Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2002-11-21
2004-05-11
Lee, John D. (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S041000, C385S045000, C385S050000
Reexamination Certificate
active
06735359
ABSTRACT:
CLAIM OF PRIORITY
This application claims priority to an application entitled “ACTIVE OPTICAL SEMICONDUCTOR HAVING A CURVED OPTICAL WAVEGUIDE,” filed in the Korean Industrial Property Office on Nov. 23, 2001 and assigned Serial No. 2001-73263, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical-communication module and, more particularly to an optical device having an optical waveguide mounted on an optical communication module.
2. Description of the Related Art
An optical-waveguide device comprises an optical waveguide through which light passes and a clad surrounding the optical waveguide to allow the light to pass only through the optical waveguide. Optical-waveguide devices may include optical semiconductors to which an optical waveguide and a clad are laminated on a semiconductor substrate.
A conventional optical communication module includes active optical devices and optical waveguide devices(or optical fibers). U.S. Pat. No. 6,273,620 issued to Kato, et al., entitled “SEMICONDUCTOR LIGHT EMITTING MODULE”, discloses an example of an optical communication module, in which the light emitting module includes a semiconductor optical amplifier with a first optical waveguide and an optical fiber grating with a second optical waveguide to which a Bragg grating is printed.
In the conventional optical communication module, the alignment between an active optical device and an optical waveguide device, which may be a passive optical semiconductor, optical fiber, or another active optical semiconductor, plays a vital role because the misalignment between them causes coupling loss between the end surfaces of the active optical device and the optical waveguide device.
FIG. 1
is a schematic partial view of the active optical device and the optical waveguide device and, in particular shows the optical loss caused by the misalignment therebetween. As shown, the optical waveguide device
120
is aligned on an optical axis
130
and includes a second optical waveguide
122
forming a passage for the light to pass therethrough and a clad
124
surrounding the second optical waveguide
122
. An active optical device
110
is aligned on the optical axis
130
and includes a first optical waveguide
112
which forms a passage for light to pass therethrough, a clad
114
surrounding the first optical waveguide
112
, and upper and lower electrodes (not shown) which generate and amplify the light by means of injected carriers.
In addition, the optical waveguide device
120
and the active optical device
110
contain alignment lines
118
and
126
, respectively, so that they can be used to align the devices
110
and
120
. For example, when the optical waveguide device
120
and the active optical device
110
are mounted on a submount (not shown), the alignment lines
118
and
126
are aligned with auxiliary lines (not shown) that are marked on the submount to correspond to the alignment lines
118
and
126
, such that the optical waveguide device
120
and the active optical device
110
can be aligned correctly. This type of alignment is known as a passive alignment method.
Another alignment is known as an active alignment method. In the active alignment method, for example, the optical waveguide device
120
is fixed, then the active optical device
110
is moved while the light output from the optical waveguide device
120
is monitored, so that the location of the active optical device
110
at which the light output has a maximum value can be found.
In comparison with the passive alignment method, it can be easily seen that the active alignment method as described above requires a more time during the manufacturing stage, thus not desirable to be used in mass-production.
Referring back to
FIG. 1
, the light generated in the active optical device
110
is discharged through one end surface of the active optical device
110
, and the discharged light is introduced into the second optical waveguide
122
through the end surface of the optical waveguide device
120
. In this case, the active optical device
110
and the optical waveguide device
120
are aligned on the optical axis
130
and the end surface of the optical waveguide device
120
is in parallel with the end surface of the active optical device
110
, such that the light reflected by the end surface of the optical waveguide device
120
can transmit into the first optical waveguide
112
. The light transmitting back into the first optical waveguide
112
serves as noise, thereby deteriorating the output characteristics of the active optical device
110
.
FIG. 2
is a schematic partial view of an active optical device and an optical waveguide device, and it shows optical loss due to a size error of the active optical device when the active optical device and an optical waveguide device are packaged according to a passive alignment method. As shown, the first and second optical axes
230
and
250
are not in parallel to each other. The optical waveguide device
240
is aligned on the second optical axis
250
, and the active optical device
210
is aligned on the first optical axis
230
using the alignment lines
218
and
246
.
The optical waveguide device
240
is aligned on the second optical axis
250
by means of a second alignment line
246
, and includes a second optical waveguide
242
forming a passage for the light to pass through and a clad
244
surrounding the second optical waveguide
242
. The active optical device
210
is aligned on the first optical axis
230
by means of a first alignment line
218
and includes a first optical waveguide
212
forming a passage for light to pass through, a clad
214
surrounding the first optical waveguide
212
, and upper and lower electrodes (not shown) which generate and amplify light by means of injected carriers. The first optical waveguide
212
is tilted with respect to an end surface
215
of the active optical device
210
such that the reflected light at the end surface
215
does not couple back into the first optical waveguide
212
.
In operation, the light
260
generated in the active optical device
210
is emitted through the end surface
215
of the active optical device
210
. In the case of the designed active optical device
220
, light
270
(shown by a broken line) emitted from the designed active optical device
220
can be incident to the second optical waveguide
242
. However, when the fabricated active optical device
210
shown by solid lines has a size different from that of the designed active optical device
220
shown by broken lines, the light
260
emitted from the first optical waveguide
212
is not incident to the second optical waveguide
242
, thus its coupling efficiency is deteriorated. Note that the designed active optical device
220
represents the boundary where the proposed optical device
220
supposed to line up according to the design specification, whereas the fabricated active optical device
210
represents the actual product manufactured and positioned according to the design specification. The size difference between the designed active optical device
220
and the fabricated active optical device
210
is due to fabrication error, which occurs when cleaving a processed wafer into the designed bars. The size error due to this cleaving inaccuracy is around ±10 &mgr;m when working with InP or GaAs compound semiconductors. As a result, the light emitted from the end surface
215
of the active optical device
210
misses the second optical axis
250
.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-mentioned problems occurring in the prior art and provides additional advantages, by providing an optical device that can prevent the deterioration of the optical coupling efficiency due to the size error in the optical device when the optical device and an optical waveguide device are packaged according to a passive alignment method.
Accordingly, there is provided an optical commu
Cha & Reiter L.L.C.
Lee John D.
Samsung Electronics Co,. Ltd.
Wong Eric
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