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Organic Molecular Nonlinear Optical Materials and Devices
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
Sum-frequency generation is the mixing of two incident light waves of frequencies ω1 and ω2 creating a wave of ω3 = ω1 + ω2. This situation is represented by the nonlinear polarization: () Piω3=ε0χijk(2)(−ω3,ω1,ω2)Ejω1Ekω2.
How to Measure Femtosecond Pulses (Part 2)
Published in Marcos Dantus, Femtosecond Laser Shaping, 2017
Consider the nonlinear optical process of second-harmonic generation or, in general, sum-frequency generation. This multiphotonic process involves the sum of the energies of two photons (input) to produce a third photon (output) with energy equal to the sum of the two photons. The phase of the output photon equals the sum of the phases of the input wavelengths. Assume the input pulse is centered at 800 nm. Note that 400-nm photons can be generated from the sum of two photons with 800 nm wavelength (recall that photon energy is inversely related to the photon wavelength). Similarly, 400-nm photons can also be generated from the sum of one photon with 795 nm wavelength and one photon with 805 nm wavelength. The phase of the 400-nm resulting photon equals the sum of the phases of the input wavelengths. When the input pulse is transform limited (all photons having the same phase), then the 400-nm photons from the two different combinations (2 × 800 and 795 + 805) of photons have the same phase and add up constructively (1 + 1)2 = 4. Constructive interference would cause the output to be the sum of the two fields squared. This can be drastically changed if the phase of the 795-nm photon, for example, is changed to be out of phase with that of the 800-nm and 805-nm photons. Now, the resulting 400-nm photon from the sum of (795 + 805) is out of phase with the 400-nm photon produced by the 800-nm photons. The two sources of 400-nm photons interfere destructively (1 − 1)2 = 0 and no photons emerge at 400 nm. Controlling nonlinear optical interference through manipulation of the spectral phase of the pulse is a process known as multiphoton intrapulse interference (MII) (Figure 10.1).
Bio-interactive nanoarchitectonics with two-dimensional materials and environments
Published in Science and Technology of Advanced Materials, 2022
Xuechen Shen, Jingwen Song, Cansu Sevencan, David Tai Leong, Katsuhiko Ariga
Accordingly, there has been a lot of interest in analysing and understanding various phenomena at interfacial environments as seen in recent literature. Investigations on two-dimensional lipid membranes formed at interfacial environments have been progressing continuously. For example, Ishibashi and co-workers elucidated diffusion coefficients of trans-stilbene embedded within a lipid bilayer membrane of dimyristoylphosphatidylcholine formed at a silica–water interface [147]. Two different observed values of effective viscosity imply local inhomogeneity of the lipid membrane as a fluidic two-dimensional medium. Oxidation of unsaturated phospholipids with various head groups under low-level ozone environments at the air–water interface was systematically investigated using heterodyne-detected sum frequency generation spectroscopy as reported by Inoue, Ye, and co-workers [148]. Makiura et al. investigated two-dimensional assemblies of amphiphilic mesogens with different peptide chains at the air–water interface [149]. The knowledge obtained from these model studies is useful for understanding the ordering of liquid crystalline materials at various interfaces. Kinjo et al. reported theoretical approaches for molecular dynamics simulation of fractures at interfaces between polyphenylene sulfide and aluminum oxide under tensile force [150]. It was revealed that fracturing between the polymer and solid is initiated by small voids forming within the polymer layer.
Effect of solvent used for isocyanate primer on interphase formation
Published in The Journal of Adhesion, 2021
Additionally, Figure 8(d) shows a strong correlation between the relative permittivity and the change in Rdia/Rge. This correlation suggests that the phenomenon related to the relative permittivity may affect the interphase formation. One of the phenomena affected by the relative permittivity is the orientation of polymer functional groups. Urata et al. reported that the effect of the solvent relative permittivity on the orientation of the polymer side-chain functional groups varies by a sum-frequency-generation spectroscopy observation. If the orientation of functional groups in the epoxy polymer chain is changed by the organic solvent, gaps are created in the polymer chain.[23] The possibility of MDI passing through the gap and penetrating the matrix should then be considered.
Extreme ultraviolet time-resolved photoelectron spectroscopy of aqueous aniline solution: enhanced surface concentration and pump-induced space charge effect
Published in Molecular Physics, 2021
Christopher W. West, Junichi Nishitani, Chika Higashimura, Toshinori Suzuki
Photoelectron spectroscopy has a finite probing depth, which depends on the electron attenuation length (EAL) in the material at a given electron kinetic energy (eKE) [13–16,36–39]. EAL in liquid remains as a subject of intense debate; however, the following features are known. The electron-electron inelastic scattering in liquid water requires collision energy greater than the band gap of liquid water (7 eV), so that inelastic scattering at low eKE (<7 eV) is exclusively electron-vibron or electron-phonon scattering. Since these processes have small cross-sections and small energy loss per collision, EAL is relatively long in the low eKE region, even though it is still in the scale of nanometers [13] owing to combinational effects from elastic and inelastic scattering. As eKE increases above 11 eV, electron-electron scattering and electron impact ionisation can occur, so that EAL becomes about or less than a nanometer in the eKE range of tens of eV [16,36–38]. Thus, although XUV-TRPES is not rigorously surface selective, unlike non-linear optical spectroscopies based on the second harmonic generation or sum-frequency generation [40–42], its probing depth is limited to on the order of a nanometer. When the solute has an enhanced surface concentration, photoelectron signal predominantly originates from molecules at the interface.