Investigation of second order optical nonlinearity at the surface of GaP nanowaveguides

Nonlinear optical properties of semiconductor nanowaveguides/nanowires are determined by both their crystal symmetry and geometry. For diameters comparable to the wavelength, high contrast of refractive index between the nanostructure and surrounding air leads to strong optical anisotropy. It has been shown that for nanowaveguides with certain diameters (depending on the wavelength), the effect of electric field with polarization normal to the surface becomes significant. The induced surface effect can consequently be utilized for second harmonic generation (SHG) in nanowaveguide. Nonlinear optical susceptibility at the surface results from the material discontinuity and electric quadrupole contribution, whereas the bulk nonlinearity is defined by the crystal symmetry.