor laser device.

Furthermore, the refractive index distribution of the waveguide layer may be low at the center of the waveguide layer and increase outward from the center in an N-shaped or stepwise manner.

(Effects of the Invention) As is clear from the above description, according to the semiconductor laser device of the present invention, the radiation angle of the laser beam is determined depending on the design of the gradient index waveguide included in the semiconductor laser device. The length of the layer or the length of this waveguide layer and the width of the groove can be adjusted by presetting. Therefore, when optically coupling the semiconductor laser element, there is no need to use a lens to make the laser beam a black light or to make the laser beam into parallel light. Therefore, the optical axis alignment should be performed when optically coupling the semiconductor laser element Optical axes of objects such as optical fibers and semiconductor laser elements can be aligned more easily than before, and more accurate optical axes can be achieved, making optical coupling easier than before. In addition, it can be expected that the optical system will be simplified, instead of being complicated as in the past.

In general, according to the present invention, it is easy to adjust the radiation angle of the laser beam to make the laser beam a focused beam or a parallel beam, thereby narrowing the spread of the laser beam due to the diffraction phenomenon.

The laser beam emission pattern, which normally has an elliptical shape, can also be configured to have a circular pattern.

For this reason, it is possible to increase the coupling efficiency of optical coupling in optical coupling that requires undesirable precision in optical axis alignment, such as in optical fibers with small shaft diameters.

[Brief explanation of drawings]

FIGS. 1A to 1C are diagrams for explaining the present invention in detail, and FIG. 2 is a diagram for explaining the conventional example. 11...Substrate, 13.17...Clad layer 15...Active layer, 28...Semiconductor laser element 31...Vacancy, 33...Gradient index waveguide layer 33a, 33b , 33c - Waveguide layer 35... Light emitting surface (end face of resonator) 37... Groove.

Claims (5)

[Claims] (1) A graded refractive index waveguide layer is provided facing the light emitting surface and has a refractive index that sequentially changes outward from the center opposite to the center of the end face of the resonator within the light emitting surface. A semiconductor laser device characterized by the ability to (2) A semiconductor laser device according to claim 1, characterized in that a gradient index waveguide layer is provided facing the light emitting surface and is spaced apart from the light emitting surface. (3) The semiconductor laser device according to claim 1, further comprising a gradient index waveguide layer provided facing the light emitting surface and in contact with the light emitting surface. (4) Claims 1 to 3 include a distributed refractive index waveguide layer in which the refractive index is high at the center and continuously changes and decreases toward both outer sides. The semiconductor laser device according to any one of the above. (5) Claims 1 to 3 include a distributed refractive index waveguide layer in which the refractive index is high at the center and gradually changes and decreases toward both outer sides. The semiconductor laser device according to any one of the above.