Second harmonic generation from nanoparticles of noncentrosymmetric geometry*

The nonlinear polarization resulting in generation of second harmonic (SH) radiation from centrosymmetrical (CS) media mostly takes place at the surface where the inversion symmetry is lost. This local disruption of symmetry disappears globally for a symmetrical particle, suppressing its total SH polarization. In this work, we explore SHG from particles of CS materials with non-CS geometry. We choose an isolated cylindrical particle with a deformed circular cross-section in the presence of an external field with a long wavelength. Assuming a small deformation parameter, a perturbative scheme is employed to analytically solve the linear and quadratic field equations, employing the dipolium model [1] to calculate the SH bulk and surface polarization. We report the SH dipolar and quadrupolar hyperpolarizability tensors, their spectra, the radiation patterns, and the conversion efficiency.

[1] B. S. Mendoza and W. L. Mochán, Phys. Rev. B 53, 4999 (1996).