JPH05167181A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an optical semiconductor device which is excellent in coherence characteristics and free from light intensity deterioration. CONSTITUTION:Since an endless waveguide 19 having a plurality of reflecting surface is arranged, the light generating type waveguide length can be made sufficiently long. Hence laser light which oscillates in the waveguide 19 as a resonator can be obtained as follows; a prism 20 is formed on a reflecting surface which prism reflects the greater part of light and transmits a part of light, and light is made to circulate in the waveguide 19. The resonator length can be made sufficiently long, so that coherence characteristics of laser light can be improved. When the greater part of light is transmitted by the prism 20, the waveguide 19 turns to an active region for optical amplification, and large output amplified by the sufficiently long waveguide 19 can be led out from the prism 20 with high efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device which can be used as a laser oscillator, an optical amplifier, an optical demultiplexer or the like.

[0002]

2. Description of the Related Art FIG. 13 shows the structure of a semiconductor laser as an example of a conventional optical semiconductor device. From the figure, the semiconductor laser 1
00 forms a waveguide 103 in the heteroepitaxial crystal 102 grown on the GaAs substrate 101, and oscillates a laser beam by passing a current through both ends of the semiconductor laser 100.

When the semiconductor laser 100 is used as a light amplifying element, the cleaved end face is coated with a non-reflective film to introduce light from the outside into the waveguide.
Then, a current is applied to both ends of the semiconductor laser 100 in synchronization with this light, thereby increasing the gain of the waveguide and amplifying the incident light.

Next, another conventional example of an optical semiconductor device is shown in FIG.
Shown in. As shown in the figure, a ring-shaped waveguide is formed in the semiconductor laser 110, and laser oscillation and light amplification are performed by passing a current between the electrodes. Since the semiconductor laser 110 is a laser diode having an infinitely long resonator length, the coherence characteristic is improved.

[0005]

By the way, the conventional semiconductor laser 100 is limited to two laser light emitting surfaces, and the cavity length cannot be made very long. Therefore, it is necessary to improve the coherence characteristics. An external mirror was needed.
Therefore, the structure becomes complicated, which is a problem.

Further, in the conventional semiconductor laser 110, since the laser light travels in the ring-shaped waveguide, the light easily leaks to the outside. Therefore, the light intensity is reduced, and the light intensity of the output light is reduced. Moreover, the method of extracting the output light from the ring-shaped waveguide is also a difficult problem.

The present invention aims to solve such a problem.

[0008]

In order to solve the above-mentioned problems, an optical semiconductor device of the present invention comprises an endless waveguide having a plurality of reflecting surfaces, and causes the waveguide to emit light by passing an electric current.

[0009]

According to the optical semiconductor device of the present invention, since the endless waveguide having the plurality of reflecting surfaces is provided, the length of the light generating type waveguide can be made sufficiently long. For this reason, when a prism is provided on a certain reflecting surface to allow most of the light to be reflected while part of the light is transmitted, the light circulates in the waveguide,
Laser light that oscillates using the waveguide as a resonator can be obtained. Since the cavity length can be made sufficiently long, the coherence characteristic of laser light is improved.

On the other hand, when most of the light is transmitted by the prism, the waveguide becomes an active region for optical amplification, and a large output amplified by the sufficiently long waveguide can be efficiently extracted from the prism.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical semiconductor device of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing the structure of the optical semiconductor device of this embodiment. From the figure, in the optical semiconductor device 10 of the present invention, the GaAlAs layer 12 which is the n-type cladding region on the n-type GaAs substrate 11 is
On the aAlAs layer 12, for example, a GaAs-based active layer 13 having a multiple quantum well structure, which is an active region, is formed on the active layer 13.
Type GaAlAs layers 14 that are clad regions are epitaxially formed, and so-called GaAs / A
It has a structure called a 1-GaAs type double heterojunction. Furthermore, n-type GaA is formed on the GaAlAs layer 14.
The s layer 15 is formed epitaxially, the p-side electrode 16 is formed on the GaAs layer 15, and the n-side electrode 17 is formed on the back surface of the GaAs substrate 11. The GaAs layer 15 is doped with a P-type additive to form ap ⁺ diffusion region 18.

By adopting such a structure, electrons and holes injected from the GaAlAs layer 12 and the GaAlAs layer 14 sandwiching the active layer 13 have a low bandgap energy, and the active layer 13 becomes a potential well. Can be efficiently confined. Further, the p ⁺ diffusion region 18 is formed on the (0-1-1) plane which is a cleavage plane with respect to the (100) plane of the GaAs substrate 11 or on the square plane cleaved from the (0-1-1) plane, respectively. Is a square stripe structure that is in contact with the side at an angle of 45 degrees (-1 in the crystal plane coordinates indicates the negative direction of the crystal axis). Then, the injected carriers in the p ⁺ diffusion region 18, p ⁺ diffusion region 18
Lateral optical confinement is performed in the lower active layer 13 by the gain guide method. Further, a desired protective film is formed on each cleaved end face. By this protective film, most of the laser light reaching the cleaved end face is totally reflected.

The operation of the optical semiconductor device 10 is as follows. First, when a current is passed between the p-side electrode 16 and the n-side electrode 17, light is generated in the waveguide 19. Since the waveguide 19 is an endless waveguide having a plurality of reflecting surfaces, the length of the light-generating waveguide can be made sufficiently long. Therefore, when a prism 20 such as a resin glass or a crystal is provided on a certain reflecting surface so that a part of the light is transmitted while reflecting most of the light, the light circulates in the waveguide 19 and Laser light oscillating with 19 as a resonator is obtained. Since the cavity length can be made sufficiently long, the coherence characteristic of laser light is improved.

On the other hand, when most of the light is transmitted by the prism 20, most of the light generated in the waveguide 19 is output from the prism 20 without circulating. Therefore, the waveguide 19 can be used as an active region for optical amplification, and since the waveguide length is sufficiently long, a large optical output can be efficiently extracted from the prism 20.

Next, an example of extracting the laser light from the cleaved end face is shown in FIG. FIG. 2A shows a predetermined cleavage end face (hereinafter,
This is an example of emission when the prism 20 is provided such that the light output portion of the light extraction surface) and one side (excluding the oblique side) of the prism 20 are aligned. Further, FIG. 2B is an emission example in the case where the prism 20 is provided with the light extraction surface and the hypotenuse of the prism 20 aligned. Further, FIG. 2C shows the prism 2
In this example, instead of 0, resins having a refractive index intermediate between the refractive index of air and the protective film of the cleaved end face or the refractive index of the crystal are provided on the light extraction surface. In particular, when the reflectances of the three cleaved end faces other than the light extraction face are increased, all of them are totally reflected at a critical angle or more, so that a laser property with good coherence characteristics with little loss of light intensity at the end face can be obtained. .

Next, application examples in which the optical semiconductor device 10 of this embodiment is used as an optical amplifier and a demultiplexer will be described with reference to FIGS.
Will be explained. FIG. 3A shows prisms 21 to 2 each having an isosceles right triangle on each surface of the cleaved end surface of the optical semiconductor device 10.
It is an example in which 4 is attached. In particular, FIG. 3 shows that the non-slope surface of the prism 21 and the cleaved end surface are optically coupled.
Different from the example of (b). First, while keeping the waveguide 19 through which light propagates active, the entrance / exit window 21a of the prism 21
An optical signal is incident on. This optical signal is amplified by stimulated emission in the waveguide 19a, and a part thereof is emitted from the emission window 22a of the prism 22. The other optical signals are reflected to be amplified by the waveguide 19b, a part of which is emitted from the emission window 23a of the prism 23, and the other optical signals are reflected to form the waveguide 1
Proceed to 9c. Similarly, the optical signal is transmitted through the waveguides 19c and 19c.
The light is amplified at d and emitted from the emission window 24 a of the prism 24 and the incident / emission window 21 b of the prism 21. Also,
When an optical signal is made incident through the entrance / exit window 21b of the prism 21, it is amplified by the waveguide 19 and exits the exit windows 24b, 23b, 2 and 2.
2b and the entrance / exit window 21a, respectively. Thus, since one optical signal is demultiplexed in four directions while being amplified, the optical semiconductor device 10 of this embodiment can be used as an optical amplification type demultiplexer. Moreover, since the optical signal incident on the input / output window 21a goes around the waveguide 19 and is output from the input / output window 21b, the output signal can be fed back.

FIG. 3B is also an example in which prisms 21 to 24 each having an isosceles right triangle are attached to each surface of the cleaved end surface of the optical semiconductor device 10. This example is different from the example of FIG.
The inclined surfaces of the prisms 21 to 24 and the cleaved end surface are optically coupled. The optical signal incident on the entrance / exit window 21a is
The light is amplified by the waveguide 19 and demultiplexed into four directions, and the output window 22
Light is emitted from a, 23a, 24a and the entrance / exit window 21b, respectively. In addition, the optical signal incident on the entrance / exit window 21b is
The light is amplified by the waveguide 19 and is demultiplexed in four directions, and the output window 24
b, 23b, 22b, and the entrance / exit window 21a, respectively. Further, it is also possible to calculate two signals by matching the incident timings of the optical signal incident on the incident / exit window 21a and the optical signal incident on the incident / exit window 21b.

Similarly to the example of FIG. 3B, FIG. 4 also shows an example in which prisms 21 to 24 of an isosceles right triangle are attached to each cleaved end face of the optical semiconductor device 10. This is an application example of a laser light source that emits laser light generated by flowing a current between both electrodes in eight directions. With this device, the optical signal can be used more effectively.

FIG. 5 shows an example in which three waveguides are arranged in parallel. In this example, the number of laser beams emitted from the prism 20 is six. If a prism is provided on each end face, the total number of emitted laser beams will be 24.

FIG. 6 shows an example in which two optical semiconductor devices 30 and 31 are optically coupled into an array and prisms 32 to 37 are provided on each cleaved end face. First, the optical signal that has entered the input / output window 32a of the prism 32 is amplified by the waveguides 38 and 39 and is demultiplexed into six directions, and the output windows 37a, 36a and 33 are formed.
Light is emitted from a, 34a, 35a and the entrance / exit window 32b, respectively. Further, the optical signal incident on the input / output window 32b is amplified by the waveguides 38 and 39 and is demultiplexed in six directions, and the output window 35 is formed.
b, 34b, 33b, 36b, 37b, input / output window 32a
Is emitted from each. In this way, by forming an array of a plurality of optical semiconductor devices, the optical signal can be demultiplexed in many directions.

FIGS. 7A and 7B show an example in which two optical semiconductor devices 40 and 41 having prisms are vertically joined to form a stack. In this example, the four corners of the optical semiconductor device 40 and the optical semiconductor device 41 are molded in the shape of an isosceles right triangle, and this portion is used as a prism. Specifically, the optical semiconductor device 40 and the optical semiconductor device 41
Face each other and join them so that their prisms mesh with each other. The laser light generated in the optical semiconductor device 40 is emitted from the prism portion of the optical semiconductor device 41, and the laser light generated in the optical semiconductor device 41 is emitted from the prism portion of the optical semiconductor device 40. The emission state of such an optical signal is shown in FIG.

Next, the detailed structure of the optical semiconductor device of this embodiment is shown in FIGS. FIG. 9 is a perspective view showing the structure of the mesa type optical semiconductor device 50. From the figure, in the optical semiconductor device 50, the GaAlAs layer 52, which is an n-type cladding region, is formed on the n-type GaAs substrate 51, the GaAs-based active layer 53, which is an active region, is formed on the GaAlAs layer 52, and the active layer 53. A GaAlAs layer 54 which is a p-type clad region is formed on the upper surface, and a p-type GaAs layer is formed on the GaAlAs layer 54.
Layers 55 are each epitaxially formed. A p-side electrode 56 is formed on the GaAs layer 55, and an n-side electrode 57 is formed on the back surface of the GaAs substrate 51.

FIG. 10 is a perspective view showing the structure of an optical semiconductor device 60 of the mesa type and the electrode separation type. From the figure, in the optical semiconductor device 60, the GaAlAs layer 62, which is an n-type cladding region, is formed on the n-type GaAs substrate 61, the GaAs-based active layer 63, which is an active region, is formed on the GaAlAs layer 62, and the active layer 63 is formed. A GaAlAs layer 64, which is a p-type cladding region, is formed on the upper surface, and a p-type GaAs layer is formed on the GaAlAs layer 64.
Layers 65 are each epitaxially formed. Further, on the GaAs layer 65, the p-side electrodes 66 and 67 are formed of Ga.
N-side electrodes 68 are formed on the back surface of the As substrate 61, respectively. The power of the laser output can be controlled by the amount of electricity supplied to the p-side electrode 66.

FIG. 11 is a perspective view showing the structure of a buried step growth type optical semiconductor device 70. As shown in the figure, the optical semiconductor device 70 has an n-type Ga on a p-type GaAs substrate 71.
As layer 72, GaAlAs layer 73 which is a p-type cladding region on GaAs layer 72, GaAs active layer 74 which is an active region on GaAlAs layer 73, and active layer 74.
A GaAlAs layer 75, which is an n-type cladding region, is formed on the
Further, an n-type GaAs layer 76 is epitaxially formed on the GaAlAs layer 75. Also, GaA
An n-side electrode 77 is formed on the s layer 76, and a p-side electrode 78 is formed on the back surface of the GaAs substrate 71.

FIG. 12 is a perspective view showing the structure of a buried step growth type and electrode separation type optical semiconductor device 80. From the figure, in the optical semiconductor device 80, the n-type GaAs layer 82 is formed on the p-type GaAs substrate 81, and the GaAlAs layer 83, which is the p-type cladding region, is formed on the GaAs layer 82.
A GaAs-based active layer 84 which is an active region on the s layer 83
Is an n-type cladding region of GaAl on the active layer 84.
The As layer 85 is formed on the GaAlAs layer 85 by n-type G
The aAs layers 86 are epitaxially formed. Further, on the GaAs layer 86, n-side electrodes 87, 88
However, p-side electrodes 89 are formed on the back surface of the GaAs substrate 81, respectively. The power of the laser output can be controlled by the amount of electricity supplied to the n-side electrode 87.

As described above, the optical semiconductor device of this embodiment enables a large number of laser oscillations, amplifications, and branches. By using an optical material or a superlattice multi-layer crystal of the same crystal for the emitting portion (prism) of the emitting end surface of the optical semiconductor device of this embodiment, it is possible to function as an on / off switch for emitted light.

[0027]

According to the optical semiconductor device of the present invention, when a prism is provided on a certain reflecting surface to reflect most of the light, the waveguide functions as a resonator having a sufficiently long resonator length. You can Therefore, it is possible to oscillate laser light having good coherence characteristics. Further, if most of the light is transmitted by the prism, the waveguide can function as an active region for light amplification with a sufficiently long optical path length. Therefore, it is possible to output an optical signal having a high amplification factor.

Therefore, the optical semiconductor device of the present invention is effective when applied to an optical oscillator, a light receiver, an amplifier, a branch signal calculator, and the like. In particular, LAN (Local Area Network)
rk) has a high utility value as an optical device.

Further, in the optical semiconductor device of the present invention, since two laser beams having different traveling directions travel as a ring laser in the device, the device is rotated to measure the phase difference between the clockwise and counterclockwise directions. Can be used as a light source for an optical gyro.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of an optical semiconductor device of this embodiment.

FIG. 2 is a plan view showing how to take out laser light.

FIG. 3 is a plan view showing an application example of the present embodiment.

FIG. 4 is a plan view showing an application example of the present embodiment.

FIG. 5 is a plan view showing an application example of the present embodiment.

FIG. 6 is a plan view showing an application example of the present embodiment.

FIG. 7 is a perspective view showing an application example of the present embodiment.

FIG. 8 is a plan view showing an application example of the present embodiment.

FIG. 9 is a perspective view showing a detailed structure of an optical semiconductor device of this example.

FIG. 10 is a perspective view showing a detailed structure of an optical semiconductor device of this example.

FIG. 11 is a perspective view showing a detailed structure of an optical semiconductor device of this example.

FIG. 12 is a perspective view showing a detailed structure of an optical semiconductor device of this example.

FIG. 13 is a perspective view showing the structure of a conventional semiconductor laser.

FIG. 14 is a perspective view showing the structure of a conventional semiconductor laser.

[Explanation of Codes] 10 ... Optical semiconductor device, 11 ... GaAs substrate, 12 ... Ga
AlAs layer, 13 ... Active layer, 14 ... GaAlAs layer, 1
5 ... GaAs layer, 16 ... P-side electrode, 17 ... N-side electrode, 1
8 ... p ⁺ diffusion region, 19 ... Waveguide, 20 ... Prism.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Matsui 1 1126, Nomachi, Hamamatsu City, Shizuoka Prefecture 1126 Hamamatsu Photonics Co., Ltd. (72) Hirofumi Miyajima 1126, 1126 Ichinocho, Hamamatsu City, Shizuoka Prefecture Hamamatsu Photonics Within the corporation

Claims (5)

[Claims] 1. An optical semiconductor device, comprising an endless waveguide having a plurality of reflecting surfaces, wherein the waveguide is caused to emit light by passing an electric current. 2. The optical semiconductor device according to claim 1, wherein a prism is provided on at least one of the reflecting surfaces. 3. The optical semiconductor device according to claim 1, wherein the planar shape of the waveguide is a polygon. 4. The prism is provided with an electrode, and a refractive index of light incident on the prism is changed by applying a voltage to the electrode. Optical semiconductor device. 5. A plurality of electrodes are provided in the vicinity of the waveguide, and the electric field strength of the waveguide is controlled by applying a voltage to a desired electrode.
5. The optical semiconductor device according to claim 4.