Optical waveguides – Planar optical waveguide – Thin film optical waveguide
Reexamination Certificate
1999-02-24
2001-10-30
Palmer, Phan T. H. (Department: 2877)
Optical waveguides
Planar optical waveguide
Thin film optical waveguide
C385S014000, C385S132000, C385S131000
Reexamination Certificate
active
06311003
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to optical electronic integrated circuits (OEICs). More specifically, the invention relates to techniques for fabricating OEICs having optical interconnects in the form of waveguides capable of transmitting light.
BACKGROUND OF THE INVENTION
In recent years, artisans have made significant advances in fabricating and using optical electronic integrated circuits (OEICs). These improved circuits, which often contain active optical devices capable of operating in the femtosecond regime, have found significant applications in a number of fields including optical computing and communications. However, those concerned with designing OEICs have recognized the need for developing improved optical interconnects capable of transmitting light between the active devices that form these integrated circuits.
Conventional OEICs usually employ thin-film optical waveguides as device interconnects. Specifically, circuit fabricators have used thin films of semiconductor materials to form optical waveguides directly on the surface of OEIC structures. Although many of these waveguides have served the purpose, none have proved entirely satisfactory because of difficulties encountered in fabricating optical waveguides with sufficiently high transmission efficiencies to operate effectively with most of the recently developed high-speed OEIC devices. Fabricators of OEICs have therefore recognized the need to develop improved techniques of forming optical waveguides on OEIC structures such that the waveguides do not absorb appreciable amounts of the transmitted light while at the same time they contain the light. The present invention fulfills this need.
SUMMARY OF THE INVENTION
The general purpose of this invention is to provide techniques for fabricating OEICs having waveguides that efficiently transmit light. One aspect of the present invention is directed to a method of fabricating an optical waveguide for transmitting radiation having a predetermined range of wavelengths. The method comprises forming a semiconductor substrate and depositing, in an oxygen-free atmosphere, a film of semiconductor material on the substrate at a temperature that substantially diminishes the porosity of the film and the diffusion of material from the substrate into the film. Finally, the deposited film, which has an index of refraction greater than that of the substrate, is etched to form optical waveguides on the substrate.
Another aspect of the invention is directed to an optical waveguide structure for transmitting radiation having a predetermined range of wavelengths. The waveguide structure includes a semiconductor substrate and an optical waveguide mounted on the substrate. The optical waveguide is formed from a film of semiconductor material grown on the substrate surface. The film of semiconductor material has an index of refraction that is greater than that of the substrate and has a relatively small, uniform absorption coefficient over the predetermined range of wavelengths. The semiconductor film preferably comprises germanium and the semiconductor substrate may be formed from gallium-arsenide. The semiconductor film is deposited at a temperature of about 100 degrees centigrade such that the film has a substantially diminished porosity and contains a substantially diminished amount of gallium-arsenide.
The exact nature of this invention, as well as other objects and advantages thereof, will be readily apparent from consideration of the following specification relating to the annexed drawing.
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Dubey Madan
Han Weiyu
Jones Kenneth A.
West Lawrence C.
Mooney Michael P
O'Meara John M.
Palmer Phan T. H.
The United States of America as represented by the Secretary of
Zelenka Michael
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