Optical waveguide

Details Optical waveguide Optical waveguide

2001-05-18

2002-12-03

Ullah, Akm E. (Department: 2874)

Optical waveguides

Having particular optical characteristic modifying chemical...

Of waveguide cladding

C385S143000

Reexamination Certificate

active

06490400

ABSTRACT:

The present invention relates to an optical waveguide having a clad made of a fluorinated alicyclic structure-containing polymer having functional groups, which has a high adhesion to the substrate, and which has low transmission loss.
It has been known that by using an amorphous fluorine-containing polymer as a material for an optical waveguide, the transmission loss can be made small, the rate of the moisture absorption can be made low, and the light scattering resulting from birefringence can be suppressed (JP-A-4-190202).
However, if the amorphous fluorine-containing polymer is used for the clad of an optical waveguide, the adhesion to the substrate tends to be low. Accordingly, in the case where layers of clad and core are successively formed on a silicon substrate, and the core is processed to have a desired shape to prepare an optical waveguide, for example, the clad made of the amorphous fluorine-containing polymer is likely to peel off from the substrate or the core. Further, in the case where the optical waveguide part is cut out from the substrate after the optical waveguide is formed, the clad is likely to peel off from the substrate. Still further, in the case where the amorphous fluorine-containing polymer is used for the core of the optical waveguide, as the refractive index of the material itself is low, a material having a lower refractive index required for the clad of the optical waveguide is hardly available.
Under these circumstances, it is the object of the present invention to overcome the above-mentioned problems of prior art, and to provide an optical waveguide having improved adhesion between the clad and the substrate, without impairing excellent properties of the amorphous fluorine-containing polymer.
The present invention resides in an optical waveguide provided on a substrate, which comprises a core for transmitting light and a clad formed around the core, wherein the clad is made of a fluorinated alicyclic structure-containing polymer having functional groups.
Now, the present invention will be described in detail with reference to the preferred embodiments.
In the present invention, the optical waveguide is a basic component for an opto-device formed on a semiconducting substrate such as a silica glass substrate or a silicon substrate, and can constitute various passive optical parts.
The optical waveguide has a structure having a core for transmitting light and a clad formed around the core, and includes an optical fiber. For the core for transmitting light, it is necessary to employ a material having a higher refractive index than the material for the clad. The transmitted light is entrapped in the waveguide, and the transmitted light is controlled by a signal from the exterior. It is classified into an optical modulator, an optical switch, a wave selecting device, an optical integrated circuit or the like, depending upon the function.
The optical waveguide usually comprises a clad formed on a substrate, a core formed on the clad, and a clad formed on the core.
As a method to form the clad around the core on the substrate, a clad is formed on the substrate, a core is formed on the clad, a portion of the core is removed by etching, and a clad is formed on the remaining core to obtain a constitution wherein the core is surrounded by the clad.
The polymer having a fluorine-containing alicyclic structure of the present invention (hereinafter sometimes referred to as fluoropolymer) is preferably one obtained by polymerization of a monomer having a fluorine-containing alicyclic structure, or a polymer having a fluorine-containing alicyclic structure in its main chain, obtained by cyclic polymerization of a fluorine-containing monomer having at least two polymerizable double bonds.
“Having a fluorine-containing alicyclic structure in its main chain” means having a structure in which at least one carbon atom constituting the aliphatic cycle is a carbon atom in the carbon chain constituting the main chain, and fluorine atoms or fluorine-containing groups are bonded to at least some of carbon atoms constituting the aliphatic cycle.
The material for the clad in the present invention is a fluorinated alicyclic structure-containing polymer having functional groups (hereinafter sometimes referred to as functional group-containing fluoropolymer).
The material for the core is not particularly limited so long as it has a higher refractive index than the material for the clad. However, an amorphous fluorine-containing polymer is preferred as the core material, in view of the properties and the adhesion to the clad. The particularly preferred core material is a fluorine-containing alicyclic structure-containing polymer which is the same type as the clad material. As the core material, a crosslinked product of a crosslinking-curable fluorine-containing compound as well as the polymer having a fluorine-containing alicyclic structure which is the same type as the clad material, may be used. For example, by using a perfluoro compound having at least two cyano groups, an amorphous fluorine-containing polymer can be obtained by crosslinking by trimerization of the cyano groups (a reaction to form a s-triazine ring from three cyano groups). By using such a crosslinking-curable fluorine-containing compound, a core made of a crosslinked amorphous fluorine-containing polymer can be formed. As the crosslinked product has an s-triazine ring, it has a high refractive index as compared with a polymer having a fluorine-containing alicyclic structure as mentioned hereinafter, and the refractive index can be changed by controlling the amount of the s-triazine rings.
The particularly preferred core material is the polymer having a fluorine-containing alicyclic structure which is the same type as the clad material, and which is a material wherein the affinity with the clad material is high, and irregularity at the interface between the clad and the core is less likely to form. Now, the present invention will be explained with reference to an example wherein the polymer having a fluorine-containing alicyclic structure which is the same type as the clad material is used as the core material.
The polymer having a fluorine-containing alicyclic structure to be used for the core material may have functional groups, or may not have functional groups. However, one having functional groups is preferred as it is excellent in the adhesion to the clad material. Further, to raise the refractive index of the core material, it is preferred to blend in the polymer having a fluorine-containing alicyclic structure, a substance having a higher refractive index than the polymer.
The polymer having a fluorine-containing alicyclic structure in its main chain, obtained by polymerization of a monomer having a fluorine-containing alicyclic structure, may, for example, be a polymer having a fluorine-containing alicyclic structure in its main chain, obtained by homopolymerization of a monomer having a fluorine-containing alicyclic structure such as perfluoro(2,2-dimethyl-1,3-dioxole), or by copolymerization of the monomer with a radical polymerizable monomer such as tetrafluoroethylene, chlorotrifluoroethylene or perfluoro (methyl vinyl ether) (JP-B-63-18964).
The polymer having a fluorine-containing alicyclic structure in its main chain, obtained by cyclic polymerization of a fluorine-containing monomer having at least two polymerizable double bonds, may, for example, be a polymer having a fluorine-containing alicyclic structure in its main chain, obtained by cyclic polymerization of a monomer such as perfluoro(allyl vinyl ether) or perfluoro(butenyl vinyl ether), or by copolymerization of the monomer with a radical polymerizable monomer such as tetrafluoroethylene, chlorotrifluoroethylene or perfluoro(methyl vinyl ether) (JP-A-63-238111, JP-A-63-238115).
A polymer having a fluorine-containing alicyclic structure in its main chain can be obtained also by copolymerization of a monomer having a fluorine-containing alicyclic structure such as perfluoro(2,2-dimethyl-1,3-dioxole) with a fluorine-containing mon

Affiliated with

Also associated with

Rating

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

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2964222