1,720,994 research outputs found
Microwave cavities for vapor cell frequency standards
No full textIn this paper, we report an analysis of the design criteria of microwave cavities for vapor cell frequency standards. Two main geometries exploited in those devices are considered: the cylindrical cavity, used, for example, in the coherent population trapping maser and in the pulsed optically pumped (POP) clock, and the spherical cavity used in the isotropically laser cooled clock. The cavity behavior is described through a lumped equivalent circuit in which the input coupling loop, the dielectric cell containing the atoms and the diodes for frequency tuning or Q control are taken into account. In particular, the effect of the cell on the cavity resonance frequency is analytically evaluated via a first-order perturbation approach. The theory is found in good agreement with the experiments performed with two different cylindrical cavities used for the POP clock; the model here developed can then be helpful in the design of the cavity system. The general principles here reported can be adapted to other standards, such as atomic fountains and hydrogen masers, and to other modes and/or geometries
Enhanced temperature sensitivity in vapor-cell frequency standards
No full textWe report on the measurement of an anomalously large temperature sensitivity of the clock frequency in a Rb cell with buffer gas. The effect is observed in a prototype of pulsed optically pumped frequency standard which allows high resolution measurements because of its frequency stability at the level 1.7 x 10^-13 for 1 s of measurement time. We attribute this phenomenon to the geometry of the interaction and to the presence in the cell of temperature inhomogeneities that may enhance the temperature sensitivity of the clock frequency via the buffer gas pressure coefficient. We also propose some solutions to reduce this unwanted effect that may limit the medium-long-term performances of highfrequency- stability vapor-cell clocks
Coherent-population-trapping maser: Noise spectrum and frequency stability
No full textWe examine in this paper the spectral characteristics of a coherent population trapping (CPT) maser in order to evaluate the frequency stability achievable by this kind of passive frequency standard. The peculiar features of the coherent microwave emission associated with the coherent population trapping phenomenon are theoretically examined taking into account the impact of the various noise contributions on the physical principle of operation. The theoretical predictions are then compared with the experimental results obtained with a laboratory prototype of 87Rb CPT maser. The measured frequency stability is mainly limited in the short term by the system thermal noise and in the medium term by the thermal drift and turns out to be in agreement with the computations within a factor of 2
Physics characterization and frequency stability of the pulsed rubidium maser
No full textIn this paper we report the theoretical and experimental characterization of a pulsed optically pumped vapor-cell frequency standard based on the detection of the free-induction decay microwave signal. The features that make this standard similar to a pulsed passive maser are presented. In order to predict and optimize the frequency stability, thermal and shot noise sources are analyzed, as well as the conversions of the laser and microwave fluctuations into the output frequency. The experimental results obtained with a clock prototype based on 87Rb in buffer gas are compared with the theoretical predictions, showing the practical possibility to implement a frequency standard limited in the medium term only by thermal drift. The achieved frequency stability is σy(τ)=1.2×10−12τ−1∕2 for measurement times up to τ≈105 s. It represents one of the best results reported in literature for gas cell frequency standards and is compliant with the pre..
Multistep preparation into a single Zeeman sublevel in a 87Rb vapor cell: Theory and experiment
No full textImproving short and long term stability of pulsed optically pumped vapor cell frequency standards
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