Coherent light generators – Particular resonant cavity – Distributed feedback
Reexamination Certificate
2001-03-30
2003-07-22
Davie, James (Department: 2828)
Coherent light generators
Particular resonant cavity
Distributed feedback
C372S108000
Reexamination Certificate
active
06597720
ABSTRACT:
Japanese Patent Application No. 2000-98766, filed on Mar. 31, 2000, is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface emitting semiconductor laser which emits laser light in a direction perpendicular to a semiconductor substrate, and a method of manufacturing the surface emitting semiconductor laser.
2. Description of Related Art
A surface emitting semiconductor laser is a semiconductor laser which emits laser light in a direction perpendicular to a semiconductor substrate, with a resonator provided on a semiconductor substrate in a direction perpendicular to the semiconductor substrate. This resonator generates then emits the laser light, and comprises a reflecting layer, active layer, and reflecting layer, in that order.
Outstanding characteristics that can be cited of a surface emitting semiconductor laser compared with an end-surface laser, are that the direction of laser emission is uniform, and can be made small, and it therefore provides high efficiency coupling of optical elements. A surface emitting semiconductor laser therefore holds great promise in application as a light source particularly in optic fiber communications using for example terminal large-diameter core optic fiber.
In terminal optic fiber communications, it is required for the structure of an optical transmission module to be simplified, for the installation to be made easier, and for the cost to be reduced. Since a surface emitting semiconductor laser is suited to a large-diameter core optic fiber, such as for example a plastic optic fiber or the like, and the method may be considered in which no lens is provided between the optic fiber and the light source, and the laser light is emitted directly into the optic fiber, to improve the optical efficiency. By this method, since the laser light can be emitted efficiently into the optic fiber, an optical transmission module of extreme simplicity can be realized.
However, plastic optic fibers have the drawback that the light losses are large, and when a long transmission path is required, a light source with a high power laser light output is required. As one means of increasing the laser light output of a surface emitting semiconductor laser may be cited an increase in the laser light emission aperture. However, if the laser light emission aperture is made larger, the problem occurs that the laser light emission angle increases. An increase in the laser light emission angle invites a loss of coupling efficiency and a decrease in the fitting margins, and this makes it difficult to simplify the structure of an optical communications module. That is to say, it has been difficult to achieve the twin aims of ensuring the transmission distance, while simplifying the structure of the optical communications module.
SUMMARY OF THE INVENTION
The objective of the present invention is the provision of a surface emitting semiconductor laser and method of manufacturing the surface emitting semiconductor laser, such that a high laser output is obtained, and the laser emission angle is narrow.
(A) According to the present invention, there is provided a surface emitting semiconductor laser which has a resonator formed on a semiconductor substrate in a direction perpendicular to the semiconductor substrate, to emit laser light from the resonator in a direction perpendicular to the semiconductor substrate, wherein:
a pillar-form semiconductor deposition is provided in at least part of the resonator;
an emission portion having a convex lens form is formed on an upper surface of the semiconductor deposition;
the semiconductor deposition has an embedded structure, and is embedded in an embedding layer; and
the embedding layer is formed from a substance having non-affinity with a material used to form the emission portion.
By a substance having non-affinity with the material used to form the emission portion is indicated a substance whose properties are such as to repel the material used to form the emission portion. Therefore, the material used to form the emission portion has low wettability with respect to the substance.
As the substance having non-affinity with the material used to form the emission portion may be cited an inorganic material or a resin. For example, in the case of a resin, a fluorine-based resin can be used.
By means of this structure, a high laser output can be obtained, and the laser emission angle of the surface emitting semiconductor laser can be made narrow. This is described in more detail in the embodiments of the present invention.
This surface emitting semiconductor laser has some features as shown by following examples (1) to (3).
(1) An electrode which supplies current to the resonator may be formed on the upper surface of the semiconductor deposition.
In this case, the electrode may be formed of a metal.
(2) The diameter of the emission portion in a plane of adhesion of the semiconductor deposition and the emission portion, and the diameter of the upper surface of the semiconductor deposition may be substantially equal. By means of this structure, since the diameter of the emission portion in the plane of adhesion of the semiconductor deposition and the emission portion can be made equal to the diameter of the upper surface of the semiconductor deposition, particularly for surface emitting semiconductor lasers formed in an array, emission portions of matching sizes can be formed. Since the diameter of the upper surface of the semiconductor deposition and the diameter of the emission portion in the plane of adhesion of the semiconductor deposition and the emission portion substantially coincide, the optical axis of the emission portion, and the axis passing through the center of the semiconductor deposition and perpendicular to the upper surface of the semiconductor deposition substantially coincide. Further, the optical axis of the emitted laser light is substantially coincident with the axis passing through the center of the semiconductor deposition and perpendicular to the upper surface of the semiconductor deposition. Therefore, the optical axis of the emission portion, the optical axis of the laser light, and the axis passing through the center of the semiconductor deposition and perpendicular to the upper surface of the semiconductor deposition substantially coincide, as a result of which a surface emitting semiconductor laser with little deviation from the optical axis can be obtained.
(3) The emission portion may be formed of a polymer compound.
(B) According to the present invention, there is provided a method of manufacturing a surface emitting semiconductor laser comprising the steps of:
(a) forming a resonator including a pillar-form semiconductor deposition on a semiconductor substrate;
(b) forming an electrode which supplies current to the resonator in a state with a predetermined region of an upper surface of the semiconductor deposition exposed;
(c) forming an embedding layer around the semiconductor deposition to give the semiconductor deposition an embedded structure by embedding the periphery of the semiconductor deposition in a substance having non-affinity with a liquid which is used to form an emission portion having a convex lens form by curing;
(d) disposing the liquid on the upper surface of the semiconductor deposition; and
(e) curing the liquid to form the emission portion.
The liquid refers to the material used to form the emission portion, and by a substance having non-affinity with the liquid is indicated a substance whose properties are such as to repel the liquid. That is to say, the liquid has the property of low wettability with respect to the substance.
According to this method, the periphery of the semiconductor deposition is embedded in the substance having non-affinity with the liquid, whereby an embedding layer is formed on the periphery of the semiconductor deposition, and the resonator is given an embedded structure, while further, by simply supplying the liquid to the upper surface of the semiconductor dep
Davie James
Oliff & Berridg,e PLC
Seiko Epson Corporation
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