Coherent population trapping resonances in pure alkaline micrometric thin cells are considered as an interesting alternative for the development of miniaturized atomic frequency references. Theoretical and experimental results are presented.
We investigate theoretically dark resonance spectroscopy for a dilute atomic vapor confined in a thin (micrometric) cell. We identify the physical parameters characterizing the spectra and study their influence. We focus on a Hanle-type situation, with an optical irradiation under normal incidence and resonant with the atomic transition. The dark resonance spectrum is predicted to combine broad wings with a sharp maximum at line center, which can be singled out when detecting a derivative of the dark resonance spectrum. This narrow signal derivative, shown to broaden only sublinearly with the cell length, is a signature of the contribution of atoms slow enough to fly between the cell windows in a time as long as the characteristic ground state optical pumping time. We suggest that this dark resonance spectroscopy in micrometric thin cells could be a suitable tool for probing the effective velocity distribution in the thin cell arising from the atomic desorption processes, and notably to identify the limiting factors affecting desorption under a grazing incidence.
A low-cost, potentially compact and robust microwave frequency reference can be constructed by use of vertical-cavity surface-emitting lasers and coherent population-trapping resonances in Cs vapor cells. Fractional frequency instabilities of 2×10-11/τ/s have been achieved with a minimum of 7×10-13 at τ=1000 s. The performance of this device as a function of external parameters such as light intensity, optical detuning, and cell temperature is discussed. The dependence of the dark-line resonance signal on these parameters can be understood largely by means of a simple, three-level model. The short-term stability depends critically on the optical detuning, whereas the long-term stability is limited currently by line shifts due to drifts in cell temperature.
Recently developed micrometric thin cells (MTC) containing atomic vapor of micrometric column thickness allow one to study peculiarities of Electromagnetically Induced Transparency (EIT) phenomenon, along with the accompanying velocity selective optical pumping/saturation (VSOP) resonances. MTC are filled with pure Rb and neither buffer gas nor paraffin-coated walls were used. the Lambda-system on D2 lines of 85RB have been studied with the use of two separate diode lasers. There are several dramatic distinctions in formation of EIT and VSOP resonances in MTC as compared with conventional cm-size cells. Particularly, in the case of MTC the narrowest EIT resonance is formed when the couple laser is resonant with the corresponding atomic transition, meanwhile the increase of the couple detuning leads to the rapid linewidth broadening. The theoretical model used well explains the experiment.