Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1999-08-24
2001-08-28
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S091000, C385S093000, C385S094000, C385S033000
Reexamination Certificate
active
06282350
ABSTRACT:
The present invention relates to a photoelectronic device (semiconductor optical module) and a method of manufacturing the same and, more particularly, to a technique effective for bonding and securing an optical fiber to a silicon substrate having a groove on the surface thereof referred to as “silicon platform” using a bonding element such as thermosetting resin or an ultraviolet-setting adhesive.
BACKGROUND OF THE INVENTION
Photoelectronic device incorporating a semiconductor laser (semiconductor laser chip) are used as light sources for information processing apparatuses and light sources for optical communication.
One well-known type of photoelectronic devices is photoelectronic devices (semiconductor laser devices) having a box-type package structure.
Referring to passive alignment mounting utilizing a silicon platform, for example, passive alignment type optical modules are known which has a structure in which a silicon platform is mounted in a package having leads and a cover; a laser diode, a monitor photodiode and a pig-tail optical fiber are mounted on the silicon platform; and a presser plate is mounted.
SUMMARY OF THE INVENTION
The inventors are working on techniques for securing an optical fiber on a silicon platform in a short period of time and techniques to reduce the cost of packaging in optoelectonic apparatuses incorporating a semiconductor laser (passive alignment type optical module).
The inventors made the following studies of techniques for securing an optical fiber on a silicon platform in a short period of time.
In a conventional semiconductor optical module utilizing a silicon platform (support substrate), an optical fiber embedded in the silicon platform is secured after adjusting optical coupling between the end of the optical fiber embedded in a groove on the silicon platform so as to trail along it and a semiconductor laser chip secured on the surface of the silicon platform. It is secured using (1) a technique for securing it with thermosetting resin (thermosetting epoxy resin) or an adhesive such as an ultraviolet-setting adhesive and (2) a technique for securing the optical fiber while pressing it against the silicon platform with a presser plate.
When an optical fiber is secured with thermosetting resin, a process of applying and setting the thermosetting resin must be performed with the optical fiber pressed against the silicon platform to remain static after adjustment of optical coupling.
However, this method reduces the efficiency of an operation of securing optical fiber because the thermosetting resin takes a long time to be set. For example, in the case of epoxy resin used as thermosetting resin, the setting process takes about two minutes even at a temperature of 150° C. which is in the excess of the guaranteed temperature for an optical fiber.
Since the adjustment of optical coupling is performed using a fiber inserting apparatus, the long time spent for the adjustment of optical coupling results in a reduction in the operating efficiency of the fiber inserting apparatus. In addition, a fiber inserting apparatus is expensive and consequently increases the cost for the adjustment of optical coupling.
The method of setting thermosetting resin on a fiber inserting apparatus after the adjustment of optical coupling has had a problem in that the process of setting thermosetting resin can not be performed on a batch process basis and this reduces the operating efficiency of a fiber inserting apparatus further.
The efficiency of the conventional operation of securing an optical fiber with thermosetting resin is thus reduced, which hinders any reduction in the manufacturing cost of a photoelectronic device (optical module).
The conventional technique for securing an optical fiber with thermosetting resin results in a reduction of the yield of optical axis alignment because the state of optical coupling can change if the optical fiber is moved before the thermosetting resin is reliably set.
Referring to the technique of securing an optical fiber on a silicon platform by applying an ultraviolet-setting adhesive to a part of the optical fiber and silicon platform and thereafter irradiating the ultraviolet-setting adhesive with ultraviolet light to set the ultraviolet-setting adhesive, it secures an optical fiber with reduced reliability because regions which can not be irradiated with ultraviolet light are not set, although the setting process utilizing ultraviolet irradiation allows an optical fiber to be secured in a short period of time.
A possible solution is a two-step processing mode which involves setting by means of irradiation with ultraviolet beams and heat setting using an ultraviolet-setting adhesive which can be set by both ultraviolet beams and heat. In this case, the efficiency of an operation of securing an optical fiber (turnaround time: TAT) is reduced because the setting process using heat takes time. An example of this type of ultraviolet-setting adhesives takes a heating time as long as 60 minutes at 120° C.
A heat setting process at a processing temperature as high as 120°C. and with a long processing time as described above can result in deterioration of resin covering an optical fiber (the region of a fiber cable).
In a structure in which a metalized layer is provided on the surface of an optical fiber comprising a core and a clad (optical fiber core) and in which the metalized layer is used to secure the optical fiber to a silicon platform or a cylindrical fiber guide for guiding the optical fiber with solder, when an optical fiber is fitted in a groove on a silicon platform so as to trail along it, variation of the thickness of the metalized layer can make it difficult to adjust optical coupling between the core of the optical fiber and a semiconductor laser chip.
Under such circumstances, the inventors are studying a technique as described below for securing an optical fiber on a silicon platform, although it is not a known technique. Specifically, in a conventional method in which a silicon platform (support substrate) having a groove on the surface thereof is prepared; a photoelectric conversion element (semiconductor laser chip) is thereafter secured on the surface of the support substrate at one end of the groove; an optical fiber is fitted in the groove so as to trail along it; and, thereafter, the state of transmission and reception of light between the photoelectric conversion element and the optical fiber is adjusted and the optical fiber is secured on the support substrate with thermosetting resin, according to the technique, the optical fiber is preliminaryly secured using securing means in a securing time shorter than the setting time of the thermosetting resin while it is pressed against the support substrate, and is thereafter finally secured with thermosetting resin with the pressing cancelled.
For example, an ultraviolet-setting adhesive is applied to a part of the optical fiber and support substrate; the ultraviolet-setting adhesive is set by irradiating it with ultraviolet light to preliminary secure the optical fiber on the support substrate; and a part of the optical fiber which is farther from the semiconductor laser chip than the preliminary secured position is covered with thermosetting resin.
According to this technique, since preliminary securing is carried out using an ultraviolet-setting adhesive, a support substrate and the like can be moved even after the application of thermosetting resin and before the thermosetting resin is set. This allows the support structure and the like to be removed from a fiber inserting apparatus in a short period of time, and the process of setting the thermosetting resin (final securing) can therefore be carried out on a batch process basis. Such a batch process makes it possible to reduce the time required for securing an optical fiber on one support substrate. The reliability of optical coupling is also improved.
In addition to the employment of this technique, the inventors also studied techniques for reducing the cost of a package. In order to achieve a re
Eguchi Shuji
Miura Toshimasa
Naka Hiroshi
Takahashi Shoichi
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
Palmer Phan T. H.
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