Periodic arrays of silver nanoparticles on a Nd3+-doped periodically poled ferroelectric laser crystal are selectively self-assembled by photochemical methods. By exploiting the unique features of plasmonic nanostructures to concentrate electromagnetic fields, an enhancement of Nd3+ luminescence is demonstrated as well as a remarkable increase of the quadratic nonlinear second harmonic generation by a factor of 20, which occurs with the periodicity of the metallic arrays.