Government of the United States of America, As Represented by the Secretary of Commerce

Other

Leo W Hollberg

John Kitching

John L Hall

Svenja Knappe

Brahim Dahmani

Jon H Shirley

Robert Wynands

Ma Long-sheng

A method is provided for optimizing the performance of laser-pumped atomic frequency references with respect to the laser detuning and other operating parameters. This method is based on the new understanding that the frequency references short-term instability is minimized when (a) the laser frequency is tuned nominally a few tens of MHz away from the center of the atomic absorption line, and (b) the external oscillator lock modulation frequency is set either far below or far above the inverse of the optical pumping time of the atoms.

Method of minimizing the short-term frequency instability of laser-pumped atomic clocks

A microwave frequency standard is provided which allows for miniaturization down to length scales of order one micron, comprising a modulated light field originating from a laser that illuminates a collection of quantum absorbers contained in a micro-machined cell. The frequency standard of the present invention can be based on all-optical excitation techniques such as coherent population trapping (CPT) and stimulated Raman scattering or on conventional microwave-excited designs. In a CPT-based embodiment, a photodetector detects a change in transmitted power through the cell and that is used to stabilize an external oscillator to correspond to the absorber's transition frequency by locking the laser modulation frequency to the transition frequency. In a stimulated Raman scattering (SRS) embodiment, a high-speed photodetector detects a laser field transmitted through the cell beating with a second field originating in the cell. Both the locked laser modulation frequency and the beat frequency are very stable as they are referenced directly to the atomic transition.

Miniature frequency standard based on all-optical excitation and a micro-machined containment vessel

An optical method and apparatus is disclosed for stabilizing the frequency f semiconductor lasers. The basic system includes only the optical elements of a conventional semiconductor laser optically coupled to a separate, external resonator having an optical cavity with a particular resonance frequency. The optical geometry is configured such that the output from the resonator is fed back to the laser only when the laser frequency matches or substantially matches the resonance frequency. In other disclosed embodiments, optical electronic feedback loops are used to modulate the laser injection current to stabilize the frequency and to adjust the phase of the optical feedback signal.

Optical feedback locking of semiconductor lasers

A method and apparatus are disclosed for precisely stabilizing a laser to a sub-Doppler resonance of an absorbing gas contained in a cell located external to the laser resonator. Stabilization is based on the detection of modulation transferred onto a previously unmodulated probe beam by the non-linear interactions of the absorbing gas located in a cell which is subject to a counter-running, frequency-modulated saturation beam. Alternatively, the further modulation of the saturation beam can be detected.

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Englewood, CO, United States of America

Leo W Hollberg