Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
2000-02-07
2002-05-07
Font, Frank G. (Department: 2877)
Coherent light generators
Particular active media
Semiconductor
C372S043010, C372S005000
Reexamination Certificate
active
06385223
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for connecting an a optical waveguide and an optical semiconductor device and an apparatus for connecting the same, particularly to an improvement of a passive alignment system.
2. Description of the Prior Arts
There has existed an electric-optical conversion device called an optical module, which is constituted by integrating an optical semiconductor device such as a semiconductor laser diode and an optical waveguide such as an optical fiber.
In fabricating the optical module, it is an important challenge to allow an emitted light from the optical semiconductor device to be incident onto the optical waveguide with minimal waste and to increase optical coupling coefficiency.
As methods to connecting the optical semiconductor device and the optical waveguide, there have existed an active alignment method and a passive alignment method.
The active alignment method is the one performed as follows. Specifically, an optical semiconductor device is actually made to emit a light and the emitted light is incident onto an optical waveguide. Relative positions of the optical semiconductor device and the optical waveguide with respect to each other are finely adjusted so as to maximize an intensity of the emitted light from the optical waveguide, thus connecting the optical semiconductor device and the optical waveguide.
On the other hand, the passive alignment method is performed as follows. Specifically, the optical semiconductor device is actually not made to emit a light, but alignment marks previously formed in both of the optical semiconductor device and the optical waveguide are made to be coincident with each other. Thus finely adjusting the relative positions of the optical semiconductor device and the optical waveguide with respect to each other to connect them.
In Japanese Patent Laid-Open No. Hei 7 (1995)-43565, published on Feb. 14, 1995, a method to connect the optical waveguide and the optical semiconductor device using the passive alignment method is disclosed. A technology written in the gazette will be described as a first conventional example.
FIG. 10
is a perspective view showing a method for connecting an optical waveguide and an optical semiconductor device of the first conventional example.
In
FIG. 10
, an optical semiconductor device
102
is loaded onto a sub substrate
101
. A thin film for shielding infrared ray is formed entirely on an overall bottom surface
102
a
of the optical semiconductor device
102
other than regions of markers
161
and
162
. The sub substrate
101
has a thin film for shielding infrared ray only at regions of markers
131
and
132
, and accommodates an optical fiber
104
in its V-shaped groove
105
.
Next, the infrared ray (not shown) is made to transmit through the sub substrate
101
upward from an infrared ray source (not shown) provided below the sub substrate
101
, and the markers
131
,
132
,
161
and
162
are photographed by an infrared ray camera (not shown) provided above the sub substrate
101
.
FIG. 11
is a schematic view showing a photographed image in the first conventional connection method.
In
FIG. 11
, the photographed image of the markers
131
,
132
,
161
and
162
undergoes an image processing, and relative positions of the optical semiconductor device
102
and the sub substrate
101
with respect to each other are corrected so that areal centers of gravity of the markers
131
and
132
and areal centers of gravity of the markers
161
and
162
are coincident with each other. Thereafter, the optical semiconductor device
102
is loaded onto the sub substrate
101
and jointed to the sub substrate
101
, whereby a precision in the connection of the optical semiconductor device
102
and the optical fiber
104
is increased.
Moreover, in Japanese Patent Laid-Open No. Hei 8 (1996)-111600, published on Apr. 30, 1996, a high precision mounting method using a passive alignment method for controlling relative positions of an optical semiconductor device and an optical waveguide based on an overlapping state of polygonal markers is disclosed. A technology written in the gazette is described as a second conventional example.
FIG. 12
is a perspective view showing a method for connecting an optical waveguide and an optical semiconductor device of a second conventional example.
In
FIG. 12
, an optical semiconductor device
228
is loaded onto a silicon substrate
225
. In the optical semiconductor device
228
, first markers having parallelogram-shape which allow an infrared ray R (
FIG. 13
) to transmit through are perforated, and second markers
238
are formed on a bottom surface. An infrared ray R is shielded in other regions than the region of the markers
238
. In the silicon substrate
225
, a rectangular-shaped holes, which allows the infrared ray R to transmit through, are perforated, and first markers
237
are formed. The infrared ray R is shielded in other regions than the region of the markers
237
.
FIG. 13
is a perspective view showing an apparatus for connecting the optical waveguide and the optical semiconductor device of the second conventional example.
In
FIG. 13
, the infrared ray R is irradiated upward from an infrared-ray source
222
located below the silicon substrate
225
and the optical semiconductor device
228
, and an image of the infrared ray R having transmitted through the silicon substrate
225
and the optical semiconductor device
228
is photographed by an infrared-ray camera
231
.
FIG. 14
is a schematic view showing an infrared-ray-photographed image in the method for connecting the optical guide and the optical semiconductor device of the second conventional example.
Based on the photographed image as shown in
FIG. 14
, a deviation of the first and second markers
236
and
238
from each other is obtained, and a parts-moving stage
226
(
FIG. 13
) and a substrate moving stage
223
(
FIG. 13
) are controlled so as to make coincident the first and second markers
236
and
238
with each other, thus positioning the silicon substrate
225
and the optical semiconductor device
228
.
Moreover, the image of the infrared ray R having transmitted through the first and second markers
236
and
238
is taken out by a half mirror
233
(FIG.
13
), and measured by an optical intensity detector
235
(FIG.
13
). The silicon substrate
225
and the optical semiconductor device
228
are fixed at a position where an intensity of the image comes to be maximum or minimum, whereby a positioning precision of the silicon substrate
225
and the optical semiconductor device
228
is increased.
As a still another conventional example, in Japanese Patent Laid-Open No. Hei 9 (1997)-205255, published on Aug. 5, 1997, an optical semiconductor device using an passive alignment method, in which areal centers of gravity of alignment marks provided respectively on a semiconductor laser chip and a sub-mount are made to be coincident with each other, and a method for manufacturing the same are disclosed.
Moreover, in Japanese Patent Laid-Open No. Hei 9 (1997)-292542, published on Nov. 11, 1997, an optical part mounting substrate using a passive alignment method, in which alignment marks provided respectively on a semiconductor laser chip and an optical part fixing member are detected thus mounting one on another, is disclosed.
However, the connection methods for the optical waveguide and the optical semiconductor device in the conventional examples have the following problems.
In the first conventional example shown in
FIG. 10
, when a working error exists on an outgoing surface
102
b
of the optical semiconductor device
102
, a distance from the outgoing surface
102
b
of the optical semiconductor device
102
to an incident surface
104
a
of the optical fiber
104
shifts from a designed distance. Thus, an optical coupling coefficiency of the optical semiconductor device
102
and the optical fiber
104
reduces.
The reason is as follows. Specifically, when the optical semiconductor devi
Flores Ruïz Delma R.
Font Frank G.
Michael Best & Friedrich LLC
Whitesel J. Warren
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