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A systematic study of the effects of thionation in naphthalene dimide derivatives to tune their nonlinear optical properties
摘要： In the present study, the number and position of sulfur atoms on naphthalene diimide (NDI) is systematically investigated to tune its nonlinear optical (NLO) response properties. Our DFT calculations for third-order polarizability (γ) show that the thionation significantly influences the nonlinear optical property of NDI as it is seen among its several designed derivatives (NDI-1 to NDI-10). The smallest and the largest γzzzz amplitudes are 503.49×10?36 and 1299.5×10?36 esu for NDI-1 (having tetraone group) and NDI-10 (having tetrathione group), respectively. The increase in γzzzz amplitude for NDI-10 is 796×10?36 esu, which is ~150% from the γzzzz amplitude of NDI-1. A comparison of the γzzzz amplitudes of our designed derivatives are made with para-nitroaniline i.e. a prototype NLO molecule. The γzzzz amplitude of pNA is found to be 42.64×10?36 esu at the same B3LYP/DZVP2 level of theory. Using two-level model, the origin of larger γzzzz amplitudes is traced in lower transition energy of NDI-10. Furthermore, the calculation of vertical ionization potentials (VIPs) shows that the thionation does not affect the stability of designed derivatives, where a slight difference of 0.06 eV is seen between the VIPs of NDI-1 (6.63 eV) and NDI-10 (6.57 eV). Thus, a systematic comparison of the third-order polarizability and other electro-optical properties of our designed derivatives shows that our derivative systems possess good potential for their practical realization in the field of optical and NLO materials.
关键词： Naphthalene Diimide,Nonlinear Optical Properties,Third order-NLO polarizability,Polarizability,Frontier Molecular Orbitals
更新于2025-09-09 09:28:46
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Effect of Aluminium doping on photoluminescence and third-order nonlinear optical properties of nanostructured CdS thin films for photonic device applications
摘要： The work presented here reports the influence of Aluminium (Al) doping on CdS thin films for the structural, morphological, optical and third-order nonlinear optical (NLO) properties. Thin films of Pure CdS and Al-doped CdS (Cd1-xAlxS) with x= 0, 0.01, 0.05 and 0.1 are prepared on the glass substrate at 350oC using the spray pyrolysis technique. The observed X-Ray Diffraction (XRD) patterns of CdS films are found to a polycrystalline hexagonal structure and are not much affected by Al doping. Also the films have been examined by Field Emission Scanning Electron Microscopy (FESEM) images. The transmittance of the CdS films is observed to be 50 to 60% in the visible region and that decreased at higher doping concentrations and with higher Al doping the direct optical band gap is decreased from 2.52 to 2.38 eV. To understand the defect states characteristics, the corresponding room-temperaturephotoluminescence (RTPL) spectra have also been taken and found the nonlinear behavior in a band to band-edge emission in the prepared samples upon Al incorporation. The sign and the magnitude of the third-order NLO properties were determined using the Z-scan technique with a continuous wave laser as the excitation source. It is observed that the material exhibit strong two-photon absorption (2PA) with the nonlinear absorption (NLA) coefficient (β) in the range of 10-4 cmW-1 and nonlinear refractive index (NRI) n2 ~10-9 cm2W-1. The third-order NLO susceptibility has found to be enhanced from 3.12 x10-5 esu to 6.36 x10-5 esu upon Al incorporation. Optical limiting characteristics of the prepared films are studied at the experimental wavelength. The results suggest that the Cd1-xAlxS is a promising material for nonlinear optical devices at 532 nm and optical power limiting applications.
关键词： photoluminescence,spray pyrolysis,Al-doped CdS thin films,Z-scan,structural,nonlinear optical properties
更新于2025-09-09 09:28:46
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Frontispiece: Fluorooxoborates: Ushering in a New Era of Deep Ultraviolet Nonlinear Optical Materials
摘要： Fluorooxoborates: Ushering in a New Era of Deep Ultraviolet Nonlinear Optical Materials
关键词： Fluorooxoborates,Nonlinear Optical Materials,Deep Ultraviolet
更新于2025-09-09 09:28:46
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Oscillatory behaviour in the energy and nonlinear optical rectification spectra of elliptic quantum rings under electric field: influence of impurity and eccentricity
摘要： We have theoretically investigated the electronic properties and nonlinear optical rectification spectra of GaAs/AlGaAs anisotropic quantum ring, modelled by an outer ellipsis and an inner circle, in connection to the presence of a donor off-centre impurity, structural distortions and in-plane electric field. The one-electron energy spectrum and wave functions are found using the adiabatic approximation and the finite element method within the effective-mass model. The energy spectrum of the ring reveals an anomalous oscillatory behaviour in the region of relatively small values of the electric field (< 12 kV/cm) followed by linear Stark effect at higher field values. We showed that this unusual behaviour is strongly affected by the ratio of the outer/inner ring radii, the displacement of the inner circle (eccentricity) along the x or y axis and the impurity presence. The related nonlinear optical rectification spectra present maxima whose positions mirror this oscillatory behaviour and consequently can be used as an excellent tool to distinguish the presence of an impurity or the direction of the eccentricity.
关键词： nonlinear optical rectification,eccentricity,Quantum ring,donor impurity,electric field
更新于2025-09-09 09:28:46
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Facially Polarized Molecule for Alkalides and Superalkalides with Considerable Nonlinear Optical Response
摘要： In this work, alkali M (Li and K) and superalkali M’3O (M’ = Li and Na) combined with facially polarized molecule, all-cis 1,2,3,4,5,6-Hexafluorocyclohexane (L, C6H6F6), were utilized to design novel alkalides L-M-L-M’ and superalkalides L-M-L-M’3O, respectively. Computational results show that alkalides L-M-L-M’ and superalkalides L-M-L-M’3O have high thermodynamic stability, and the superalkalides L-M-L-M’3O are more stable than the alkalides L-M-L-M’. Importantly, they also possess remarkable NLO responses, the electronic contribution of the static first hyperpolarizability (β0e) has upped to 3.42 × 106 (a.u.) for L-K-L-Li3O. In particularly, the number of ligand L considerably impacts on β0e value, namely, the β0e value of Li-L-Li3O can be improved two orders of magnitude by adding additional ligand L, 1.31 × 106 (a.u.)(L-Li-L-Li3O) > 7.76 × 104 (a.u.)(Li-L-Li3O). We hope this work can attract researchers to design and synthesize novel excess electron compounds with high performance NLO materials.
关键词： Nonlinear Optical Response,Facially Polarized Molecules,Alkalide and Superalkalide
更新于2025-09-09 09:28:46
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All-optical field-free three-dimensional orientation of asymmetric-top molecules
摘要： Orientation and alignment of molecules by ultrashort laser pulses is crucial for a variety of applications and has long been of interest in physics and chemistry, with the special emphasis on stereodynamics in chemical reactions and molecular orbitals imaging. As compared to the laser-induced molecular alignment, which has been extensively studied and demonstrated, achieving molecular orientation is a much more challenging task, especially in the case of asymmetric-top molecules. Here, we report the experimental demonstration of all-optical field-free three-dimensional orientation of asymmetric-top molecules by means of phase-locked cross-polarized two-color laser pulse. This approach is based on nonlinear optical mixing process caused by the off-diagonal elements of the molecular hyperpolarizability tensor. It is demonstrated on SO2 molecules and is applicable to a variety of complex nonlinear molecules.
关键词： ultrashort laser pulses,nonlinear optical mixing,hyperpolarizability tensor,molecular orientation,asymmetric-top molecules
更新于2025-09-09 09:28:46
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Dynamic theory of nanophotonic control of two-dimensional semiconductor nonlinearities
摘要： We introduce a Maxwell-Bloch simulation approach which self-consistently combines a microscopic description of the carrier and polarization dynamics of a transition-metal-dichalcogenide (TMDC) monolayer with a spatiotemporal full-wave time-domain simulation of Maxwell’s equations on the basis of a ?nite-difference time-domain (FDTD) method beyond the slowly varying amplitude or paraxial approximations. This offers a platform to realistically model, in particular, the typical ultrafast optical excitation experiments in micro- and nanocavities. Our simulations con?rm that the weak screening of the Coulomb interaction in TMDC monolayers yields pronounced exciton lines in the linear spectrum and we uncover the second-order nonlinearity represented in the semiconductor Maxwell-Bloch equations by an intraband dipole moment. This allows us to calculate the spectral shape of the exceptionally strong second-harmonic generation around the exciton lines of TMDC monolayers. We demonstrate that the second-harmonic signal can remarkably be further enhanced by several orders of magnitude through a suitably designed (one-dimensional) photonic microcavity. Due to its self-consistency, ?exibility, explicit spatio-temporal resolution on the nanoscale and the ready access to light ?eld and electron dynamics, our theory and computational approach is an ideal platform to design and explore spatiotemporal nonlinear and quantum dynamics in complex photonic or plasmonic micro- and nanostructures for optoelectronic, nanophotonic and quantum applications of TMDC monolayers.
关键词： second-harmonic generation,nonlinear optical response,TMDC monolayer,Maxwell-Bloch simulation,photonic microcavity
更新于2025-09-09 09:28:46
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Dispersion measurement method with down conversion process
摘要： Proper characterization of nonlinear crystals is essential for designing single photon sources. We show a technique for dispersion characterization of a nonlinear material by making use of phase matching in the process of parametric down conversion. We use our procedure to improve the Sellmeier coefficients measured by another methods. Our method is demonstrated on an exemplary periodically poled potassium titanyl phosphate KTiOPO4 crystal phase-matched for 396 nm to 532 nm and 1550 nm. We show a procedure to characterize the dispersion in the range of 390 to 1800 nm by means of only one spectrometer for the UV–visible range.
关键词： second order nonlinear optical processes,single photon sources,spontaneous parametric down-conversion,dispersion measurement
更新于2025-09-09 09:28:46
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Tailoring the Linear and Second-Order Nonlinear Optical Responses of the Titanium-MIL-125 Metal-Organic Framework through Ligand Functionalization: A First Principles Study
摘要： Density functional theory calculations have been performed to investigate the linear and second order nonlinear optical (NLO) properties of titanium-based MIL-125 metal-organic frameworks in crystalline form, in which the 1,4-benzene-dicarboxylate (BDC) linkers are modified by introducing different functional groups or by extending BDC ligand to contain two (MIL-126) and three (MIL-127) benzene rings. Our results reveal that the functionalization of BDC linker tends to increase the dielectric constants and the magnitude of birefringence of MIL-125, especially for the aminated derivatives. Correspondingly, the incorporation of substituent group will improve the phase matching performance of MIL-125. As for the second harmonic generation (SHG) susceptibility, the SHG activity of the pristine MIL-125 is comparable to KDP, which can be attributed mostly to the contributions of TiO5(OH) octahedra. It is noted that after introducing substituent group into BDC linker, the organic part will have a remarkable influence on the SHG intensity. However, the specific effect on the NLO response is dependent on the type of functional group incorporated into BDC ligand, and only the inclusion of amine group that is strongly electron-donating can obviously enhance the SHG activity of MIL-125. In addition, MIL-126 and MIL-127 with longer aromatic linking unit are not suitable to act as NLO materials due to their poor phase matching abilities, but they are the promising candidates for the low dielectric constant materials. The present study can provide theoretical insights to design new second-order NLO materials based on MIL-125.
关键词： Nonlinear Optical Properties,Density Functional Theory,Hybrid Materials,Ligand Functionalization,Metal-Organic Framework,Plasmonics,Optical,Magnetic
更新于2025-09-04 15:30:14
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Optical, dielectric properties and thermal analysis on sodium sulfanilate dihydrate nonlinear optical single crystal
摘要： Nonlinear optical sodium sulfanilate dihydrate (SSD) single crystal was grown by slow evaporation solution method at ambient temperature. Unit cell parameters were elucidated with the study of single crystal X-ray diffraction. Fourier transform infrared spectroscopic analyses were performed to indentify a variety of functional groups present in the grown SSD crystal. The level of optical transmittance of the grown SSD crystal was investigated by UV–Vis–NIR spectral analysis. The lower cut off wavelength of the grown crystal was observed at 243 nm and the band gap energy is found to be 5.23 eV. The spectral study of photoluminescence was carried out for the grown crystal which shows a sharp emission peak at 485 nm resulting blue–green emission that is suitable for the optical communication applications. Mechanical strength was measured by utilizing Vickers microhardness test and the value of n is found to be 2.25 asserting that the crystal belongs to soft material category. The dielectric properties were studied as a function of frequency at various temperatures and also the grown SSD crystal has been correlated with electro-optic properties. Thermogravimetric analysis was undertaken by a thermal analyzer with the temperature starting from 30 to 800 °C and TGA/DTA results show that the crystal has good thermal stability and useful for laser applications. Etching analysis also was performed for the grown SSD single crystal proving that it has good crystalline nature with fewer defects.
关键词： Thermal analysis,Sodium sulfanilate dihydrate,Nonlinear optical materials,Dielectric properties,Optical properties,Crystal growth
更新于2025-09-04 15:30:14