Optical: systems and elements – Optical modulator – Light wave directional modulation
Reexamination Certificate
2001-12-21
2004-12-07
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave directional modulation
C359S298000, C359S315000
Reexamination Certificate
active
06829079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical path control apparatus with a mirror section and a manufacturing method for the same.
2. Description of the Related Art
With the request of the communication of a large amount of data, it has been studied to apply a large capacity of optical communication to real time parallel transmission between computers, switching apparatuses, and large-scaled computers or to a subscriber system in the advanced data service. Also, the further spreading of the optical communication is demanded.
An optical module is used in the optical communication is composed of optical elements such as an optical fiber, a laser diode device (LD), a light-emitting diode (LED), and a photodiode (PD). The application fields of the optical module are being widened as the result of the high performance and high functioning of the passive and active elements of the optical module. For the optical communication to the subscriber system, it is demanded to reduce the prices of each optical element and optical module using the optical elements.
For the low price of the optical circuit, a planar type optical circuit is desirable in which the optical elements are arranged on a substrate, compared with a coaxial type module structure in which the optical elements are arranged in a block.
FIG. 1
shows a first conventional example of a planar type optical module for bidirectional communication. A laser diode (LD)
102
, a photodiode (PD)
103
, an optical waveguide
104
, a wavelength filter
105
, and an optical fiber
106
are arranged on a Si substrate
101
. Output light outputted from the laser diode
102
as a transmission source and having the wavelength of 1.3 &mgr;m is inputted to the optical waveguide
104
, and is outputted from the optical fiber
106
via the wavelength filter
105
. An optical signal transmitted through the optical fiber
106
and having the wavelength of 1.55 &mgr;m is inputted to the optical waveguide
104
, an optical path of the optical signal is changed into an adjacent waveguide by the wavelength filter
105
, and then the optical signal is inputted to the photodiode (PD)
103
for reception of the optical signal. In this way, using the planar type light circuit, a small optical transmission and reception module can be realized. In a conventional semiconductor process, grooves are formed for positioning the optical waveguide
104
, the wavelength filter
105
, and the optical fiber
106
on the Si substrate
101
. With this, it is possible to reduce the manufacturing cost, and the installation cost and the decrease of the installation area is realized.
Optical devices are divided into a first type of optical devices such as the light-emitting diode (LED) and the photodiode (PD) and a second type of optical devices such as the laser diode (LD). When the optical device is installed, the light is emitted or received from and by the surface of the optical device in the first type of optical device, while light is emitted from or received by the side surface. When the two types of devices in which light axes are orthogonal to each other should be arranged on the substrate and optically coupled to each other, the optical path conversion of 90 degrees is needed.
As shown in a second conventional example of
FIG. 2
by Masataka Itoh, et. al., (46th Electronic Component & Tecnology Conference, p. 1), an output light from an optical fiber
106
is reflected by a sloped reflection plane
109
which is produced by anisotropically etching a silicon substrate
101
. Thus, an optical path is changed into the direction to the photodiode (PD)
103
. However, in this method, the substrate material is limited to silicon and a substrate of other material cannot be handled.
Also, as shown in a third conventional example of
FIG. 3
disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 7-159658), a prism is known as an optical path conversion element. The optical path of a light beam
107
outputted from an optical waveguide
104
is changed by 90 degrees by a prism
108
or a reflection surface
109
of a reflection mirror. The manufacturing cost of the prism smaller than 1-mm size is high and the use of such a smaller prism causes the increase of the number of parts and takes a long installation time.
A fourth conventional example in which an optical path is not changed is shown in FIG.
4
. For the installation of a photodiode (PD)
103
in a non-planar state, a three-dimensional position adjusting tool is newly necessary. For example, it is necessary to add another substrate
110
to support the photodiode (PD)
103
and parts to fix the substrate on an adjustment position, resulting in more increase of the manufacture cost.
By the way, light outputted from light-emitting device such as a light-emitting diode or a laser diode has a radiation angle. Therefore, even if a waveguide or an optical fiber is arranged in the neighborhood of the radiation section of the light-emitting device, a light loss is large. However, it is difficult to produce a lens with a good light convergence for a small light loss, resulting in more increase of the manufacturing cost.
Even if the above problems are supposed to have been solved, a light switch as an optical path control apparatus becomes necessary for the optical path conversion. As the optical path control apparatus, an un-movable switch and a movable switch are known. The technique using the electro-optic effect and magneto-optics effect of optical crystal is known in the un-movable switch. As the movable switch, the technique to drive an optical fiber mechanically is known as shown by R. Jebens et. al., (Sensors and Actuators 20, pp. 65-73, 1989), or the technique to drive a small mirror (Micro-opto-electro-mechanical-systems: MOEMS) is known as shown by L. Y. Lin. et. al., (IEEE Photon Technol. Lett. 10, 1425, 1998) and by J. Mohr et. al., (Technical Digest of International Conf. on Optical MOEMS and Their Applications, p221-226). The latter technique is expected as the technique for realizing a large-scale light switch cheaply.
The above-mentioned light switch of MOEMS is produced by applying a semiconductor fine fabrication technique to a silicon substrate. According to the above technique, there is a problem that the substrate material is limited to silicon, and the light switch cannot be realized on a printed circuit board whose inside layer wiring is possible. An example in which a mirror and an electrostatic actuator are formed by a Ni plating method in LIGA (Lithographie Galvanoforming Abforming) process is known. However, there is a problem in that the surface roughness of the mirror is large and the light loss is large.
An optical path adjustment between the optical fiber and the photodiode (PD) in the optical module is mainly carried out using the flat surface of the silicon substrate as shown in above-mentioned technique (Masataka Itoh, et. al.). However, because a substrate other than the silicon substrate cannot be used as the substrate for the optical module, the flexibility of manufacturing the optical module is restricted strongly.
In conjunction with the above description, an optical waveguide—optical device coupling structure is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 7-159658). In this reference, an optical waveguide and an optical device are optically coupled which are formed by laminating different dielectric layers on a dielectric substrate. The dielectric substrate has a groove section provided in front of an end of the optical waveguide on the installation side of the optical device, to have a base surface parallel to the optical waveguide surface. A prism is installed on a position where the light axis of the optical waveguide and the light axis of the optical device are coincident with each other. The optical device is installed onto the dielectric substrate over the prism and the optical waveguide.
Also, a manufacturing method of a micro mirror is disclosed in Japanese Laid Open Patent Application (JP-A-
Kitajo Sakae
Kouta Hikaru
Oda Mikio
Sasaki Yasuhiro
Shimada Yuzo
Katten Muchin Zavis & Rosenman
NEC Corporation
Schwartz Jordan M.
Stultz Jessica
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