Array waveguide grating and method of manufacture thereof

Details Array waveguide grating and method of manufacture thereof Array waveguide grating and method of manufacture thereof

2001-08-02

2003-04-29

Kim, Robert H. (Department: 2882)

Optical waveguides

With optical coupler

Input/output coupler

C385S047000

Reexamination Certificate

active

06556749

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an array waveguide grating and a manufacturing method of the same.
2. Description of the Related Art
FIG. 6
of the accompanying drawings is a plan view showing an example of conventional array waveguide gratings.
The array waveguide grating
1
shown in this figure is includes a substrate
2
, an input channel waveguide
3
formed on top of the substrate
2
for accepting wavelength-multiplexed signal light at one end thereof (in the figure, the left end), an input-side fan-shaped slab waveguide
4
connected to the input channel waveguide
3
at one end thereof, an array of a plurality of channel waveguides
5
, one end of which array is connected to the other end (in the figure, the right end) of the input-side fan-shaped slab waveguide
4
such that lengths of the channel waveguides
5
become successively longer by a desired variation, an output-side fan-shaped slab waveguide
6
, one end of which is connected to the other ends of the array channel waveguides
5
, and a plurality of output channel waveguides
7
, each of which has one end connected to the other end of the output side fan-shaped slab waveguide
6
for outputting signal lights which have been split.
Signal light of various wavelengths (&lgr;1, &lgr;2, . . . , &lgr;n) introduced to the input channel waveguide
3
is spread out in the input-side slab waveguide
4
by diffraction because it is not trapped in the transverse direction (surface direction of the substrate
2
) in the input-side fan-shaped slab waveguide
4
, and is propagated along the array of channel waveguides
5
. In this array
5
, the channel waveguides extend different lengths (successively elongated by a desired length) so that equiphase planes of the signal light are inclined in accordance with the wavelengths of the signal light. Thus, the points of convergence of the signal light shift at the connecting face between the output-side fan-shaped slab waveguide
6
and the output channel waveguides
7
.
Therefore, the signal light of different wavelengths is incident on the output channel waveguides
7
respectively, and the signal light of different wavelengths (&lgr;1, &lgr;2, . . . , &lgr;n) is outputted from the output ends of the output channel waveguides
7
respectively.
FIGS. 7A and 7B
are diagrams showing the relationship between converging beam fields of the output-side fan-shaped slab waveguide and fields of the output channel waveguides of the array waveguide grating shown in FIG.
6
.
FIGS. 8A and 8B
are diagrams of wavelength-loss characteristics of the array waveguide grating
1
shown in
FIG. 6
, in which the horizontal axis indicates wavelength and the vertical axis indicates loss.
The loss of the array waveguide grating
1
is proportional to the overlap integral (hatched portion) of the electric field distribution &phgr;f of the converging beam and the electric field distribution &phgr;o of the output waveguides as shown in
FIGS. 7A and 7B
. Because the electric field of the output channel waveguide
7
has a single-peaked distribution, the loss is lowest at the wavelength that matches the peak of the converging beam &phgr;f, making for a peaky wavelength-loss characteristic (FIG.
8
A).
Accordingly, a waveguide structure that uses Y-branching or a parabolic shape is employed such that the electric field distribution of the input channel waveguide
3
(or the output channel waveguide
7
) has a dual-peaked shape as shown in FIG.
7
B. In this case, even if the points of convergence of the beams shift to a certain extent, the value of the overlap integral hardly changes, making for a flat wavelength-loss characteristic (FIG.
8
B).
FIG. 9
is an enlarged view of part of the wavelength-loss characteristic of the array waveguide grating shown in FIG.
6
. The horizontal axis indicates the wavelength, and the vertical axis indicates the loss.
When the electric field distribution of the output waveguide (or the input waveguide) has a dual-peaked shape, it is difficult to achieve total flatness in the wavelength-loss characteristics distribution. Further, 2 to 3 dB of additional loss is generated to realize the flatness. When application in a wavelength-multiplexed optical telecommunications system is considered, this loss increase is a problem and loss improvement must be made. When a yet flatter wavelength-loss characteristics is sought in this structure, another problem arises; a ripple appears in the transmission region as shown in
FIG. 9
, greatly affecting transmission characteristics.
Accordingly, an object of the present invention is to provide an array waveguide grating, which solves the above-mentioned problems, and which has approximately flat wavelength-loss characteristics in the transmission region without causing an increase in loss, and a manufacturing method of the array waveguide grating.
SUMMARY OF THE INVENTION
An array waveguide grating of the present invention comprises a substrate, an input channel waveguide formed on top of the substrate for receiving wavelength-multiplexed signal light at one end thereof; a plurality of output channel waveguides disposed parallel to the input channel waveguide for outputting split output signal light from respective one ends thereof; a fan-shaped slab waveguide connected to the other end of the input channel waveguide at one end thereof and to the other ends of the output channel waveguides at the same one end thereof, an array of a plurality of channel waveguides connected to the other end of the fan-shaped slab waveguide at one end thereof such that lengths of the channel waveguides are successively elongated by a desired variation &Dgr;L, and an array of Fabry-Perot resonators connected to the other end of the array of channel waveguides at one end thereof such that lengths of the resonators are successively elongated by twice the channel waveguide length variation &Dgr;L.
The signal light obtained by splitting the wavelength-multiplexed signal light in the array of channel waveguides is reflected inside the Fabry-Perot resonators, and this split signal light is caused to pass through the array of channel waveguides once again. Therefore, the array waveguide grating provided by the invention has approximately flat wavelength-loss characteristics in the transmission region without increasing loss.
Preferably a reflectance of the Fabry-Perot resonator array at its face connecting with the channel waveguide array is approximately 11%, and a reflectance at its face opposite the connecting face is approximately 100% (full reflection).
The face of the Fabry-Perot resonator array in contact with the channel waveguide array may be coated with a metallic film having a reflectance of approximately 11%, and the opposite face may be coated with either a metallic film having a reflectance of approximately 100%, or a multilayer dielectric film of TiO
2
and SiO
2
having a reflectance of approximately 100%.
The Fabry-Perot resonator array may be constituted from an array of semicircular concentric channel waveguides, respective one ends of which are connected to the other ends of the array channel waveguides such that lengths of the semicircular concentric channel waveguides become successively longer by twice the waveguide length variation &Dgr;L, a reflective film formed between the channel waveguide array and semicircular channel waveguide array and having a reflectance of approximately 11%, and another reflective film formed at the other end of the semicircular channel waveguide array and having a reflectance of approximately 100%.
Alternatively the Fabry-Perot resonator array may be constituted from a second array of channel waveguides, respective one ends of which are connected to the other ends of the first array of channel waveguides such that lengths of the second channel waveguides are successively elongated by twice the first waveguide length variation &Dgr;L, a first groove transversely crossing the first and second channel waveguide arrays at the connecting portion of these a

Affiliated with

Also associated with

Rating

Array waveguide grating and method of manufacture thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Array waveguide grating and method of manufacture thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Array waveguide grating and method of manufacture thereof will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3093647