JP3238734B2 - Optical semiconductor device - Google Patents

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 that can be used as a laser oscillator, an optical amplifier, an optical demultiplexer, and the like.

[0002]

2. Description of the Related Art FIG. 13 shows a structure of a semiconductor laser as an example of a conventional optical semiconductor device. As shown in FIG.
In the case of 00, a waveguide 103 is formed in the heteroepitaxial crystal 102 grown on the GaAs substrate 101, and a laser beam is oscillated by applying a current to both ends of the semiconductor laser 100.

When the semiconductor laser 100 is used as an optical amplifying element, the cleavage end face is coated with a non-reflective film, and external light is introduced into the waveguide.
Then, by passing a current through both ends of the semiconductor laser 100 in synchronization with this light, the gain of the waveguide is increased and the incident light is amplified.

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 flowing a current between the electrodes. Since the semiconductor laser 110 is a laser diode having an infinitely long resonator, the coherence characteristics are improved.

[0005]

By the way, the conventional semiconductor laser 100 has a laser light emitting surface limited to two places, and the cavity length cannot be made too long. An external mirror was needed.
For this reason, the configuration becomes complicated and there is a problem.

In the conventional semiconductor laser 110, since laser light travels through a ring-shaped waveguide, light easily leaks to the outside. For this reason, the light intensity was reduced, and the light intensity of the output light was reduced. Also, a method of extracting output light from the ring-shaped waveguide is difficult and problematic.

An object of the present invention is to solve such a problem.

[0008]

In order to solve the above-mentioned problems, an optical semiconductor device according to the present invention comprises an endless waveguide having a plurality of reflection surfaces, and emits light by causing a current to flow in the waveguide. An apparatus, wherein a plurality of electrodes are provided near a waveguide, a voltage applied to a desired electrode controls an electric field intensity of the waveguide, and a prism provided on at least one reflection surface. Further comprising
An electrode is provided on the prism, and the refractive index of light incident on the prism is changed by applying a voltage to the electrode.

[0009]

According to the optical semiconductor device of the present invention, since the endless waveguide having the plurality of reflection surfaces is provided, the length of the light-generating waveguide can be sufficiently long. For this reason, if a prism is provided on a certain reflection surface so that a part of the light is transmitted while reflecting most of the light, the light circulates in the waveguide,
Laser light oscillating using the waveguide as a resonator is obtained. The coherence characteristic of the laser beam is improved because the resonator length can be made sufficiently long. Further, since a plurality of electrodes are provided near the waveguide, the electric field intensity of the waveguide can be controlled by applying a voltage to a desired electrode.

On the other hand, if most of the light is transmitted by the prism, the waveguide becomes an active region for light amplification, and a large output amplified by a sufficiently long waveguide can be efficiently extracted from the prism. Further, the refractive index of light incident on the prism can be changed by applying a voltage to an electrode provided on the prism.

An embodiment of the optical semiconductor device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing a structure of an optical semiconductor device of a reference example. As shown in the figure, in the optical semiconductor device 10 of the present invention, the GaAlAs layer 12 as an n-type cladding region
An active region, for example, a GaAs-based active layer 13 having a multiple quantum well structure is formed on the aAlAs layer 12 on the active layer 13.
A GaAlAs layer 14 serving as a cladding region of the mold type is formed epitaxially, and a so-called GaAs / A
It has a structure of an lGaAs double heterojunction. Further, on the GaAlAs layer 14, n-type GaAs
An s layer 15 is formed epitaxially. A p-side electrode 16 is formed on the GaAs layer 15, and an 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 a p + 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 band gap energy and are contained in the active layer 13 serving as a potential well. It can be confined efficiently. Further, the p ⁺ diffusion region 18 is formed on the (0-1-1) plane, which is the cleavage plane for the (100) plane of the GaAs substrate 11, or on the square plane cleaved from the (0-1-1) plane. (A -1 in the coordinates of the crystal plane indicates the negative direction of the crystal axis). Then, the injected carriers in the p ⁺ diffusion region 18, p ⁺ diffusion region 18
Light is confined in the lateral direction by a gain guide method in the lower active layer 13. Also, a desired protective film is formed on each cleavage end face. Most of the laser light reaching the cleavage end face is totally reflected by this protective film.

The operation of the optical semiconductor device 10 is as follows. First, when a current flows 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 sufficiently long. Therefore, if a prism 20 made of resin glass, crystal, or the like is provided on a certain reflection surface so that most of the light is reflected and some of the light is transmitted, light circulates in the waveguide 19, and Laser light oscillating with 19 as a resonator is obtained. The coherence characteristic of the laser beam is improved because the resonator length can be made sufficiently long.

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. For this reason, the waveguide 19 can be used as an active region for optical amplification, and the waveguide length is sufficiently long, so that a large optical output can be efficiently extracted from the prism 20.

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

Next, an application example in which the optical semiconductor device 10 of the reference example is used as an optical amplifier and a duplexer will be described with reference to FIGS. FIG. 3A shows right and isosceles triangular prisms 21 to 24 on each of the cleavage end faces of the optical semiconductor device 10.
This is an example in which is attached. In particular, the point that the non-inclined surface of the prism 21 is optically coupled to the cleavage end surface is shown in FIG.
This is different from the example of (b). First, while keeping the waveguide 19 through which light propagates in an active state, the entrance / exit window 21a of the prism 21
An optical signal is made incident on the substrate. 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. Other optical signals are reflected and amplified by the waveguide 19b, a part of the light is emitted from the exit window 23a of the prism 23, and other optical signals are reflected and reflected by the waveguide 1b.
Proceed through 9c. Similarly, optical signals are transmitted through the waveguides 19c and 19c.
After being amplified at d, the light is emitted from the exit window 24a of the prism 24 and the input / output window 21b of the prism 21. Also,
When an optical signal is incident from the entrance / exit window 21b of the prism 21, it is amplified by the waveguide 19 and exits from the exit windows 24b, 23b, 2b.
2b, the light is emitted from the entrance / exit window 21a. As described above, 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 entrance / exit window 21a goes around the waveguide 19 and exits from the entrance / exit window 21b, it is possible to feed back the exit signal.

FIG. 3B also shows an example in which prisms 21 to 24 each having a right-angled isosceles triangle are attached to each of the cleavage end faces of the optical semiconductor device 10. This example is different from the example of FIG.
Each inclined surface of the prisms 21 to 24 is optically coupled to the cleavage end surface. The optical signal incident on the entrance / exit window 21a is:
The light is amplified by the waveguide 19 and demultiplexed in four directions.
a, 23a and 24a, and the light exits from the entrance / exit window 21b. The optical signal incident on the entrance / exit window 21b is:
The light is amplified by the waveguide 19 and demultiplexed in four directions.
b, 23b, 22b, and the light exits from the entrance / exit window 21a. Furthermore, it is also possible to calculate two signals by matching the incident timing of the optical signal incident on the incident / exit window 21a with the incident timing of the optical signal incident on the incident / exit window 21b.

FIG. 4 shows an example in which prisms 21 to 24 each having a right-angled isosceles triangle are attached to each cleavage end face of the optical semiconductor device 10 as in the example of FIG. 3B. 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. Here, if a prism is provided on each end face, a total of 24 laser beams are emitted.

FIG. 6 shows an example in which two optical semiconductor devices 30 and 31 are optically coupled to form an array, and prisms 32 to 37 are provided on each cleavage end face. First, an optical signal incident on the entrance / exit window 32a of the prism 32 is amplified by the waveguides 38 and 39 and demultiplexed in six directions, and the exit windows 37a, 36a, 33
a, 34a, 35a, and the light exits from the entrance / exit window 32b. The optical signal incident on the entrance / exit window 32b is amplified by the waveguides 38 and 39 and demultiplexed in six directions.
b, 34b, 33b, 36b, 37b, entrance / exit window 32a
Respectively. Thus, by arraying a plurality of optical semiconductor devices, an optical signal can be split in many directions.

FIGS. 7A and 7B show an example in which two optical semiconductor devices 40 and 41 each having a prism are vertically joined and stacked. In this example, the corners in four directions of the optical semiconductor device 40 and the optical semiconductor device 41 are formed in the shape of a right-angled isosceles triangle, and this portion is used as a prism. Specifically, the optical semiconductor devices 40 and 41
And are joined so that the prisms of the two mesh with each other. Then, the laser light generated by the optical semiconductor device 40 is emitted from the prism portion of the optical semiconductor device 41, and the laser light generated by the optical semiconductor device 41 is emitted from the prism portion of the optical semiconductor device 40. FIG. 8 shows the state of emission of such an optical signal.

Next, FIGS. 9 and 11 show the detailed structure of an optical semiconductor device as a reference example, and FIGS. 10 and 12 show the detailed structure of the optical semiconductor device including the features of this embodiment. FIG.
3 is a perspective view showing a structure of a mesa-type optical semiconductor device 50. FIG. As shown in the figure, the optical semiconductor device 50 has an n-type GaAs substrate 51 and a GaAlAs layer 5 serving as an n-type cladding region.
2 is a GaAs active region on the GaAlAs layer 52.
Active layer 53, a GaAlAs layer 54 as a p-type cladding region on active layer 53, and a GaAlAs layer 5
4, a p-type GaAs layer 55 is formed epitaxially. 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 a mesa-type and electrode-separated type optical semiconductor device 60. As shown in the figure, in the optical semiconductor device 60, a GaAlAs layer 62 as an n-type cladding region is formed on an n-type GaAs substrate 61, and a GaAs-based active layer 63 as an active region is formed on the GaAlAs layer 62. A GaAlAs layer 64 as a p-type cladding region is formed thereon, and a p-type GaAs layer is further formed on the GaAlAs layer 64.
The layers 65 are each formed epitaxially. On the GaAs layer 65, p-side electrodes 66 and 67 are
On the back surface of the As substrate 61, an n-side electrode 68 is formed. The power of the laser output can be controlled by the amount of current supplied to the p-side electrode 66.

FIG. 11 is a perspective view showing the structure of an optical semiconductor device 70 of the buried step growth type. As shown in the figure, the optical semiconductor device 70 has an n-type Ga on a p-type GaAs substrate 71.
The As layer 72 includes a GaAlAs layer 73 as a p-type cladding region on the GaAs layer 72, and a GaAs-based active layer 74 as an active region on the GaAlAs layer 73.
A GaAlAs layer 75 which is an n-type cladding region is formed thereon.
Further, an n-type GaAs layer 76 is epitaxially formed on the GaAlAs layer 75, respectively. 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 an optical semiconductor device 80 of a buried step growth type and an electrode separation type. As shown in the figure, in the optical semiconductor device 80, an n-type GaAs layer 82 is formed on a p-type GaAs substrate 81, and a GaAlAs layer 83, which is a p-type cladding region, is formed on the GaAs layer 82.
GaAs active layer 84 as an active region on s layer 83
Is an n-type clad region GaAl on the active layer 84.
An As layer 85 further has an n-type G layer on the GaAlAs layer 85.
Each of the aAs layers 86 is epitaxially formed. Further, on the GaAs layer 86, n-side electrodes 87, 88
However, a p-side electrode 89 is formed on the back surface of the GaAs substrate 81. The power of the laser output can be controlled by the amount of current supplied to the n-side electrode 87.

As described above, with the optical semiconductor device of this embodiment, many laser oscillations, amplifications, and branches can be performed. In addition, when the light emitting portion (prism) of the light emitting end face of the optical semiconductor device of the present embodiment is made of an optical material or a superlattice multilayer crystal of the same crystal, it can function as an on / off switch of the emitted light.

[0027]

According to the optical semiconductor device of the present invention, if a prism is provided on a certain reflection surface to reflect most of the light, the waveguide can function as a sufficiently long resonator. Can be. Therefore, laser light having good coherence characteristics can be oscillated. If most of the light is transmitted by the prism, the waveguide can function as an active region for light amplification having a sufficiently long optical path. Therefore, an optical signal having a high amplification factor can be output.

Therefore, it is effective to use the optical semiconductor device of the present invention for an optical oscillator, a light receiver, an amplifier, a branch signal calculator, and the like. In particular, LAN (Local Area Network)
rk) is highly useful as an optical element.

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

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of an optical semiconductor device of a reference example.

FIG. 2 is a plan view showing how to extract a laser beam.

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

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

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

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

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

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

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

FIG. 10 is a perspective view showing a detailed structure of the optical semiconductor device of the present example.

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

FIG. 12 is a perspective view showing a detailed structure of the optical semiconductor device of the present example.

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

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

[Explanation of symbols]

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.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ken Matsui 1126, Nomachi, Ichinomachi, Hamamatsu City, Shizuoka Prefecture Inside (72) Inventor Hirofumi Miyajima 1126, Nomachi, Ichinomachi, Hamamatsu City, Shizuoka Prefecture Hamamatsu Photonics Co., Ltd. (56) References JP-A-3-6078 (JP, A) JP-A-61-67977 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 5/10

Claims (1)

(57) [Claims] 1. An optical semiconductor device comprising: an endless waveguide having a plurality of reflection surfaces, wherein said waveguide emits light by passing an electric current, wherein a plurality of electrodes are provided near said waveguide. And
The electric field intensity of the waveguide is controlled by applying a voltage to a desired electrode, and further includes a prism disposed on at least one of the reflection surfaces, wherein the prism is provided with an electrode, and An optical semiconductor device, wherein a refractive index of light incident on the prism is changed by applying a voltage.