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.
ABSTRACT
In high definition mapping of the plasmonic patterns on the surfaces of nanostructures, the diffraction limit of light remains an important obstacle. Here we demonstrate that this diffraction limit can be completely circumvented. We show that upon illuminating nanostructures made of nickel and palladium, the resulting surface-plasmon pattern is imprinted on the structures themselves; the hotspots (regions of local field enhancement) are decorated with overgrowths, allowing for their subsequent imaging with scanning-probe techniques. The resulting resolution of plasmon pattern imaging is correspondingly improved.
ABSTRACT
In optics, chirality is typically associated with circularly polarized light. Here we present a novel way to detect the handedness of chiral materials with linearly polarized light. We performed Second Harmonic Generation (SHG) microscopy on G-shaped planar chiral nanostructures made of gold. The SHG response originates in distinctive hotspots, whose arrangement is dependent of the handedness. These results uncover new directions for studying chirality in artificial materials.
ABSTRACT
We present a new electromagnetic phenomenon-the asymmetric second-harmonic generation from planar chiral structures. The effect consists in distinguishing the handedness of a chiral material by rotating the sample in an experiment involving solely linearly polarized light. This phenomenon originates in the surface plasmon resonance of chiral gold nanostructures, where homodyne interference of anisotropic and chiral electric and/or magnetic multipoles appears to play an important role.
ABSTRACT
The present article highlights the lattice-imperfection and compositional origins of the nonlinear optical response in bismuth-substituted iron garnet films. In particular the roles of lattice mismatch strain and micro-strain on second harmonic generation in (Bi,Y)(3)(Fe,Ga)(5)O(12) films are elucidated based on experimental findings. It is found that lattice mismatch strain drives the second harmonic signal in (Bi,Y)(3)(Fe,Ga)(5)O(12) films, in agreement with theoretical predictions; however micro-strain was found not to correlate significantly with the second harmonic signal at the micro-strain levels present in these samples. The present study also elaborates on the influence of the film's constitutive elements and finds the nonlinear response to increase with yttrium concentration.
Subject(s)
Bismuth/chemistry , Bismuth/radiation effects , Iron/chemistry , Iron/radiation effects , Membranes, Artificial , Elastic Modulus , Light , Scattering, Radiation , Stress, MechanicalABSTRACT
The enhanced second-harmonic (SH) generation from Si (111) stripes induced by external cylindrical strain is investigated. The dependence of the intensity of the strain-induced SH on the sample azimuth shows that the Si under cylindrical strain has 3m symmetry, which is similar to that of the Si (111) surface. Further studies indicate that the intensity of the enhanced SH is a quadratic function of the cylindrical strain within the magnitude that the Si stripe can bear. For the p-polarized and s-polarized SH, the intensities are, respectively, enhanced by 47.9% and 13% at epsilon(0)=2.93x10(-4). The enhancement of SH is due to the contributions from the strain-induced second-order nonlinear susceptibility chi(strain)(2) to the bulk dipole.
ABSTRACT
Optical second-harmonic (SH) generation in porous-silicon-based photonic microcavities is observed in the form of hyper-Rayleigh scattering (HRS), with the SH radiation being diffuse and depolarized. Infiltration of sodium nitrite into the pores essentially suppresses HRS and results in generation of specular and partially polarized SH. Dissimilarly, the third-harmonic (TH) radiation from both unfilled and infiltrated samples is specular and polarized. These results indicate different spatial localization of the SH and TH sources.
ABSTRACT
Surface-enhanced optical third-harmonic generation (THG) is observed in silver island films. The THG intensity from Ag nanoparticles is enhanced by more than 2 orders of magnitude with respect to the THG intensity from a smooth and homogeneous silver surface. This enhancement is attributed to a local plasmon excitation and resonance of the local field at the third-harmonic wavelength. The diffuse and depolarized component of the enhanced THG is associated with the third-order hyper-Rayleigh scattering in a two-dimensional random array of silver nanoparticles.
ABSTRACT
Ferroelectric ordering, the electroclinic effect, and chiral smectic C(SmC*)-smectic A phase transitions in thin planar ferroelectric liquid crystal (FLC) cells are studied by means of linear electro-optic and second harmonic generation (SHG) techniques. The ferroelectric switching is detected in biased FLC cells by measuring azimuthal dependences of linear and nonlinear responses. The applied dc electric field rotates the FLC symmetry axis with initial and final orientations in the cell plane. Comparative studies of the SHG switching behavior in reflection and transmission geometries allows one to distinguish the contributions from the bulk and the subsurface layers of the cell. The analysis of SHG temperature dependences shows the existence of a strong surface coupling. The temperature-dependent nonlinear polarization shows a critical behavior with the exponent approximately 0.3 in SmC* phase.
ABSTRACT
Optical second-harmonic generation (SHG) is used as a noninvasive probe of two-dimensional (2D) ferroelectricity in Langmuir-Blodgett (LB) films of the copolymer vinylidene fluoride with trifluoroethylene. The surface 2D ferroelectric-paraelectric phase transition in the topmost layer of the LB films and a thickness-independent (almost 2D) transition in the bulk of these films are observed in temperature studies of SHG.
ABSTRACT
We report a new spectroscopic technique to measure simultaneously the intensity and the phase of second-harmonic (SH) radiation over a broad spectral range without laser tuning. Temporally separated SH pulses from two sources, excited by the same broad-bandwidth 15-fs Ti:sapphire fundamental pulse, interfere in a spectrometer to yield frequency-domain interference fringes. We demonstrate the technique by measuring the strongly bias-dependent phase of SH radiation from a Si/SiO(2)/Cr metal-oxide-semiconductor capacitor in the spectral range of the SiE(1) critical point.
ABSTRACT
The use of specific symmetry properties of optical second-harmonic generation (the s, s-exclusion rule) has allowed us to observe high-contrast hyper-Rayleigh interference patterns in completely diffuse light, an effect that has no analog in the case of linear (Rayleigh) scattering.
ABSTRACT
For what is to our knowledge the first time, electric-field-induced optical second-harmonic generation (SHG) is studied at the Si-SiO(2) interface by the use of a metal-oxide-semiconductor (MOS) structure. The crystallographic anisotropy of this phenomenon is studied for MOS structures. Experimental results indicate that the MOS technique of dc electric-field application to the Si-SiO(2) interface can be effectively used for studying electroinduced effects on SHG.
