Second‐harmonic spectroscopy of nano‐interfaces

Current address: School of Physics, Peking University, Beijing 100871, China
physica status solidi (c) 11/2005; 2(12):4067 - 4071. DOI: 10.1002/pssc.200562228


Optical second-harmonic is shown to be a noninvasive, interface-sensitive probe of silicon nanocrystals. The TEM01 spatial mode of SHG radiation from a silicon nanocrystal composite indicates there is nonlocal dipolar (quadrupolar) polarization source which is proportional to the gradient of the incoming electric field. With two orthogonally polarized laser beams, we enhanced the SHG from nanocrystals by creating wavelength-scale, forward-radiating gradient in the second-harmonic polarization. The quantitative features of two-beam SHG were also studied with a fused silica slide. We demonstrate several techniques for isolating the nano-interface signal from the (bulk-quadrupolar) substrate signal in our samples. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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Available from: Wolf Luis Mochán, Oct 09, 2015
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    ABSTRACT: We calculate the nonlinear dipole and quadrupole moments induced at the second harmonic (SH) frequency 2ω in a dielectric nanosphere by an inhomogeneous monochromatic electric field of frequency ω. We neglect finite size effects and assume that the surface region of the nanosphere is thin enough so that the surface may be considered locally flat. Then, we calculate the nonlinear optical response of a centrosymmetric semiinfinite composite made by the nanospheres. Within the dipole approximation, SH is forbidden in the centrosymmetric bulk, but allowed at the surface of the composite where the symmetry is broken. Therefore, the components of the surface susceptibility tensor, χijk, different from zero are calculated. As an application, we evaluate χijk for a composite made of Si nanospheres.
    Optical Materials 10/2006; 29(1):1–5. DOI:10.1016/j.optmat.2006.03.018 · 1.98 Impact Factor
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    ABSTRACT: Extending previous second-harmonic generation (SHG) single-wavelength studies [1] of Si nanocrystals (NCs) embedded in fused silica, we implement spectroscopic cross-polarized two-beam SHG (XP2-SHG) by employing an optical parametric amplifier as a source of widely tunable (1.6 ≤ Eph ≤ 2.4 eV) femtosecond pulses.Subsequent isolation of the SH signal produced by the NCs yields the oscillator strength and phase of their nonlinear response. We obtain a broad resonance between bulk Si E1 and E2 critical points. Possible explanations for the spectroscopic result are discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 06/2008; 5(8):2662 - 2666. DOI:10.1002/pssc.200779125