JPS607791A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To vary the radiation pattern individually by providing a branch wave- guide path for separating a part of the laser beam wave-guided into the main wave-guide path and emitting it outward and by providing an accepted light phase modulation part for varying the phase of the laser beam in a part of said branch path. CONSTITUTION:An n type main wave-guide path 11 is formed into a stripe form on a part of the main plane of the clad layer 2 on an n type crystal substrate 1 to wave-guide a laser beam. A p type active layer 3a is formed on the main plane of the wave-guide path 11 and n type branch wave-guide paths 12a and 12b are formed on the part on the both sides of the wave-guide path 11 on the main plane on the layer 2. The paths 12a and 12b connect with the wave-guide path 11 optically on the side of the end F2 and separate and emit a part of the laser beam from another side of the end F1. Each of the wave-guide paths 12a and 12b is provided with the accepted light phase modulation parts 13a and 13b for varying the phase of the laser beam emitted outward. Furthermore, drive electrodes 14a and 14b are formed corresponding to the modulation parts 13a and 13b to easily vary the pattern of emission toward the outside individually a part from the emission output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor laser element used as a light source for optical communication, optical information processing, etc.

[Prior art]

FIG. 1(A) is a plan view showing an example of a conventional semiconductor laser device, and FIG. 1(B) is a sectional view taken along a stranded line in FIG. 1(A).

In the figure, (1) is an n-type crystal substrate, (2), (3
) and (4) are an n-type rad layer, a p-type active layer, and a p-type active layer formed sequentially on the main surface of the n-type crystal substrate (1), respectively.
shaped rad layer, (5) is an insulating film formed on the main surface of p-shaped rad layer (4), (6) is a part of insulating film (5) formed with the p-shaped rad layer (4). End face F shown in Figure 1 (A)
1 to the end face F2 facing back to the end face F1, and (7) is the main opening formed in the shape of a drive, and (7) is the insulating film (5
) is a branch opening formed in a part other than the forming part of the main opening (6) from a part of the main opening (6) in the longitudinal direction and reaching the end surface F1, (8) is an insulating film ( 5)
The insulating film is passed over the part of the p-shaped rad layer (4) facing the main opening (6) from above the part of the surface of the main opening (6) opposite to the branch opening (7) side. The main anode (9) is formed so as to reach a part of the branch opening (7) side with respect to the main opening (6) on the surface of the insulating film (5). 6) Regarding the branch opening (
7) on the side part and the branch opening of the p-shaped rad layer (4) (
A branch anode is formed over the portion facing 6) so as not to contact the main anode (8), and 00 is a common cathode formed on the main surface of the n-type crystal substrate (1). (I) When a forward voltage is applied between the main anode (8) and the common cathode αO, the forward current is concentrated in the part of the p-type active layer (3) corresponding to the main opening (6). When a forward voltage is applied between the branch anode (9) and the common cathode section, the main element part (IT) that generates laser oscillation generates a forward current that flows through the branch opening (7) of the p-type active layer (3). ) is a branching element portion where the flow is concentrated in the portion corresponding to the laser beam and oscillates as a laser beam.

In the conventional example configured in this way, the portion of the p-type active layer (3) corresponding to the portion between the end surface F2 and the portion where the branch opening (7) of the main opening (6) branches is the main element. Part (1
) and the branching element section (II), the laser beams oscillated by these element sections (I) and (If) pass through the common gain medium, so that the optical The coupling is performed, and these element parts (I) and (II
The laser beams emitted from the end face F1 of ) have a predetermined phase relationship, and a desired radiation pattern is obtained by their interference.

However, by changing the forward current of the branch element part (n) of the pixel element parts (1) and (H), for example, the branch element part (I
When trying to change the radiation output of the branching element (II), the carrier concentration of the gain medium of the branching element (II) changes due to a change in the forward current of the branching element (II), causing a change in the refractive index. This change in refractive index occurs in the branching element part (II
) changes the wavelength of the oscillated laser light, the phase relationship of the laser light emitted to the outside of the pixel elements (1) and (n) changes, and the radiation pattern changes. Moreover, even when trying to change the radiation output of the main element part (1) by changing the forward current of the main element part (1), the branch element part (
The radiation pattern changes as in case II). Also,
Contrary to the above case, when trying to change the radiation pattern, it is necessary to change the phase relationship of the laser beams emitted to the outside of the pixel elements (1) and (II).
The forward current of the main element part (1) or the branch element part (II) must be changed, and the radiation output of the main element part (1) or the branch element part (It) is changed by changing the forward current. Change.

In short, this conventional example has the drawback that it is not easy to change the radiation pattern independently of the change in radiation output.

[Summary of the invention]

This invention was made with the aim of eliminating such drawbacks, and the laser light oscillated by the active layer is optically coupled to the main waveguide and a part thereof to be radiated into four waves to the outside, thereby guiding the main waveguide. It has a branching waveguide that branches a part of the waving laser light and radiates it to the outside. The present invention provides a semiconductor laser device in which the radiation pattern can be changed independently of the radiation output by providing a variable passive optical phase modulation section.

[Embodiments of the invention]

FIG. 2(A) is a plan view showing a semiconductor laser device according to the first embodiment of the present invention, and FIG. 2(B) is a
-■ It is a cross-sectional view along the B line.

In the figure, the same reference numerals as those in the conventional example shown in FIG. 1 indicate equivalent parts. αυ is made of an n-type crystal layer, and is located on a part of the main surface of the n-type rad layer (2) from the end face F shown in FIG. The n-type main waveguide (3a) is formed in a stripe shape across the facing end face F2 and guides the laser light, and the n-type main waveguide (3a) is made of a p-type crystal layer and is formed so as to overlap the main surface of the n-type main waveguide αη. A p-type active layer that oscillates laser light (12a
) and (12b) are n-type crystal layers, and each side surface on one end side is an n-type main waveguide on both outer parts of the n-type main waveguide αυ on the main surface of the n-type rad layer (2). The n-type main waveguide is optically coupled to the side surface of the end on the end face F2 side of the waveguide αD and is formed so that the end face on the other end side is flush with the end face F1 of the n-shaped rad layer (2). (13a) first and second n-type branch waveguides that branch a part of the laser light guiding αυ and radiate it to the outside from the end face on the end face F1 side;
and (rsb) are p-type crystal layers, and a first an n-type branch waveguide (12a) and a second n-type branch waveguide (x2
b) are provided to form a pn junction between the first n-type branch waveguide [12a) and the second n-type branch waveguide (
(4a) is a p-type crystal layer and an n-shaped rad layer (2);
An n-type main waveguide αD and an n-type branch waveguide (12
a), (12b) and passive optical phase modulation section (13
a), (13b) is a p-type rad layer formed to cover the p-type rad layer (5a) is an insulating film formed on the main surface of the p-type rad layer (4a), (8a) is an insulating film (5a) ) through the part corresponding to the p-type active layer (3a)
i(4a)K main anode formed to be connected, (
14a) and (14blti) respectively insulating film (5a)
The first passive optical phase modulation section (13a) and the second passive optical phase modulation section (11) are formed so as to penetrate through the parts corresponding to the first passive optical phase modulation section (13a) and the second passive optical phase modulation section (11) and to be connected to the p-shaped rad layer (4a). This is a drive electrode that drives the passive optical phase modulation section (13a) and the second passive optical phase modulation section (13b). (Summer) is the main element part where when a forward voltage is applied between the main anode (8a) and the common cathode αO, a forward current flows concentratedly in the p-type active layer (3a) and oscillates as a laser.

Next, the operation of this embodiment will be explained.

Here, passive optical phase modulation sections (13a), (13b
) functions.

When a reverse bias voltage is applied between the drive electrodes (14a), (14b) and the common electrode 00, the n-type branch waveguide (
12a) + (12b) and passive optical phase modulation section (1
3a) and (13b), a depletion layer is formed in the portions of the n-type branch waveguides (12a) and (12b) that are in contact with the passive optical phase modulation sections (xsa) and (1sb). This depletion layer creates an n-type branch waveguide (xz
The refractive index of the depletion layer forming portion of a) and (xzb) changes. Let the amount of change in this refractive index be △n, and the n-type branch waveguide (1
The wavelength of the laser light guided by 2a) and (12b) is λ
and n of the passive optical phase modulators (13a) and (13b)
If the length in the direction along the branched waveguides (12a) and (1zb) is L, then the amount of change φ in the phase of the laser beam is given by the amount of change Δn in the refractive index as shown below.

φ=2π・L△n/λ For example, Δn = 0.0035, λ=Q, 13μ
m and L=23oμm, then φ=2π.

Now, with a required reverse bias voltage applied between the drive electrodes (14a), (14b) and the common electrode Qf, a forward current is caused to flow through the main element section (1).
When the laser beam is oscillated in the p-type active layer (3a), the laser beam oscillated in the p-type active layer is guided by the n-type main waveguide αυ, and a part of this laser beam is transmitted to the n-type branch waveguide (12
a) and (12b), and a passive optical phase modulator (13
a).

(13b) causes a required phase change, and the n-type branch waveguide (12a) is radiated to the outside from the end of the n-type main waveguide αυ (12b). It is radiated to the outside from the end face on the F1 side.Then, these n-type branch waveguides (12a), (12b) and n
A desired radiation pattern is obtained by interference of laser light emitted to the outside from the end face on the end face F1 side of the shaped main waveguide 0υ.

In this embodiment, when changing the radiation pattern, only the radiation pattern can be changed by changing the reverse bias voltage to the drive electrodes (14a) and (14b) without changing the radiation output. It can be changed. Therefore, when trying to change only the direction of radiation output, the radiation pattern also changes due to the change in the forward current to the main element section (1). Drive electrode (14a).

This can be easily eliminated by changing the reverse bias voltage to (14b).

In short, in this embodiment, it is possible to change the radiation pattern independently of the change in the radiation output. FIG. 3(B) is a cross-sectional view taken along the line ■B--■B of FIG. 3(A), and FIG. 3(0) is a cross-sectional view taken along the line ■c-4Hc of FIG. 3(A).

In the figure, the same reference numerals as those shown in FIGS. 1 and 2 indicate equivalent parts. Main waveguide Q
l), the side surface on one end side is optically coupled to the side surface on the end surface F2 side of the n-type main waveguide (11), and the other end side is the first part. (1201) and a second part (x2cz).
2C1), (12c2) is formed so that its end face is flush with the end face F1 of the n-shaped rad layer (2).
A part of the laser light guided by the 0υ type branch waveguide is branched to the end face of the first part (12cl) and the second part (1202).
An n-type branch waveguide radiating to the outside from the end face of (13c
l) and (13c2) are p-type crystal layers, and the first part ( The first part (12c2) is provided so as to form a pn junction between the first part (12cl) and the second part (12c2).
01) and the second part (12c2), the first and second passive optical phase modulators change the phase of the laser beam guided and radiated to the outside, αO is the n-type main waveguide 0υ
The laser light propagating through the n-type main waveguide αυ provided at the interface in contact with the n-type rad layer (2) is transmitted through the n-type main waveguide αυ.
It is a diffraction grating with wavy irregularities that prevents almost no radiation from being emitted to the outside from both end faces of υ.

In this embodiment, since almost no laser light is emitted to the outside from the end face of the n-type main waveguide (11) due to the diffraction grating α, the first portion (
A radiation pattern is obtained by interference of only the laser beams emitted from the end face of the second portion (12cl) and the end face of the second portion (12c2). Therefore, when changing the radiation output direction, n
Since almost no laser light is emitted from the end face of the shaped main waveguide (1), it is possible to minimize changes in the radiation pattern due to changes in radiation output.

Note that in the first embodiment, an n-type branch waveguide (12a
), , (12b), for example, the second n-type branch waveguide (12b) can be omitted, the same effect as in the first embodiment can be obtained, and the second n-type branch waveguide (12' Even if b) is omitted and the end portion of the first n-type branch waveguide (12a) on the end face F1 side is divided into two or more parts, the same effect as in the first embodiment can be obtained. In addition, in the second embodiment, an n-type branch waveguide (
Although the end face F of 12c) is divided into two, it may be divided into three or more parts.In addition, in the second embodiment, the laser beam is transmitted from the end face of the n-type main waveguide θη to the outside. A diffraction grating Q$ was used to reduce radiation, but the main element part (1
) may be made to have a sufficiently large reflectance.

In the first and second embodiments described above, the case where the junction formed between the passive optical phase modulator and the n-type branch waveguide is a pn junction, but the present invention is not limited to this. It can also be applied to key joints and M/S joints. 1. In the first and second embodiments above,
Although the case where an n-type crystal substrate is used has been described, the present invention is not limited thereto, and can also be applied to a case where a p-type crystal substrate is used. In this case, in the first and second embodiments, the n shadow area may be changed to the p shadow area, and the p shadow area may be changed to the n shadow area.

〔Effect of the invention〕

As explained above, in the semiconductor laser device of the present invention, the active layer is formed on the main surface, and the laser light oscillated by the active layer is guided and emitted to the outside through the main waveguide and a part thereof. It has a branching waveguide that is optically coupled and branches a part of the laser light guided by this main waveguide and radiates it to the outside, and a part of the branching waveguide is guided by this branching waveguide. Since a passive optical phase modulation section capable of changing the phase of the laser light emitted to the outside is provided, the radiation pattern formed by interference of the laser light emitted to the outside from the main waveguide and the branch waveguide, respectively, is changed. In this case, by changing the phase of the laser light guided in the branch waveguide by the passive optical phase modulation section, the radiation output of the laser light radiated to the outside from the main waveguide and the branch waveguide can be adjusted. It is possible to change only the radiation pattern without changing the radiation pattern. In short, changes in the radiation pattern can be made independently of changes in the radiation output.

[Brief explanation of the drawing]

FIG. 1(A) is a plan view showing an example of a conventional semiconductor laser device, FIG. 1(B) is a sectional view taken along line IB-IB of FIG. 1(A), and FIG. 2(A) is a plan view of this example. A plan view showing the semiconductor laser device of the first embodiment of the invention, FIG. 2(B) is similar to FIG.
), FIG. 3(A) is a plan view showing a semiconductor laser device according to a second embodiment of the present invention, and FIG. 3(B) is a cross-sectional view taken along line IIB-IB of FIG. 3(A). 3(0) is a sectional view taken along line -111B, and FIG. 3(0) is a sectional view taken along line ■0--■0 in FIG. 3(A). In the figure, (1) is an n-type crystal substrate (16th conductivity type crystal substrate), (2) is an n-type rad layer (first conductivity type cladding layer), and (3a) is a p-type active layer (16th conductivity type crystal substrate). 2 conductivity type activity 1
i1N), (4a) are p-type cladding layers (the second conductivity type cladding layer L (8a) is the main electrode, 00 is the common electrode, 01
) is an n-type main waveguide (first conductivity type main waveguide), (1
2a), (12b) and (2c) are n-type branch waveguides (branch waveguides of the second conductivity type), (1201) and (12c2) are the first branch waveguides from which the n-type branch waveguide (12Q) is divided. and the second part, (13a), (13b)
, (13cl) and (13c2) are passive optical phase modulators, (14a) and (14b) are drive electrodes, and (1G is a diffraction grating. In addition, the same reference numerals in the figures indicate the same or corresponding parts. Person Masuo Oiwa Figure 1 (A) (B) I II Figure 2 CB) 3rd iM ■(A) (Go) A

Claims (1)

[Scope of Claims] (1) A crystal substrate of a first conductivity type, a cladding layer of a first conductivity type formed on a main surface of this crystal substrate, and a portion on the main surface of this cladding layer of a first conductivity type. a main waveguide of the first conductivity type, which is formed in a stripe shape from a first end face of the cladding layer of the first conductivity type to a second end face directly opposite to the first end face, and through which the laser beam is guided; , an active layer of a second conductivity type that is formed on the main surface of the main waveguide and oscillates a laser beam;
A side surface of the main surface of the first conductivity type cladding layer on at least one outside of the main waveguide, and a side surface of the main waveguide on the second end surface side of the main waveguide. The main waveguide is optically coupled, and the other end side thereof is spaced apart from the main waveguide, and the end face thereof is flush with the first end face of the cladding layer of the first conductivity type. A branching waveguide of a first conductivity type that branches a part of the laser light guided by the waveguide and radiates it to the outside from an end face on the side of the first end face, and the first end face of the main face of the branching waveguide. a passive optical phase modulation section that is provided on the side end so as to form a junction with the branch waveguide and changes the phase of the laser light that is guided by the branch waveguide and radiated to the outside;
The main waveguide and the active layer are provided on the main surface of the cladding layer of the first conductivity type. A cladding layer of a second conductivity type formed to cover the branch waveguide and the passive optical phase modulation section; an electrode, a drive electrode formed on the main surface of the second conductivity type cladding layer at a portion corresponding to the passive optical phase modulation section and driving the passive optical phase modulation section, and formed on the main surface of the crystal substrate. A semiconductor laser device with a common electrode. (2) The semiconductor laser device according to claim 1, wherein the junction formed between the passive optical phase modulator and the branching waveguide is a pn junction. (3) The branching waveguide 3. The semiconductor laser device according to claim 1, wherein the end portion on the first end face side is divided into several pieces. (4) A diffraction grating is provided at the interface of the main waveguide in contact with the cladding layer of the first conductivity type so that most of the laser light guided through the main waveguide is not radiated to the outside from both end surfaces of the main waveguide. 4. A semiconductor laser device according to claim 3, further comprising a semiconductor laser device.