Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1999-03-30
2001-06-12
Font, Frank G. (Department: 2877)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S091000
Reexamination Certificate
active
06244754
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor laser module. More particularly, the invention relates to a semiconductor laser module structure which is formed by integrating a semiconductor laser as a light source with an optical fiber as an optical waveguide and to a method of manufacturing such a semiconductor laser module.
2. Description of the Related Art
A typical semiconductor laser module is basically formed by integrating a semiconductor laser such as an Laser Diode (LD) which is an electro-optical conversion element with an optical fiber for efficiently propagating the laser light. In a semiconductor laser module, the relative position between the light emitting surface of the semiconductor laser and the incident end of the optical fiber must be accurately aligned to improve the optical coupling efficiency. Optical cavity is defined by the distance between two edge surface in ordinal semiconductor laser and the cavity length is just equal to the dimension of the semiconductor laser chip. On the other hand, it is defined by the distance between the grating formed in the core region of the optical fiber and the edge surface which is not facing to the optical fiber. In such an optical module, it will take longer time than the semiconductor laser itself from carrier injection into the cavity to generating a coherent light and deteriorate the high frequency performance of the optical module. In order to improve the performance at high frequency, it is desirable to couple the semiconductor laser directly to the optical fiber without inserting any optical members between them. Conventional semiconductor laser module mentioned above are described in, for example, U.S. Pat. No. 5,221,170.
The semiconductor laser module disclosed in that patent has a boxlike package. A ferrule is passed through one of the sidewalls of the package and fixed thereat. The grating is formed in the core region of the optical fiber protected by the ferrule. When the ferrule is thus fixed, it is precisely positioned so that a semiconductor laser and an optical fiber are efficiently coupled. In this semiconductor laser module, moreover, the ferrule is fixedly supported on its leading and rear end sides. Fine aligniment can readily be carried out by utilizing a length of the ferrule as a lever with a fixed point close to the leading end as a fulcrum.
The laser module mentioned above are subjected to a high order of alignment accuracy during the production. However, the desired performance such as optical coupling efficiency may not be always available when the laser module is installed in a system. Lowering of optical output power not relating to the deterioration of a semiconductor laser chip itself may occur. The conventional laser module has been so structured as to secure each of the members for supporting a ferrule to the wall surface of a package. Misalignment may occur because it can not avoid physical distortion by the stress induced at the packaging of the module and the temperature change in a operating even if precisely adjustment is attained at the production. A wavelength shift of the emitted light may also occur because the light reflection characteristics of the grating depends on the modulation interval of the refractive index in the grating and its absolute value. The stress applied to the package changes the modulation interval and the temperature change affects the refractive index of the grating.
A method of manufacturing the conventional semiconductor laser module has comprised the steps of securing each support member to the wall surface of the package and then fixing the ferrule to the support members. In order to pass the ferrule through these support members, however, the inner diameters of the through-holes formed in the respective support members must be greater than the outer diameter of the ferrule. Fine adjustment has been difficult because a aligning tolerance of the ferrule is too large.
SUMMARY OF THE INVENTION
An object of the present invention intended to solve the foregoing problems is to provide a semiconductor laser module so structured as to reduce performance deterioration due to a physical arrangement between a semiconductor laser and an optical fiber.
Another object of the present invention is to provide a method of manufacturing such a semiconductor laser module.
To achieve the above objects, a semiconductor laser module according to the present invention is formed by integrating a semiconductor laser contained in a package with an optical fiber and comprises: a ferrule in to which the light incident end of the optical fiber is inserted; a submount including a horizontal portion for supporting the semiconductor laser and a vertical portion perpendicularly raised from the horizontal portion in such a manner as to cross an optical path, whereupon a through-hole having an inner diameter sufficiently greater than the outer diameter of the ferrule is provided in the vertical portion so that the ferrule can be inserted into the through-hole; a first support member provided with a through-hole whose inner diameter is substantially equal to the outer diameter of the ferrule and mounted close to the leading end of the ferrule; and a second support member provided with a through-hole whose inner diameter is substantially equal to the outer diameter of the ferrule and mounted close to the rear end of the ferrule, wherein the ferrule whose leading end has been inserted into the through-hole in the vertical portion is fixed to and supported by the submount via the first support member close to the leading end and via the second support member close to the rear end thereof.
According to the preferred embodiment of the invention, it is preferable that the semiconductor laser module further comprises an extension member which is cylindrical having an inner diameter sufficiently greater than the outer diameter of the ferrule. One end of the extension member is fixed to the vertical portion of the submount, wherein the second support member is fixed to the vertical portion of the submount via the extension member.
A method of manufacturing the aforesaid semiconductor laser module comprises the steps of:
(1) passing the ferrule through each of the through-holes in the second support member, the extension member and the first support member and fixing the first support member close to the leading end of the ferrule;
(2) aligning the semiconductor laser installed in a horizontal portion of the submount with the optical fiber so as to optically couple to each other and fixing the first support member to the submount;
(3) fixing the extension member to the vertical portion of the submount;
(4) fixing the second support member close to the rear end of the ferrule; and
(5) aligning the semiconductor laser and the optical fiber again and then fixing the second support member to the extension member.
The “aligning” in the aforesaid method of manufacturing the semiconductor laser module means that the mutual position and the angle between the semiconductor laser and the light incident end of the optical fiber are adjusted to couple the semiconductor laser to the optical fiber with the maximum efficiency.
A semiconductor laser module according to the present invention is provided with a ferrule fixed to the submount, which is the most important feature. The ferrule which is fixed in such a configuration is separated completely from the package. The positioning of the ferrule as well as the aligning of an optical fiber is set free from the stress applied to the package.
According to a preferred embodiment of the invention, the submount is fixed to the package via a temperature control element such as a Peltier element. With this arrangement, not only a semiconductor laser but also the whole member including the submount and the ferrule is affected by the Peltier element. The misalignment and the wavelength shift of emitted light due to temperature change in environment hardly occurs. Each of the members such as the submount and the f
Kato Takashi
Takagi Toshio
Font Frank G.
Lee Andrew H.
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
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