Optical Two-Dimensional Coherent Spectroscopy of Cold Atoms

Optical Two-Dimensional Coherent Spectroscopy (2DCS) provides sensitive and background-free detection of many-body interactions and correlations in atomic vapors. Since cold atoms are an ideal system with a well-controlled environment, applying optical 2DCS in cold atoms will be useful. In this presentation, we report an experimental demonstration of optical 2DCS in cold atoms. The experiment combines a collinear 2DCS setup with a magneto-optical trap (MOT), in which cold rubidium (Rb) atoms are prepared at a temperature of about 200 μK and a number density of 10¹⁰ cm^-3. We measured the second and fourth-order nonlinear signals in one dimension. Then we acquired one-quantum and zero-quantum 2D spectra. The experiment demonstrates that our 2DCS technique has sufficient sensitivity to obtain a 2D spectrum from cold atoms. The results of this experiment represent an important first step toward optical 2DCS applications in ultracold systems, opening the possibility of performing a 2DCS study in an atom array with a deterministic number of atoms and spatial distributions.