Second harmonic generation from alkali metals

Abstract

Nonlinear optical constants of the alkali metals, responsible for the second harmonic generation, are calculated using the Drude model. It is found that the electric quadrupole term of the nonlinear polarization is larger than that of a previous theory of Jha by a major factor of ω 2 p/ω 2. By considering a more realstic electron density distribution, we also obtain an additional dipole term due to symmetry breakdown at the surface. The new nonlinear polarization gives the reflected second harmonic intensity in good agreement with experiments.