Search results for "harmonic generation"

From magnetic to nonlinear optical switches in spin-crossover complexes

2013

ISI Document Delivery No.: 109TF Times Cited: 0 Cited Reference Count: 173 Lacroix, Pascal G. Malfant, Isabelle Real, Jose-Antonio Rodriguez, Vincent Wiley-v c h verlag gmbh Weinheim Si; Various attempts to combine magnetic and nonlinear optical (NLO) properties in a molecule are reviewed, with a special focus on the possibility of interplay between the magnetic component and the quadratic (proportional to E-2) NLO response. This multidisciplinary research leads to the idea of spin-crossover-induced (SCO-induced) NLO switching and is evaluated at the synthetic level, with insights provided by computational chemistry. The need for nontraditional experimental setups to record NLO properties i…

Deviations from Kleinman symmetry of the second-order polarizability tensor in molecules with low-lying perpendicular electronic bands

1993

Abstract 4-Nitroaniline (pNA) and 3,5-dinitro-aniline (3,5-DNA) were studied by electric field induced second harmonic generation (EFISH) and electrooptical absorption measurements (EOAM) in dioxane solution at T = 298 K. The measurements were carried out for two polarization conditions, the electric field vector of the linearly polarized incident light being parallel or perpendicular to the static electric field. The second-order polarizability tensor of pNA is confirmed to be Kleinman symmetric, while a strong deviation from index permutation symmetry is observed for 3,5-DNA. The latter is quantitatively interpreted by contributions of a low-lying electronic band with transition dipole pe…

ChemInform Abstract: Electron Crystallography and Organic Materials with Non-Linear Optical Properties

2010

Results of electron microscopic studies of crystal structures of a number of bis-benzylidene cyclohexanones are presented. It is shown that some of these compounds are efficient crystalline non-linear optically active (NLO) chromophores with second harmonic generation (SHG) properties. Appropriately functionalized chromophores of this type can be used as a polycondensation comonomer to produce partly crystalline main-chain NLO-active polymers. Electron diffraction crystal structural data, obtained for very small crystals, allowed us to get reasonable estimations of macroscopic crystal NLO-coefficients, relating quantum-chemically calculated molecular first hyperpolarizability components to …

Quadratic Nonlinear Behaviour of Various Langmuir-Blodgett Molecules

1989

The Langmuir-Blodgett (L-B) technique is well known as a method of building-up ordered arrays of organic molecules, and especially as a means of imposing a noncentrosymmetric structure from molecules that crystallize in a centrosymmetric space group(1–3). L-B films for use in quadratic nonlinear optics can be ordered in a statistically noncentrosymmetric lattice. The method involves the compression of a mono-layer of the organic molecule, spread on top of a water surface, into a two-dimensional solid, followed by the repeated dipping of the substrate to be coated into and out of the subphase. Monolayers may be deposited onto the substrate both on immersion and withdrawal, resulting in a cen…

Second harmonic generation in ferroelectric liquid crystalline thiadiazole derivatives

1995

Diffractive optics for spectral tuning of second harmonic and supercontinuum generated in nonlinear crystals

2011

It is shown that diffractive lenses can tune the spectrum of femtosecond pulses after nonlinear optical processes. We focus on spectra of second-order pulses generated in birefringent crystals and supercontinuum in sapphire crystals. The tunability is achieved by changing the relative distance between the nonlinear crystal and the diffractive lens.

High-pressure phase ofLaPO4studied by x-ray diffraction and second harmonic generation

2016

The pressure-induced phase transition of monazite-type ${\mathrm{LaPO}}_{4}$ at $\ensuremath{\approx}26$ GPa is studied by single-crystal x-ray diffraction and second harmonic generation (SHG) up to 31 GPa. The structure of the postmonazite phase of ${\mathrm{LaPO}}_{4}$ has been obtained and it is shown that it corresponds to a post-barite-type structure with an acentric space group $P{2}_{1}{2}_{1}{2}_{1}$. A strong increase of the SHG signal at the transition confirms that the high-pressure polymorph is noncentrosymmetric. The phase transition involves a significant discontinuous decrease of the unit-cell volume by 6%, which is mainly due to a strong contraction of the $a$ lattice parame…

Dispersion Compensation in Holograms Reconstructed by Femtosecond Light Pulses

2014

This chapter describes how the spatiotemporal dispersion associated with the diffraction of broadband femtosecond light pulses through computer generated holograms (CGHs) can be compensated to a first order with a properly designed dispersion compensation module (DCM). The angular dispersion of the beam associated to CGHs leads to both spatial and temporal distortion of the pulse. Some experiments in one-shot second harmonic generation, wide-field two-photon microscopy, and parallel micromachining are shown to study the quality of the compensation performed with the DCM.

Monte Carlo simulation of high‐order harmonics generation in bulk semiconductors and submicron structures

2004

To qualify the feasibility of standard semiconductor materials and Schottky‐barrier diodes (SBDs) for THz high‐order harmonic generation and extraction, the harmonic intensity, intrinsic noise and signal‐to‐noise ratio are calculated by the Monte Carlo method when a periodic high‐frequency large‐amplitude external signal is applied to a semiconductor device. Due to very high signal‐to‐noise ratio heavily doped GaAs SBDs are found to exhibit conditions for frequency mixing and harmonic extraction that are definitively superior to those of bulk materials. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Silencing and enhancement of second-harmonic generation in optical gap antennas

2012

International audience; Amplifying local electromagnetic fields by engineering optical interactions between individual constituents of an optical antenna is considered fundamental for efficient nonlinear wavelength conversion in nanometer-scale devices. In contrast to this general statement we show that high field enhancement does not necessarily lead to an optimized nonlinear activity. In particular, we demonstrate that second-harmonic responses generated at strongly interacting optical gap antennas can be significantly suppressed. Numerical simulations are confirming silencing of second-harmonic in these coupled systems despite the existence of local field amplification. We then propose a…