Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1999-01-05
2001-08-07
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S092000, C385S011000, C385S014000, C385S093000, C372S703000
Reexamination Certificate
active
06270261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor laser module provided with an optical isolator used in optical communications systems.
2. Description of the Prior Art
As optical communication is coming into wider use recently, semiconductor laser modules are required to be lower in price and smaller in size. In an attempt to meet these requirements, for example, Yamauchi et al. described a semiconductor laser module which can be made smaller in size in a presentation titled “Surface-Mounted Optical Circuit Module Suited For Automatic Assembly” in 1995 general conference of The Institute of Electronics, Information and Communication Engineers. The semiconductor laser module described in this presentation does not require the adjustment of optical axis, and therefore allows for cost reduction and mass production.
In an optical communications system, there occurs such a problem that light emitted by a semiconductor laser diode chip is reflected from an input end or an output end face of an optical fiber, which transmits the light, and returns to the semiconductor laser diode chip, thus spreading the spectrum of the laser light and/or increasing noise. In order to reduce the reflected light in the prior art systems, simple measures have been taken such as AR coating and oblique cutting of the optical fiber at the end. As more essential means, it is effective to provide optical isolator between the semiconductor laser diode and the optical fiber.
However, when an optical isolator is used, there has been a problem such that, in addition to the high cost of the optical isolator, lenses are required an front and at the back of the optical isolator resulting an increased number of components which inhibits cost reduction of the system as a whole. There has also been such a problem that the use of the optical isolator requires complicated adjustment of the optical axis which increases the cost in terms of an adjustment operation. Further, there has been a problem such that integrating the optical isolator and the lenses into the optical system inhibits size reduction of the system.
SUMMARY OF THE INVENTION
That is, an object of the present invention is to provide a small and low-cost semiconductor laser module incorporating an optical isolator therein, thereby contributing to a reduction in size and cost of optical communications systems.
In order to achieve the object described above, the semiconductor laser module of the present invention comprises a semiconductor laser diode chip mounted on a substrate, a first optical waveguide formed on the substrate for transmitting laser light emitted by the semiconductor laser diode chip, a second optical waveguide formed on the substrate and separated by a predetermined space from the first optical waveguide, and an optical isolator chip mounted between the first optical waveguide and the second optical waveguide.
With this configuration, it becomes possible for the laser light emitted by the semiconductor laser diode chip to transmit through the first optical waveguide, the optical isolator chip and the second optical waveguide, thereby to be output to the outside, while preventing the reflected light from entering back into the semiconductor laser diode chip and maintaining stable laser oscillation.
In the semiconductor laser module of the present invention, it is preferable that the first and the second optical waveguides be made by dividing one optical waveguide, which is formed on the substrate, by means of a groove formed in the optical waveguide, for the purpose of aligning the optical axes of the waveguides.
At least one of the two side walls of the groove is preferably formed in a direction not at right angles to the optical axis of the first optical waveguide or the second optical waveguide. This configuration causes the reflected light to propagate in a direction different from the optical axis of the optical waveguide, thereby making it possible to more effectively prevent the reflected light from entering back into the laser diode.
Also according to the present invention, the optical isolator chip preferably comprises a Faraday rotator and polarizing elements provided on both sides of the Faraday rotator.
The semiconductor laser module of the present invention also preferably comprises a magnet of semi-cylindrical shape provided to cover the optical isolator chip, in order to apply magnetic field to the optical isolator.
Also in the semiconductor laser module of the present invention, magnets may be mounted on the first and the second optical waveguides on both sides of the optical isolator chip.
Further in the semiconductor laser module of the present invention, magnets may also be mounted to interpose the optical isolator chip therebetween inside the groove.
Also in the semiconductor laser module of the present invention, the substrate preferably has the semiconductor laser diode chip, the first and the second optical waveguides and a cover which covers the optical isolator hip provided thereon, while a magnet may be mounted on the cover for applying magnetic field to the optical isolator chip.
Also in the semiconductor laser module of the present invention, it is preferable to form a lens on the output end of the first optical waveguide and form a lens on the input end of the second optical waveguide.
REFERENCES:
patent: 4375910 (1983-03-01), Seki
patent: 4904036 (1990-02-01), Blonder
patent: 4978189 (1990-12-01), Blonder et al.
patent: 5082376 (1992-01-01), Beylat et al.
patent: 5566264 (1996-10-01), Kuke et al.
patent: 6055102 (2000-04-01), Park
Yamauchi et al., “A Surface Mount Type Optical Module for Automatic Assembly”, Proceeding of the 1995 Synthesis Conference, C-184, p. 184.
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
Sanghavi Hemang
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