Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Having diverse electrical device
Reexamination Certificate
2000-08-30
2003-02-18
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Having diverse electrical device
C438S023000, C257S080000, C257S082000
Reexamination Certificate
active
06521471
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor opto-electronic component comprising at least two optically active sections each having a waveguide buried in a cladding layer.
For this type of multi-section opto-electronic component, it is important to have high electrical insulation between each section in order to prevent interactions between these during the functioning of the component. The invention relates more particularly to any opto-electronic component comprising at least one receiving element integrated with another element.
The objective of the present invention is to permit simultaneous functioning of the optically active structures without any interaction between the transmitter and receiver and/or between the different receivers detecting signals at different wavelengths.
FIG. 1
depicts a diagram in longitudinal section of a conventional in-line transceiver component, denoted 1D-TRD (“In-line Transmitter Receiver Device” in British and American literature), obtained by the monolithic integration of a laser
20
and detector
30
on the same substrate
10
. The laser
20
sends a signal towards an optical fibre, for example, whilst the detector
30
receives a signal coming from this same optical fibre. The emission wavelength of the laser
20
is less than the reception wavelength of the detector
30
. For example, the emission wavelength is equal to 1.3 &mgr;m whilst the reception wavelength is 1.55 &mgr;m. In this case, given that the emission wavelength is less than the reception wavelength, and that the laser
20
is situated close to the detector
30
, the laser can cause optical interference on the detector. This is because the laser also emits, in the direction of the detector, light at 1.3 &mgr;m which dazzles the latter.
To prevent this dazzling of the detector, the component has a third section, disposed between the laser
20
and detector
30
, forming an optical isolator
40
. This optical isolator absorbs the light emitted at 1.3 &mgr;m in the direction of the detector, so that the latter can detect the 1.55 &mgr;m optical signal coming from the optical fibre without being disturbed by the laser.
The substrate
10
, or bottom layer, can for example be n-doped InP. The waveguides, respectively
31
of the detector
30
and
21
of the laser
20
and of the optical isolator
40
, are etched in the form of ribbons and buried in a highly doped cladding layer
11
. The waveguides are said to be of the BRS (“Buried Ridge Structure” in British and American literature) type. The cladding material
11
is p+ doped when the substrate is n doped. Naturally, this type of ribbon is only one example. Other types of ribbon can be suitable. The n and p dopings of the different layers can also be reversed.
The composition and dimensions of the waveguides are of little importance. In the example in
FIG. 1
, the waveguide
31
of the detector
30
is for example produced from ternary material, whilst the waveguide
21
of the laser
20
and of the optical isolator
40
is produced in a structure with quantal wells.
In addition, metallic electrodes
22
,
32
,
42
and
14
are formed on the different sections and on the bottom of the component, so as to enable it to function.
An absorbent layer
12
doped with the same type of carrier as the cladding layer
11
is situated between the conductive layer
11
and the metallic electrodes
22
,
32
,
42
so as to afford good electrical contact and in order to collect the carriers which make it possible to detect the signal on the electrode
32
of the detector
30
. This absorbent layer
12
can consist of a ternary material, for example.
Because of the presence of conductive layers
11
, the component also has electrical isolation areas
50
, or resistivity areas, between the different sections
20
,
30
,
40
in order to prevent any electrical disturbance of one section vis-à-vis another during the functioning of the component.
This type of in-line transceiver, having a central part
40
for absorbing all the light flux sent at 1.3 &mgr;m to the detector, functions very well for all the light which is guided in the waveguide ribbons
21
.
However, not all the light emitted is entirely guided. This is because there exists also spontaneous light which is emitted throughout the volume of the component. In addition, some of the stimulated light can also be diffracted in the component because of the presence of defects in the waveguide
21
.
The curves in
FIG. 2
show the penalties noted on the sensitivity of the detector, in dB, for different operating modes. Curve A represents a reception reference when the laser is off, curve B represents a reception reference when the laser is on continuously and curve C represents the simultaneous functioning of the laser and detector. A penalty of 4.5 dB is found between curve B and curve C, when the laser and detector are modulated simultaneously. This penalty is also increased by increasing the power of the laser.
This penalty is principally optical. It is caused by the non-guided light emitted at 1.3 &mgr;m, in all directions, which interferes with the detector at 1.55 &mgr;m.
This optical disturbance is depicted highly diagrammatically in
FIG. 1
by the wave
60
. The metallic electrode
14
, disposed at the substrate/air interface, can play the role of an optical reflector in the substrate
10
. Some of the spontaneous light emitted in the volume of the component can therefore be reflected by the electrode
14
and be coupled with the waveguide
31
of the detector
30
from below. Likewise, some of the stray light
60
can also be reflected on the electrodes
42
and
32
since the absorbent layer
12
does not absorb all this stray light
60
.
Naturally, the disturbance of the detector
30
by the non-guided light
60
is in reality much more complex than a simple reflection. This is because some of the stray light can also undergo multiple reflections in the bottom layer
10
and top layer
11
. Another part of this stray light can also dazzle the detector in glancing incidence, for example.
Techniques have already been envisaged for combating the penalty of 4.5 dB found in the example given in
FIG. 2
, which occurs during the simultaneous functioning of the laser and detector. The techniques envisaged are essentially electronic techniques.
These techniques consist, for example, of taking part of the laser modulation signal, and then subtracting it in reception. The use of these electronic processing techniques has demonstrated a reduction of 2 dB in the penalty. However, they require the development, manufacture and adjustment of specific electronics for this type of particular transceiver component, so that they considerably increase the cost of this component. However, it is being sought to manufacture this type of component on a large scale and therefore to reduce its cost price to the maximum possible extent. Consequently these electronic processing techniques can not be used for the mass production of such a component.
In addition, an in-line transceiver is intended to be installed at subscribers and must be able to function between 0 and 70° C. without any temperature regulation. However, the reliability of these electronic techniques has not been demonstrated over this range of temperatures and it is not proved that they can automatically adjust themselves according to the temperature.
SUMMARY OF THE INVENTION
One aim of the present invention therefore consists of producing an inexpensive opto-electronic component including a detector and a parasitic element for this detector, such as a laser or any other element, the operating wavelength of the parasitic element being less than the reception wavelength of the detector, and in which the interference of 4.5 dB on the detector by the parasitic element (according to the example in FIG.
2
), which occurs during their simultaneous operation, is considerably reduced.
To this end, the invention proposes to reduce the active proportion of the detector able to detect a signal, whilst the
Chaumont Christine
Leroy Arnaud
Mallecot Franck
Plais Antonina
ALCATEL
Picardat Kevin M.
Sughrue & Mion, PLLC
LandOfFree
Multi-section opto-electronic component does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-section opto-electronic component, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-section opto-electronic component will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3179019