Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1999-03-18
2001-02-13
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S015000, C385S024000, C385S115000
Reexamination Certificate
active
06188819
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an optical integrated circuit and, more particularly, to a planar type optical integrated circuit used in optical communication or optical control and which may be used with advantage for wavelength multiplexing optical transmission system.
BACKGROUND OF THE INVENTION
In the waveform multiplexing optical transmission system, a device is indispensable which splits plural wavelength multiplexed signal light beams into separate wavelength light beams, or which combines plural signal light beams into a sole wave guide path. As a device having such functions, a device employing an array waveguide lattice, referred to hereinafter as array wave guide (AWG), is felt to be promising. As an example of the AWG, a planar structure of an AWG disclosed in Takahashi et al, Meeting Abstracts to Autummn Meeting of the Society of Electronic Information Communication, Vol.4, page 272, is shown in FIG.
13
.
In this AWG element, shown in
FIG. 13
, a quartz based light guide path is formed on a waveguide substrate, formed by a Si substrate. There are provided 11 input light waveguide paths
52
, an inputside star coupler
53
, as a recessed slab waveguide path, an array waveguide lattice
54
, an output side star coupler
55
, and an output waveguide path
56
. Plural signal light beams of different wavelengths, entering one of the 11 input light waveguide paths
52
, are subjected to phase shift determined by the wavelength by the array waveguide lattice
54
so as to be output at different output ports. Thus, it is possible to split the wavelength multiplexed signal light beams.
Takahashi et al manufactured a wave synthesizer/splitter, using 41 array waveguide lattices, in a 1.5 &mgr;m wavelength band, with a frequency interval of 10 GHz and 11 channels, to achieve characteristics with −14 dB crosstalk, an insertion loss of 8 dB and a 3 dB transmission bandwidth of 6.5 GHz. The specific refractive index difference is 75%, with a substrate size being 4 cm by 56 cm. Meanwhile, a similar AWG device is disclosed in, for example, JP Patent Kokoku JP-B-7-117612.
SUMMARY OF THE DISCLOSURE
However, in the course of the investigations toward the present invention the following problems have been encountered. Namely, the above-described conventional AWG device has the following disadvantages.
The first problem is the increased device size. The reason is that a waveguide path needs to be provided separately in each path of light, with there being placed limitations on the bending radius of each waveguide path.
The second problem resides in difficulties met in reducing the crosstalk. The reason is that leakage of optical signals occurs to a certain extent unavoidably even if the differential refractive index between a core and a clad constituting a waveguide channel is increased, while the waveguide pitch cannot be set to a sufficiently large magnitude because of the above-mentioned device size limitations.
It is therefore an object of the present invention to provide a wavelength dividing circuit suitable for high integration through reduction in the device size and improved device characteristics or performance, such as high speed or high transmission efficiency.
Further objects of the present invention will become apparent in the entire disclosure.
According to an aspect of the present invention there is provided a wavelength dividing circuit in which a substrate itself is endowed with wavelength deflection characteristics without forming a waveguide path for each of the wavelengths. More specifically, in the wavelength dividing circuit of the present invention, a periodic structure comprised of mediums of different refractive indices is formed generally in a two-dimensional lattice structure.
According to a second aspect, there is provided a wavelength dividing circuit, wherein
mediums with different refractive indices are periodically arrayed in an entire waveguide area to create wavelength dispersion characteristics not found in usual optical crystals, the wavelength dispersion characteristics being controlled (or defined) to split the wavelength.
The wavelength dividing is performed by using a “heavy photon” state exhibiting strong dispersion among the wavelength dispersion characteristics.
The waveguide region is within a substrate, and the wavelength dispersion characteristics are controlled by arranging materials with different refractive indices in a two-dimensional periodic array.
The two-dimensional periodic array is in the form of a triangular lattice to create the “heavy photon” state.
The difference in the refractive index is created by providing the substrate with a two-dimensional periodic array of through-holes.
According to a third aspect, there is provided a wavelength dividing circuit, wherein a waveguide region having wavelength distribution anisotropy of the refractive index by two- dimensionally arranging in a background medium a plurality of mediums having a refractive index different from that of the background medium at a predetermined pitch so that the incident light to the waveguide region has its transmission path changed in dependence upon the wavelength.
According to a fourth aspect, there is provided a wavelength dividing circuit wherein a plurality of mediums having refractive indices different from that of a substrate are arranged in the form of a two-dimensional lattice as viewed from the surface of the substrate to endow the substrate itself with wavelength deflection characteristics so that the light incident on the substrate has its transmission path changed within the substrate in dependence upon the wavelength.
REFERENCES:
patent: 5940548 (1999-08-01), Yamada et al.
patent: 7-117612 (1995-12-01), None
1992 Denshi Joho Tushin Gakkai Autumn Meeting Yokoshu, vol. 4, p. 272.
Optics Letters,vol. 21, No. 21, Nov. 1, 1996, Shawn-Yu Lin etal., “Highly Dispersive Photonic Band-Gap Prism”.
Kawakami Shojiro
Kosaka Hideo
NEC Corporation
Palmer Phan T. H.
Scully Scott Murphy & Presser
LandOfFree
Wavelength dividing 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 Wavelength dividing circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wavelength dividing circuit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2604690