Optically-detected spin-echo method for relaxation times measurements in a Rb atomic vapor

We introduce and demonstrate an experimental method, optically-detected spin-echo (ODSE), to measure ground-state relaxation times of a rubidium (Rb) atomic vapor held in a glass cell with buffer-gas. The work is motivated by our studies on high-performance Rb atomic clocks, where both population and coherence relaxation times ( <i>T</i>1 and <i>T</i>2 , respectively ) of the ‘ clock transition ’ (5² S_1/2 ∣ <i>F_g</i> = 1, <i>m_F</i> = 0⟩ ↔ ∣ <i>F_g</i> = 2, <i>m_F</i> = 0⟩) are relevant. Our ODSE method is inspired by classical nuclear magnetic resonance spin-echo method, combined with optical detection. In contrast to other existing methods, like continuous-wave double-resonance ( CW-DR ) and Ramsey-DR, principles of the ODSE method allow suppression of decoherence arising from the inhomogeneity of the static magnetic field across the vapor cell, thus enabling measurements of intrinsic relaxation rates, as properties of the cell alone. Our experimental result for the coherence relaxation time, specific for the clock transition, measured with the ODSE method is in good agreement with the theoretical prediction, and the ODSE results are validated by comparison to those obtained with Franzen, CW-DR and Ramsey-DR methods. The method is of interest for a wide variety of quantum optics experiments with optical signal readout.