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Optical Kerr effect spectroscopy of CS <sub/>2</sub> in monocationic and dicationic ionic liquids: insights into the intermolecular interactions in ionic liquids
摘要： A comparative study of the intermolecular dynamics of CS2 in monocationic and dicationic ionic liquids (ILs) was performed using optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). The reduced spectral densities (RSDs) of mixtures of CS2 in 1-alkyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]amide ([CnC1im][NTf2] for n = 3–5) and 1,2n-bis(3-methylimidazolium-1-yl) alkane bis[(trifluoromethane)sulfonyl]amide ([(C1im)2C2n][NTf2]2 for n = 3–5) were investigated as a function of concentration at 295 K. An additivity model was used to obtain the CS2 contribution to the RSD of a mixture in the 0–200 cm?1 region. One of the aims of this study is to show how CS2 can be used as a probe of intermolecular/interionic interactions in ILs. The concentrations were chosen such that the CS2-to-imidazolium ring mole fraction of a mixture with [(C1im)2C2n][NTf2]2 (DIL(2n)) is the same as that of a mixture with [CnC1im][NTf2] (MIL(n)). As found previously for CS2 in monocationic ILs, the intermolecular spectrum of CS2 in dicationic ILs is lower in frequency and narrower than that of neat CS2. The new result is that the intermolecular spectrum of CS2 is higher in frequency in DIL(2n) than in the corresponding MIL(n), indicating that CS2 molecules experience a stiffer potential in dicationic ILs than in monocationic ILs. The intermolecular dynamics of CS2 being higher in frequency in DIL(2n) than in MIL(n) is consistent with recent molecular dynamics simulations (Lynden-Bell and Quitevis, J. Chem. Phys., 2018, 148, 193844) that show the stiffer potential is the result of greater confinement of CS2 in DIL(2n) than in MIL(n). We also show in this study how effects due to dilution and the intermolecular potential seen by a solute molecule in solution are unraveled.
关键词： monocationic,reduced spectral densities,CS2,ionic liquids,dicationic,intermolecular interactions,Optical Kerr effect spectroscopy
更新于2025-09-19 17:15:36
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Annealing effect on laser-induced magnetization dynamics in Co/Ni-based synthetic antiferromagnets with perpendicular magnetic anisotropy
摘要： We report a comprehensive study of annealing treatment modulation on the laser-induced ultrafast magnetic behaviors in antiferromagnetically exchange-coupled [Ni/Co]4/Ru/[Co/Ni]3 multilayers with perpendicular magnetic anisotropy (PMA). Magnetic hysteresis loops indicate that the uniaxial PMA ?eld Hkeff decreases monotonously with the increase in annealing temperature Ta, but the variation of interlayer coupling ?eld Hex is rather complicated. Time-resolved magnetic-optical Kerr effect (MOKE) measurements demonstrate that the laser-excited demagnetization and precession process relies signi?cantly on Ta. Upon laser impulsion, the MOKE signal immediately shows a nonchanging transient increase and decrease with H increasing for low Ta, but only the ultrafast decreasing behavior for high Ta. From the subsequent dynamic precession spectra, the optical and acoustic precession modes are identi?ed. By ?tting the ?eld-dependent frequency curves via the deduced dispersion relations, both Hkeff and Hex are determined and their variation trends agree well with the results from the static magnetic measurement. Moreover, it is found that the critical ?eld where the ultrafast signal decrease occurs is dependent on the co-effect of Hkeff and Hex, whereas the maximum ?eld at which the optical mode precession disappears shares the same trend as Hex. The magnetic damping of acoustic mode is seen to increase with Ta due to the increased inhomogeneities. Our ?ndings provide a deep understanding of the magnetic properties in synthetic antiferromagnetic multilayers with high annealing temperatures, which will be helpful for designing advanced spintronic devices.
关键词： time-resolved magnetic-optical Kerr effect,laser-induced ultrafast magnetic behaviors,annealing treatment,synthetic antiferromagnets,perpendicular magnetic anisotropy
更新于2025-09-16 10:30:52
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Tunable multimodal magnetoplasmonic metasurfaces
摘要： The spectrally controllable enhancement of the transverse magneto-optical Kerr effect is realized in 2D hybrid metal-dielectric magnetoplasmonic metasurfaces. The light diffracted at different interfaces allows one to manipulate light phase in the condition of plasmonic and waveguiding resonance excitation controllable via the azimuthal angle. The multimodal nature of the system provides the flexible tunability of its magneto-optical response.
关键词： azimuthal angle,magneto-optical Kerr effect,magnetoplasmonic metasurfaces,plasmonic resonance,waveguiding resonance
更新于2025-09-16 10:30:52
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Efficiency evaluation of the transverse magneto-optical Kerr effect in magnetoplasmonic structures
摘要： In this study the new approach to the efficiency evaluation of the transverse magneto-optical Kerr effect is considered. To assess the prospects for the practical use of structures based on TMOKE, the Figure of Merit (FOM) parameter is introduced, which is the product of the reflected/transmitted light intensity and the Kerr signal of the structure. Kerr signal defined as absolute value of the difference of light intensities at opposite magnetizations. It is shown that parameter Figure of Merit (FOM) in proposed form can give more information than the most commonly used relative value of TMOKE. The advantages of the introduced parameter are demonstrated on the example of a magnetoplasmonic structure with thin magnetite films.
关键词： transverse magneto-optical Kerr effect,magnetoplasmonic structures,Figure of Merit,TMOKE
更新于2025-09-12 10:27:22
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Wide-band enhancement of the transverse magneto-optical Kerr effect in magnetite-based plasmonic crystals
摘要： The transverse magneto-optical Kerr effect (TMOKE) in magnetite-based magnetoplasmonic crystals is studied experimentally and theoretically. We analyze angle-resolved TMOKE spectra from two types of structures where noble metallic stripes are incorporated inside a thin magnetite film or located on top of a homogeneous film. A multiple-wide-band enhancement of the TMOKE signal in transmission is demonstrated. The complex dielectric permittivity and gyration are experimentally determined using the ellipsometry technique as well as Faraday rotation and ellipticity measurements. The obtained parameters are used in rigorous coupled-wave analysis (RCWA) calculations for studying the optical resonances. Our RCWA calculations of transmittance and TMOKE are in good agreement with the experimental data. The role of guiding and plasmonic modes in the TMOKE enhancement is revealed. We demonstrate that the TMOKE provides rich information about the studied optical resonances.
关键词： transverse magneto-optical Kerr effect,ellipticity measurements,gyration,magnetoplasmonic crystals,Faraday rotation,dielectric permittivity,optical resonances,RCWA,magnetite,TMOKE
更新于2025-09-12 10:27:22
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Design of Linear Block Code Encoder and Decoder Using Electro-optical and All-optical Units
摘要： In this paper novel designs for linear block code encoder and decoder using optical techniques have been proposed. The structures are designed and simulated using lithium niobate based Mach–Zehnder Interferometer (LN-MZI) and nonlinear material MEH-PPV [poly (2-methoxy-5-(28-ethylhexyloxy)-PPV)] (plasmonic) based MZI (P-MZI). The proposed LN-MZI designs offer attractive parameters such as high extinction ratio (> 35 dB) and low insertion loss (< 0.095 dB), while the proposed P-MZI designs possess a compact structure (3,020–12,375 μm2). An analytical comparison between the two design methodologies and other earlier proposed designs is presented. Each design is presented with a verified mathematical structure. Other performance parameters like contrast ratio and amplitude modulation have also been computed for the presented designs.
关键词： electro-optic,Pockel effect,Kerr effect,error detection,syndrome bits,plasmonic,Mach–Zehnder interferometer,lithium niobate,parity,linear block code
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Random Mode Coupling Assists Kerr Beam Self-Cleaning in a Graded-Index Multimode Optical Fiber
摘要： Spatiotemporal light beam dynamics in multimode ?bers (MMF) recently has attracted renewed interest in both fundamental physics and various ?elds of practical application [1,2]. Recent experiments [2,3] have shown that, owing to the Kerr effect, a process of beam self-cleaning can be observed in graded-index (GRIN) MMFs. As a result, one observes a robust nonlinear beam, which has a size that is close to the fundamental mode at the ?ber output, in contrast to a speckled output beam, which is obtained in the case of the linear regime. In this paper, we numerically investigate the process of beam self-cleaning in GRIN MMFs. Unlike previous approaches [3], where the nonlinear propagation of a spatial beam along the multimode ?ber was described by the generalized 3D nonlinear Schrdinger equation, we use the coupled-mode model, which has the following form: 2i dAp,m dζ = D(n + 1)2Ap,m + p ∑ m+m1=m2+m3 ∑ p+p1=p2+p3 f m,m1,m2,m3 p,p1,p2,p3 Ap1,m1Ap2,m2Ap3,m3 + ∑ m1,p1 Cm,m1 p,p1 Ap1,m1 . These equations separately describe the evolution of the amplitude of each mode Ap,m. The coupled mode approach signi?cantly reduces the computation time, due to the use of a large integration step. To account for the various imperfections of the multimode ?ber, caused by fabrication, bending or tilting, we added a random linear coupling term to the equation. Fig. 1 Dynamics of energy distribution by modes and the output ?eld for the model without random linear coupling (a) and with random linear coupling between degenerate modes (b). In this contribution, we describe various models of random linear coupling between spatial modes, including coupling between all modes, or only between degenerate ones, and investigate the effects of random mode coupling on the beam self-cleaning process. Fig. 1a shows the spatial dynamics of energy distribution among the modes, corresponding to a model without any random linear coupling. In this case, in spite of being in a strong nonlinear regime, the power of the fundamental mode oscillates along the ?ber, and we still obtain a speckled beam at the ?ber output. On the other hand, if we consider a model with random linear coupling between spatial modes with equal mode numbers, one readily observes the appearance of a self-cleaning effect, and the fundamental mode power swiftly stabilizes upon the propagation (see Fig. 1b). The output beam in this case has a size that is close to that of the fundamental mode. The results of numerical investigations are in complete agreement with our experimental data.
关键词： Kerr effect,graded-index multimode optical fiber,beam self-cleaning,random mode coupling
更新于2025-09-11 14:15:04
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Optical and Magneto-Optical Properties of Multilayer Nanosized [Co/TiO2]n Films
摘要： The optical and magneto-optical properties of the metal–dielectric multilayer [Co/TiO2]n structures with 2–4-nm-thick layers prepared on a silicon substrate Si(001) by ion-beam deposition have been studied. The complex permittivity of multilayer [Co/TiO2]n structures has been measured by the optical ellipsometry technique in the spectral range of 0.6–5.6 eV and analyzed using the optical reflection matrices for isotropic multilayer dielectric structures taking into account the optical losses and also using the method of anisotropic effective medium. The magneto-optical Kerr effect has been measured by the polarimetric technique in the spectral range of 1.2–4.5 eV in the polar and longitudinal geometries. The magnetic anisotropy type is determined on the base of the field dependences of the magneto-optical Kerr effect. It is found that the nanosized [Co/TiO2]n structures can be considered as artificial optically uniaxial media with a strong magnetic and optical anisotropy at room temperature.
关键词： silicon substrate,Co/TiO2,magneto-optical properties,multilayer nanosized films,optical properties,complex permittivity,magneto-optical Kerr effect,magnetic anisotropy,optical ellipsometry,ion-beam deposition
更新于2025-09-10 09:29:36
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Sub-20 fs All-Optical Switching in a Single Au-Clad Si Nanodisk
摘要： Dielectric nanoantennas have recently emerged as promising elements for nonlinear and ultrafast nanophotonics due to their ability to concentrate light on the nanometer scale with low losses, while exhibiting large nonlinear susceptibilities. In this work, we demonstrate that single Si nanodisks covered with a thin 30-nm thick layer of Au can generate positive and negative sub-20 fs reflectivity modulations of ?0.3% in the vicinity of the first-order anapole mode, when excited around the second-order anapole mode. The experimental results, characterized in the visible to near infrared spectral range, suggest that the nonlinear optical Kerr effect is the responsible mechanism for the observed all-optical switching phenomena. These findings represent an important step toward nanoscale ultrafast all-optical signal processing.
关键词： anapole modes,optical Kerr effect,ultrafast all-optical switching,pump-probe spectroscopy,Dielectric nanoantennas
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Portland, OR, USA (2018.11.13-2018.11.14)] 2018 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Linear Ring Modulators with DC Kerr Phase Shifters
摘要： We demonstrate a silicon ring modulator with linear phase shift versus voltage, derived from the interplay between plasma dispersion effect and DC Kerr effect. The dynamic range is 103.6 dB. Hz2/3 at a 1.2 GHz carrier.
关键词： silicon ring modulator,plasma dispersion effect,linear phase shift,dynamic range,DC Kerr effect
更新于2025-09-09 09:28:46