Résultat de la recherche
Light effects in the atomic-motion-induced Ramsey narrowing of dark resonances in wall-coated cells
We report on light shift and broadening in the atomic-motion-induced Ramsey narrowing of dark resonances prepared in alkali-metal vapors contained in wall-coated cells without buffer gas. The atomic-motion-induced Ramsey narrowing is due to the free motion of the polarized atomic spins in and out of the optical interaction region before spin relaxation. As a consequence of this effect, we observe a narrowing of the dark resonance linewidth as well as a reduction of the ground states’ light shift when the volume of the interaction region decreases at constant optical intensity. The results can be intuitively interpreted as a dilution of the intensity effect similar to a pulsed interrogation due to the atomic motion. Finally the influence of this effect on the performance of compact atomic clocks is discussed.
Quantitative study of the destructive quantum-interference effect on coherent population trapping
We investigate experimentally and theoretically the coherent population trapping (CPT) effect occurring in 87Rb D1 line due to the interaction with linearly polarized laser light (lin∥lin CPT). In this configuration, the coherence is strongly influenced by the structure of the excited state; consequently, the quantum interference between dark states is an essential feature of this interaction scheme. We study the lin∥lin CPT resonance as a function of the laser optical detuning. The comparison between experimental and theoretical results allows us to quantify the contribution from different dark states to the total signal. Based on these results, we investigate the signal depending on both the pressure broadening of the optical transition and the laser linewidth, and we find in which conditions the laser linewidth does not degrade the lin∥lin CPT resonance.
A new method of dark resonance excitation on D2 line in 87Rb vapor
A new method based on optical pumping is proposed for increasing the parameters of dark resonance excitation on D2 line in 87Rb vapor. The pumping is provided by linearly polarized two-frequency laser radiation propagating in the direction perpendicular to the probing field directed along the cell with atomic rubidium vapor. This method significantly improves the dark resonance parameters as compared to the case of pumping by a circularly polarized field. Qualitative considerations are confirmed by the results of numerical calculations.
Evaluation of the lin
We have investigated the lin∥lin CPT signal in the 87Rb D1 manifold when the atoms are contained in low pressure buffer gas cells. We predict the achievable clock frequency stability, basing our considerations on the signal-to-noise measurements. We show that a short-term stability of about 2 · 10-11 τ1/2 may be reached in a compact system using a modulated VCSEL, this value is mainly limited by the detection noise level and can be improved up to a factor 4 by using high frequency phase sensitive detection. Under the same experimental condition a challenging short-term stability of 1-3 · 10-13 τ1/2 can be achieved by using the PL ECDLs.
Pseudoresonance mechanism of all-optical frequency-standard operation
We propose an approach to all-optical frequency standard design, based on a counterintuitive combination of the coherent population trapping effect and signal discrimination at the maximum of absorption for the probe radiation. The short-term stability of such a standard can achieve the level of 10−14/√τ. The physics beyond this approach is a dark resonance splitting caused by the interaction of the nuclear magnetic moment with the external magnetic field.
High-contrast dark resonance on the D2 - line of 87Rb in a vapor cell with different directions of the pump - probe waves
We propose a novel method enabling to create a high-contrast dark resonance in the 87Rb vapor D2-line. The method is based on an optical pumping of atoms into the working states by a two-frequency, linearly-polarized laser radiation propagating perpendicularly to the probe field. This new scheme is compared to the traditional scheme involving the σ+-polarized probe beam only, and significant improvement of the dark resonance parameters is found. Qualitative considerations are confirmed by numerical calculations.
Influence of laser sources with different spectral properties on the performance of vapor cell atomic clocks based on lin‖lin CPT
We evaluate the influence of 2 types of laser sources with different spectral profiles on the performance of vapor cell atomic clocks based on lin
Optimized scheme of a rubidium all-optical frequency standard
A new approach to the creation of a quantum frequency standard based on the phenomenon of coherent population trapping is proposed, which employs linearly polarized radiation and involves signal discrimination at the absorption maximum.