Rockwell International Corporation

US Government As Represented by the Secretary of the Army

David E Thompson

Shi-Kay Yao

Rudolf R August

Dean B Anderson

Disclosed is a method of producing an integrated optical grating device having extremely low scattering losses. The method employs a highly polished and prepared silicon chip for receiving a grating pattern or any other surface relief feature on the silicon wafer surface for its predetermined use. The pattern after it is generated is etched to a predetermined period, for example, when the pattern is for a waveguide device. An SiO.sub.2 growth layer is thermally grown to a thickness of about 4 to 8 micrometers to replicate the generated pattern in the SiO.sub.2 growth layer. This method yields a waveguide or similar optical grating device having undulations of extremely low values as determined by SEM photographs of this device.

Integrated optical grating device by thermal SiO.sub.2 growth on Si

A Sagnac interferometer gyroscope includes a semiconductor chip on which is formed an optical waveguide. Means are provided on the optical waveguide to inject a laser light beam into the waveguide and onto a divider to produce first and second divided beams. Second and third dividers are provided in the waveguide to generate a reference signal onto a pair of photodectors disposed to receive the divided light waves. The light waves are modulated with first and second frequencies prior to their second division by a pair of Bragg frequency shifter interdigital transducers. The divided and modulated light beams are then directed through an optical path encompassing an axis of sensitivity of the gyro. In one embodiment the path is formed by an optical fiber with connections to the chip. In another embodiment the optical path is defined within the chip itself by reflectors or deflectors at selected locations about the peripheral of the chip. The respective light beams after having traversed the light path are then combined and detected by a second pair of photodectors. The signals of the photodectors are compared to determine the rotation of the gyroscope about the axis of sensitivity.

Interferometer gyroscope formed on a single plane optical waveguide

An interferometer gyro employing a coiled optical fiber includes a pair of acousto-optic modulators to modulate first and second frequencies onto two components divided from the light of a light source. The light source need not exhibit the high degree of source coherence heretofore required, and can be an incandescent bulb in many applications. The first and second modulated light components are injected in opposite or counter-rotating directions into the optical fiber wherein they experience phase changes due to the apparent change in optical length of the optical fiber upon rotation of the fiber about an axis of sensitivity. The light components are then, after being removed from the fiber, combined and compared with the signals applied at the input. The phase difference therebetween is then established to measure the rate of rotation of the optical fiber about the axis of sensitivity.

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Placentia, CA, United States of America

David E Thompson