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Holographic Techniques for Fabrication of Optical Waveguide Networks

IP.com Disclosure Number: IPCOM000075596D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 27K

Publishing Venue

IBM

Related People

Pennington, KS: AUTHOR [+2]

Abstract

Described are methods whereby suitable photosensitive materials can be used to fabricate thin-film optical waveguide networks. The methods combine the use of thin films of material, which have the property that they can be photosensitized locally and holographic techniques in order to yield optical waveguide devices such as power division junctions, reflectors, couplers, resonators, equalization filters, lenses, encoders and other linear passive network functions.

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Holographic Techniques for Fabrication of Optical Waveguide Networks

Described are methods whereby suitable photosensitive materials can be used to fabricate thin-film optical waveguide networks. The methods combine the use of thin films of material, which have the property that they can be photosensitized locally and holographic techniques in order to yield optical waveguide devices such as power division junctions, reflectors, couplers, resonators, equalization filters, lenses, encoders and other linear passive network functions.

The methods are based on the preparation of thin films of material which have optical properties suitable for the propagation of optical surface waves, while at the same time having the property that the materials can be locally photosensitized. One such material is gelatin. Gelatin can be hardened, such that it is able to withstand the further chemical processing which is inevitably performed in the fabrication of useful integrated optical devices. However, the gelatin film can be photosensitized locally by the addition of suitable chemicals, such as ammonium or potassium dichromate, to relevant regions of the film. A suitable technique for the preparation of the gelatin films, is to prepare a 5-12% gelatin solution with about 0.1% formaldehyde added. This solution is spun onto a wafer at speeds varying from 2-5000 rpm and at temperatures from 20-50 degrees C. The resulting films are from 0.1-10V thick. These films are then hardened by baking in a vacuum oven for about 10 hrs. at 200 degrees C. The resultant film is hard enough to be wiped with tissue and sufficiently chemically stable to withstand immersion in salt solutions (e.g. dichromates), hot alcohols and AZ 1350* photoresist and photoresist developer.

An important feature in the fabrication of holographic optical waveguide elements, is the ability to photosensitize the resulting thin films. It has been found that the hardened gelatin films described can be used for propagation of an optical surface wave. Further, it is possible to sensitize these hardened gelatin films locally, by spot application of a drop of 10% dichromate solution in the desired area. The dichromate diffuses into the g...