Optical waveguides – Integrated optical circuit
Reexamination Certificate
1999-08-30
2001-12-11
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Integrated optical circuit
C385S031000, C385S047000
Reexamination Certificate
active
06330377
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical transmitting/receiving method and apparatus and more particularly to an optical transmitting/receiving method and apparatus wherein optical parts and electronic parts are mounted on the same substrate.
2. Description of Related Art
With rapid progress of IC (Integrated Circuit) technology and LSI (Large Scale Integrated Circuit) technology, the operating speed and integration density of these circuits have been improved, thereby accelerating improvement in performance of MPU (Micro-Processing Unit: Microprocessor) and of operation rate and capacity of memory chip. Under the situation explained above, particularly in the case of high speed digital signal transmission and in the case where a high speed bus or the like is required between MPU and memory chip, delay by the electrical wiring and deterioration of crosstalk due to the high speed and high density transmission by signal wire have been bottle neck for realization of higher performance. As the technique for solving such problem, attention is paid to optical wiring (optical inter-connection).
This optical wiring may be thought applicable in various levels, for example, between apparatuses, boards in the apparatus, chips in the board, etc. For signal transmission in comparatively short distance, for example, between chips, an optical transmitting/receiving method using optical waveguide as the transmission path has been effective.
An example of the optical transmitting/receiving method of the related art using such optical waveguide as the transmission path will be explained with reference to FIG.
1
and FIG.
2
. Here,
FIG. 1
is a schematic cross-sectional view illustrating an example of the optical transmitting/receiving system of the related art of
FIG. 1
, while
FIG. 2
is an enlarged view of optical waveguide and 45° micro-mirror of the optical transmitting/receiving method of FIG.
1
.
As illustrated in
FIG. 1
, on the upper surface of a multilayer substrate
70
on which the first to fourth insulating layers
70
a
,
70
b
,
70
c
,
70
d
are sequentially laminated, a couple of plane type optical emitting/receiving elements
72
a
,
72
b
are face-down mounted with the flip chip joining method, namely mounted with the optical emitting/receiving surface directed downward.
Although not illustrated, a wiring layer is also formed at the upper surface and lower surface of the multilayer substrate
70
and between the first to fourth insulating layers
70
a
,
70
b
,
70
c
,
70
d
and moreover these wiring layers are connected through holes formed to the first to fourth insulating layers
70
a
,
70
b
,
70
c
,
70
d
, to form a multilayer wiring structure as a whole. Moreover, on the upper surface of multilayer substrate
70
, optical emitting drive and optical receiving and amplifying circuit, LSI circuit and electronic parts such as inductor, capacitor and resistor or the like are mounted in addition to the plane type optical emitting/receiving elements
72
a
,
72
b
, utilizing the flip chip joining method and wire bonding joining method.
Moreover, on the upper surface of the multilayer substrate
70
, an optical waveguide
74
is formed extending in straight up to the area just under the plane type optical emitting/receiving element
72
b
from the area just under the plane type optical emitting/receiving element
72
a
. As illustrated in
FIG. 2
, this optical waveguide
74
is formed of core
76
at the center for transmitting optical signal and clad
78
consisting of a material having a refraction index which is lower than that of core
76
in order to surround the core
76
. Moreover, at both end faces of this optical waveguide
74
, the 45° micro-mirrors
80
a
,
80
b
and formed.
In the optical transmitting/receiving method illustrated in FIG.
1
and
FIG. 2
as explained above, an optical signal emitted from an optical emitting surface, for example, of the plane type optical emitting/receiving element
72
a
is totally reflected in 90 degrees by the 45° micro-mirror
80
a
located at the area just under the optical emitting surface. Thereafter, this optical signal is incident to the core
75
of the optical waveguide
74
and is then propagated within the core
76
. Moreover, the optical signal propagated within the core
76
of this optical waveguide
74
is totally reflected in 90 degrees by the 45° micro-mirror
80
b
and thereafter it is then incident to the optical receiving surface of the plane type optical emitting/receiving element
72
b
located at the area just above this 45° micro-mirror
80
b.
The optical signal emitted from the plane type optical emitting/receiving element
72
a
is then transmitted to the plane type optical emitting/receiving element
72
b
via the 45° micro-mirror
80
a
, optical waveguide
74
and 45° micro-mirror
80
b
. In the same manner, the optical signal emitted from the plane type optical emitting/receiving element
72
b
is then transmitted to the plane type optical emitting/ receiving element
72
a
via the 45° micro-mirror
80
b
, optical waveguide
74
and 45° micro-mirror
80
a.
In
FIG. 2
, the optical signal is totally reflected in 90 degrees by the 45° micro-mirror
80
a
and is then propagated within the core
76
of the optical waveguide
74
. This profile is indicated using arrow mark as the image of optical transmission. This image of optical transmission is only tentative indication for convenience of explanation. Actually, it is a matter of course that the optical signal incident in the range of predetermined critical angle is propagated by repeating total reflection at the interface of the core
76
and clad
78
of the optical waveguide
74
.
Moreover, in some cases, a very small size mirror illustrated in
FIG. 3
is used in place of the 45° micro-mirrors
80
a
,
80
b
illustrated in FIG.
1
and FIG.
2
. Namely, on the upper surface of the multilayer substrate
70
, the optical waveguide
82
extending in straight up to the other plane type optical emitting/receiving element from one plane type optical emitting/receiving element is formed. This optical waveguide
82
is also formed of the center core
84
for transmitting optical signal and clad
86
composed of a material having the refraction index lower than that of the core
84
to surround this core
84
. The small size mirror
88
is also formed on the upper surface of the multilayer substrate
70
which is neighboring to one end face of this optical waveguide
82
and is located at the area just under the optical emitting surface of one plane type optical emitting/receiving element. In addition, although not illustrated, such small size mirror is also formed on the upper surface of the multilayer substrate
70
which is neighboring to the other end face of the optical waveguide
82
and is located at the area just under the receiving surface of the other plane type optical emitting/receiving element.
In this case, the optical signal, for example, emitted from the optical emitting surface of one plane type optical emitting/receiving element is totally reflected in 90 degrees by the 45° mirror surface
90
of small size mirror
88
and thereafter the signal is then incident to the core
84
of the optical waveguide
82
and is then propagated within the core
84
. Moreover, the optical signal propagated within the core
84
of the optical waveguide
82
is totally reflected in 90 degrees by the 45° mirror surface of small size mirror (not illustrated) and thereafter it is incident to the optical receiving surface of the other plane type optical emitting/receiving element located at the area just above the mirror.
Next, the other example of the optical transmitting/receiving system of related art using the optical waveguide as the transmission path will be explained with reference to FIG.
4
. Here,
FIG. 4
is a schematic cross-sectional view illustrating the other example of the optical transmitting/receiving system of the related art. The elements like the structural elements in the opt
Connelly-Cushwa Michelle R.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Palmer Phan T. H.
Sony Corporation
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