Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
2000-11-17
2003-09-23
Lee, Eddie (Department: 2815)
Coherent light generators
Particular active media
Semiconductor
C372S046012, C372S064000, C257S103000, C257S615000, C257S014000
Reexamination Certificate
active
06625187
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor optical device including a Ga
x
In
1−x
N
y
As
1−y
semiconductor and a method of manufacturing the same.
2. Description of the Related Art
It is known to utilize a semiconductor layer formed on a semiconductor substrate for an optical waveguide. A device wherein a semiconductor optical amplifier using an InGaAsP active layer and an optical waveguide using InGaAsP for a core are integrated on an InP substrate, which is used in a network using light having the wavelength of 1.25 to 1.65 &mgr;m suitable for transmission on an optical fiber is also known.
The emission wavelength of a semiconductor laser and a semiconductor optical amplifier respectively adopting an InP semiconductor can be varied so that it covers a range of 1.25 to 1.65 &mgr;m. An optical device wherein optical elements such as a semiconductor optical amplifier and a diffraction grating are integrated on a single InP semiconductor substrate can be produced.
As a result of the review of such an optical device, the inventors discovered the following problems.
To integrate optical elements such as a semiconductor optical amplifier and a diffraction grating on a single semiconductor substrate, large area is required. However, it is technically difficult to manufacture a fine InP semiconductor wafer having a large aperture and suitable for an integrated circuit. Also, to manufacture an InP semiconductor substrate, high-priced material is required to be used.
In the meantime, when the application of optical communication is considered to be enlarged in future, a low-priced wafer and a wafer suitable for large scale integration are required more and more. Therefore, it becomes important to select low-priced semiconductor material of which a wafer suitable for large scale integration can be manufactured.
These inventors think that for such a semiconductor substrate, a GaAs semiconductor substrate is the most suitable.
However, when a GaAs semiconductor substrate is adopted, it next becomes important to select semiconductor material suitable for integrating optical elements such as a luminous element, an optical waveguide and a diffraction grating on the substrate. Then, these inventors researched on such semiconductor material. As a result, the following some documents found.
For a document related to a semiconductor laser, Japanese Patent Unexamined Publication No. Hei. 7-154023 can be given. In the document 1, an invention made to solve a problem that it is difficult to form a semiconductor laser having high characteristic temperature for irradiating a laser beam having the wavelength of 1.3 &mgr;m on an InP substrate is disclosed. To solve the problem, in the document
1
, a semiconductor laser provided with a GaAs semiconductor substrate and a GaInNAs semiconductor active layer the composition of nitrogen (N) of which is 0.5% or more on the substrate is disclosed. The oscillation wavelength of 1.3 &mgr;m of the semiconductor laser is acquired in a state in which the compressive strain quantity of a distorted GaInAsN layer does not exceed 2% because nitrogen is mixedly crystallized. However, in this invention, there is no description of a problem when plural different optical elements are integrated on a single substrate.
Also, for such a document, Japanese Patent Unexamined Publication No. Hei. 6-37355 can be given. In this document
2
, an invention made to provide new semiconductor material that can oscillate a laser beam of a short wavelength is disclosed. It is described that it is possible to provide a semiconductor laser that can continuously oscillate a laser beam of a wavelength in a range of 0.35 to 1.2 &mgr;m in case where a GaAsN semiconductor is adopted for material to achieve the object is enabled. Also, in this document, a GaInNAs semiconductor is described. According to this description, the GaInNAs semiconductor can relieve the mismatching in a lattice constant with the GaAs semiconductor. There is also only description that a luminous element of a longer wavelength than that of the GaAs semiconductor can be produced. However, there is no description of acquiring a long wave the wavelength of which exceeds 1.2 &mgr;m. Also, in this invention, there is no suggestion of the problem when plural different optical elements are integrated on a single substrate.
Further, for such a document, Japanese Patent Unexamined Publication No. Hei. 9-328357 can be given. In this document
3
, an invention made to form a mixed crystalline semiconductor in Families III to V of large composition of nitrogen to have high quality without enhancing the hole density of Family V is disclosed. To achieve such an object, a method of manufacturing a GaInNAs semiconductor according to a predetermined procedure is disclosed. However, there is no description of structure suitable for integrating optical elements required in a future optical communication network such as a luminous element, an optical waveguide and a diffraction grating. Also, there is no concrete and systematic description of a GaInNAs semiconductor that can be used in an optical integrated circuit including such an optical element and can be applied in a range of wavelengths from 1.25 to 1.65 &mgr;m.
Particularly, in these documents, there is no description of applying the GaInNAs semiconductor to a luminous element and adopting the GaInNAs semiconductor for an optical waveguide on which light related to this luminous element is transmitted.
SUMMARY OF THE INVENTION
Then, a first object of the present invention is to provide a semiconductor optical device wherein a luminous element, an optical waveguide and an optical element are integrated on a GaAs semiconductor substrate.
A second object of the present invention is to provide a method of manufacturing the semiconductor optical device.
The semiconductor optical device according to the invention is provided with a GaAs semiconductor substrate, an optical waveguide part provided on the GaAs semiconductor substrate and an optical amplification part provided on the GaAs semiconductor substrate. The optical amplification part includes at least one semiconductor optical amplifier. The optical waveguide is optically connected to the semiconductor optical amplifier.
The semiconductor optical amplifier is provided with an active layer including a Ga
x
In
1−x
N
y
As
1−y
semiconductor, a first conductive-type clad layer and a second conductive-type clad layer respectively having the active layer between them. The active layer has a refractive index larger than that of the first conductive-type clad layer and that of the second conductive-type clad layer.
The optical waveguide is composed of a core semiconductor layer including at least either of a GaInNAs semiconductor or a GaAs semiconductor, first and second clad semiconductor layers respectively having the core semiconductor layer between them.
The optical element can include an optical multiplexer having plural input ports and at least one output for example. The input ports can be optically connected to the semiconductor optical amplifier. Also, the optical element can include an optical demultiplexer having at least one input port and plural output ports for example. The output ports can be optically connected to the semiconductor optical amplifier. The optical waveguide part can include an optical multiplexer and an optical demultiplexer respectively having an optical waveguide. Each optical multiplexer and each optical demultiplexer can include AWG for example.
In case the core semiconductor layer includes a GaInNAs semiconductor, the GaInNAs semiconductor has a band gap larger than energy for the wavelength of light to be amplified in the optical amplification part. Therefore, absorption in the optical waveguide part is reduced and both light to be amplified in the optical amplification part and light amplified in the optical amplification part can be propagated in the core semiconductor layer. Also, the core semiconductor layer is in co
Ikoma Nobuyuki
Ishida Akira
Katsuyama Tsukuru
Shigematsu Masayuki
Takagishi Shigenori
Lee Eddie
Nguyen Joseph
Smith , Gambrell & Russell, LLP
Sumitomo Electric Industries Ltd.
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