Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
2000-06-28
2001-05-08
Ullah, Akm E. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C257S059000
Reexamination Certificate
active
06227723
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a substrate for mounting an optical component and an optical module which are suitably used in optical transmission, optical communication and the like.
In recent years, optical fiber communication has been put into practice in the fields of CATV and public communication. Conventionally, optical modules having a high operation speed and high reliability have been realized by the so-called coaxial or dual-inline type module construction. These optical modules have been already put into practice mainly in the so-called trunk systems.
Contrary to this, optical modules have been recently vigorously developed using a technique for highly precisely positioning and mounting optical components and an optical fiber on a silicon auxiliary substrate (auxiliary mount placed in a package, also called silicon platform) only by mechanical precision. These optical modules are targeting a practical use mainly in an area called subscriber system, and are required to be smaller, thinner and less expensive. On the other hand, it has become essential for optical modules to operate in a wider band and, accordingly, there is a demand for realization of substrate for mounting an optical components which can operate in a high-frequency region.
In the substrates for mounting an optical component, which are used for these optical modules, markers used to position optical semiconductor devices on a substrate as a base member have been frequently formed simultaneously with a V-shaped groove in which an optical fiber is mounted. For example, as shown in
FIG. 11
, markers
102
in the form of V-shaped grooves are formed in a substrate
101
by anisotropic etching by the same mask as a V-shaped groove
103
for mounting an optical fiber, using a photolithography technique. Accordingly, a relative positioning precision of the markers
102
and the V-shaped groove
103
is determined by the precision of a photomask, and the markers
102
and the V-shaped groove
103
are hardly displaced with respect to each other. Indicated at
104
is an electrode for mounting optical semiconductor devices.
Further, it is also known to form the so-called self-alignment marker for simultaneously fabricating a pattern for forming the V-shaped groove
103
, a pattern for forming electrodes
104
for mounting optical semiconductor devices and an electrode
106
for driving the optical semiconductor devices, and a pattern for forming alignment markers
105
as shown in FIG.
12
.
However, if the substrates
101
shown in
FIGS. 11 and 12
are made of a silicon monocrystal, a dielectric loss increases in a high-frequency region due to a large dielectric loss tangent if electrical signals for driving the optical semiconductor devices are high-frequency signals. This causes a problem of degraded characteristics of the optical module.
Further, in the case of the V-shaped groove markers
102
shown in
FIG. 11
, they are generally formed by anisotropic etching. Accordingly, even if the mask configuration is circular in a plane, the selective etching causes a specific rectangular configuration, consequently restricting the configuration of the markers
102
. In order to increase the mounting precision, it may be considered to combine a plurality of V-shaped groove markers formed in positions surrounding the same optical semiconductor device. However, the combination of a plurality of alignment markers makes the entire arrangement area of those markers larger. Therefore, it becomes difficult to observe each alignment marker unit by enlarging it in order to increase the mounting precision.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a substrate for mounting an optical component and an optical module which are free from the problems residing in the prior art.
It is another object of the present invention to provide a substrate for mounting an optical component and an optical module which can suitably operate even if electrical signals for driving optical semiconductor devices are high-frequency signals.
It is still another object of the present invention to provide a substrate for mounting an optical component and an optical module which enable high-precision mounting of optical semiconductor devices.
According to an aspect of the invention, a substrate for mounting an optical component is provided with a base member having a semiconductor device mounting portion including a higher located first area to have an optical semiconductor device mounted on its outer surface and a second area which is stepped down from the first area so as to be located lower than the first area, an insulation layer provided in the second area of the base member so as to have substantially the same height as the first area and having a smaller dielectric loss tangent than the base member, and a driving electrode pattern provided on the insulation layer for driving the optical semiconductor device.
According to another aspect of the invention, an optical module is provided with a base member including a semiconductor device mounting portion having a higher located first area to have an optical semiconductor device mounted on its outer surface and a second area which is stepped down from the first area so as to be located lower than the first area, and a waveguide mounting portion where a optical waveguide to be optically coupled to the optical semiconductor device is to be mounted, an insulation layer provided in the second area of the base member so as to have substantially the same height as the first area and having a smaller dielectric loss tangent than the base member, a driving electrode pattern provided on the insulation layer for driving the optical semiconductor device. Further, there are provided an optical semiconductor device mounted in the first area of the semiconductor device mounting portion and an optical waveguide mounted in the waveguide mounting portion to be optically coupled to the optical semiconductor device.
With the above constructions, since the insulation layer provided in the second area of the base member has a smaller dielectric loss tangent than the base member, the loss in the driving electrode pattern provided on the insulation layer can be small even if a drive signal fed to the optical semiconductor device is a high-frequency signal. Therefore, a substrate for mounting an optical component having excellent electrical performance and reliability can be realized. Further, alignment markers for positioning the optical semiconductor device during mounting on the base member can be easily formed in the first area. If such alignment markers are formed in the first area, the optical semiconductor device can be highly precisely mounted. In this respect as well, a substrate for mounting an optical component and an optical module having excellent electrical performance and reliability can be realized.
According to still another aspect of the invention, a substrate for mounting an optical component is provided with a base member having a semiconductor device mounting portion where an optical semiconductor device is to be mounted and a waveguide mounting portion formed with a groove for mounting an optical waveguide to be optically coupled to the optical semiconductor device; a first insulation film formed on an outer surface of the semiconductor device mounting portion of the base member, a second insulation film which is so formed on an outer surface of the semiconductor device mounting portion of the base member as to expose at least a portion of the first insulation film and is thicker than the first insulation film, a mounting electrode pattern for mounting the optical semiconductor device which pattern is formed to extend over the first insulation film, and a driving electrode pattern for driving the optical semiconductor device which pattern is formed to extend over the second insulation film.
According to further aspect of the invention, an optical module is provided with a base member having a semiconductor device mounting portion where an opt
Masuda Yuji
Shinya Masato
Takemura Koji
Hogan & Hartson LLP
Kyocera Corporation
Ullah Akm E.
LandOfFree
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