Influence of steps on second-harmonic generation from vicinal metal surfaces

We demonstrate that the optical second-harmonic (SH) efficiency of a clean metal surface is strongly influenced by the presence of monatomic steps. Vicinal Al surfaces, oriented between 0 and ±{}10^∘{} of the (100) plane, were prepared in vacuum; the SH light was produced by picosecond laser pulses with 570820 nm incident at angles up to 67.5^∘{}. From the dependence of the SH signal on angle of incidence, wavelength, surface orientation, and oxygen exposure, we conclude that the macroscopic SH polarization of the vicinal Al surface contains comparable contributions from the (100) terraces and the surface steps.