Phase conjugation using the surface nonlinearity of a dense potassium vapor

We observe optical phase conjugation using the surface nonlinearity of a dense atomic potassium vapor. For an atomic number density of 1.5×${10}^{17}$ ${\mathrm{cm}}^{\mathrm{-}3}$, phase-conjugate reflectivities of 4×${10}^{\mathrm{-}5}$ are measured for pump intensities approaching the saturation intensity of 10 W ${\mathrm{cm}}^{\mathrm{-}2}$. We also demonstrate aberration correction using surface phase conjugation. The measured properties of the surface-phase-conjugate signal are in excellent agreement with the predictions of a theory of surface phase conjugation by degenerate four-wave mixing, in which the origin of the nonlinear response is saturated absorption.