Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
2002-01-07
2004-08-17
Leung, Quyen P. (Department: 2828)
Coherent light generators
Particular active media
Semiconductor
C372S036000, C372S108000
Reexamination Certificate
active
06778574
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a semiconductor laser device widely used in optical communication systems and optical sensor systems, such as, for example, communication, medical and industrial sensors, and a method for producing the same. In particular, the present invention relates to a semiconductor laser device used for a light source, for emitting light into an outside space, which is directly viewed by humans: for example, a light source for wireless communication, a light source for a sensor or the like. The present invention also relates to a method for producing such a semiconductor laser device, and an optical communication system and an optical sensor system using such a semiconductor laser device to provide guaranteed safety.
BACKGROUND ART
As an example of a conventional space-emission semiconductor light emitting device,
FIG. 10
shows a space-emission semiconductor light emitting device disclosed in Japanese Laid-Open Publication No. 8-264885.
This semiconductor light emitting device has a structure in which a laser chip
1
is soldered to a metal heat sink
6
and a tip area of the laser chip
1
and an electrode (lead frame)
3
are electrically connected to each other by a wire
3
a
. The heat sink
6
is integrated on a stem
8
. The laser chip
1
is sealed by a cap
9
having a diffusive plate
5
bonded thereto.
In such a semiconductor light emitting device, light emitted from the laser chip
1
radiates toward the diffusive plate
5
. The direction and phase of the light are disturbed by the diffusive plate
5
, and thus the light is scattered. In this manner, the coherency of the radiating light is reduced so that safety for the eyes of a viewer is guaranteed, before the light is released to the outside space.
According to another known method for realizing a light-diffusive function, a laser chip is covered with a molded mixture of a silica-based resin and an epoxy-based resin. By this method, the laser light is scattered due to a difference in refractive index between the epoxy-based resin and the silica-based resin, thereby reducing the coherency of the radiating light. A material containing a small amount of silica-based resin mixed with an epoxy-based resin is generally used since the epoxy-based resin is light-transmissive and the silica-based resin is not light-transmissive.
In the case where a semiconductor device including the diffusive plate
5
shown in
FIG. 10
is used, problems occurs such as, for example, the diffusive plate is broken when an apparatus having the semiconductor device mounted thereon is dropped or the like. As a result, a high output of coherent light can be undesirably released to the outside space.
In the case where the laser chip is covered with a molded resin containing a light-diffusive material, for example, a resin containing a silica-based resin, the following or other problems occur. Due to the high moisture permeability of the silica-based resin, wires are worn and broken or end surfaces of the laser chip are deteriorated over time. This reduces the reliability.
The present invention made to solve these problems of conventional devices has an objective of providing a semiconductor laser device for guaranteeing safety for the eyes by preventing a high output of coherent light from being released to the outside space so as to improve reliability, a method for producing the same, and an optical communication system and an optical sensor system using the same.
DISCLOSURE OF THE INVENTION
A semiconductor laser device according to the present invention includes a resin section in which a light-diffusive surface thereof is entirely or partially roughened, or a surface thereof facing a laser chip is entirely or partially roughened. The roughened portion of the resin section diffuses light so as to reduce coherency of the radiating light. Thus, the above-described objective is achieved.
A semiconductor laser device according to the present invention includes a resin section for integrating a container accommodating a laser chip and a sealing member having a light-diffusive function. The sealing member diffuses light so as to reduce coherency of the radiating light. Thus, the above-described objective is achieved.
A semiconductor laser device according to the present invention includes a resin section formed of a resin material in which a different resin material having a different refractive index from that of the first resin material is mixed or a resin section formed of a birefringent resin material, the resin section being provided so as not to contact a laser chip. The resin section diffuses light so as to reduce coherency of the radiating light. Thus, the above-described objective is achieved.
A semiconductor laser device according to the present invention includes a resin section, a portion of which is an area formed of a resin material in which a different resin material having a different refractive index from that of the first resin material is mixed or an area formed of a birefringent resin material, the area being provided so as not to contact a laser chip. The area diffuses light so as to reduce coherency of the radiating light. Thus, the above-described objective is achieved.
Preferably, an area at a center and the vicinity thereof of a surface of the resin section facing the laser chip is a curved surface having a light outgoing point of the laser chip as the center of curvature.
Preferably, a peripheral area of the surface of the resin section facing the laser chip is a curved surface having the center of curvature on a side opposite to the laser chip.
Preferably, an area at a center and in the vicinity of a surface of the resin section facing the laser chip is substantially flat and a peripheral area is convex.
Preferably, a normal to at least a light passing area of the convex area of the resin section is at an angle of larger than 0° and 3° or smaller with respect to a peak vector of a light beam emitted from the laser chip.
Preferably, an area at a center and in the vicinity of a surface of the resin section facing the laser chip is substantially flat and a peripheral area is roughened.
The resin section may be formed of a birefringent resin material.
A semiconductor laser device according to the present invention includes a resin section formed of a birefringent resin material and a laser chip integrated together, wherein the resin section diffuses light so as to reduce coherency of the radiating light. Thus, the above-described objective is achieved.
Preferably, a relationship of &Dgr;n
2
>0.0015 is fulfilled, where An is an inherent birefringence value of light having an oscillating wavelength of the semiconductor laser device and n is an average refractive index for a light having the oscillating wavelength.
The birefringent resin material may be one material, a polymer blend of at least two materials, or a polymer blend containing at least one material of polyimide, polycarbonate, polyallylate, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyallyl sulfone, polyamideimide, polyolefin, polyacrylonitrile, cellulose and polyester.
The birefringent resin material may be an aromatic polyester.
The aromatic polyester may be polyallylate or polycarbonate.
The aromatic polyester may be polyallylate obtained from a divalent phenol compound represented by chemical formula (I) and an aromatic dicarboxylic acid or polycarbonate obtained from the phenol compound and phosgene:
A method for producing a semiconductor laser device according to the present invention produces a semiconductor laser device including a resin section in which a light-diffusive surface thereof is entirely or partially roughened, or a surface thereof facing a laser chip is entirely or partially roughened. The method includes the steps of immersing a laser chip or a container accommodating a laser chip in a resin material; and curing the resin material and roughening a corresponding portion. Thus, the above-described objective is achieved.
A method for producing a semiconductor laser device produces
Emoto Kazuhiro
Kawanishi Hidenori
Shimonaka Atsushi
Birch Stewart Kolasch & Birch, LLP.
Leung Quyen P.
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