Large Nonlinear Optical Properties Research Articles

Role of Spatial Impurity Spread on the Transition Dynamics of Doped GaAs Quantum Dot in Presence of Noise

The present study thoroughly explores the time‐average population transfer rate (TAPTR) of impurity‐doped GaAs quantum dot (QD) pursuing the change in the spatial impurity spread (SIS). The said excitation rate is studied under the influence of Gaussian white noise (GWN). The rise of the ground‐state electronic density takes place due to different types of time‐changing fluctuations, viz. simple sinusoidal field, time‐dependent confinement potential, and time‐dependent magnetic field. GWN couples with the QD by additive and multiplicative modes. In this work, the joint influence of SIS and GWN and its pathway of inclusion and the nature of the time‐dependent perturbations are examined on the attributes of the TAPTR. The TAPTR curves are composed of steadfast rise, steadfast diminish, maximization (relevant to generation of large nonlinear optical properties), minimization, and saturation (suggesting dynamic freezing). The findings elucidate the means of fine‐tuning the TAPTR among the doped GaAs QD eigenstates in presence of noise, when the SIS undergoes a gradual change.

Defect-mediated saturable absorption and carrier dynamics in tin (II) monosulfide quantum dots.

Tin (II) monosulfide (SnS) has attracted considerable attention in emerging photonics and optoelectronics because of high carrier mobility, large absorption coefficient, anisotropic linear and nonlinear optical properties, and long-time stability. In this Letter, we report third-order nonlinear absorption and refraction of SnS quantum dots (QDs). Under excitation with 800-nm femtosecond pulses, QDs exhibit saturable absorption (saturation intensity ∼ 47.69 GW/cm2) and positive refractive nonlinearity (nonlinear refraction coefficient ∼ 1.24 × 10-15 cm2/W). Nonetheless, we investigate charge carrier dynamics using femtosecond transient absorption spectroscopy and propose the presence of midgap defect states which not only dictate carrier dynamics but also give rise to nonlinear optical properties in SnS QDs.

Introducing a novel C50N10 azafullerene with chained nitrogen atoms on a buckyball pole: structure, stability, vibration, and electronic properties.

Fullerenes are of high significance due to their unique chemical properties and various applications in technology, particularly materials science, drug delivery, electronics, and nanoelectronics. In the recent years, many attempts have been focused to introduce new heteroatom-doped fullerenes having advanced chemical properties and tunable electronic traits, which make them a potential candidate for application in many branches of sciences. In this study, a novel C50N10 azafullerene with a fascinating structure of chained nitrogen atoms on a buckyball pole, with different electronic and optical properties compared to its other analogs, is introduced and trace of N-N substructures on the surface of C60 fullerene cage is investigated. For this molecule, four structural isomers including 3 structures with chain N atoms on a fullerene buckyball pole (NP isomers) and one isomer with separated N atoms (SN isomer) have been studied. All isomers have been studied with and without symmetry constraints, and the symmetry influence on the structure and stability of each isomer has been investigated. Although the studied NP structures have lower stability than the SN isomer, some reasons (such as their more all-carbon hexagonal rings, breaking some of their N-N bonds for partial opening of the cage and creating bigger rings in order to get rid of the unfavorable strain, as well as decreasing the N-N lone pair repulsions) lead to the acceptable stability of these structures with the bonded N atoms. The results of atomization energy and vibrational frequency calculations indicate that isomers with the bonded N atoms have acceptable stabilities and do not decompose into their constituent components. Investigation on the structural parameters demonstrates important roles of the number of all-carbon hexagonal rings, the number of N-N junction, and the molecule symmetry in the stability of the structures with the bonded N atoms. Study on the electronic and optical properties indicates that the target structures exhibit high electronic polarizability, relatively small HOMO/LUMO gap, high first- and second-order hyperpolarizability, and also large third-order nonlinear optical properties. All calculations have been performed using Gaussian G09 software using density functional theory (DFT) approach. Three-parameter Beck hybrid exchange functional (B3) hybridized with nonlocal correlation functional of Lee, Yang, and Parr (LYP) has been employed as the level of DFT calculations. All optimizations have been performed at double-zeta polarized (DZP) split valence 6-31G(d,p) and also at split valence TZP 6-311G(d,p) basis sets. The global minimum structures have been confirmed by frequency calculations at the same level of optimizations. The natural bond orbital (NBO) analyses, frontier orbital surfaces imaging, atomic charges, and charge transfer analyses have been achieved by GenNBO program package.

Silicon rib-loaded LiNbO3 waveguide polarization beam splitter based on bound state in the continuum design

Over the last years, LiNbO3 on insulator (LNOI) has emerged as one of the most important platforms for integrated photonic applications because of its large refractive index contrast, outstanding electro-optical and nonlinear optical properties. Rib-loaded waveguide technology is an efficient approach to avoid high surface and sidewall roughness and to relax the difficulty in construction of sub-wavelength structures with steep sidewalls in case of dry-etched LNOI on-chip nanowires. The main issue for the development of rib-loaded LNOI waveguides is the intrinsic TM loss which is caused by the mode conversion between different polarizations at rib boundaries. In this work we show that the intrinsic TM loss can be eliminated by precise control of the waveguide cross section, and a silicon rib-loaded LNOI polarization beam splitter (PBS) is proposed theoretically based on a symmetric directional coupler design. The PBS is designed with a compact size of 42-μm coupling length and relatively large bandwidth of ∼90 nm for extinction ratio above 15 dB. It is, to the best of our knowledge, the first PBS proposed on rib-loaded LNOI waveguide. We believe this work paves the way for exploration of functional integrated devices based on rib-loaded LNOI waveguides.

Beyond Graphene: Low-Symmetry and Anisotropic 2D Materials

Low-symmetry 2D materials—such as ReS2 and ReSe2 monolayers, black phosphorus monolayers, group-IV monochalcogenide monolayers, borophene, among others—have more complex atomistic structures than the honeycomb lattices of graphene, hexagonal boron nitride, and transition metal dichalcogenides. The reduced symmetries of these emerging materials give rise to inhomogeneous electron, optical, valley, and spin responses, as well as entirely new properties such as ferroelasticity, ferroelectricity, magnetism, spin-wave phenomena, large nonlinear optical properties, photogalvanic effects, and superconductivity. Novel electronic topological properties, nonlinear elastic properties, and structural phase transformations can also take place due to low symmetry. The “Beyond Graphene: Low-Symmetry and Anisotropic 2D Materials” Special Topic was assembled to highlight recent experimental and theoretical research on these emerging materials.

Spectroscopic, DFT and Z-scan approach to study linear and nonlinear optical properties of Disperse Red 277

Nonlinear optical properties of 4-(diethylamino)-7-imino-7H-benzo[4,5]imidazo[1,2-a]chromeno[3,2-c]pyridine-6-carbonitrile (C.I. Disperse Red 277), a red fluorescent dye estimated spectroscopically are found in good agreement with the values estimated with density functional theory based on ab initio method using the global hybrid (GH) and range separated hybrid (RSH) functionals in combination with the basis sets (6–311++G (d,p)), (cc-pVDZ) and (cc-pVTZ). Z-Scan measurement suggests that dye possess large third order nonlinear optical (NLO) properties. Estimated polarizability (αCT), first order hyperpolarizability (β0) and second order hyperpolarizability (γ) from the, GH functionals - BMK, M062X and the RSH functionals – M11, CAM-B3LYP, HISSbPBE are having very nearly similar values and are in close agreement with spectroscopically obtained values. Solvent environment plays influential role in NLO properties of this dye as solvent polarity increases the NLO characteristics also increase from non-polar to polar solvents. The dye has shown highest NLO response. Δα, β0, γ and α0 values increase with decreasing HOMO-LUMO band gap.

Non-Linear Optical Properties of Disperse Blue 354 and Disperse Blue183 by DFT and Z-Scan Technique

(Z)-2-(2-(4-(Dihexylamino)-2-methylbenzylidene)-1,1-dioxidobenzo[b]thiophen-3(2H)ylidene)malononitrile (C.I.Disperse Blue 354) and (E)-N-(2-((2-bromo-6-cyano-4-nitrophenyl)diazenyl)-5-(diethylamino)phenyl)propionamide (C.I.Disperse Blue 183) are investigated for nonlinear optical (NLO) properties using Density Functional Theory (DFT) and Z-scan technique. The Z-scan results suggest that both the dyes possess considerably large NLO properties. C.I.Disperse Blue 183 showed major mean first hyperpolarizability (β 0) values. B3LYP/6311++G(d,p) performs better compared to other functionals for computing NLO properties of the dyes. Solvent environment contribute an influential role for NLO properties of the dyes as NLO characteristics of dyes increases from non-polar to polar solvents.

Control of nonlinear refractive index of AuNPs doped with nematic liquid crystal under external electric field

The nonlinear refractive index of gold nanoparticles (Au NPs) doped with nematic liquid crystal (NLC) is determined using Z-scan technique. The Au NPs were synthesized by laser ablation (Nd: YAG laser at 1064 nm) dispersed in liquid deionized water and then mixed by nematic liquid crystal. The effect of external electric field onto the nonlinear refractive index of the Au NPs was investigated using a close aperture Z-scan technique. It’s found experimentally, that the nonlinear refractive index of the Au NPs doped with E7 can be varied by changing both the compositional percentage of Au NPs and NLC molecules. The obtained nonlinear refractive index of the samples showed that E7 NLC can act as a good material for controlling the third order nonlinear coefficient due to its large nonlinear optical properties.

Ultrafast All-Optical Modulation in 2D Hybrid Perovskites.

Two-dimensional (2D) hybrid organic-inorganic Ruddlesden-Popper perovskites (RPPs) have been recently shown to exhibit large nonlinear optical properties due to the strong excitonic effects present in their multiple quantum wells. In this work, we use nondegenerate pump-probe spectroscopy in the 600-1000 nm wavelength range to study the influence of nonlinear effects on the ultrafast dynamics of 2D RPP thin flakes. We find that, under sub-bandgap excitation, ∼100 nm thick perovskite sheets allow up to ∼2% reflectivity modulation within a 20 fs period, due to the nonlinear optical Kerr effect and two-photon absorption, surpassing by a factor of ∼5 the reported nonlinear performance of photonic metasurfaces and single nanoantennas. When the excitation is resonant with the excitonic absorption, the ultrafast nature of the nonlinear response is lost due to the presence of linear absorption creating long-lived free carriers. Our results suggest that 2D RPPs are potential nanoscale all-optical modulators in the visible/near-infrared waveband for applications such as ultrafast information processing, optical data transmission, and high-performance computing.

Enhancement of Nonlinear Optical Properties of Indole Based Dyes through Electron Acceptor and π‐Linker for Dye‐Sensitized Solar Cell Applications

AbstractSix indole based thiazole substituted donor‐π‐acceptor molecules are designed and their nonlinear optical properties (NLO) are evaluated theoretically. Different electron withdrawing groups and π‐linkers are used to understand their role in tuning the NLO properties. The NLO properties of the molecules are analyzed in gas phase and in different solvent medium through the dipole moment, static polarizability, first and second hyperpolarizabilities. Efficiency of the molecules are studied through HOMO‐LUMO gap, frontier molecular orbitals, light harvesting efficiency, ionization potential, electron affinity and reorganization energy for hole and electron. All the dyes show maximum absorption wavelength in the visible region. The computed absorption spectra are well correlated with the HOMO‐LUMO gaps of the molecules. The HOMO‐LUMO gaps of all the dyes are found to be small, which lead to large NLO response. Results indicate that hyperpolarizability increases with increasing strength of the electron withdrawing group. In addition to the study of nonlinear optical property, we also calculate relevant parameters related to photovoltaic cells for two designed dyes which emerge suitable for this purpose. Photovoltaic parameters such as electron injection efficiency, exciton binding energy, and open circuit photovoltage are evaluated for dye sensitized solar cells (DSSC) applications. This study shows that alkyne π‐linkers are better than the alkene π‐linkers for desired applications. Overall, this study highlights the optical and photovoltaic nature of the dyes and reveals the influence of different π‐linkers and electron acceptors in designing new materials for NLO and DSSC applications.

Ferroelectricity, ionic conductivity and structural paths for large cation migration in Ca10.5−xPbx(VO4)7single crystals,x= 1.9, 3.5, 4.9

Crystal structure, thermal, ionic conductivity of large cations (Ca and Pb), dielectric and non-linear optical properties were investigated for Ca10.5−xPbx(VO4)7single crystals (x= 1.9, 3.5, 4.9).

Activation of Small Molecules (H2, CO2, N2O, CH4, and C6H6) by a Porphyrinoid-Based Dimagnesium(I) Complex, an Electride.

A density functional theory-based computation has been carried out to reveal the geometrical and electronic structures of Mg2EP (1), where EP is an extended (3.1.3.1) porphyrinoid system. EP is a 22 π electronic system and is aromatic in nature. Here, we have studied the thermodynamic and kinetic stabilities of EP2–-supported Mg22+ ion. The nature of bonding has been studied using natural bond orbital and atoms in molecule schemes. The presence of a covalent Mg(I)–Mg(I) σ-bond in Mg2EP is confirmed. The occurrence of a non-nuclear attractor (NNA) with large electron population, negative Laplacian of electron density at NNA, and presence of an electron localization function basin along with large nonlinear optical properties prompt us to classify Mg2EP as the first porphyrinoid-based organic electride. Further five small molecules, viz., dihydrogen (H2), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and benzene (C6H6), are found to be activated by the electron density between the two Mg atoms in Mg2EP.

Electronic structure and large second-order non-linear optical property of COT derivatives - a theoretical exploration.

A new strategy to design new molecules based on a fused hydrocarbon ring system comprising a COT ring and two 5-membered rings has been proposed for the study of second order NLO properties. The four charge transferring groups -NR2 (R = H, Li, Na and K) in conjunction with a sufficient number of electron withdrawing groups lead to significant variation of structural parameters and polarity. The charge transfer characteristics can be strongly modulated by introducing calcium metal atoms at suitable sites. Ca metal atoms end-capping the nitrogen ends of two adjacent -CN groups lead to electride character while a Ca metal atom bonded directly to the COT ring leads to greater charge transfer. The size of the alkali metal atom has been found to have a dramatic effect on the enhancement of first hyperpolarizability. The most significant electronic asymmetry induced by the larger potassium metal atom strongly enhances the magnitude of first hyperpolarizability. The variation of first hyperpolarizability has been satisfactorily explained in terms of TD-CAMB3LYP calculated spectroscopic parameters in light of the two-state model.

Design of novel graphdiyne-based materials with large second-order nonlinear optical properties

A series of graphdiyne-based nonlinear optical materials were theoretically designed through adsorbing alkali metals (Li, Na, K) on a largely delocalized π-conjugated graphdiyne surface, and the K3@GDY cluster has a significantly enhanced first hyperpolarizability of ∼1.61 × 105 a.u.

Optical nonlinearity, limiting and switching characteristics of novel ruthenium metal-organic complex

We report the nonlinear optical properties of Ruthenium metal complex a promising organic material for use in scientific and technological applications. The thin films of newly synthesized ruthenium metal–organic complex were fabricated using spin coating technique. Z-scan and degenerate four wave mixing (DFWM) techniques used to extract the third-order nonlinear optical (NLO) parameters. The data reveals the investigated material exhibited relatively large NLO properties. The pump–probe experiments shows that the switch-on and off times of the material were in the order of μs at different pump intensities and the energy dependent transmission studies reveal good limiting property of the material in nanosecond regime.

Measurement of large nonlinear refractive index of natural pigment extracted from Hibiscus rosa-sinensis leaves with a low power CW laser and by spatial self-phase modulation technique

We have reported here, for the first time, to the best of our knowledge, a high nonlinear refractive index (n2e) of a natural pigment extracted from Hibiscus rosa-sinensis leaves by using spatial self-phase modulation technique (SSPM) with a low power CW He-Ne laser radiation at 632.8nm. It is found by UV–Vis absorption spectroscopic analysis that chlrophyll-a, chlrophyll-b and carotenoid are present in the pigment extract with 56%, 25% and 19%, respectively. The photoluminescence (PL) emission characteristics of the extracted samples have also been measured at room temperature as well as in the temperature range of 283–333K to investigate the effect of temperature on luminescent properties of the sample. By analyzing the SSPM experimental data, the nonlinear refractive index value of pigment extract has been determined to be 3.5×10−5cm2/W. The large nonlinear refractive index has been assigned due to asymmetrical structure, molecular reorientation and thermally induced nonlinearity in the sample. The presented results might open new avenues for the green and economical technique of syntheses of organic dyes with such a large nonlinear optical property.

Helquat Dyes: Helicene-like Push-Pull Systems with Large Second-Order Nonlinear Optical Responses.

Helquat dyes combine a cationic hemicyanine with a helicene-like motif to form a new blueprint for chiral systems with large and tunable nonlinear optical (NLO) properties. We report a series of such species with characterization, including determination of static first hyperpolarizabilities β0 via hyper-Rayleigh scattering and Stark spectroscopy. The measured β0 values are similar to or substantially larger than that of the commercial chromophore E-4'-(dimethylamino)-N-methyl-4-stilbazolium. Density functional theory (DFT) and time-dependent DFT calculations on two of the new cations are used to probe their molecular electronic structures and optical properties. Related molecules are expected to show bulk second-order NLO effects in even nonpolar media, overcoming a key challenge in developing useful materials.

Growth and Study of ADP Crystal Doped with Acridine Orange

Materials with large non-linear optical properties are good candidates for applications in the fields of telecommunications, solar energy conversion, laser treatment and so on. In the present study, a crystal of Ammonium Dihydrogen Orthophosphate doped with Acridine Orange, possessing excellent nonlinear optical properties were grown by the slow solvent evaporation technique at 25°C using a constant temperature bath. Ammonium dihydrogen orthophosphate doped with Acridine Orange were synthesized in a large quantity via solution growth method using aqueous mixtures of Ammonium Dihydrogen Orthophosphate and Acridine Orange. The morphological characteristics were studied by field emission scanning electron microscopy which revealed that the synthesized product possesses needle shaped microstructures. The mechanical properties are studied by Vicker’s micro hardness test.

Theoretical study on alkali-metal doped N3H3 complexes: an in-depth understanding of the origin of electride and alkalide and their large nonlinear optical properties.

By doping the model complexant N3H3 with one or two lithium atoms, the geometrical and electronic structures as well as static electric properties of the resulting Li(N3H3), (N3H3)Li' and Li(N3H3)Li' complexes can be explored using the B3LYP, BHandHLYP, CAM-B3LYP and MP2 methods. All three complexes, especially Li(N3H3), were found to have large first hyperpolarizabilities (β 0). Meanwhile, Li(N3H3) and Li(N3H3)Li' exhibited electride and alkalide characteristics, respectively. The dependance of electric properties of alkalide Li(N3H3)Li' on the alkali atoms involved and the complexant layer number were revealed by investigating the related M(N3H3)Li' and Li(N3H3)M' (M = Na and K), and Li(N3H3) n Li' (n = 2, 3) systems. Note that the β 0 value of alkalide M(N3H3)M' increased not only with the increasing atomic number of the M'(-) anion but also with that of the M(+) cation, which differs from previously reported cases. In addition, the electric properties of the Li(N3H3)Li' alkalide were enhanced by increasing the complexant layers. However, it was found that both the complexant-complexant and the complexant-Li' interactions reduced with the addition of N3H3 layers, so no stable structures were found for larger Li(N3H3) n Li' complexes. Graphical Abstract Geometrical and electronic structures as well as static electric properties of Li(N3H3), (N3H3)Li' and Li(N3H3)Li' complexes were explored using B3LYP, BHandHLYP, CAM-B3LYP and MP2 methods.

Theoretical Design of Open-Shell Singlet Molecular Systems for Nonlinear Optics

Design principles toward open-shell singlet molecular systems exhibiting remarkable nonlinear optical (NLO) responses are derived based on a two-site diradical model within the valence configuration interaction scheme. In this scheme, the concept of diradical character (y), a chemical index for bond weakness in the ground state, enables to classify singlet molecular systems into three categories: (i) closed-shell (y = 0), (ii) intermediate diradical (0 < y < 1), and (iii) pure open-shell (y = 1) systems. It is found that the second hyperpolarizabilities (and also the first hyperpolarizabilities for asymmetric systems) are enhanced in the intermediate diradical character region with respect to the other ones. This leads to a new class of open-shell singlet NLO systems, which are expected to outstrip traditional closed-shell NLO systems. On the basis of this principle, practical molecular design guidelines for tuning the diradical characters and, therefore, for achieving large NLO properties are discussed o...