High-contrast level-crossing resonances in a small cesium vapor cell for applications in atomic magnetometry

Level-crossing (LC) resonances in alkali-metal vapors are widely used for atomic magnetometry. One of the most simple and robust techniques involves a single circularly polarized light wave, while a transverse magnetic field ( B x ⊥ k) is scanned around zero to observe the subnatural-linewidth resonance of electromagnetically induced transparency (EIT) in the light wave transmission. This technique allows miniaturization of the magnetic field sensor to a great extent, maintaining high sensitivity of measurements. To obtain a high quality factor of the LC resonance and, therefore, high performance of the sensor, either a high temperature (>120 °C) or an extended volume of the vapor cell ( V ≫ 1 cm3) is usually required. Here, we propose a slight modification to the commonly used configuration, which can provide high-quality LC resonances in small ( ≪ 1 cm3) vapor cells at a relatively low temperature of 60 °C or less. The modification consists in adding the second (pump) counterpropagating light wave with opposite circular polarization ( σ + σ − configuration). In our experiments, the waves excite the D1-line ground-state level F g = 4 in cesium atoms in the presence of a buffer gas (Ne, 130 Torr). In the proposed scheme, a subnatural-linewidth electromagnetically induced absorption (EIA) resonance is observed. We compare parameters of the EIA resonance with those obtained in the single-wave scheme to show benefits of using the proposed σ + σ − configuration. The results have good prospects for developing a low-power miniaturized atomic magnetometer with a wide operating range.