JPH08330671A - Semiconductor optical element - Google Patents

Abstract

PURPOSE: To provide the structure of a semiconductor optical guide element coupled to a fiber with high efficiency, a method for simply manufacturing the same, an element structure adapted for when the method is applied to a laser, an optical amplifier, an optical switch, a photodetector or an optical guide element having the two of them monolithically integrated and a method for manufacturing the same. CONSTITUTION: The lateral width of a laser active waveguide is suitably varied thereby to enhance an optical guide element such as a semiconductor laser, and inputting or emitting beam diameter is increased to enhance the coupling efficiency with a fiber. Further, a ridge waveguide is formed in this structure to reduce the optical intensity at the emitting end face of an active layer 1. Accordingly, the output can be enhanced, the lateral mode can be stabilized, and the high reliability (long life) in the high efficiency coupling and high output state to the fiber can be easily performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical device, and more particularly to an optical communication module, an optical communication system and an optical network.
The present invention relates to a semiconductor optical device suitable for use in electronic devices.

[0002]

2. Description of the Related Art Generally, in order to increase the output of a semiconductor laser,
(1) Reduction of thermal saturation due to low resistance of the element, (2) Reduction of leakage current, (3) Stabilization of lateral mode at high output,
(4) High reliability at high output is essential. Further, in order to increase the output of the module, (5) it is important to narrow the exit beam angle of the laser to improve the efficiency of optical coupling to the fiber. Considering the above (1) to (5) regarding the setting of the active layer width, a wide active layer width is desirable for (1), (2) and (4). On the other hand, regarding (3) and (4),
A relatively narrow active layer width is desirable. That is, the above items (1) to (5) have a trade-off relationship with the active layer width. From this point of view, the active layer width is often set to the maximum active layer width that maintains a single lateral mode operation, but (1) to (5)
Is generally difficult to achieve simultaneously. Further, in a short wavelength laser having a large oscillation wavelength of about 1 μm or less in which the photon energy of the operating light is large, crystal destruction near the active layer on the end face having a large light density is the main cause of this deterioration. On the other hand, it is extremely important to reduce the light density at the position of the active layer, but at present, no effective solution has emerged.

[0003] Related to these are, for example, the Institute of Electronics, Information and Communication Engineers Autumn Meeting C-311, September 1994, and related to the latter, Applied Physics Vol. 64, N
o. 1, 2-12, 1995.

[0004]

SUMMARY OF THE INVENTION The present invention is a semiconductor optical device which can be realized by an extremely simple manufacturing method and which operates stably in a single lateral mode and has excellent temperature characteristics and coupling with an optical fiber. An object is to provide a device structure (for example, a semiconductor laser) and a manufacturing method thereof. A further object is to provide a device structure and a manufacturing method suitable for preventing deterioration of an end face of a semiconductor laser having an emission wavelength of about 1 μm or less.

[0005]

In order to achieve the above object, the inventors of the present invention have realized a high output and a horizontal output without deteriorating the characteristics of an optical waveguide element such as a semiconductor laser by only laterally modulating the waveguide. We have devised a laser structure and its fabrication method that can simultaneously achieve mode stabilization, high-efficiency coupling to fiber, and high reliability at high output with a very easy method. The lateral width of the laser active waveguide is smoothly modulated in a taper shape in the optical axis direction, and the width of the waveguide is set to be narrower than the cutoff width where the lateral mode is single at the light emission end. To be done. Further, in other waveguide regions, the lateral width is set wider than the cutoff width where the lateral mode is single. In addition, the introduction of the ridge waveguide structure further improves the above characteristics.

[0006]

In the following, a high output power, a stable horizontal mode, a high efficiency coupling to a fiber, and a high output power can be achieved without deteriorating the characteristics of an optical waveguide element such as a semiconductor laser simply by modulating the width of the waveguide. A laser structure capable of simultaneously achieving high reliability by a very easy method and a method for manufacturing the same will be described.

As shown in FIG. 1A, a buried semiconductor laser in which the lateral width of the active layer 1 is modulated in the optical axis direction is manufactured by a known method. Here, the total element length is 1200 μm
Then, the lateral width of the waveguide is smoothly modulated in a taper shape in the optical axis direction over a region of 300 μm. The lateral width of the waveguide at the light emitting end is 0.6 μm, which is set sufficiently narrower than the cutoff width (about 1.8 μm) in which the lateral mode is single.
In the other 900 μm region, the lateral width is 2.4 μm, which is set wider than the cutoff width. Width 2.4 μm
In the waveguide section, originally, higher-order modes may exist in addition to the fundamental guide mode. However, by introducing a tapered waveguide having a lateral width of 0.6 μm, which allows only the fundamental waveguide mode, only the fundamental waveguide mode can be excited in the integrated waveguide.
Therefore, since most of the waveguide can be set wide, it is possible to increase the output while maintaining stable single transverse mode operation by reducing the resistance of the element and reducing the leakage current. Also, Fig. 1 (b)
As shown in the top view of FIG. 3, in a waveguide having a narrowed width, the light confinement action is weakened, so that the beam spot is automatically expanded. As a result, the beam emission angle becomes approximately 10 degrees in the horizontal and vertical directions, and the optical coupling efficiency when the laser light is incident on the fiber can be greatly improved.

FIG. 2 (a) shows an example in which a similar semiconductor laser is similarly manufactured using a ridge-loaded waveguide. here,
The total element length is 1200 μm, and the lateral width of the waveguide is smoothly modulated like a taper in the optical axis direction over a region of 300 μm. The width of the waveguide at the light output end is 1.0 μm.
It is set to be sufficiently narrower than the cutoff width (about 2.4 μm) that makes the unitary. In the other 900 μm region, the lateral width is 3.0 μm, which is set wider than the cutoff width. Also in this case, high output and high coupling efficiency to the fiber can be achieved by introducing a tapered waveguide whose lateral width is narrowed by the same principle as the embedded laser. Further, in the case of the ridge-loaded waveguide, since the cutoff width of the waveguide exists even for the fundamental waveguide mode, when the waveguide width is narrowed close to the cutoff width, as shown in FIG. As shown in the top view of b) and the sectional view of (c), the light intensity distribution gradually shifts from the active layer to the substrate side. Therefore, as a result, the light intensity in the active layer having a narrow band gap can be greatly reduced. This phenomenon is caused by a short wavelength laser with an oscillation wavelength of about 1 μm or less, which is the main factor of device deterioration due to crystal destruction due to excessive light absorption coupling near the end surface of the active layer where the photon energy of the operating light is large and the light density is large. It is extremely effective for high reliability.

As described above, the method of realizing high output and high reliability of the semiconductor laser has been described by the extremely easy method of only introducing the tapered waveguide having the narrowed lateral width. Further, it goes without saying that this principle can be applied to increase the output of a waveguide type optical element such as a semiconductor optical amplifier, an optical modulator, etc. other than the semiconductor laser.

[0010]

Embodiments of the present invention will be described below with reference to FIGS.

Example 1 As shown in FIG. 3, an n-type (100) InP semiconductor substrate 1
N-type InP buffer layer 1.0 .mu.
m12, n-type InGaAsP lower guide layer (composition wavelength: 1.10 μm) 0.05 μm 13, 1% of 6.0 nm thickness
InGaAsP with compressive strain (composition wavelength 1.45μ
m) as a well layer and a 12 nm thick InGaAsP (composition wavelength 1.20 μm) as a barrier layer, a multi-quantum well active layer 14 of four periods, InGaAsP (composition wavelength 1.10 μm) upper optical guide layer 0.05 μm 15, p-type InP clad layer 1.9 μm 16, p-type InGaAs cap layer 0.2 μm
m17 are sequentially formed. The emission wavelength of the multiple quantum well active layer 14 is about 1.48 μm. Next, the cap layer 17 is processed into a taper stripe structure by a known method. Here, the stripe direction is [011], the length of the lateral narrowing taper portion is 300 μm, the stripe width is 3.4 μm at the laser emission end face portion, and the stripe width in other regions is 5.4 μm.
A striped taper portion is provided so that m. Subsequently, a ridge waveguide having an inverted mesa cross section having a (111) A plane as a side wall is formed as shown in the figure. As a result, the width of the bottom surface of the ridge, which is the width of the active layer, is 3.0 μm, and the width at the tip of the taper portion is 1.0 μm.

Then, a 0.20 μm thick silicon oxide film 18 is formed on the entire surface of the substrate by a known method, and then a polyimide resin 19 is formed on the entire surface of the substrate. Further, a silicon oxide film window is formed on the upper surface of the ridge by the etch back method. Finally, after the electrode 20 is formed, a cleavage process is performed.
A device having a resonator length of 1200 μm including a part of 300 μm is cut out. A highly reflective film 21 having a reflectance of 90% is formed on the end face of the ridge portion having a width of 3.0 μm which is the rear end face, and 1.0 which is the front end face.
A low reflection film 22 having a reflectance of 3% was formed on the end face of the ridge portion having a width of μm by a known method.

The fabricated device has a threshold value of 25 to 30 mA and oscillation efficiency of 0.45 to 0.50 W under continuous conditions at room temperature.
/ A, indicating good oscillation characteristics. Also, operating current 1.2
A maximum output of 400 mW was obtained at A. Operation output 300mW
The beam divergence angle is narrow at about 10 degrees in both horizontal and vertical directions. When the long-term reliability of the device was evaluated under the conditions of 70 ° C. and 200 mW, an estimated life of 200,000 hours or more was confirmed. When this device was modularized, the average coupling loss to the fiber was 1 dB, reflecting the narrowed beam, and the maximum module output of 320 mW was achieved. By using this device as a pumping light source for an erbium-doped fiber amplifier, good optical amplification characteristics with low noise intensity were confirmed.

Example 2 FIG. 4 shows an example of producing a pumping light source for a high-power erbium-doped fiber amplifier with a buried heterostructure having a wavelength of 1.48 μm by a method similar to that of the example of FIG. The width of the lateral narrowing taper portion is 300 μm, the active layer width at the laser emission end face portion is 0.4 μm, and the active layer width at other regions is 2.4 μm.
A striped taper portion is provided so that m. The embedded structure 31 is formed using a known method.

The manufactured device has a threshold value of 20 to 25 mA and oscillation efficiency of 0.40 to 0.45 W under continuous conditions at room temperature.
/ A, indicating good oscillation characteristics. Also, operating current 1.2
A maximum output of 350 mW was obtained at A. Operating output 250mW
The beam divergence angle is narrow at about 10 degrees in both horizontal and vertical directions. When the long-term reliability of the device was evaluated under the conditions of 70 ° C. and 170 mW, an estimated life of 200,000 hours or more was confirmed. When this device was modularized, the average coupling loss to the fiber was 1 dB, reflecting the narrowed beam, and the maximum module output of 280 mW was achieved. By using this device as a pumping light source for an erbium-doped fiber amplifier, good optical amplification characteristics with low noise intensity were confirmed.

Embodiment 3 FIG. 5 shows an example of manufacturing a distributed feedback laser which can oscillate at 1.55 μm and can operate in a wide temperature range by a method substantially similar to that of Embodiment 1. As shown, n-type (100)
N-type InP is formed on the InP semiconductor substrate 41 by a known method.
Buffer layer 1.0 μm 42, n-type InGaAsP lower guide layer (composition wavelength 1.10 μm) 0.05 μm 43,
A well layer of InGaAsP (composition wavelength: 1.67 μm) having a thickness of 6.0 nm and 1% compression strain, and an InGa layer having a thickness of 12 nm
A 6-period multiple quantum well active layer 44 having an AsP (composition wavelength of 1.15 μm) as a barrier layer and an InGaAsP (composition wavelength of 1.10 μm) upper optical guide layer of 0.1 μm 45 are sequentially formed. The emission wavelength of the multiple quantum well active layer 44 is about 1.5.
It is 6 μm. Next, a diffraction grating 46 having a λ / 4 phase shift structure and a period of 241 nm is formed on the upper light guide layer 45 by a known method. At this time, the diffraction grating is not formed in a region that will later become a tapered waveguide. The λ / 4 phase shift is provided in the center of the area where the diffraction grating is formed. Then, a p-type InP clad layer of 1.9 μm 4 was formed on the substrate.
7. A p-type InGaAs cap layer 0.2 μm 48 is sequentially formed.

Next, a taper-shaped ridge waveguide is formed by using the same method as in the first embodiment. The width of the width narrowing taper part is 1
50 μm, the width of the bottom of the ridge which is the width of the active layer is 3.0 μm
m, and the width of the active layer at the tip of the taper portion is set to 1.0 μm. Then, it is processed into a polyimide-embedded ridge waveguide type laser structure by the same method as in Example 1. After cutting into a device having a cavity length of 450 μm including a taper portion of 150 μm by a cleavage step, a low reflection film 49 having a reflectance of 1% was formed on both end faces by a known method.

The fabricated device has a threshold value of 8 to 12 mA under continuous conditions at room temperature and an oscillation efficiency of 0.
35 to 0.40 W / A, oscillation efficiency from rear end surface 0.1 to
It showed a good oscillation characteristic of 0.15 W / A. Despite the introduction of the λ / 4 phase shift structure, the amount of light emitted from both end faces could be made asymmetric because the tapered waveguide section without a diffraction grating acts as an optical amplifier. Is one. Further, even at a high temperature condition of 85 ° C., the threshold value is 18 to 24 mA, and the oscillation efficiency is 0.25 to 0.30 W /
It was as good as A. In addition, stable single transverse mode and longitudinal mode operation is shown even at high output of 30 mW, -40
The secondary mode suppression ratio of 40 dB or more is 9 over the entire temperature range of ~ 85 ° C.
The production yield of 0% or more was confirmed. On the other hand, the ridge width 1.
The spot diameter of the laser emitting beam from the front end face of 0 μm is 6 μm, which is three times or more that of the conventional structure. When this laser and a single mode fiber with a core diameter of 10 μm were coupled without using an optical lens, the coupling loss was 2 dB.
The following was realized with horizontal and vertical positioning accuracy of ± 3 μm. Moreover, when the long-term reliability of the device was evaluated under a high temperature condition of 90 ° C., an estimated life of 100,000 hours or more was confirmed.

Example 4 FIG. 6 is an example of producing a laser in which an emission beam in the wavelength band of 1.3 μm is expanded by the same method as in Example 3. The device structure is almost the same as that of the third embodiment except that a strained InGaAsP multiple quantum well structure 61 having an emission wavelength of 1.3 μm is introduced into the active layer and a high reflection film 62 is introduced into the rear end face.

The produced device has a threshold value of 8 to 12 mA and an oscillation efficiency of 0.50 to 0.55 W / in continuous conditions at room temperature.
A shows good oscillation characteristics. The threshold value is 16 to 24 mA and the oscillation efficiency is 0.40 even under the high temperature condition of 85 ° C.
It was good at about 0.44 W / A. Further, the spot diameter of the laser emitting beam from the front end face having a ridge width of 1.0 μm is 6 μm, which is three times or more that of the conventional one. When this laser and a single mode fiber with a core diameter of 10 μm were coupled without using an optical lens, a coupling loss of 2 dB or less was realized with horizontal and vertical positioning accuracy of ± 3 μm. Moreover, when the long-term reliability of the device was evaluated under a high temperature condition of 90 ° C., an estimated life of 100,000 hours or more was confirmed.

Example 5 FIG. 7 shows a wavelength of 0.98 μm in the same manner as in the example of FIG.
It is an example of producing an m-band pumping light source for a high-power erbium-doped fiber amplifier. As shown in the figure, n-type (10
0) n-type In0.51Ga0.49P buffer layer 3.0 μm 7 on the GaAs semiconductor substrate 71 by a known method.
2, 6.0 nm thick In0.17Ga0.83As well layer, 10 nm thick InGaAsP (composition wavelength 0.70
μm) as a barrier layer, single quantum well active layer 73, p-type I
n0.51Ga0.49P First cladding layer 0.1 μm 7
4, GaAs etching stop layer 5 nm 75, p-type In
0.51Ga0.49P Second clad layer 1.7 μm 7
6. P-type GaAs cap layer 0.2 μm 77 is sequentially formed. The emission wavelength of the single quantum well active layer 73 is about 0.98.
μm.

Next, the cap layer 77 is processed into a taper stripe structure by a known method. Here, the stripe direction is [011], and the width of the lateral narrowing taper portion is 250 μm.
m, the stripe width is 3.2 μm at the laser emission end face, and the stripe width is 5.4 μm in the other regions. Subsequently, a ridge waveguide having an inverted mesa cross section having a (111) A plane as a side wall is formed as shown in the figure. As a result, the width of the bottom surface of the ridge, which is the width of the active layer, is 3.0 μm, and the width at the tip of the taper portion is 0.8 μm.

Then, a 0.20 μm thick silicon oxide film 78 is formed on the entire surface of the substrate by a known method, and then a polyimide resin 79 is formed on the entire surface of the substrate. Further, a silicon oxide film window is formed on the upper surface of the ridge by the etch back method. Finally, after the electrode 80 is formed, a cleavage process is performed.
A device having a resonator length of 1000 μm including a part of 250 μm is cut out. A highly reflective film 81 having a reflectance of 90% is provided on the end face of the ridge portion having a width of 3.0 μm, which is the rear end face, and 0.8 is provided as the front end face.
A low reflection film 82 having a reflectance of 3% was formed on the end face of the ridge portion having a width of μm by a known method.

The produced device has a threshold value of 15 to 20 mA and an oscillation efficiency of 0.7 to 0.75 W / at room temperature and continuous conditions.
A shows good oscillation characteristics. Also, operating current 500mA
A maximum output of 500 mW was obtained and no rapid deterioration of the element due to so-called COD was observed. The beam divergence angle at an operation output of 300 mW is about 15 degrees horizontally and 20 degrees vertically, which is narrow in both directions. Observing the near-field image at the exit end,
As shown in the figure, n-type InO.
It was found that the center of the light intensity is located in the 51Ga0.49P buffer layer 72. As a result, it was possible to prevent crystal degradation due to excessive light absorption in the vicinity of the end face of the active layer and element deterioration. When the long-term reliability of the device was evaluated under the conditions of 70 ° C. and 200 mW, an estimated life of 500,000 hours or more was confirmed.
When this device was modularized, an average coupling loss to the fiber of 1.5 dB was obtained reflecting the narrowed beam, and the maximum module output of 350 mW was achieved. By using this device as a pumping light source for an erbium-doped fiber amplifier, good optical amplification characteristics with low noise intensity were confirmed.

It is needless to say that the effect of improving the device life by reducing the light density on the end surface by expanding the beam can be applied to all high-power semiconductor lasers having a wavelength of about 1 μm or less.

Example 6 FIG. 8 shows an example of producing a pumping light source for a high-power erbium-doped fiber amplifier having a ridge-embedded structure and a wavelength of 0.98 μm in a manner substantially similar to that of the example of FIG. The width of the lateral narrowing taper portion is 250 μm, the active layer width is 0.6 μm at the laser emission end face portion, and the active layer width is 3.0 μm in other regions.
A striped taper portion is provided so that m. The embedded structure 101 is formed by using a known method.

The fabricated device has a threshold value of 15 to 20 mA and an oscillation efficiency of 0.7 to 0.75 W / at room temperature and continuous conditions.
A shows good oscillation characteristics. Also, operating current 400mA
A maximum output of 400 mW was obtained and no rapid deterioration of the device due to so-called COD was observed. The beam divergence angle at the operation output of 250 mW is about 18 degrees horizontally and 25 degrees vertically, which is narrow in both directions. Observing the near-field image at the exit end,
As shown in the figure, n-type In separated from the active layer position by 0.3 μm
It was found that the center of the light intensity is located in the 0.51Ga0.49P buffer layer 72. As a result, it was possible to prevent crystal degradation due to excessive light absorption in the vicinity of the end face of the active layer and element deterioration. When the long-term reliability of the device was evaluated under the conditions of 70 ° C. and 150 mW, an estimated life of 200,000 hours or more was confirmed. When this device was modularized, an average coupling loss to the fiber of 1.5 dB was obtained reflecting the narrowed beam, and the maximum module output of 280 mW was achieved. By using this device as a pumping light source for an erbium-doped fiber amplifier, good optical amplification characteristics with low noise intensity were confirmed.

Example 7 FIG. 9 shows an example in which a semiconductor laser optical amplifier operating in the wavelength band of 1.55 μm was manufactured by a method similar to that of Example 1.

As shown in the figure, the n-type InP buffer layer 0.5 μm 112 and the n-type InGaAsP lower optical guide layer (composition wavelength 1.15 μm) 0.05 μm 113 are formed on the n-type (100) InP semiconductor substrate 111 by a known method. , 6.0
nm thickness InGaAs with 0.45% tensile strain
(Composition wavelength 1.60 μm) is a well layer, 10 nm thick In
GaAsP (composition wavelength 1.15 μm) as a barrier layer 6
Periodic strained multiple quantum well active layer 114, InGaAsP
(Composition wavelength 1.15 μm) Upper light guide layer 0.05 μm
115, p-type InP clad layer 1.9 μm 116, and p-type InGaAs cap layer 0.2 μm 117 are sequentially formed.

Next, using a well-known laser manufacturing method, a laser structure having a taper-shaped ridge stripe waveguide as shown in the figure on both end surfaces of the device is processed. Here, the width of the bottom surface of the ridge at the center of the element is 3.0 μm, but at the laser emission end, it is narrowed in a taper shape to 1.0 μm.
The taper region length in which the ridge width gradually changes is 150 μm,
The total element length is 700 μm. An antireflection film 118 having a reflectance of 0.05% was applied to both end faces of the element.

The manufactured element was kept at room temperature under continuous conditions.
A chip gain of 25 dB is obtained at an applied current of 100 mA,
The gain difference between the TE and TM modes is as good as 0.5 dB or less. The saturated output was 10 dBm.

On the other hand, the beam spot diameter at the entrance / exit end face having a ridge width of 1.0 μm is about 6 μm, which is four times larger than that of the conventional type. When this optical amplifier and a single mode fiber with a core diameter of 10 μm were coupled, the coupling loss per end face was 2 dB or less, and the positioning accuracy in the horizontal and vertical directions was ± 3.
It was realized in μm.

Example 8 FIG. 10 shows an example in which a high-power laser having a wavelength of 0.68 μm was manufactured by the same method as in Example 5. The device structure has a strained InGaP / InGaAl layer with an emission wavelength of 0.68 μm in the active layer.
The P-quantum well structure 132 is substantially the same as the fifth embodiment except that the high reflection film 133 is introduced on the rear end face.

The manufactured device has a threshold value of 25 to 30 mA and oscillation efficiency of 0.90 to 0.95 W under continuous conditions at room temperature.
/ A, indicating good oscillation characteristics. The threshold value is 50 to 60 mA and the oscillation efficiency is 0.75 even at a high temperature of 85 ° C.
It was good at about 0.80 W / A. Further, the spot diameter of the laser emitting beam from the front end face having a ridge width of 1.0 μm is 5 μm, which is three times or more that of the conventional one. As a result, the end face of the device is destroyed, and the optical output level is 1
It was more than 00 mW. Reflecting this, the long-term reliability of the device was evaluated under the conditions of 70 ° C. and 50 mW.
Confirmed life expectancy of 10,000 hours or more.

Example 9 FIG. 11 shows an example of producing a high-power laser having a wavelength of 0.78 μm in the same manner as in Example 5. The device structure is almost the same as that of the fifth embodiment except that a GaAs / AlGaAs multiple quantum well structure 142 having an emission wavelength of 0.78 μm is introduced in the active layer and a high reflection film 143 is introduced in the rear end face.

The manufactured device has a threshold value of 25 to 30 mA and an oscillation efficiency of 0.80 to 0.85 W under continuous conditions at room temperature.
/ A, indicating good oscillation characteristics. The threshold value is 50 to 60 mA and the oscillation efficiency is 0.65 even at a high temperature of 85 ° C.
It was good at about 0.60 W / A. Further, the spot diameter of the laser emitting beam from the front end face having a ridge width of 1.0 μm is 5 μm, which is three times or more that of the conventional one. As a result, the end face of the device is destroyed, and the optical output level is 2
It was more than 00 mW. Reflecting this, the long-term reliability of the device was evaluated under the conditions of 70 ° C. and 150 mW.
An estimated life of over 10,000 hours was confirmed.

[0037]

According to the semiconductor light emitting device of the present invention, a semiconductor such as a semiconductor laser, an optical amplifier, etc., which has a high output, easy optical coupling with an optical fiber, low operating current and operating voltage, and excellent high-speed characteristics. The optical element can be realized by an extremely easy method. By using the present invention, not only the element performance and the yield are dramatically improved, but also the optical communication system to which the element is applied can be easily reduced in price, increased in capacity, and increased in distance.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the operation of the present invention.

FIG. 2 is a diagram for explaining the operation of the present invention.

FIG. 3 is a diagram for explaining an example of the present invention.

FIG. 4 is a diagram for explaining an example of the present invention.

FIG. 5 is a diagram for explaining an example of the present invention.

FIG. 6 is a diagram for explaining an example of the present invention.

FIG. 7 is a diagram for explaining an example of the present invention.

FIG. 8 is a diagram for explaining an example of the present invention.

FIG. 9 is a diagram for explaining an example of the present invention.

FIG. 10 is a diagram for explaining an example of the present invention.

FIG. 11 is a diagram for explaining an example of the present invention.

[Explanation of symbols]

1 ... Active layer, 11 ... N-type (100) InP semiconductor substrate,
12 ... n type InP buffer layer 1.0 μm, 13 ... n type I
nGaAsP lower guide layer, 14 ... strained InGaAsP multiple quantum well active layer, 15 ... InGaAsP upper optical guide layer, 16 ... p-type InP clad layer, 17 ... p-type InGa
As cap layer, 18 ... Silicon oxide film, 19 ... Polyimide resin, 20 ... Electrode, 21 ... High reflection film, 22 ... Low reflection film, 31 ... Buried structure, 41 ... N-type (100) InP
Semiconductor substrate, 42 ... N-type InP buffer layer, 43 ... N-type InGaAsP lower guide layer, 44 ... Strained InGaAsP
Multiple quantum well active layer, 45 ... InGaAsP upper optical guide layer, 46 ... λ / 4 phase shift diffraction grating, 47 ... P-type I
nP clad layer, 48 ... p-type InGaAs cap layer,
49 ... Low reflection film, 61 ... 1.3 μm strained InGaAsP multiple quantum well structure, 62 ... High reflection film, 71 ... N-type (10
0) GaAs semiconductor substrate, 72 ... n-type In0.51Ga
0.49P buffer layer, 73 ... Single quantum well active layer, 7
4 ... p-type In0.51Ga0.49P first cladding layer,
75 ... GaAs etching stop layer, 76 ... p-type In0.
51Ga0.49P second cladding layer, 77 ... p-type GaA
s cap layer, 88 ... Silicon oxide film, 89 ... Polyimide resin, 90 ... Electrode, 101 ... Embedded structure, 111 ...
n-type (100) InP semiconductor substrate, 112 ... n-type InP
Buffer layer, 113 ... n-type InGaAsP lower optical guide layer, 114 ... Tensile strain InGaAs multiple quantum well active layer, 115 ... InGaAsP upper optical guide layer, 116 ...
p-type InP clad layer, 117 ... p-type InGaAs cap layer, 131 ... n-type (100) GaAs semiconductor substrate,
132 ... Strained InGaP / InGaAlP multiple quantum well structure, 133 ... High reflective film, 141 ... n-type (100) GaA
s semiconductor substrate, 142 ... GaAs / AlGaAs multiple quantum well structure, 143 ... Highly reflective film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Misuzu Sagawa 1-280 Higashi Koikeku, Kokubunji, Tokyo Metropolitan Research Laboratory, Hitachi Ltd. (72) Kiyohisa Hiramoto 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. (72) Inventor, Kazuhisa Uomi 1-280, Higashi Koikekubo, Kokubunji, Tokyo Metropolitan Research Center, Hitachi, Ltd.

Claims (15)

[Claims] 1. A semiconductor optical device having a first core layer and a cladding layer made of a material having a wider bandgap and a lower refractive index than the first core layer on both sides of the first core layer on a semiconductor substrate,
The width of the waveguide is smoothly modulated in a taper shape in the optical axis direction, and the width of the waveguide becomes a single cutoff width at the light entrance end or the light exit end or both parts. A semiconductor optical device characterized in that the width is set to be narrower than that of the waveguide and the width of the other waveguide regions is set to be wider than the cutoff width where the horizontal mode is single. 2. In a semiconductor optical device having a first core layer and a cladding layer made of a material having a lower refractive index than the first core layer on both sides of the first core layer on a substrate, the lateral width of the waveguide is in the optical axis direction. -Smoothly modulated in the shape of a line, and the width of the waveguide is 0.2 to 2 μm at the light entrance end or the light exit end or both of them.
m, and the lateral width is 2-1 in other waveguide regions.
A semiconductor optical device having a thickness of 0 μm. 3. The semiconductor optical device according to claim 1, wherein the waveguide is of a ridge loading type. 4. The peak position of the intensity distribution of the guided light at the light input end and the light output end is not located at the position of the first core layer, but is shifted to the substrate side. 4. The semiconductor optical device according to any one of 3 to 3. 5. The semiconductor optical device according to claim 1, wherein the side walls on both sides of the ridge are (111) A or (01-1) crystal planes. 6. The semiconductor optical device according to claim 1, wherein the optical device is a semiconductor laser. 7. The semiconductor device according to claim 6, wherein the oscillation wavelength is 1.2 μm or less. 8. A semiconductor optical device according to claim 6, wherein the divergence angle of the emitted beam is 20 degrees or less in both horizontal and vertical directions. 9. A semiconductor optical device according to claim 6, wherein the diffraction grating is formed at least in a part of the waveguide. 10. The semiconductor optical device according to claim 1, wherein the optical device is a semiconductor laser amplifier. 11. The semiconductor optical device according to claim 10, wherein the oscillation wavelength is 1.2 μm or less. 12. The semiconductor optical device according to claim 10, wherein the divergence angle of the outgoing beam is 20 degrees or less in both horizontal and vertical directions. 13. A semiconductor optical device according to claim 10, wherein the diffraction grating is formed at least in a part of the waveguide. 14. An optical communication module using the semiconductor optical device according to claim 1. 15. An optical communication system using the optical communication module according to claim 14.