US 5,670,914 AGranted

Miniature atomic frequency standard

AssigneeNorthrop Grumman Corporation

InventorsIrving Liberman, Peter J. Chantry

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Abstract

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.

Claims19

Dependent claims

A miniature atomic frequency standard comprising:

a microwave cavity;
a C-field winding located on said microwave cavity;
a tubular member located in and extending transversely through said microwave cavity and including first and second ends extending beyond said microwave cavity but within a magnetic shield surrounding both said microwave cavity and said tubular member, said tubular member having a vapor chamber situated within said microwave cavity and containing a vapor with specified atomic transition frequencies/wavelengths including an optical resonance wavelength and a microwave atomic transition frequency;
heater means directly applied to said first and second ends for heating said vapor;
light beam generating means for injecting a beam of light at said optical resonance wavelength into said vapor in said chamber through said first end of said tubular member including an optic fiber having an angle of divergence which substantially fills the vapor chamber without the necessity of any collimating lens;
photodetector means generating a detector signal in response to light from said light beam generating means which has passed through said vapor in said chamber to said second end of said tubular member;
and
control means responsive to said detector signal for controlling said light beam to said optical resonance wavelength and for applying a microwave signal locked to the microwave atomic transition frequency to said microwave cavity, said control means also generating a frequency standard signal at a frequency proportional to said microwave atomic transition frequency.

5 more elements

A miniature atomic frequency standard comprising:

a microwave cavity;
a tubular member extending transversely across said microwave cavity and having a chamber within said microwave cavity, said chamber containing a vapor with specified atomic transition frequencies/wavelength including an optical resonance wavelength and a microwave atomic transition frequency;
heater means for heating the vapor in said chamber and being located on an outer surface of said microwave cavity;
magnetic shield means surrounding said microwave cavity and tubular member;
a C-field winding located within said magnetic shield means and being spaced away from said microwave cavity;
light beam generating means comprising a laser diode unit external to said magnetic shield means and generating a beam of light at said optical resonance wavelength, and an optic fiber extending from said laser diode unit through said magnetic shield means and microwave cavity and to a first end of said tubular member for injecting said beam of light at said optical resonance wavelength into said vapor in said chamber said optic fiber having and angle of divergence which substantially fills the vapor chamber without the necessity of any collimating lens;
photodetector means generating a detector signal in response to said light beam at a second end of said tubular member after the light beam has passed through said vapor;
and
control means responsive to said detector signal for controlling said light beam to said optical resonance wavelength and for applying a microwave signal locked to the microwave atomic transition frequency to said microwave cavity, said control means also generating a frequency standard signal at a frequency proportional to said microwave atomic transition frequency.

6 more elements

Dependencies are inferred from the claim text.