JPH0231484A - Phase-locked type semiconductor laser array and its manufacture - Google Patents

Abstract

PURPOSE:To radiate an optical output from a semiconductor laser array part as an optical output in a 0 deg.-phase mode by a method wherein a new phase shifter is integrated in the semiconductor laser array part which is oscillated in a 180 deg.-phase mode. CONSTITUTION:In order to give a phase shift to an optical output from individual light waveguides 13 in a semiconductor laser array part 11, a part 39a corresponding to individual light waveguides 25a to 25c in a semiconductor layer 39 is formed of a semiconductor layer of a multiple-quantum-well structure; a part 39c corresponding to other light waveguides 23a to 23c is formed of a semiconductor layer of the multiple-quantum-well structure after this layer has been made disordered so as to obtain a prescribed refractive index. Parts between the individual light waveguides are filled with a part 39b after the semiconductor layer of the multiple-quantum-well structure has been made disordered in the same manner as the semiconductor laser array part 11. By using a phase shifter part 21 of the above structure, it is possible to produce a difference in a refractive index of about 1% between adjacent light waveguides. Thereby, beams radiated from the semiconductor laser array part 11 in a 180 deg.-phase mode become an identical phase at a radiation end face and can be made a 0 deg.-phase mode.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a phase-locked semiconductor laser array having a plurality of optical waveguides, which stably oscillates in zero phase mode up to high output. The present invention relates to arrays and methods of manufacturing the same.

(Prior Art) A phase-locked semiconductor laser array (hereinafter sometimes abbreviated as a laser array) having multiple optical waveguides exceeds the upper limit of the maximum optical output of a semiconductor laser having a single optical waveguide. It was devised from the desire to produce a high-output semiconductor laser. As this type of laser array, for example, the literature (Journal of the Institute of Electronics and Communication Engineers 00E86
-64 pp, 25-30) (As disclosed here, there have been gain-guided laser arrays and ones with mote selection.However, this single laser array has a 180 The oscillation gain of the multiple phase mode tends to be high, and therefore the oscillation is usually in the 180 multiple phase mode.Therefore, the far-field pattern tends to be multimodal, and the far-field pattern tends to be multimodal, which is not the case in many application fields of semiconductor lasers. It is much more difficult to obtain a far-field image than with a semiconductor laser having a single optical waveguide.

In order to obtain a unimodal far-field image, that is, to stably oscillate a phase-locked semiconductor laser array in the ○° phase mode, conventional techniques include: ■... changing the width of each optical waveguide provided in the laser array. By varying the spacing between the waveguides, we create an asymmetric stripe structure and create a gain difference between each waveguide.
- Forming an optical waveguide with a structure that cuts off the 180-fold phase mode, ■... Phase shifter (phase adjuster) made of an insulating film on the end face of a predetermined optical waveguide among each optical waveguide of the laser array. ).

(Problems to be Solved by the Invention) However, a laser array including an optical waveguide with an asymmetric stripe structure has a problem in that the launch of the 0° phase mode becomes unstable at high output. Also, 180
The method of cutting off the multiple phase mode (highest order mode) requires highly accurate patterning (according to the above-mentioned literature, microfabrication on the order of O, Ium), which is problematic. In addition, when a phase shifter made of an insulating film is provided at a predetermined position on the end face of a laser array, there is a problem in that the insulating film formed on the end face must be photoretched, which requires a very difficult technique. Ta.

This invention was made in view of these points, and therefore, the purpose of this invention is to provide a phase-locked type that can solve the above-mentioned problems and obtain a stable unimodal far-field image up to high output. An object of the present invention is to provide a semiconductor laser array and a method for manufacturing the laser array.

(Means for Solving the Problem) In order to achieve this object, a phase-locked semiconductor laser array according to the first invention of this application is provided with a semiconductor laser array section that oscillates in a 180 phase mode and has a plurality of optical waveguides. and a phase shifter section having the same number of optical waveguides as the semiconductor laser array section, each optical waveguide being composed of a semiconductor layer, and each optical waveguide having a refractive index different from that of an adjacent optical waveguide. A phase shifter section is provided such that the optical axis of each optical waveguide of the phase shifter section and the optical axis of each optical waveguide of the semiconductor laser array section are substantially on the same line.

Further, the second invention of this application is a semiconductor laser array section that oscillates in a 180 multiphase mode having a plurality of optical waveguides, and a phase shifter section that has the same number of optical waveguides as the semiconductor laser array section, and each optical waveguide. The optical axis of each optical waveguide in the phase shifter part and the semiconductor laser array part A method for manufacturing a phase-locked semiconductor laser array comprising optical axes of each optical waveguide on substantially the same line includes a semiconductor layer common to the semiconductor laser array section and the phase shifter section, comprising: A step of forming a multi-quantum well structure semiconductor layer that is in contact with the active layer via a cladding layer or directly in contact with the active layer, and a plan for forming each optical waveguide in the semiconductor laser array section and the phase shifter section in this semiconductor layer. No 'M' in areas other than the area! A step of introducing an impurity into every other region of the semiconductor layer corresponding to the region where each optical waveguide is to be formed in the phase shifter section described above. The method is characterized in that it includes a step of disorganizing the territory.

(Function) According to the phase-locked semiconductor laser array of the present invention, 1
The optical output from the semiconductor laser array section, which is stably oscillating in the 80° phase mode, is phase-adjusted in the phase shifter section and is emitted as the optical output in the 0° phase mode.

Furthermore, since the phase shifter section according to the present invention is not provided on the output end face, it is easy to manufacture.

Furthermore, according to the present invention (this phase shifter section), the phase of light from the laser array section is adjusted by adjusting the refractive index of the optical waveguide. If the phase change amount per length is set to be small, processing variations during work between folds etc. 1
Thus, even if the dimensions of the optical waveguide deviate from the desired dimensions, the amount of phase shift can be reduced, making it easier to obtain a desired phase shifter section.

Further, according to the method for manufacturing a phase-locked semiconductor laser array of the present invention, impurities are introduced into regions of the semiconductor layer having a multiple quantum well structure other than the regions where optical waveguides are to be formed in the semiconductor laser array section and the above-mentioned phase shifter section. By making this region disordered, regions for separating each optical waveguide can be easily formed.

Further, by introducing impurities into every other region of the semiconductor layer of the multi-quantum well structure corresponding to the regions where each optical waveguide of the above-mentioned phase shifter section is to be formed, and disordering this region vt, It becomes possible to easily vary the refractive index between the optical waveguides in contact with each other in the phase shifter section. Furthermore, the refractive index can be easily controlled depending on the amount of this impurity introduced.

(Example) Hereinafter, with reference to the drawings, an example of the structure of the AufEaAs/GaAs phase-locked semiconductor laser array (hereinafter also referred to as a laser array) in which the present invention is applied, and Examples of the manufacturing method of this laser array will be explained separately.The figures used in the explanation are only schematic illustrations to the extent that this invention can be understood, and therefore, the dimensions of each component, It should be understood that the shape etc. are not limited to only this illustrated example.

It is provided so that the optical axis is substantially on the same line. Figure 1 (
A) to (C) are diagrams for explaining embodiments of such a laser array, and FIG. 1(A) is a plan view thereof;
Figure CB) is a cross-sectional view taken along the line n-II of Figure 1(A), and Figure 1(C) is a cross-sectional view showing the laser array section included in this laser array. It is a diagram showing the phase shifter section provided, and is I
It is a sectional view cut along the -I line. Note that the following explanation will be given using an example using an n-type GaAs substrate.

The laser array of the present invention has a plurality of optical waveguides.
a semiconductor laser array section that oscillates in an 80° phase mode;
A phase shifter section having the same number of optical waveguides as the semiconductor laser array section, in which each optical waveguide is composed of a semiconductor layer and the refractive index of each optical waveguide is different from that of an adjacent optical waveguide. The optical axis of each optical waveguide of the phase shifter section and each optical waveguide of the semiconductor laser array section...Schematic explanation In FIG. 1(A), IO indicates the laser array of the embodiment. , 11 indicates a semiconductor laser array section, 21 indicates a phase shifter section, and 15 indicates an end face reflection film. The detailed structures of the semiconductor laser array section 11 and the phase shifter section 21 will be described later, but their outline will be as explained below.

The semiconductor laser array section 11 is a stripe (optical waveguide)
It has a phase-locked structure having seven optical waveguides 13 with a width W of 2 um and a stripe interval W2 of 4 am, and is assumed to operate stably in a normal 18° phase mode.

The phase shifter section 21 has the same number of optical waveguides 23a, 23b, 23c, 23 as the semiconductor laser array section 11, seven in this case.
d.

25a, 25b, and 25c, each of which has a structure in which the optical axis of each optical waveguide is substantially on the same line as the optical axis of the corresponding optical waveguide of the semiconductor laser array section 11; however, 25a , 25b and 25c have the same refractive index as the optical waveguide 13 in the semiconductor laser array section, and 23a, 23b, 23c and 2
The four optical waveguides indicated by 3d are 25a, 25b or 25
It is assumed that the optical waveguide has a refractive index different from that of the optical waveguide indicated by c.

(2) Explanation of Semiconductor Laser Array Section 11 describes the detailed structure of the semiconductor laser array section 11.

The semiconductor laser array section 11 includes n-type A'no, aGa
(,, sAs cladding layer 33, GaAs active layer 35, p-type A (J-o, 3Gao, 7As cladding layer 37
and a semiconductor layer 39 consisting of a p-type AQGaAs/GaAs multiple quantum well structure semiconductor layer 39a and a disordered portion 39b (hatched area) of the multiple quantum well structure semiconductor layer.
(Details will be described later.), p-type AQo, 4Gao,
It includes an eAs cladding layer 41 and a p-type GaAs contact layer 43 in this order. And contact layer 4
3 from the surface of the predetermined region to the cladding layer 41.
Roughly speaking, an n-type electrode 47 is provided under the n-type GaAs substrate 31, and an n-type electrode 49 is provided on the p+-type GaAs contact layer 43. In this structure, the light generated in the active layer 35 leaks out from the cladding layer 37 and the semiconductor layer 39a1 having the multiple quantum well structure, so that the light generated in the active layer 35 leaks out from the semiconductor layer 39a having the multiple quantum well structure and the active layer. 35 and a multi-quantum well structure semiconductor layer 39 of the crat layer 37
An optical waveguide is constituted by the portion corresponding to a.

Here, the structure of the semiconductor layer 39 mentioned above will be explained in detail. In this case, the semiconductor layer 39a having a multiple quantum well structure is made of Ga.
It has a layer structure of As/ALGaAs=60 people/60λ, and the disordered portion 39b is originally a GaAs/A1GaAs multiple quantum well structure semiconductor layer, but this region is disordered by introducing n-type impurities into it. This was obtained by converting the The semiconductor laser array section 11 having such a configuration normally operates stably in the 18° phase mode.

■...Description of phase shifter section 21 Next, the detailed structure of the phase shifter section 21 will be explained.

The difference between the phase shifter section 21 and the semiconductor laser array section 11 is that it does not have any of the n-type electrode 49, the n-type electrode 47, and the current confinement layer 451Fr formed by injecting H+ oil. Therefore, the optical waveguides 23a to 2 of the phase shifter section 21
3d and 25a to 25c serve only as optical waveguides. Another difference is the structure of the semiconductor layer 39. That is, in order to provide a phase shift to the optical output from each optical waveguide 13 of the semiconductor laser array section 11, the semiconductor layer 3
9 each of the optical waveguides 25a to 25c (the corresponding portion 39a
is made of a multi-quantum well structure semiconductor layer itself, and the portion 39c corresponding to the other optical waveguides 23a to 23d is made of a multi-quantum well structure semiconductor layer disordered to have a predetermined refractive index. Similarly to the semiconductor laser array section 11, the space between each optical waveguide is filled with a disordered portion 39b of a semiconductor layer having a multi-1N well structure. Note that the refractive index of the disordered portion indicated by 39c is
Each disorder is made so that the refractive index becomes smaller than that of the disordered portion shown by 39b, so that the desired optical confinement can be achieved.

According to the phase shifter section 21 having the structure as described above, it is possible to generate a refractive index difference of about 1% between adjacent optical waveguides. For example, when the emission wavelength of the laser array is 0.83 am, a refractive index difference of about 0.03a occurs between the optical waveguide shown by P and the optical waveguide shown by Q in FIG. 1(B). In this case, the phase of the light in the optical waveguide P is delayed from the light in the optical waveguide Q by π for each length of the optical waveguide of approximately 70 um. Therefore, the length of each optical waveguide of the phase shifter 21! If you keep it around 70um, it will be 1
The light emitted from the semiconductor laser array unit 118 in the 8o phase mode becomes the 0° phase mode in which the light has the same phase at the output end face (which is also the end face of the phase shifter unit 21).

Regarding the phase shift and the structure of the part, if the refractive index difference between each optical waveguide provided in this is small and the total length is a certain length, and the phase can be changed by T[1]. Other structures may also be used.

Further, in the laser array of the embodiment, the semiconductor layer 39L
Although it is provided above the active layer 35 when viewed from the GaAs substrate 31 side, it is clear that it may be provided between the active layer 35 and the GaAs substrate 31 in principle. Further, in the embodiment, a cladding layer 3 is provided between the semiconductor layer 39 and the active layer 35.
However, depending on the design, this cladding layer 37 may be omitted.

Next, an embodiment of the method for manufacturing a phase-locked semiconductor laser array according to the second invention will be explained using an example of manufacturing the laser array shown in FIG. Figures 2 (A) to (C) show the state of the laser array at the main steps in the manufacturing process.
3 is a cross-sectional view taken along the line 1--2 in FIG.

First, a process of forming a semiconductor layer having a multiple quantum well structure, which is common to the semiconductor laser array section and the phase shifter section and is in contact with the active layer via a cladding layer or directly in contact with the active layer, will be described. This embodiment shows an example in which a semiconductor layer having a multiple quantum well structure is in contact with an active layer through a cladding layer, and the semiconductor layer having a multiple quantum well structure is located above the active layer when viewed from the substrate side.

On the n-type GaAs substrate 31, n-type A'; L 6.5 Gao, , As
Cladding layer 33, active layer 35, p-type Ato, 3G
ao, ? AS cladding layer 37 and p-type AllGaA
A semiconductor layer 39 having an s/GaAs multiple quantum well structure is grown in this order.

Next, a process of introducing impurities into regions of this semiconductor layer 39 other than the regions where optical waveguides are to be formed in the semiconductor laser array section 11 and phase shifter section 21 described above to disorder the regions will be described.

In this embodiment, the semiconductor layer 39 having a multiple quantum well structure is
A mask pattern, for example, a mask pattern 51 as shown in FIG. 3(A), is formed to prevent introduction of impurities on regions where disorder is not desired, that is, regions that will become part of the optical waveguide of the semiconductor laser section 11 and the phase shifter section 21. 0, p-type A (lGaAs/GaAs semiconductor layer 3) with multi-quantum well structure
9, an n-type impurity is ion-implanted. As a result, the n-type impurity is implanted into the region exposed from the mask pattern 51 of the semiconductor layer 39.Next, this wafer is subjected to heat treatment under predetermined conditions to disorder the region into which the impurity has been introduced. A type AuGaAs cladding layer 39b is formed.

Next, every other region of the multi-quantum well structured semiconductor layer 39 corresponding to the regions where each optical waveguide of the above-mentioned phase shifter section 21 is planned to be formed, that is, corresponds to the optical waveguides indicated by 23a to 23d. The process of introducing impurities into a region to disorder the region will be explained.

In this embodiment, the semiconductor layer 39 having a multiple quantum well structure is
A mask pattern 53 for preventing impurity introduction on regions other than the regions corresponding to the optical waveguides shown by 23a to 23d, for example, a mask pattern 53 as shown in FIG. Type A included GaAs/GaA
N-type impurity ions are implanted into the s-semiconductor layer 39. As a result, the n-type impurity is implanted into the region exposed from the mask pattern 53 of the semiconductor layer 39.Next, this wafer is subjected to heat treatment under predetermined conditions to disorder the region into which the impurity has been introduced. A part 39c of the optical waveguide having a different refractive index from the optical waveguide shown by 25c is formed.

Thereafter, a semiconductor layer 19 is formed using a conventionally known crystal growth technique.
A p-type/II (1, Jao, 6AS cladding layer 41) and a p-type GaAs contact layer 43 are grown in this order thereon. Next, a current confinement layer 45 is formed by a conventionally known proton injection method.Furthermore, An n-type GaAs substrate 3 is formed using a conventionally known film forming technique and)
An n-type electrode 47 and an n-type electrode 49 are formed on the lower side of the p-type GaAs contact layer 43 and the p-type GaAs contact layer 43, respectively. Roughly,
The amount of sugar was measured at a predetermined position on the GaAs substrate.
A laser array shown in C) is obtained.

Note that the first and second inventions of this application are not limited to the above-described embodiments, and can be modified in various ways, such as those described below.

Each of the above embodiments has been explained using an example in which the substrate is an n-type GaAs substrate, but in this invention, the substrate is a p-type Ga^S and the conductivity type of each semiconductor layer is the opposite conductivity type from that in the embodiment. Even in this case, the same effect as in the embodiment can be obtained.

Also, if the multi-quantum well structure p-type, 4uGaAs/G
When the aAs semiconductor layer 39 is provided on the GaAs substrate 31 side of the active layer 35, the process order is different from that in the embodiment.

However, since the change is easy, the explanation thereof will be omitted.

Further, each of the above-mentioned embodiments describes the present invention as AQGaAs/GaAs.
An example of application to an As-based semiconductor laser is explained. However, it is clear that the present invention can also be applied to semiconductor laser arrays constructed of other materials.

Furthermore, although each embodiment is described using a laser array having seven optical waveguides as an example, the number of optical waveguides is not limited to this example and can be changed according to the design. Furthermore, it is clear that the width W of the optical waveguide and the interval W2 between the wA optical waveguides may be changed depending on the design.

(Effects of the Invention) As is clear from the above explanation, according to the phase-locked semiconductor laser array of the present invention, a novel phase shifter that has not been seen before is integrated in the semiconductor laser array section that oscillates in a 180° phase mode. By doing so, the optical output from the semiconductor laser array section can be emitted as optical output in the O° phase mode. Furthermore, since this phase shifter section is not provided on the output end face, it is easy to manufacture.

In general, according to the phase shifter unit according to the present invention, the refractive index of the optical waveguide provided therein can be set so that the amount of phase change per unit length of the optical waveguide is small. Therefore, even if the dimensions of the optical waveguide slightly deviate from the desired dimensions due to variations in processing accuracy during processing such as opening the opening, the amount of phase shift can be reduced, making it easier to obtain a desired phase shifter section.

Furthermore, the semiconductor laser array section of this invention has a diameter of 180 mm.
Since it is necessary to stably oscillate in the ° phase mode, there is an advantage that there is basically no need to consider cutting off higher-order modes. In general, up to high output 1
Since it is easy to manufacture a phase-locked semiconductor laser array that stably oscillates in the 80° phase mode, it is also easy to form a semiconductor laser section that oscillates in the 180° mode.

Further, according to the method for manufacturing a phase-locked semiconductor laser array of the present invention, by selectively disordering a predetermined region of a semiconductor layer having a multiple quantum well structure, the semiconductor laser array section and the above-mentioned phase shifter section can be easily fabricated. It can be formed into

[Brief explanation of the drawing]

FIG. 1(c) is a plan view providing an explanation of an embodiment of the phase-locked semiconductor laser array of the present invention; FIG.
1(C) is a cross-sectional view for explaining the semiconductor laser array section included in the phase-locked semiconductor laser array of the embodiment, and FIG. 2(A) to 2(C) are manufacturing process diagrams for explaining an embodiment of the method for manufacturing a phase-locked semiconductor laser array of the present invention, and FIGS. 3(A) and 3(B) are sectional views. It is a figure provided for explanation of the mask pattern used in the manufacturing method of an Example. 10... Phase-locked semiconductor laser array + 1-...
Semiconductor laser array section 13...optical waveguide, +5-/end face reflection film 2
1... Phase shifter sections 23a to 23d... Optical waveguide 25 including disordered regions
a to 25c... Optical waveguide 31 - n-type GaAs substrate 33 - n-type A (105Gao, 5AS crat layer 3
5...Active layer 37/p-type A9o, 5Gaa, 7AS cladding layer 3
9-... Semiconductor layer 39a - p-type A9GaAs/G with multiple quantum well structure
aAs layer (part of optical waveguide) 39b, 39c...Disordered region 41 of semiconductor layer with multiple quantum well structure -p type A'no, aGao, eAs crat layer 43...p+ type GaAs contact layer 45.・H+
Current confinement layer by injection 47...n-type electrode, 49...n-type electrode 51
．． 53...Mask pattern. Patent Applicant: Oki Electric Industry Co., Ltd. 10: Phase-locked semiconductor laser array 11: Semiconductor laser array section 13: Optical waveguide 15: End face reflection film 21: Phase shifter sections 25a to 25c: Optical waveguide embodiment - Description of laser array 9X1 (A) 31: n-type GaAs substrate 37: p-type ALo, 5Gao, 7AS cladding layer 3
9: Semiconductor layer 39a: p-type A9GaAs/GaA with multiple quantum well structure
s layer (part of optical waveguide) 41: p-type ALU, 4Gao, sAs cladding layer 4
3: p+ type GaAs contact layer 45: current confinement layer by H◆ injection 47: n type electrode 49: n type electrode Cross-sectional view for explaining the semiconductor laser array part of the embodiment (
C) Diagrams for explaining the phase shifter section of the embodiment (C)

Claims (2)

[Claims] (1) A semiconductor laser array section that oscillates in a 180° phase mode and has a plurality of optical waveguides, and a phase shifter section that has the same number of optical waveguides as the semiconductor laser array section, each optical waveguide being composed of a semiconductor layer; A phase shifter section in which the refractive index of each optical waveguide is different from that of an adjacent optical waveguide, and an optical axis of each optical waveguide of the phase shifter section and the optical axis of each optical waveguide of the semiconductor laser array section. What is claimed is: 1. A phase-locked semiconductor laser array, characterized in that it is arranged such that its axes are substantially on the same line. (2) A semiconductor laser array section having a plurality of optical waveguides and oscillating in a 180° phase mode, and a phase shifter section having the same number of optical waveguides as the semiconductor laser array section, each optical waveguide being composed of a semiconductor layer; A phase shifter section in which the refractive index of each optical waveguide is different from that of an adjacent optical waveguide is connected between the optical axis of each optical waveguide of the phase shifter section and the optical axis of each optical waveguide of the semiconductor laser array section. In manufacturing a phase-locked semiconductor laser array having axes substantially on the same line, a semiconductor layer that is common to the semiconductor laser array section and the phase shifter section, and that is formed through an active layer and a cladding layer. a step of forming a semiconductor layer having a multi-quantum well structure that is in contact with or in direct contact with the semiconductor layer; and a step of introducing impurities into every other region of the semiconductor layer corresponding to the regions where each optical waveguide of the phase shifter section is to be formed, thereby making the region disordered. A method of manufacturing a phase-locked semiconductor laser array, comprising: