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In this research, Zn(1−x)CrxAl2O4 (x = 0.00, 0.05, 0.10, 0.20) nanoparticles were prepared by a simple and green chemistry synthesis using gelatin as a polymerization agent. X-ray diffraction technique and scanning electron microscopy imaging were used to analyze the structural and morphological properties of the samples. X-ray diffraction results revealed that all samples were polycrystalline and crystallized in a cubical spinel phase. With increasing the x from 0.00 to 0.20, the main Bragg peaks shift to smaller angles, and the crystallite size and energy bandgap of samples decrease as well. The nonlinear absorption coefficient, β, and nonlinear refractive index, n2, of Zn(1−x)CrxAl2O4 were meticulously studied by the Z-scan approach. The orders of n2 and β are 10−7 and 10−4 cm/W, respectively. The saturable absorption and the self-defocusing effect are the main factors in the appearance of β and n2, respectively. The experimental results confirmed that increasing the percentage of Cr caused nonlinear coefficients to increase. [ABSTRACT FROM AUTHOR]

In this research, manganese ferrite (MnFe2O4) thin film and spherical nanoparticles were synthesized using the e-beam evaporation type of PVD and sol-gel method, respectively. Also, the effect of morphology on the structural, linear, and nonlinear optical properties of samples was investigated. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to assess the surface morphology of the specimens. The nonlinear optical (NLO) properties were also explored by the Z-scan technique utilizing CW laser at 532 nm. Different incident powers of laser were evaluated during nonlinearity assessments. In this research, MnFe2O4 nanoparticles showed higher nonlinear responses than MnFe2O4 thin film. The nonlinear refractive (NLR) indices and nonlinear absorption (NLA) coefficient of MnFe2O4 nanoparticles were 10−4 cm2/W and 10 W/cm, respectively. The obtained optical nonlinearity can be assigned to the two-photon absorption and the self-focusing effect. In addition, thermal nonlinearity explains the changes in the value of β and n2 for MnFe2O4 nanoparticles and thin films. The higher nonlinearity in the nanoparticle sample than thin film can be due to nanoparticle clusters in solution of MnFe2O4. The good nonlinear optical properties of MnFe2O4 indicate that this material can be the promising potential in nonlinear photonic devices. [ABSTRACT FROM AUTHOR]

γ-Al2O3 nanoparticles (NPs) with a mean diameter of 60 nm were prepared through the sol–gel technique and characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), and ultraviolet–visible (UV-Vis) spectroscopy. The formation of cubic structures with the γ phase for Al2O3 NPs confirms. The average particle size obtained is about 60 nm by the FESEM image. The nonlinear optical properties were examined by a single-beam Z-scan method using a Gaussian visible continuous wave Nd:YAG laser (532 nm). The Z-scan findings indicated a self-focusing nonlinearity and saturable absorption process in order of 10−8 (cm2/W) and 10−4 (cm/W) in the synthesized γ-Al2O3 NPs, respectively. Moreover, Kramers–Kronig relations were applied to determine the complex refractive index and dielectric coefficient of the specimens by Fourier-transform infrared spectroscopy. The transversal and longitudinal optical (TO and LO) modes are the two intersection points in the real and imaginary parts of the complex refractive index. Also, the maximum position of the Im(−1/ ε) plot is related to LO frequency. [ABSTRACT FROM AUTHOR]

• The optical indexes of synthesized BA 2 MAPb 2 I 7 perovskites were determined. • The optical bandgap was obtained at ∼ 1.95 eV for BA 2 MAPb 2 I 7 thin films. • The NLO properties of BA 2 MAPb 2 I 7 thin films was studied by Z-scan method with different laser powers. Ruddlesden-Popper-type halide perovskites (RPPs) have been widely investigated because of their tunable optical properties. The BA 2 MAPb 2 I 7 (BA = CH 3 (CH 2) 3 NH 3 and MA = CH 3 NH 3) powder is synthesized by a chemical solution-based method at low temperature and deposited on a glass substrate by spin coating technique. The optical transmission, reflection, and absorption investigations are conducted to determine the optical constants of the nano-powder and thin film of BA 2 MAPb 2 I 7. The obtained results reveal that the optical band gap energy of BA 2 MAPb 2 I 7 thin film and BA 2 MAPb 2 I 7 nanoparticles are ∼ 1.95 and ∼ 2.02 eV, which is close to the photoluminescence (PL) peak at around 2.15 eV (576 nm). The optical indexes such as n, k, ε 1, and ε 2 are assessed based on reflectance spectra data and the Kramers-Kronig (KK) method. Moreover, the third-order nonlinear optical (NLO) characteristics, including nonlinear absorption coefficient (β), nonlinear refractive index (n 2), third-order susceptibility (χ (3) ) and second-order hyperpolarizability (γ) are investigated at different laser power. The positive signs of the n 2 and β reveal that the BA 2 MAPb 2 I 7 thin film exhibits self-focusing and saturable absorption (SA) properties due to thermal nonlinearity under the continuous wave (CW) laser regime. The magnitude of χ 3 is from 20.275 × 10 - 2 to 29.908 × 10 - 2 e s u and the value of γ is from 19.633 × 10 - 27 to 28.961 × 10 - 27 e s u. The superior NLO responses of BA 2 MAPb 2 I 7 thin-film open the path for the future design and synthesis of desirable and distinct materials for optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this study, lead sulfide quantum dots (PbS QDs) have been prepared by an aqueous method with a mixture of TGL and DTG as a capping agent with different situations of synthesis. The XRD study defends mono-phase formation of PbS having a cubic system with a crystallite size of 2.9–3.6 nm. The SEM images show that the particles are at the nanoscale. The band gap energies of these samples were obtained 2.47–2.53 eV using UV–Vis absorption spectra. In addition, the optical limiting (OL) method was used to obtain linear absorption coefficient, α. The results of Kramers-Kronig (KK) relations show by increasing pH, the intensity increased in complex refractive index as well as complex dielectric constant. Moreover, regarding the transverse optical and longitudinal optical frequencies of PbS QDs, by increasing synthesized environment pH, both frequencies had significantly blue shifts. Owning the high dielectric constant of the sample, PbS QDs were revealed an appropriate candidate to employ in smart materials. Besides, standard single-beam Z-scan techniques with various laser powers have been employed for detecting nonlinear optical (NLO) characteristics. This research reports the relaxation time and pH-dependent third-order NLO properties of PbS QDs. The consequences have revealed that the nonlinear refractive (NLR) and nonlinear absorption (NLA) coefficients of PbS QDs have been improved by increasing laser power except at 55 mW, reaching values of 1.68 × 10−7 cm2/W and 6.8 × 10−4 cm/W in pH of 9.2 and relaxation time of 1 h at 45 mW, respectively. [ABSTRACT FROM AUTHOR]

According to the BBL law, when the absorption is low, a relationship between absorption and reflection can be written similar to that of the absorption and transmission [2]. The (Bouguer-) Beer-Lambert (BBL) law seems to be the fundamental law in infrared spectroscopy. According to the BBL law, the quantity absorbance, defined as the ratio of intensity of light after leaving the sample and the intensity before entering it, is proportional to the B thickness b of the sample and the concentration of absorbing entities. [Extracted from the article]

In this research, colloidal gold NPs were synthesized by turkevich method. XRD spectrum after irradiation showed the different peaks but the most important distinctive was related to (111) peaks at (2θ = 38.41°) which give an indication that the structure is cubic. The Raman spectroscopy results indicated that the intensity of peaks with the wave number of 3450 cm −1 was increased in the colloidal gold NPs irradiated due to improvement of the crystalline properties of colloidal gold NPs. SEM images showed significant changes in the morphology and size of gamma irradiated colloidal gold NPs. For 10 kGy dose, gamma-ray irradiated crystals, the optical absorption increases compared to that of before irradiation which may be the consequence of the formation of point defects due to gamma-rays. Comparing nonlinear studies, the magnitude of nonlinear refraction index, n 2 and nonlinear absorption coefficient, β increase after gamma-ray irradiation. The measurement of mass attenuation coefficients result shows that the gamma-ray irradiation has an influence on radiation absorption coefficients of colloidal gold NPs. It is an evidence which shows that in addition to the atomic mass number of elements, the molecular structure may affect on the attenuation coefficients and nonlinear optical properties. [ABSTRACT FROM AUTHOR]

Undoped ZnS nanoparticles and doped with selected magnetic metal ions (Fe 2+ , Co 2+ , and Ni 2+ ) have been synthesized by a solvothermal method utilizing low dopant concentrations (1%) and employing poly(vinylpyrrolidone) (PVP) as a capping agent. Cubic structure of undoped and doped ZnS nanoparticles has been observed from X-ray diffraction results. The SEM images show that the particles have smooth surface and the average grain size was found to be in range of 39–60 nm for undoped and doped ZnS nanoparticles. The optical direct band gap of undoped and doped ZnS nanoparticles have been studied using UV–vis spectra. The band gap energy value was in the range of 3.49–3.92 eV. The result of UV–vis spectroscopy shown that the absorption edge shifted to lower wavelengths with doping. The linear absorption of synthesized nanoparticles have been characterized by optical limiting (OL) method. The third order nonlinear coefficients are investigated with the help of z-scan experimental set-up using Nd: YAG laser. The samples clearly exhibit a two photon absorption effect and self-defocusing process. The results show nonlinear optical properties by doping is reduced. [ABSTRACT FROM AUTHOR]

The synthesized TiO 2 nanoparticles (NPs) doped to nematic liquid crystals (NLCs) with 1% wt. for both alignments (homeotropic and homogeneous). Dielectric permittivity of samples was measured by LCR meter at different temperatures. TiO 2 NPs doped into NLCs show higher permittivity than pure NLCs. According to the obtained results, the permittivity of ε ⊥ increases more than ε ׀׀ in samples. The magnitude and temperature dependence of the refractive indices of TiO 2 NPs doped into NLCs are reported. Investigated electrical behavior of the sample was studied over a wide range of frequency using a complex impedance spectroscopy (CIS) technique. The third-order nonlinear optical properties of TiO 2 NPs doped into NLCs which tested by a Z -scan method with continuous wave (CW) He: Ne laser beam, are reported. The Z-scan results revealed that the TiO 2 NPs in NLCs exhibit self-focusing nonlinearity and saturable absorption effect for both alignments. The results showed that NLCs doped with a small amount of TiO 2 NPs can have significantly improved electro-optic properties. [ABSTRACT FROM AUTHOR]

• The simple calcination method was employed to fabricate dispersed Ag/g-C 3 N 4 nanostructures. • SPR effect of Ag nanoparticles enhanced visible-light absorption of Ag/g-C 3 N 4. • NLO properties of g-C 3 N 4 and Ag/g-C 3 N 4 are compared by using Z-scan results. • TO and LO frequencies have red shifts in Ag doped g-C 3 N 4 in comparison with g-C 3 N 4. In this work, g-C 3 N 4 and Ag/g-C 3 N 4 nanomaterials were prepared and their structural, dielectric and optical properties are compared. The UV–Vis spectrophotometry, XRD pattern, FESEM image, FTIR spectroscopy, KK method and Z-scan measurements were applied to characterize the obtained nanomaterials. The Z-scan method was used to analyze third-order nonlinearity studies such as the nonlinear refractive (NLR) index, n 2 , and nonlinear absorption (NLA) coefficient, β by using Nd: YAG laser with 50 mW power at 532 nm under different concentration of Ag/g-C 3 N 4 nanostructure. The impact of concentration on the nonlinear optical (NLO) properties have been investigated in detail. NLO properties of the Ag/g-C 3 N 4 nanostructure are enhanced, reaching values of 2.99 × 10−8 cm2/W and 6.53 × 10−4 cm/W for the third-order NLR and NLA coefficients, respectively. In addition, this material possesses large optical characteristics in the IR region. The complex refractive index and dielectric coefficient of Ag/g-C 3 N 4 nanostructure is investigated. Moreover, the Ag/g-C 3 N 4 nanostructure's IR light responsiveness has significantly improved. The red shifts of longitudinal and transversal frequencies for Ag/g-C 3 N 4 is more visible than g-C 3 N 4. This research might lead to fresh ideas and a new way to make high-stability supported Ag optical devices. [ABSTRACT FROM AUTHOR]