Jacques Vanier

On the signal-to-noise ratio and short-term stability of passive rubidium frequency standards

Results are presented on theoretical calculations of the signal-to-noise ratio and of the short-term stability realizable in passive rubidium frequency standards. Measurements made on systems using either the separate hyperfine filter or the integrated hyperfine filter approach are reported. It is concluded that shot noise produced by the lamp at the photodetector is responsible for the observed white frequency noise spectrum limiting the stability in the short-term region.

On the use of intensity optical pumping and coherent population trapping techniques in the implementation of atomic frequency standards

The paper summarizes the relative advantages and disadvantages of coherent population trapping (CPT) or intensity optical pumping (IOP) for the implementation of a passive atomic frequency standard using the isotope /sup 87/Rb. This paper outlines the basic principles common to both CPT and IOP when using laser optical pumping, and makes explicit their similarities and their differences. This paper describes experimental results obtained in the same cell on the characteristics of the CPT and IOP /sup 87/Rb-hyperfine-resonance line. The measurements showed that the signal contrast is larger in CPT than in IOP for the same resulting line width; the light shift is smaller in CPT than in IOP, and is easier to control; in principle, a passive frequency standard based on CPT has a smaller size than that based on IOP, due to the absence of a microwave cavity. Conclusions on overall expectations for the future of such frequency standards are drawn.

The light shift effect in the coherent population trapping cesium maser

The light shift, as observed in the coherent population trapping (CPT) maser, was investigated theoretically and experimentally. It was found that the light shift originates from the various sidebands that are present in the spectrum of the frequency-modulated laser used to observe the CPT phenomenon.

Transfer of Frequency Stability from an Atomic Frequency Reference to a Quartz-Crystal Oscillator

This paper presents a study of the transfer of frequency stability from an atomic reference to a quartz-crystal oscillator. The study is done for the cases of active and passive atomic frequency standards in which one makes use of a phase-lock loop and of a frequency-lock loop, respectively. The analysis is made in both the frequency and time domains and covers the cases of the hydrogen and rubidium masers and the passive cesium-and rubidium-frequency standards. The results obtained from numerical calculations are presented under the form of graphs. These results include the fractional frequency spectral density Sy(f) as a function of the Fourier frequency f, and the two sample variance ?2(?) as a function of ?, the sampling time.

The coherent population trapping passive frequency standard [Rb example]

Coherent population trapping in alkali atoms has opened a new avenue in the implementation of atomic frequency standards having promising characteristics for field use. The paper reviews the state of the art in this subject and describes recent results obtained in the case of a passive Rb standard implemented using such an approach.

Coherent microwave emission without population inversion: a new atomic frequency standard

The description of a new type of frequency standard based on coherent population trapping (CPT) in cesium is given. The phenomenon creates a magnetization oscillating at the hyperfine frequency. Microwave radiation emitted by such a magnetization is detected by means of a microwave cavity. The process takes place without population inversion. Results are given for continuous and pulsed operation. The possibility of using the CPT coherent microwave emission as the basis of a frequency standard is analyzed.

Practical realization of a passive coherent population trapping frequency standard

The paper outlines the practical realization and characteristics of a small, totally autonomous passive frequency standard based on the coherent population trapping (CPT) phenomenon. The frequency standard, including physical characteristics, block diagrams of the optical control CPT resonance system and of the digital control electronics, is described. The characteristics of the frequency standard relative to general functionality and frequency stability are given, as measured on several units.

Cesium microwave emission without population inversion

The use of coherent population trapping (CPT) for the realization of a Cs coherent microwave emitter without population inversion is described. Preliminary experimental results are reported regarding the radio frequency spectrum of the emitted microwave radiation, the emission profile width, and the transient behavior of the output power. This new approach, based on the coherence properties of the laser radiation, allows the implementation of a microwave frequency standard where the linear light shift is absent and the thermal noise limit for the frequency instability is below 10/sup -12/ for an integration time of 1 s.

Coherent microwave emission in coherent population trapping: origin of the energy and of the quadratic light shift

A physical explanation is given for the origin of the coherent microwave emission in the coherent population trapping maser. The origin of the quadratic light shift is also investigated.

Pressure and Temperature Coefficients of the More Commonly Used Buffer Gases in Rubidium Vapor Frequency Standards

The temperature and pressure coefficients of three buffer gases, N2, Ar, Kr, commonly used in passive Rb57 frequency standards have been accurately determined. Techniques for filling cells reproducibly, are described. From the results obtained, calculations are made on the expected characteristics of gas mixtures. Graphs are given which can be used to select the proper buffer gas mixture and pressure to obtain specially required frequency shift and temperature coefficient in a given cell.