OPTICAL 2ND-HARMONIC GENERATION AS A PROBE OF ELECTRIC-FIELD-INDUCED PERTURBATION OF CENTROSYMMETRIC MEDIA

Polarization-selective optical second-harmonic generation (SHG) is app lied to monitor nonuniform polarization distributions in centrosymmetr ic media modulated by an external de electric field. Two different sys tems are investigated: first, optical SHG from a Au-Si(100) Schottky B arrier is shown to be a direct probe of the electric field polarity ne ar such a metal-semiconductor interface. Second, a poled polymer exhib its a strong anisotropic SHG signal under normal incidence, indicating a nonuniform field enhancement at the edges of the poling electrode. The results demonstrate the sensitivity of SHG to small symmetry pertu rbations. Consequences for device applications are discussed.