Browse Prior Art Database

Micromachined Alkali-Atom Vapor Cells and Method of Microfabrication

IP.com Disclosure Number: IPCOM000130467D
Original Publication Date: 2005-Oct-24
Included in the Prior Art Database: 2005-Oct-24
Document File: 23 page(s) / 63K

Publishing Venue

National Institute of Standards and Technology

Related People

Leo Hollberg: INVENTOR [+7]

Abstract

Atomic clocks are utilized in various systems which require extremely accurate and stable frequencies, such as in bistatic radars, GPS (global positioning system) and other navigation and positioning systems. Atomic clocks are also used in communications systems, cellular phone systems and for conducting various types of scientific experiments.

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Micromachined Alkali-Atom Vapor Cells and Method of Fabrication

Related Application

            The present application is based upon United States Provisional Patent Application Serial No. 60/461,692, filed April 9, 2003 to which priority is claimed under 35 U.S.C. §120.

Technical Field

            The present invention relates to compact gas-filled cells.  More particularly, the present invention relates to methods of fabricating compact hollow cells and filling the compact cells with alkali-atom vapor with the optional inclusion of a buffer gas or gases.

Background Art

            Atomic clocks are utilized in various systems which require extremely accurate and stable frequencies, such as in bistatic radars, GPS (global positioning system) and other navigation and positioning systems.  Atomic clocks are also used in communications systems, cellular phone systems and for conducting various types of scientific experiments.

            One type of atomic clock utilizes a cell containing an active medium such as cesium (or rubidium) vapor.  The alkali vapor cell functions as a container for atoms that have natural resonant frequencies when irradiated with optical energy at a given frequency/wavelength.  Light from an optical source pumps the atoms of the vapor from a ground state to a higher state from which they fall to a state which is at a hyperfine frequency different from the initial ground state.  A microwave signal can then be applied to the vapor cell and an oscillator controlling the microwave signal can be tuned to a particular frequency so as to repopulate the initial ground state.  In this manner a controlled amount of the light is propagated from the cell and detected by means of a photodetector.

            By examining the output of the photodetector, a control means provides various control signals to the oscillator to ensure that the wavelength of the propagated light and microwave frequency are precisely controlled, e.g. so that the microwave input frequency and hyperfine wavelength frequency are locked.  The oscillator thereafter provides a highly accurate and stable frequency output signal for use as a frequency standard or atomic clock.

            The current method of fabricating atom vapor cells is based on conventional glass-blowing techniques.  In these methods, the cell preform is typically made by fusing glass windows onto a glass tube with a fill-hole in the side.  A filling tube is attached using a torch and the cell is then attached to a vacuum system for cleaning and filling. 

            There is a need, both in the military and civilian sectors, for an ultra small, completely portable, highly accurate and extremely low power atomic clocks.  In many applications such atomic clocks must operate continuously for 24 hours per day to perform useful functions.  For this reason and the desire to allow battery powered operation,...