  Mapping the potential landscape with high spatial resolution is crucial for
quantum technologies based on ultracold atoms. Yet, imaging optical dipole
traps is challenging because purely optical methods, commonly used to profile
laser beams in free space, are not applicable in vacuum. In this work, we
demonstrate precise in-situ imaging of optical dipole traps by probing a
hyperfine transition with Ramsey interferometry. Thereby, we obtain an absolute
map of the potential landscape with micrometer resolution and
shot-noise-limited spectral precision. The idea of the technique is to control
the polarization ellipticity of the trap laser beam to induce a differential
light shift proportional to the trap potential. By studying the response to
polarization ellipticity, we uncover a small but significant nonlinearity in
addition to a dominant linear behavior, which is explained by the geometric
distribution of the atomic ensemble. Our technique for imaging of optical traps
can find wide application in quantum technologies based on ultracold atoms, as
it applies to multiple atomic species and is not limited to a particular
wavelength or trap geometry.
