We numerically investigate the second harmonic generation from different plasmonic systems and evidence the key role played in their nonlinear response by the phase at the fundamental wavelength. In the case of a single plasmonic nanorod, the interference between the second harmonic dipolar and quadrupolar emission modes depends on their relative phase, which is deeply related to the excitation wavelength. The knowledge obtained in this simple case is then used to describe and understand the nonlinear response from a more complex structure, namely a gold nanodolmen. The complex phase evolution associated with a Fano resonance arising at the fundamental wavelength enables dramatically modifying the second harmonic emission patterns from plasmonic metamolecules within minute wavelength shifts. These results emphasize the importance of the phase in the nonlinear optical processes arising in plasmonic nanostructures, in addition to the increase in conversion yield associated with the excitation of localized surface plasmon resonances.
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http://dx.doi.org/10.1364/OE.24.017138 | DOI Listing |
J Mech Behav Biomed Mater
December 2024
Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, 2, Dublin, Ireland; Discipline of Mechanical, Manufacturing, and Biomedical Engineering, School of Engineering, Trinity College Dublin, 2, Dublin, Ireland; Advanced Materials and Bioengineering Research Centre (AMBER), Trinity College Dublin, Ireland. Electronic address:
Aortic stenosis is a prevalent disease that is treated with either mechanical or bioprosthetic valve replacement devices. However, these implants can experience problems with either functionality in the case of mechanical valves or long-term durability in the case of bioprosthetic valves. To enhance next generation prosthetic valves, such as biomimetic polymeric valves, an improved understanding of the native aortic valve leaflet structure and mechanical response is required to provide much needed benchmarks for future device development.
View Article and Find Full Text PDFUltrasonics
January 2025
College of Aerospace Engineering, Chongqing University, Chongqing 400044, China. Electronic address:
This study delves into the feasibility of leveraging quasi-static component (QSC) generation during primary Lamb wave propagation to discern subtle alterations in the interfacial properties of a two-layered plate. Unlike the second-harmonic generation of Lamb waves, QSC generation doesn't necessitate precise phase-velocity matching but rather requires an approximate matching of group velocities to ensure the emergence of cumulative growth effects. This unique characteristic empowers the QSC-based nonlinear ultrasonic method to effectively surmount the limitations associated with inherent dispersion and multimode traits of Lamb wave propagation.
View Article and Find Full Text PDFMolecules
December 2024
Department of Physical and Quantum Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland.
We report the results of calculations of the linear polarizability and second hyperpolarizability of the H molecule in the bond dissociation process. These calculations were performed for isolated molecules, as well as molecules under spatial confinement. The spatial confinement was modeled using the external two-dimensional (cylindrical) harmonic oscillator potential.
View Article and Find Full Text PDFInorg Chem
January 2025
Henan Provincial Key Laboratory of Surface and Interface Science, Zhengzhou University of Light Industry, Zhengzhou 450002, P. R. China.
Three two-dimensional (2D) chiral Ag(I) complexes with formulas [Ag(L)(5-nipa)] (), [Ag(L)(5-nipa)] (), and {[Ag(L)(5-hipa)]·2HO} () were prepared through the reactions of AgO with enantiopure -monodentate N-donors (L/L) and different dicarboxylic acids bearing A (acceptor)-π-- and D (donor)-π--type structural features, where / = (-)/(+)-2-(4'-pyridyl)-4,5-pinene-pyridine, 5-Hnipa = 5-nitroisophthalic acid, and 5-Hhipa = 5-hydroxyisophthalic acid. A study of their nonlinear optical responses reveals that chiral and enantiomeric pairs with the A-π--type dicarboxylic acid ligand simultaneously display second- and third-harmonic generation (SHG and THG) responses, while chiral containing the D-π--type dicarboxylic acid ligand only exhibits a very strong THG response. The THG intensity of is 451 × α-SiO, being about 27 and 24 times larger than those of and , respectively.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2025
Department of Chemistry, University of California, Berkeley, CA 94720.
Combining Deep-UV second harmonic generation spectroscopy with molecular simulations, we confirm and quantify the specific adsorption of guanidinium cations to the air-water interface. Using a Langmuir analysis of measurements at multiple concentrations, we extract the Gibbs free energy of adsorption, finding it larger than typical thermal energies. Molecular simulations clarify the role of polarizability in tuning the thermodynamics of adsorption, and establish the preferential parallel alignment of guanidinium at the air-water interface.
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