AZIMUTHAL AND INCIDENT ANGLE DEPENDENCES IN THE 2ND-HARMONIC GENERATION FROM ALUMINUM

Optical second-harmonic generation (SHG) from clean Al(111) surface has been investigated using a Nd:YAG laser at 1064 nm. The second-harmonic signal exhibits both isotropic and anisotropic responses with respect to the rotation of the crystal azimuthal angle. The isotropic response can be largely accounted for by a free-electron contribution; the data agree with recent jellium-model calculations. On the other hand, the observation of anisotropic SHG suggests that the surface or bulk band structure of the material plays an important role in SHG and cannot be neglected in the description of SHG even for a simple-metal surface.