Optical waveguides – Integrated optical circuit
Reexamination Certificate
2001-12-27
2004-03-30
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Integrated optical circuit
C385S033000, C372S045013
Reexamination Certificate
active
06714696
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a light-wave circuit module used for optical communication, optical information processing or the like, and to a method for manufacturing the same.
Optical devices, such as semiconductor lasers, photodetectors, optical switches and the like, which are used for optical communication and optical information processing for example, are usually coupled with an optical fiber, such that light can be input and output, to send/receive signal light. Conventionally, various optical modules have been produced, such as an optical fiber modules, in which an optical fiber is assembled in a module.
On the other hand, different from these optical fiber modules, planar light-wave circuit (PLC) modules have been proposed, in which planar optical waveguides including optical waveguides, and optical function elements, such as a semiconductor laser or a photodetector, are integrated on the same substrate. With such PLC modules, automation of the assembly is possible, so that they are very promising as one of the compact optical modules for optical waveguide integrated devices.
Conventionally, PLC modules have been developed mainly as optical switches and optical branch couplers. As the optical waveguides used in PLC modules, there are quartz-based optical waveguides, which are based on quartz, and organic optical waveguides, which are based on an organic polymer material. Among these, even though organic polymer-based optical waveguides are problematic regarding heat resistance and performance, they can be easily formed into transparent films, so that they are promising with regard to cost, number of processing steps etc.
A conventional organic polymer-based PLC module is disclosed in Japanese Laid-Open Patent Publication No. 08-264748. This PLC module is explained with reference to FIG.
8
.
FIG. 8
schematically shows the cross-sectional configuration of the PLC module disclosed in this publication. As shown in
FIG. 8
, in this PLC module, in a substrate
1
made of Si, a groove
2
is formed extending in the longitudinal direction of the substrate
1
, and a concave portion
3
that is wider than the groove
2
is formed in a perpendicular direction to the groove
2
. A translucent organic material is applied or filled into the groove
2
and the concave portion
3
, and this translucent organic material constitutes an organic optical waveguide
6
made of a core layer
4
and a ground layer
5
. A semiconductor laser
7
, which is accommodated in the concave portion
3
, is buried by the translucent organic material.
In the substrate
1
, an oblique mirror surface
8
is formed at an angle of 45° with the principal surface of the substrate
1
, and a reflective film
9
is provided on the oblique mirror surface
8
. A rear-side coupling photodetector
10
, which has its photodetecting portion at a position where laser light that has been reflected by the reflective film
9
is irradiated, is arranged above the oblique mirror surface
8
,
With the conventional configuration shown in
FIG. 8
, a PLC module can be attained, in which the optical waveguide
6
does not peel off easily from the substrate
1
, and in which the positioning precision of the optical waveguide
6
and the reliability of the optical coupling with the semiconductor laser
7
are high. Furthermore, the laser light from the oblique mirror surface
8
can be monitored with the photodetector
10
on the substrate
1
.
However, the above-described conventional PLC module provided with a photodetector poses the following problems. In conventional PLC modules, the oblique mirror surface
8
is planar, so that when broadened laser light is incident on the oblique mirror surface
8
, then also the reflected laser light is broadened when it is incident on the photodetector
10
. Therefore, it is not possible to utilize the laser light with high efficiency.
Furthermore, if the optical waveguide
6
is shifted with respect to the horizontal direction of the substrate
1
, then the position where the intensity of the reflected laser light is large shifts with respect to the position of the photodetecting portion of the photodetector
10
, and as a result, there is the problem that the laser light cannot be utilized efficiently.
It is an object of the present invention to solve these problems, and to provide a light-wave circuit module in which laser light that has passed through an optical waveguide can be coupled with high efficiency into a photodetector.
SUMMARY OF THE INVENTION
A first light-wave circuit module in accordance with the present invention includes a substrate having a spot of substantially circular concave shape, an optically reflective film formed along an inner surface of the spot, and a planar optical waveguide passing through the spot, wherein light of the optical waveguide is reflected and focused obliquely upward by the optically reflective film in the spot.
In a preferable embodiment, a portion of the planar optical waveguide is located in the spot, the portion of the planar optical waveguide is formed on the substrate with the optically reflective film being disposed between the portion and the substrate, and light that is guided along the planar optical waveguide leaks into the spot and is focused on a focal point that is set by the substantially circular concave shape.
A second light-wave circuit module in accordance with the present invention includes a substrate having a spot of substantially circular concave shape, and a groove that is formed on the substrate and linked to a portion of a perimeter of the spot, wherein at least a portion of a planar optical waveguide is formed in the groove, wherein an optically reflective film is formed on an inner surface of the spot, wherein an end face of the planar optical waveguide is located at a periphery of the spot, and wherein light that is guided by the optical waveguide enters the spot from the end face and is focused on a focal point that is determined by the substantially circular concave shape.
A third light-wave circuit module in accordance with the present invention includes a substrate having a spot of substantially circular concave shape, and a slanted path that is formed on the substrate and linked to at least a portion of a perimeter of the spot, wherein at least a portion of a planar optical waveguide is formed on the slanted path, and wherein, on an inner surface of the spot, an optically reflective film is formed at least on a side that is in opposition to the side linked to the slanted path.
A fourth light-wave circuit module in accordance with the present invention includes a substrate having a spot of concave shape, and a groove that is formed on the substrate and linked to a portion of a perimeter of the spot, wherein at least a portion of a planar optical waveguide is formed in the groove, wherein an optically reflective film is formed on an inner surface of the spot, and wherein a bottom surface of the groove is located near a bottom surface of the optically reflective film in the spot.
A fifth light-wave circuit module in accordance with the present invention includes a substrate on which a plurality of spots of substantially circular concave shape are formed, and an optically reflective film formed along inner surfaces of the spots, wherein the spots are linked by a planar optical waveguide.
In a preferable embodiment, the planar optical waveguide includes branched portions, the branched portions are linked to the spots, and at least a portion of the branched portions is made of a medium that transmits or reflects a certain wavelength, and photodetectors are provided above the spots.
A sixth light-wave circuit module in accordance with the present invention includes a substrate having a first surface and a second surface substantially in opposition to the first surface, a spot of substantially circular concave shape that is formed on the first surface of the substrate, and an optically reflective film that is formed along an inner surface of the spot, wherein a first planar optica
Kishimoto Yoshio
Mitsuda Masahiro
McDermott & Will & Emery
Palmer Phan T. H.
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