Magnetic-field-insensitive coherent-population-trapping resonances excited by bichromatic linearly polarized fields on the D1 line of Cs133

Abstract

We have experimentally demonstrated that magnetic-field-insensitive coherent-population-trapping (CPT) resonances are generated between the ground hyperfine levels on the ${D}_{1}$ line of $^{133}\mathrm{Cs}$ using a two-photon $\mathrm{\ensuremath{\Lambda}}$ scheme excited by lin||lin polarizations. The frequency shift of the CPT resonance is 0.04 Hz for the deviation of $1\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{T}$ at a ``magic'' magnetic field of $139\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{T}$ and is 50 times smaller than that of the conventional clock transition at a typical bias magnetic field for the clock operation. The amplitude of the CPT spectrum excited by lin||lin polarizations is enhanced as the excitation intensity increases and is well explained by the three-level model without trap levels. Thus, the CPT resonance on the ${D}_{1}$ line of $^{133}\mathrm{Cs}$ excited by a simple lin||lin scheme will be one of the best candidates for frequency reference of miniature atomic clocks.