Westinghouse Electric Corporation

Northrop Grumman Systems Corporation

Irving Liberman

Peter J Chantry

Harvey C Nathanson

Chi-sheng Liu

Robert J Zollweg

Frederick Brimberg

Physics package apparatus for a cell type atomic clock includes a cell structure having a central plate sandwiched between top and bottom plates. The central plate has a central interior aperture which together with the top and bottom plates forms an internal cavity for containment of an active vapor. The central plate includes a reservoir for holding a source of the active vapor, and a channel connecting the reservoir with the internal cavity. A heater is provided on the underside of the bottom plate for heating the vapor. The plates are batch processed on respective wafers which are subsequently joined together and cut into individual cell structures.

Physics package apparatus for an atomic clock

A miniature atomic frequency standard utilizes a tubular vapor cell extending transversely through a TE.sub.210 microwave cavity. In one embodiment of the invention, the vapor cell is heated directly by electric heaters secured to ends of the tubular vapor cell which extend outside the microwave cavity. The vapor cell is insulated by thermal insulation inside the microwave cavity and between the microwave cavity and a magnetic shield. In another embodiment of the invention, the entire microwave cavity is heated which eliminates the need for thermal insulation inside the cavity and thus it can be made smaller, but additional thermal insulation is provided between the microwave cavity and the magnetic shield. Preferably, the C-field coil is wound on the thermal insulation just inside the magnetic shield to reduce heat loss by conduction. A laser diode outside the magnetic shield transmits light to the vapor cell through optic fiber without need for a collimating lens and a photodiode with an integral lens is used as the detector.

Miniature atomic frequency standard

The wavelength of light generated by a diode laser optically pumping vapor in the gas cell of an atomic time-standard is stabilized against variations in ambient temperature by application of pressure to the semiconductor laser by a piezoelectric transducer, preferably implemented as thin films on the diode structure. Closed loop control of the pressure is provided by feeding back a detector signal, which is a measure of light transmitted through the vapor, to a null seeking servo the output of which is converted to a control signal which is a function of temperature/pressure. The control signal, which is applied to the piezoelectric transducer, which in turn is preferably implemented as a thin film on the diode structure, can be dithered to sense and maintain the desired resonant atomic transition frequency. The vapor is additionally excited by a microwave signal locked to an atomic transition frequency through feedback of the detector signal.

Atomic time standard with piezoelectric stabilization of diode laser

A gas cell for a miniature atomic frequency standard. The gas cell functions not only to contain the cesium vapor, but also as a resonator for the microwave signal used to excite the vapor. By combining the functions of gas cell and resonator into a single structure, and by taking advantage of the intensity of light available from a laser diode, the overall size of an atomic frequency standard can be reduced by two orders of magnitude when compared to prior art devices of comparable accuracy.

Gas cell for a miniaturized atomic frequency standard

A laser beam is projected from either an underwater body or an overhead support platform, with the laser energy being detected by the other piece of apparatus using a photo detector. Either the projecting or the receiving optics is servo driven to maximize the light energy received by the photo detector. The relative position of the underwater body with respect to the support platform, typically a tracking aircraft, is determined by measuring the position of a driven element laser or photo detector, in either one or two planes, i.e., two or three dimensions, to provide a measure of the trailing distance and when desirable, the lateral offset distance.

Laser location apparatus for underwater bodies

The invention provides a metal vapor Raman cell structure for laser wavelength conversion and a method for mounting a sapphire window onto a metal tube having a known outside diameter in the manufacture of the aforesaid Raman cell. According to the method of this invention, a sapphire window and a metal tube having a dissimilar coefficient of thermal expansion are mounted and sealed together. The method of sealing the sapphire window onto the metal tube comprises the steps of: (1) cutting a narrow circular groove in one face of the sapphire window; (2) mounting the metal tube into the seat defined by the groove cut into the sapphire window; and (3) disposing a sealing material between the outer face of the seat defined by the groove and the metal tube disposed therein. According to this technique, the sealing material disposed in the groove is placed under compression during the operation of the vapor Raman cell so constructed. The narrow circular groove cut into the sapphire window defines a seat having a bottom portion, an inner face, and an outer face. This seat is adapted to receive therein the metal tube of a known outside diameter. Once the metal tube is mounted into the seat defined by the groove, the sealing material is disposed between the outer face of the seat and the metal tube disposed therein.

Growing community of inventors

Pittsburgh, PA, United States of America

Irving Liberman