Optical waveguide circuit

Details Optical waveguide circuit Optical waveguide circuit

2001-02-08

2003-03-25

Kim, Robert H. (Department: 2882)

Optical waveguides

Planar optical waveguide

C385S132000

Reexamination Certificate

active

06539158

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical waveguide circuit such as an arrayed waveguide grating type optical multiplexer/demultiplexer used in optical communications or the like.
2. Description of the Related Art
In recent years, optical wavelength division multiplexing communications has been actively researched and developed in the hope of increasing exponentially data transmission capacity in optical communications, and it is beginning to be put into practice. Optical wavelength division multiplexing communications is to transmit data by putting, for example, a plurality of light beams having different wavelengths through wavelength division multiplexing. In such an optical wavelength division multiplexing communications system, the transmitted plural light beams with different wavelengths have to be picked separately on the basis of the wavelength by the receiver of the light beams. Therefore, a light transmissive element that transmits only a light beam having a predetermined wavelength, or like other elements, is indispensable for the system.
An example of the light transmissive element is an arrayed waveguide grating (AWG) shown in FIG.
1
. The arrayed waveguide grating has, on a substrate
11
of silicon or the like, an optical waveguide forming region structure as shown in FIG.
1
. The optical waveguide structure of the arrayed waveguide is composed of: one or more optical input waveguides
12
arranged side by side; a first slab waveguide
13
connected to the exit ends of the one or more optical input waveguides
12
; an arrayed waveguide
14
composed of plural channel waveguides
14
a
arranged side by side connected to the exit end of the first slab waveguide; a second slab waveguide
15
connected to the exit end of the arrayed waveguide
14
; and a plurality of optical output waveguide
16
arranged side by side and, connected to the exit end of the second slab waveguide. The arrayed waveguide
14
propagates light that is outputted from the first slab waveguide
13
, and is composed of a plurality of channel waveguides
14
a
arranged side by side. Lengths of adjacent channel waveguides are different each other with the difference preset. The number of optical output waveguides
16
is determined, for example, in accordance with how many light beams having wavelengths different from one another are to be created as a result of demultiplexing or multiplexing of signal light by the arrayed waveguide grating. The channel waveguides constituting the arrayed waveguide are usually provided in a large number 100 for example. However,
FIG. 1
is simplified and the number of the channel waveguides, the optical output waveguide
16
, and the optical input waveguides
12
in FIG.
1
does not exactly reflect the actual number therof.
The optical input waveguides
12
are connected to, for example, transmission side optical fibers so that light having undergone the wavelength division maltiplexing is introduced to the optical input waveguides. The light having traveled through the optical input waveguide and been introduced to the first slab waveguide, is diffracted by the diffraction effect thereof, and enters the arrayed waveguide to travel along the arrayed waveguide.
Having traveled through the arrayed waveguide
14
, the light reaches the second slab waveguide
15
, and then is condensed in the optical output waveguides
16
to be outputted therefrom. Because of the preset difference between adjacent channel waveguides
14
a
of the arrayed waveguide
14
, the light beams after traveling through the arrayed waveguide
14
have phases different from one another. The wavefront of the traveled light is tilted in accordance with this difference and the position where the light is condensed is determined by the angle of this tilt. Therefore, the light beams having different wavelengths are condensed at positions different from one another. By forming the optical output waveguides
16
at these positions, the light beams having different wavelengths can be outputted from their respective optical output waveguides
16
that are provided for the respective wavelengths.
For instance, as shown in
FIG. 1
, light beams having undergone the wavelength division multiplexing and having wavelengths of &lgr;
1
, &lgr;
2
, &lgr;
3
. . . &lgr;n (n is an integer equal to or larger than 2), respectively, are inputted to one of the optical input waveguides
12
. The light beams are diffracted in the first slab waveguide
13
, reach the arrayed waveguide
14
, and travel through the arrayed waveguide
14
and the second slab waveguide
15
. Then, as described above, the light beams are respectively condensed at different positions determined by their wavelengths, enter different optical output waveguides
16
, travel along their respective optical output waveguides
16
, and are outputted from the exit ends of the respective optical output waveguides
16
. The light beams having different wavelengths are taken out through optical fibers for outputting light that are connected to the exit ends of the optical output waveguides
16
.
In this arrayed waveguide grating, wavelength resolution of the grating is in proportion to the difference in length (&Dgr;L) among the adjacent channel waveguides
14
a
of the arrayed waveguide
14
that constitutes the grating. When the arrayed waveguide grating is designed to have a large &Dgr;L, it is possible to multiplex/demultiplex light to accomplish wavelength division multiplexing with a narrow wavelength interval, which has not been attained by other type optical multiplexer/demultiplexer of prior art. It is thus possible for the arrayed waveguide grating to have a function of multiplexing/demultiplexing a plurality of signal light beams, specifically a function of demultiplexing or multiplexing a plurality of optical signals with a wavelength interval of 1 nm or less, which is a function deemed necessary for optical wavelength division multiplexing communications of high density.
The above arrayed waveguide grating is an optical waveguide circuit in which an optical waveguide portion
10
having an under cladding, a core and an over cladding formed from silica-based glass or the like is formed on the substrate
11
of silicon or the like. The under cladding is formed on the substrate
11
, the core with the above optical waveguide structure is formed thereon, and the over cladding is formed on the core to cover the same. The over cladding is formed from silica-based glass obtained by, for example, doping pure silica with a 6 mol % of B
2
O
3
and a 6 mol % of P
2
O
5
(SiO
2
—B
2
O
3
—P
2
O
5
).
FIGS. 4A
to
4
D illustrate a process of manufacturing the arrayed waveguide grating, and described below with reference to
FIGS. 4A
to
4
D is a method of manufacturing the optical waveguide circuit. First, as shown in
FIG. 4A
, a layer for an under cladding
1
b
is formed on the substrate
11
and a layer for a core
2
is subsequently formed thereon. Next, the layer for the core
2
to form an optical waveguide pattern of the arrayed waveguide grating, thereby forming the core
2
with the optical waveguide structure described above as shown in
FIG. 4C
, by photolithography reactive ion etching method using a mask
8
as shown in FIG.
4
B.
Then a layer for an over cladding
1
a
is formed on the core
2
so as to cover the core
2
as shown in FIG.
4
D. The each layer for the under cladding, the core and the over cladding
1
a
is formed by flame hydrolysis deposition method and consolidating the glass particles
50
at a temperature of, for example, 1200° C. to 1250° C.
In the optical wavelength division multiplexing communications as above, when only a horizontally polarized wave is transmitted as signal light, a vertically polarized wave perpendicular to the horizontally polarized wave turns into a noise that degrades the transmission characteristic of the above communications. The noise causes reduction in data transmission capacity and transmission distance and, hence, fewer vertic

Affiliated with

Also associated with

Rating

Optical waveguide circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Optical waveguide circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical waveguide circuit will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3025567