Nonlinear spectroscopy and optical phase conjugation in cold cesium atoms

We have employed a sample of cold cesium atoms in a magneto-optical trap to study nonlinear spectroscopy and four-wave-mixing optical phase conjugation using a noncycling transition. Reflectivities of the order of 1% have been measured for moderate levels of pump power and large angular aperture. In particular, we have performed nonlinear spectroscopy in a three-level V-type system and observed directly the ac Stark splitting of the cesium 6S(1/2), F=4 ground state.