Light Shift Suppression in Coherent-Population-Trapping Atomic Clocks in the Field of Two Circularly Polarized Light Beams

Abstract

The state-of-the-art miniature atomic clocks (MACs) are based on the phenomenon of coherent population trapping (CPT) in alkali-metal atomic vapors (Rb or Cs). Increasing frequency stability of the clocks is an urgent issue that will lead to significant progress in many fields of application. Here, we examine a light field configuration composed of two bichromatic light beams with opposite handedness of their circular polarization. The beams are in resonance with optical transitions in the Cs D${}_1$ line ($\lambda$$\approx$$895$ nm). This configuration has already been known for observing CPT resonances of an increased contrast compared to a standard single-beam scheme. However, in contrast to previous studies, we use a scheme with two independent pump and probe beams, where the probe beam transmission is separately monitored. The experiments are carried out with a buffer-gas-filled $5$$\times$$5$$\times$$5$ mm${}^3$ vapor cell. It is shown that the resonance's line shape acquires asymmetry which can be efficiently controlled by a microwave (Raman) phase between the beams. As a proof of concept, we study the way how this asymmetry can help to significantly mitigate the influence of ac Stark (light) shift on a long-term frequency stability of CPT clocks. The experimental verification is performed both with a distributed-Bragg-reflector (DBR) laser and a vertical-cavity surface-emitting laser (VCSEL). The latter has a particular importance for developing MACs. The results of experiments are in qualitative agreement with analytical theory based on a double $\Lambda$ scheme of atomic energy levels.

arXiv comment13 pages, 10 figures, 67 references

References in corpus (13)

• Metrological characterization of the pulsed Rb clock with optical detection
• On the unique possibility to increase significantly the contrast of dark resonances on D1 line of ${}^{87}$Rb
• High-performance coherent population trapping clock with polarization modulation
• Coherent Population Trapping Resonances in Buffer Gas-filled Cs Vapor Cells with Push-Pull Optical Pumping
• Theory of dark resonances for alkali vapors in a buffer-gas cell
• Generalized auto-balanced Ramsey spectroscopy of clock transitions
• Performance of a prototype atomic clock based on lin||lin coherent population trapping resonances in Rb atomic vapor
• Pseudoresonance mechanism of all-optical frequency standard operation
• Ramsey Spectroscopy with Displaced Frequency Jumps
• Coherent population trapping with polarization modulation
• Nonlinear propagation of polarized light pulses in a medium of atoms with degenerate energy levels: adiabatic approach
• Magnetic-field-insensitive coherent-population-trapping resonances excited by bichromatic linearly polarized fields on the $D_1$ line of ${}^{133}$Cs
• Transit Ramsey EIT resonances in a Rb vacuum cell

Cited by in corpus (3)

• Reduction of Magnetic-Field-Induced Shift in Quantum Frequency Standards Based on Coherent Population Trapping
• Addition to the dynamic Stark shift of the coherent population trapping resonance
• The ultimate bounds to precision of atomic clock frequency measurement techniques