Method and system for operating a laser self-modulated at alkali-metal atom hyperfine frequency

Abstract

The present invention provides a method and apparatus for making atomic clocks or atomic magnetometers as self-modulated laser systems based on the physics of push-pull optical pumping. An atomic vapor cell is required to be in the laser cavity. With proper conditions, spontaneous push-pull optical pumping can occur inside the laser cavity. This causes the laser beam to be modulated at hyperfine-resonance frequency. With a fast photodetector, the modulated laser signal can be converted into the electrical signal, which serves as the atomic clock ticking signal or magnetometer signal. The self-modulated laser system does not use any local oscillator and the microwave circuit to lock the oscillator frequency to the hyperfine-resonance frequency, and therefore can consume less power and become more compact than conventional systems. This invention will benefit applications of time measurements and magnetic-field measurements.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application is a continuation-in-part of U.S. patent application Ser. No. 11 / 052,261 filed Feb. 7, 2005, claiming priority to U.S. Provisional Application No. 60 / 545,359, filed on Feb. 18, 2004, and this application claims priority to U.S. Provisional Application No. 60 / 630,024, filed on Nov. 22, 2004, the disclosure of each application is hereby incorporated by reference in its entirety.STATEMENT OF GOVERNMENT FUNDED RESEARCH [0002] This work was supported by the Air Force Office Scientific Research F49620-01-1-0297. Accordingly, the Government has certain rights in this invention.BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The present invention relates to the field of optically pumped atomic clocks, optically pumped atomic magnetometers, pulse laser systems, and more particularly to a laser that is self-modulated by alkali-metal vapor at 0-0 atomic-clock frequency by using light of alternating polarization ...

AI Technical Summary

Benefits of technology

[0010] The problem of conventional CPT has been solved by Push-Pull pumping technique. Push-pull pumping can boost up the CPT signal by a significant factor and therefore effectively improve the performance of CPT atomic clocks. The present invention provides a method and apparatus for operating atomic clocks or magnetometers without a local oscillator and without an electronic feed-back loop for stabilizing the local-oscillator frequency. The atomic-clock signal is directly obtained from self-modulated laser light. The method and system is based on the physics of a push-pull optical pumping technique using an alkali-metal vapor cell placed inside a laser cavity to modulate the laser light at the frequency of the hyperfine resonance. In the laser cavity, a photonic gain medium, such as laser diodes or other kinds, can amplify the photon flux at different optical frequencies. Depending on the cavity configuration, optics may be needed to control the light polarization and the optical bandwidth. A fast photodetector can convert the modulated light into the clock ticking signal in electrical form with some optics.

Problems solved by technology

The conventional CPT method with fixed circularly polarized light and FM modulation suffers from the effects of population dilution and high buffer-gas pressure.

As for the power consumption of a conventional passive atomic clock, the local oscillator and the microwave circuitry can be a major draining source because of the complexity of the microwave circuitry and feedback loops of the passive-type atomic clocks.

For a portable atomic-clock device, relatively high power consumption can reduce the battery lifetime and therefore decrease the utility of the miniature atomic clock.

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