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By studying the linear and nonlinear properties of four-level quantum system near plasmonic nanostructure (PS), it is realized that the diffraction efficiency of weak probe light can be controlled by plasmon induced linear and nonlinear modulation. We investigated that due to presence of plasmonic nanostructure, the giant Kerr nonlinearity with vanishing linear and nonlinear absorption can be obtained. In this case, a weak probe light can be diffracted to the higher-order direction due to modulation of nonlinear susceptibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • Improved experimental protocol combining Z-scan thermal lens measurements with circular top-hat beams. • Extension of the standard experimental procedure to higher absorbances. • Measurements of the photothermal efficiency of gold spherical nanoparticles of 5 , 40 , 60 and 80 n m diameters at blue, green and red wavelengths. • Good agreement between the experimentally measured photothermal efficiencies and those calculated with Mie theory. Using continuous-wave (cw) single-beam Z-scan technique, the absorption and scattering efficiencies of spherical gold nanoparticles (NPs) of varying diameter are determined experimentally through the thermal lens (TL) effect for three different wavelengths in the blue, the green and the red. The main characteristics of the measurement method are detailed, extending the usual experimental procedure for weak absorption with Gaussian beams to higher absorption with top-hat beams. To confirm the validity of our approach, the experimental TL data were compared to the theoretical values from Mie theory and found to be in good agreement within the experimental errors. As expected, the photothermal efficiency of spherical gold NPs increases with lower diameters and towards shorter wavelengths. [ABSTRACT FROM AUTHOR]

Noncritical phase-matched (NCPM) fourth harmonic generation (FHG) of 1053 nm was conducted at different regions of a traditional grown large-size 65.8% deuterated potassium dihydrogen phosphate (DKDP) crystal. NCPM FHG was realized at the temperature of 32.1–32.4 °C. The 0.3 °C variation of the temperature is induced by the 0.12% inhomogeneity of deuterium content. Comparing with 2.3 °C of temperature acceptance, the 0.3 °C variation is acceptable. Thus, the traditional grown DKDP crystal is in good homogeneity of deuterium content in view of NCPM FHG. On the other hand, the linear absorption coefficient varies from 0.08 cm −1 to 0.12 cm −1 . When driven with 0.85 GW/cm 2 of second harmonic radiation, the FHG conversion efficiency reaches 68.9%. Larger linear absorption leads to 3% reduction of the conversion efficiency. Therefore, measures should be taken to suppress the linear absorption. [ABSTRACT FROM AUTHOR]

Abstract In this work, total (linear and nonlinear) optical absorption from InTl 1−x Sb x QD structures was studied. It is shown that these Tl-based QD structures have high absorption at long wavelengths. Nonlinear absorption at high power levels was preferred at some slow-light applications. The structures studied assess the possibility of infrared applications of Tl-based structures. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two novel dinuclear Cu(I) and Ag(I) complexes were designed, synthesized. [•] The molecular geometry optimization is based on crystal data. [•] The complexes display significantly enhanced two-photon absorption. [•] The Ag(I) complex possesses a large χ (3) in near IR region. [Copyright &y& Elsevier]

Abstract: A series of mono-, di- and hexa-branched pyrimidine derivatives possessing two-photon absorption have been synthesized. The spectral features of the dyes showed solvatochromic with significant bathochromic shifting of the emission spectra and large Stokes shifts in more polar solvents mainly due to the intramolecular charge-transfer. The two-photon absorption cross-section values were measured by two-photon excited fluorescence and open aperture Z-scan methods. The results revealed that the two-photon absorption cross-section values were enhanced with increasing electron-donating strength of the end group and branch number. The photophysical properties of the dyes were further investigated with the aid of theoretical calculations. In addition, the di-branched dyes has the largest values of two-photon absorption cross-section per molecular weight, low cytotoxicity and can be internalized by human liver cancer cell line and accumulates in the cytoplasm, allowing for live cell two-photon fluorescence imaging, so it is promising for in vitro and vivo cellular imaging applications. [Copyright &y& Elsevier]

Abstract: Two novel bent-shaped D–π–A–π–D chromophore molecules, 2-pyrazolyl-4,6-bis (4-N,N-ethylaminostyryl)pyrimidine (Z1) and 2-imidazolyl-4,6 –bis- (4-N,N- ethylaminostyryl) pyrimidine (Z2), were synthesized and fully characterized. It was found that the both bent-shaped chromophore molecules crystallize in the orthorhombic system, space group of P212121. The photophysical properties and the connections between structure and properties of the chromophores were investigated both experimentally and theoretically. It was revealed that both absorption and single-photon excited fluorescence (SPEF) spectra show remarkable bathochromic shifts with increasing polarity of the solvents. The two chromophores have strong two-photon excited fluorescence and large two-photon absorption cross-sections in the near-infrared range. Additionally, two-photon microscopy (TPM) fluorescent imaging of BEL-7402 cells labeled with the Z1 and Z2 revealed their potential application as a biological fluorescent probe. [Copyright &y& Elsevier]

Abstract: Four novel dyes are prepared by thiophene as π bridge between carbazole central core and other terminal groups by Suzuki and Heck coupling reactions. These dyes are fully characterized by IR, 1H NMR, 13C NMR, MS and elemental analysis. Linear absorption, single- and two-photon excited fluorescence in various solvents are experimentally investigated. The calculated two-photon absorption cross sections of 9-Hexyl-3,6-di((5-phenyl)-2-thienyl)carbazole (1), 9-Hexyl-3,6-di((5-thienyl)-2-thienyl)carbazole (2), 9-Hexyl-3,6-di((5-p-vinylpyridyl)-2-thienyl)-carbazole (3) and 9-Hexyl-3,6-di-((5-o-vinylpyridyl)-2-thienyl)carbazole (4) for the lowest excited state are 537.84, 550.76, 1292.95 and 1340.40 × 10−50 cm4 s photon−1, respectively. Calculated and experimental data have shown that thiophene as π electron bridge improves the two-photon absorption cross sections greatly. Two-photon optical data recording experiments have been carried out at 820 nm laser radiation. [Copyright &y& Elsevier]

Abstract: A new donor–bridge–acceptor (D–π–A) type ligand (L: 4′-(4-[4-(imidazole)styryl]phenyl)-2,2′:6′,2″-terpyridine) with two-photon absorption and coordination ability was designed and synthesized. Self-assembly of the ligand with HgX2 (X = Cl, Br, I) yielded a series of new coordination complexes (Dyes 1–3) with five-coordinated mercury (ΙΙ), which were characterized by single crystal X-ray diffraction determination. Solvent molecules and various weak interactions, including hydrogen bonds (C–H···N, C–H···X) and π–π interactions played significant roles in the final topological structures. Linear and nonlinear optical properties of the ligand and three dyes were described. Experimental results revealed that two-photon absorption cross sections of three dyes are extraordinary stronger than that of ligand. [Copyright &y& Elsevier]

Abstract: In this paper, we investigated the temperature dependence and optical contrast variations of a nonlinear optical material. The experiments were performed using the close and open aperture z-scan technique using a CW laser beam at 632.8 nm. The nonlinear optical behavior is attributed to thermo-optical effect. The absorption variation as function of temperature is studied. The linear absorption variation induces changes in nonlinear refraction. The nonlinear optical properties of the samples reduce when the temperature increases. [Copyright &y& Elsevier]

Abstract: The linear absorption spectra of the crystals of anthracene, tetracene, and pentacene have been calculated in the case of coupling between Frenkel excitons (FEs), charge transfer excitons (CTEs) and intramolecular vibrations. The model and its parametrization for FEs and CTEs in the plane of those crystals, first developed by Petelenz et al. have been used in the numerical simulations of the linear absorption. The calculated excitonic and vibronic spectra allow us to draw two main conclusions. First, CTEs and their vibronics will manifest themselves in the linear absorption of light polarized along the monoclinic axis only (i.e. for tetracene and pentacene along the crystallographic -axis). Second, the vibronic coupling (FE-phonon and CTE-phonon) emphasizes and increases the number of the maxima due to CTEs manifested in the linear absorption. [Copyright &y& Elsevier]

Abstract: We consider a linear stack of periodically arranged donor and acceptor molecules. Such a stack can carry Frenkel excitons (FEs) and charge-transfer excitons (CTEs). We study the case that the FE, excited at the donor, and the CTE, the hole of which is localized at the donor with the electron sitting at one of the neighboring acceptors, are transported through the stack, and that they interact among each other and with local vibrations at the donor and the acceptor. For this system we calculate the excitonic and one- as well as two-vibronic lines. [Copyright &y& Elsevier]

Abstract: The linear absorption spectra of a molecular stack of alternatingly and regularly arranged donor and acceptor (D, A) molecules have been studied theoretically for the vibronic spectral regions. The vibronic excitations consist of charge-transfer excitons (CTEs) plus one or two quanta of the intramolecular vibrational mode of the D (A) molecule. The model of CTEs on a DA molecular stack considered by Haarer, Philpott and Morawitz is extended by including the linear and quadratic coupling between CTEs and intramolecular vibrations and represents the basis for the theoretical calculations of the linear optical susceptibility and of the absorption coefficient using the methods of Green’s functions and of canonical transformations. The parameters of the CTEs and of the vibrations obtained in the experimental studies of the absorption, reflection and electroreflectance spectra of the anthracene-PMDA crystal have been introduced in the numerical simulations of the absorption coefficients in pure excitonic, in one- and in two-phonon vibronic spectra. In the case of a relatively weak transfer of the components of the CTEs (of electrons between acceptors and holes between donors) the vibronic spectra will manifest the bound (one-particle) exciton–phonon states only. In the case of stronger transfer, the vibronic absorption spectra will be modified by the impact of many-particle (unbound) exciton–phonon states and the absorption curve will be asymmetrical and broadened (non-Lorentzian). The calculated derivative of the absorption coefficient gives information on vibronic states in both cases of weak and strong transfer. [Copyright &y& Elsevier]

Abstract: The linear absorption spectra in the excitonic and vibronic regions in the case of mixing of Frenkel excitons (FEs) and charge-transfer excitons (CTEs) have been theoretically studied for the exciton parameters of the crystals of MePTCDI and PTCDA. Two coupling parameters for the exciton–phonon coupling are introduced: the FE–phonon coupling and the CTE–phonon coupling. The main features of the vibronics in the absorption spectra are the following: (a) the existence of a doublet structure in the vibronic spectra of CTEs; (b) the vibronic levels of the FE at intermediate values of both coupling parameters are located in the continuum of the many-particle exciton–phonon states which makes its absorption line wide and flat; (c) in the case of strong coupling (coupling constants larger than 1) a doublet of bound states appears above this continuum; (d) in the case of vanishing CTE–phonon coupling the vibronics of the charge transfer excitons practically disappear in the absorption spectra. [Copyright &y& Elsevier]

The commonly used shrinking core model (SCM) envisages a sorbing species to diffuse through a particle as a sharp inward-moving front separating a completely untouched core ahead of the front from a completely saturated shell behind the front. However, in many situations involving the uptake of water soluble species onto sorbent particles and ion exchange resins, the assumption of a completely saturated shell may not be justified. The objective of this communication is to derive a model that generalizes the SCM to allow for an incompletely saturated shell. As with the SCM, the advance of the sorbate into the particle is marked by a distinct interface moving inward with a velocity dictated by the interplay between the rates of diffusion and uptake onto the solid matrix. Local equilibrium is considered to exist between the diffusing sorbing species in the pore space and the form bound to the matrix, as with many homogeneous models such as the linear absorption model (LAM). The model is general enough to accommodate any function describing this local equilibrium. We show that this model simplifies to the conventional SCM as a special limiting case. As an example, the model is applied to previously reported data for the uptake of Cu2+ ions onto calcium alginate gel beads and shown to fit well, comparable to that obtained previously using the SCM and LAM. However, the predicted concentration profiles within a particle during sorption are shown to vary markedly depending on the model. [Copyright &y& Elsevier]

• Surface morphology greatly affects ultrashort pulse laser processing of sapphire. • Total internal reflection (TIR) at rough exit surface enhanced nonlinear absorption. • TIR at rough exit surface resulted in concurrent scribing on entry and exit surfaces. For ultrashort pulse laser processing of a sapphire wafer, nonlinear absorption of laser energy at sufficiently high laser intensity is essential. This study found that in ultrashort pulse laser processing of a sapphire wafer, its surface morphology can have a significant effect on nonlinear absorption and its threshold. Interestingly, for a single side polished wafer, the orientation of the rough or smooth surface towards or away from the laser source (i.e. if the laser is an incident or exit beam) is a critical parameter on the processing outcomes. The orientation of the grinded rough surface affects the amount of light internally reflected within the material; this has a direct impact on the laser energy absorbed and nonlinear absorption threshold. Indeed, the presence of a grinded rough exit surface increases the possibility of total internal reflection of the laser beam at the exit surface; this traps the laser's energy within the material more efficiently and thus promoting nonlinear absorption. This unique characteristic of having total internal reflection at the rough exit surface can result in laser scribing at both the smooth entry and rough exit surfaces simultaneously. This mechanism can be exploited to improve the laser processing of sapphire sample. [ABSTRACT FROM AUTHOR]

The beam waist relative variation (BWRV) method known as a Z-scan based technique is used to demonstrate its feasibility in characterizing the thermal effects induced by a continuous laser beam in different materials. A study of several classical solvent-based solutions (water, ethanol, methanol ...) is carried out before introducing the extension of the BWRV method to laterally map the tested sample. We show that the transverse xy-scan of the sample allows to extract an image of the phase shift due to local thermal heating. This new device, called XYZ-scan, is designed for the thermal characterization of inhomogeneous samples. An example will be given on an inhomogeneous 1.6 μ m thick thin film doped with silver nanoparticles. [ABSTRACT FROM AUTHOR]

• Three novel cadmium (II) complexes were synthesized. • The complexes were characterized by different methods. • Optical absorption and photoluminescent properties of complexes were investigated. • Complex 1 has got very good emission intensity compared to the literature. Three new cadmium–3-fluorobenzoate complexes with pyridine-3-carboxamide/pyridine-3-carboxylate complexes, namely, [Cd 2 (C 7 H 4 FO 2) 4 (C 6 H 6 N 2 O) 2 (H 2 O) 2 (1), [Cd 2 (C 7 H 4 FO 2) 4 (C 6 H 6 N 2 O) 2 (H 2 O) 2 (2), [Cd(C 7 H 4 FO 2)(C 6 H 4 NO 2)(H 2 O)] (3) were obtained under classical and two different hydrothermal conditions, respectively. The structures of all prepared complexes were characterized by elemental analysis, FT-IR and 1H NMR spectroscopy, TGA/DTA and single crystal X-ray analyses. In addition, the structural features of the complexes were studied theoretically by Hirshfeld surface analysis and the X-ray diffraction analyses were supported. It was determined that the carboxylate groups of 3-fluorobenzoate and pyridine-3-carboxylate behaved as chelating bidentate ligands. Hirshfeld surface analysis indicated that H⋯H, H⋯O/O⋯H, H⋯C/C⋯H, H⋯F/F⋯H and C⋯C interactions are the significant contributors to the crystal packing of the synthesized complexes. The thermal stabilities of the synthesized complexes have been investigated and the results showed that the complexes display thermal stability about 100 °C and the decomposition product of anhydrous complexes was CdO. The linear absorption and fluorescence (emission) properties of the complexes were investigated by using UV–Vis and Fluorescence spectroscopic techniques, respectively. It was found that the complex 1 which is synthesized by classical method has got very good emission intensity compared to the materials reported in the literature. This makes the complex 1 potential member for image acquisition without lens and filter, security printing, data recording and storage and laser applications, if its solid form can be done. In addition, it was determined that the classical synthesis has superiority according to the hydrothermal synthesis on the structural, optical absorption and fluorescence properties of the complex. [ABSTRACT FROM AUTHOR]

Effect of linear absorption, intensity of fundamental laser pulse and plasma frequency on beam width parameter is investigated to study the self-focusing of Hermite-Gaussian(HG) laser beam in plasma under relativistic and ponderomotive regime. Intense short pulse laser propagates through plasma imparts oscillatory velocity to electrons and non linearity arises. Using the paraxial approach we have derived the second order differential equation for beam width parameter and the equation for normalized radius of incident beam is also obtained using the critical condition. The outcome of our study reveals that light absorption and intensity of radiation enhance the self focusing of Hermite-Gaussiam laser beam. It is observed that the beam width parameter shows significant decrease for higher values of linear absorption coefficient and plasma frequency. We also observe that radius of the incident beam decreases sharply with increasing intensity of incident pulse for higher values of plasma frequency. [ABSTRACT FROM AUTHOR]