Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
2002-01-18
2003-11-11
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S045000, C385S049000, C385S050000, C385S052000
Reexamination Certificate
active
06647184
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a PLC (planar light wave circuit) type optical waveguide device comprising a planar optical waveguide substrate and an optical waveguide formed on the optical waveguide substrate, and a method of manufacturing the optical waveguide device, and more particularly, to an optical waveguide device formed by coupling a plurality of PLC type optical waveguide chips, and a method of manufacturing such optical waveguide device.
2. Description of the Related Art
At first, an example of the PLC type optical waveguide device comprising a planar optical waveguide substrate and an optical waveguide formed on the optical waveguide substrate will be described with reference to FIG.
1
.
FIG. 1
is a perspective view showing, in outline, the construction of a PLC type optical waveguide device disclosed in Japanese Patent Application No. 28278/2000 filed on Feb. 4, 2000 by the same assignee as that of the present application. The optical waveguide device
30
comprises: an optical waveguide substrate
31
of generally rectangular shape in plan and made of, for example, silicon (Si); a generally “y”-shaped optical waveguide
2
made of glass layer or organic material thin film and formed on the surface of the optical waveguide substrate
31
; a clad layer
32
made of glass layer or organic material thin film and formed on the surface of the optical waveguide substrate
31
in such manner that the optical waveguide
2
is covered with the clad layer
32
; and a light source
33
that is a laser diode in this example and a photodetector
34
that is a photodiode in this example mounted on the optical waveguide substrate
31
at the both sides thereof in the longitudinal direction thereof respectively. Further, in the figure, though the optical waveguide
2
is shown in the manner that the top surface thereof is exposed, in reality, the top surface of the optical waveguide
2
is also covered with the clad layer
32
. In addition, a lower clad layer made of glass layer or organic material thin film has been formed under the optical waveguide
2
. The optical waveguide
2
corresponds to the core of an optical fiber having high refractive index, and the lower clad layer and the clad layer
32
(upper clad layer) correspond to the clad of the optical fiber having low refractive index.
The “y”-shaped optical waveguide
2
is constituted by two optical waveguides, one of which is an optical waveguide that forms a generally straight line and extends from one end surface of the optical waveguide substrate
31
in the longitudinal direction thereof to the other end surface of the optical waveguide substrate
31
in the longitudinal direction thereof, the other end surface being opposed to the photodetector
34
, and the other of which is an optical waveguide which is branched from the central portion of the aforesaid optical waveguide of generally straight line and extends to the end surface of the optical waveguide substrate
31
opposed to the light source
33
. Herein, the optical waveguide branched from the central portion of the optical waveguide of generally straight line will be referred to as first optical waveguide
21
, one portion of the optical waveguide of generally straight line extending from the intersection or junction with the first waveguide
21
to the aforesaid one end surface of the optical waveguide substrate
31
in the longitudinal direction thereof will be referred to as second waveguide
22
, and the other portion of the optical waveguide of generally straight line extending from the intersection to the other end surface (opposed to the photodetector
34
) of the optical waveguide substrate
31
in the longitudinal direction thereof will be referred to as third waveguide
23
.
The light source
33
is mounted on the optical waveguide substrate
31
such that the light emitting portion thereof is opposed to one end (a portion exposed on the end surface of the clad layer
32
) of the first optical waveguide
21
. One end (a portion exposed on the end surface of the clad layer
32
) of the second optical waveguide
22
is optically coupled to other optical waveguide (for example, an optical fiber) not shown. The photodetector
34
is mounted on the optical waveguide substrate
31
such that the light receiving portion thereof is opposed to one end (a portion exposed on the end surface of the clad layer
32
) of the third optical waveguide
23
.
Between the intersection of the first and second optical waveguides
21
and
22
and the other end of the third optical waveguide
23
is formed a slit or groove
35
across the optical waveguide substrate
31
at substantially a right angle thereto, the slit
35
extending from the surface of the clad layer
32
into the optical waveguide substrate
31
. Accordingly, the intersection of the first and second optical waveguides
21
and
22
is disconnected and separated from the other end of the third optical waveguide
23
by the slit
35
, and the intersection of the first and second optical waveguides
21
and
22
is opposed to the other end of the third optical waveguide
23
through the slit
35
.
Further, in this example, the slit
35
was formed by dicing (diecutting), but it is needless to say that the slit
35
may be formed by other cutting process. In addition, the light source
33
and the photodetector
34
are mounted directly on the optical waveguide substrate
31
. A sheet of glass or a thin film of organic material is used as the clad layer
32
, the thickness of the clad layer
32
being set to a value between several micrometers and about 20 micrometers in view of its strength.
A dielectric multilayer film filter
36
is inserted into the slit
35
and is fixed to the clad layer
32
by use of an appropriate adhesive
37
. As a result, the end surface of the third optical waveguide
23
is opposed to the end surface of the intersection of the first and second optical waveguides
21
and
22
through the dielectric multilayer film filter
36
. Further, a process of making the optical waveguide
2
is described in detail in Japanese Patent Application No. 28278/2000 mentioned above, and the explanation thereof will be omitted here.
The optical waveguide device
30
constructed as described above operates as a WDM (wavelength division multiplexing) device. For example, when light L
1
having its wavelength of 1.31 &mgr;m emitted from the light source
33
is incident on the end surface of the first optical waveguide
21
, this light L
1
propagates through the first optical waveguide
21
and is incident on the dielectric multilayer film filter
36
. Since the characteristic of the dielectric multilayer film filter
36
is previously set such that it reflects light having its wavelength of 1.31 &mgr;m, the dielectric multilayer film filter
36
reflects the light L
1
incident thereon and inputs the light L
1
into the end surface of the second optical waveguide
22
. Accordingly, the light L
1
propagates through the second optical waveguide
22
and is emitted to the outside (or to other optical waveguide not shown) from the other end surface of the second optical waveguide
22
. On the other hand, when light L
2
having its wavelength of 1.55 &mgr;m is incident on the other end surface of the second optical waveguide
22
from the outside or other optical waveguide, this light L
2
propagates through the second optical waveguide
22
and is incident on the dielectric multilayer film filter
36
. Since the characteristic of the dielectric multilayer film filter
36
is previously set such that it transmits light having its wavelength of 1.55 &mgr;m, the dielectric multilayer film filter
36
transmits the light L
2
incident thereon and inputs the light L
2
into the end surface of the third optical waveguide
23
. Accordingly, the light L
2
propagates through the third optical waveguide
23
to the other end surface thereof and is incident on the photodetector
34
. Thus, the above-mentioned optical waveguide device
30
operates as
Miyashita Takuya
Ukechi Mitsuo
Gallagher & Lathrop
Japan Aviation Electronics Industry Limited
Lathrop, Esq. David N.
Sanghavi Hemang
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