ABSTRACT
Plasmonic structures are extremely attractive for the light flow manipulation. In turn, the spectrum of the plasmon excitations can be controlled by external magnetic field, thus giving rise to magnetoplasmonics. However, in the case of traditional magnetoplasmonic structures, the enhancement of magneto-optical (MO) effects is often accompanied by the transmission damp, which constricts the area of their applications. This paper examines resonant optical effects in composite structures based on artificial opal films covered by a thin cobalt layer, which forms a 2D hexagonal lattice of nanoholes in the metal film. Such periodic structure exhibits surface plasmon polariton-assisted extraordinary transmission along with the increase of odd in magnetization intensity magnetooptical effect in the Voigt geometry. Local field enhancement accompanying the surface plasmon polaritons excitation in composite Co/opal structure provides a distinct enhancement of the magnetization-induced second harmonic generation (SHG) and relevant MO effects at the SHG wavelength that appear as Fano-type resonances. High transmission along with resonantly-high MO effects make Co/opal films promising in plasmonic applications.
ABSTRACT
Anisotropic metal nanostructures reveal unique optical properties providing new optical effects. Here we study experimentally the nonlinear-optical response of planar arrays of gold comma-like and crescent-like nanostructures made by colloidal lithography. We show that anisotropy of the nonlinear-optical response is defined not only by the shape of the particles, but also by the relative phase of second-order susceptibility components, which are found to be spectrally sensitive. High values of circular dichroism in the second-harmonic generation response up to 70% are observed in comma-like nanostructures.
ABSTRACT
We present the experimental studies on optical second-harmonic generation from nanostructures exhibiting magnetic dipole resonances in the visible spectral range. "Nanosandwiches" of the composition Au/MgF(2)/Au with the average disk diameter of 140 nm are packed in a square lattice with the period of 400 nm. We show that at normal incidence, the intensity of the second-harmonic (SH) wave generated by the array of nanostructures increases by an order of magnitude as the excitation wavelength approaches the magnetic-dipole resonance, while the phase of the SH wave experiences a shift up to 330°. Based on the phenomenological description of the SH process, the observed effects indicate the dominant role of the nonlinear magnetic-dipole polarization driven by the χ(emm) susceptibility in SH generation in "nanosandwiches."
ABSTRACT
Chirality effects in optical second harmonic generation (SHG) are studied in periodic planar arrays of gold G-shaped nanostructures. We show that G-shaped structures of different handedness demonstrate different SHG efficiency for the left and right circular polarizations, as well as the opposite directions of the SHG polarization plane rotation. The observed effects are interpreted as the appearance of chirality in the SHG response which allows clear distinguishing of two enantiomers.
ABSTRACT
Azimuthal anisotropy of Stokes parameters of the second harmonic generation (SHG) generated and observed in reflection from a periodic planar area of G-shaped gold nanostructures is studied. A strong anisotropy of both coherent and incoherent SHG components is observed. Finite-difference time-domain calculations prove that the observed effects are due to the anisotropic enhancement of the fundamental radiation within the G-shaped structures.
