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Three- and four-photon nonlinear absorptions are reported by z-scan techniques in ZnS and 1% Mn²⁺ doped ZnS quantum dots (QDs) with 532 and 1064 nm radiations, respectively, obtained from a Q-switched Nd:YAG laser fundamental and its second harmonic radiation. The obtained maximum value of the 3PA coefficient in the doped ZnS QDs is ~10⁵ times that of bulk ZnS. Also, intensity-dependent saturation of 3PA has been observed and the measured experimental data are explained theoretically using a 3PA saturation model and the characteristic saturation intensity is estimated to be 0.92±0.04 GW/cm².

Nanoparticles of silver-embedded indium oxide thin films have been prepared on glass and silicon substrates. Silver concentration were 3 wt.% and 5 wt.% as measured by X-ray fluorescence. X-ray diffraction reveals that indium oxide of these samples remains amorphous even after pre-annealing at 400°C. The optical absorption of the samples manifests the surface plasmon resonance (SPR) phenomena, which varies with Ag content. The Ag nanoparticles radius was estimated with Mie classical theory by using the SPR data analysis. The nonlinear optical properties of films on glass substrate were investigated using z-scan technique. Under cw excitation the films exhibit large reverse saturation absorption and negative nonlinearities. The real and imaginary parts of third order susceptibility of the samples were measured and the imaginary part which arise from the change in absorption is found to be dominant.

Nanoparticle Lead sulfide was synthesized via simple chemical method and deposited on glass substrates at different substrate temperatures by thermal evaporation technique. The synthesized nanoparticle PbS was analyzed and confirmed by X-ray diffraction (XRD), Scanning electron microscopy SEM with EDX and thermogravimetry. The structural, optical, morphological and electrical properties of the deposited films were studied using XRD, UV-Vis, Raman, SEM with EDX, atomicforce microscopy AFM and Hall Effect measurements. The thickness of the deposited samples was measured using thickness profilometer. The Raman shift in the peak occurs toward lower energy with increasing substrate temperature deposited lead sulfide. The Z-scan study with open aperture was carried out at 532 nm using 5 ns laser pulse on the deposited films which shows that nonlinear absorption arises from saturable absorption process. The deposited PbS film exhibits p-type conductivity in Hall measurement.

Alloyed CdSe_0.3Te_0.7nanocrystals (NCs) were prepared by a thermochemical method using Thioglycolic acid (TGA) as a capping agent molecule. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) analysis demonstrated hexagonal phase NCs with an average size of around 2.5 nm. Synthesized NCs indicated a narrow band emission with a peak located at 561 nm. Nonlinear optical (NLO) properties of the CdSe_0.3Te_0.7NCs have been investigated by z-scan technique using Continuum Wave He–Ne laser. The nonlinear absorption coefficient and nonlinear refraction index were obtained in the order of 10^-2 and 10^-8, respectively. The results revealed that these NCs exhibit strong NLO properties effects such as self-defocusing and two photons absorption.

Optical nonlinearity of 4-dimethyl aminopyridinium dihydrogen phosphate (DMAPDP) was studied using continuous wave of diode pumped Nd:YAG laser (532nm, 50mW). The nonlinear refractive index, nonlinear absorption coefficient and nonlinear optical (NLO) susceptibility of the sample were found to be in the order of 10${}^{-8}$cm²/W, 10${}^{-3}$cm/W and 10${}^{-6}$ esu respectively. The observed self defocusing effect was used to demonstrate the optical limiting action at 532nm. Initially, XRD analysis showed that DMAPDP crystallizes in triclinic crystal system with centrosymmetric space group $P\overline{1}$. Thermal studies explored that the material undergoes an irreversible endothermic transition at 192${}^{\circ }$C which correspond to the decomposition of material. SEM image portrays the formation of nanoparticles with grain size in the range of 45–170nm. Hence 4-dimethyl aminopyridinium dihydrogen phosphate nanoparticles can be used as potential candidate for optical limiting applications.

Saturable absorbers and optical limiters have contrary optical transmission properties. We report observations of simultaneous occurrence of both these effects in a nickel sulfide nanoparticle (average diameter ~5 nm) solution and a simultaneous quantitative measurement of both. Intensity-dependent nonlinear transmission studies carried out using a 7 ns Nd:YAG laser at 532 nm by the Z-scan method, revealed efficient optical limiting in nickel sulfide nanoparticle suspensions. Induced nonlinear optical scattering was identified to be the mechanism of optical limiting, and absorption at 532 nm was found to saturate. A modification of the conventional Z-scan implementation led to the retrieval of the saturation intensity, which is otherwise overshadowed by very strong nonlinear scattering.

Two-photon optical nonlinear absorption has been studied in quantum dots of CdS_xSe_1-x grown in borosilicate glass matrix by two-step annealing technique. Femtosecond laser and open aperture Z-scan technique has been used for measuring the third-order nonlinear two-photon absorption coefficient (β⁽³⁾). Only the third-order and not the fifth-order nonlinear effects are observed at low intensities (1.6–3.2 GW cm^-2) of laser used in the present experiment. At such low intensities, the variation of β⁽³⁾ is found to be almost intensity-independent. For a given annealing duration of the quantum dots, the value of β⁽³⁾ is found to be higher for sulfur-rich samples as compared to that for selenium-rich samples. This is attributed to the presence of shallow traps formed due to sulfur vacancies in the sulfur-rich samples. Further, the value of β⁽³⁾ increases with the increase in the size of quantum dots and the rate of increase of β⁽³⁾ with the increase of average radius is found to be higher for sulfur-rich samples.

The paper was retracted as the authors have submitted the same manuscript to two completely different journals, which is seriously academic fraud and against academic ethics.

Nanostructured nonlinear optical (NLO) materials are attracting increasing interest as optical limiters for various applications. In this study, one-dimensional nanostructured Na₂Ti₃O₇ was synthesized by a typical hydrothermal method and systematically characterized. The results showed that one-dimensional nanostructured Na₂Ti₃O₇ has good crystallinity and thermal stability. Its morphology can be easily controlled to form nanotubes, nanobelts and nanorods by altering the amounts of added NaOH. The robustness of the NLO properties of one-dimensional nanostructured Na₂Ti₃O₇ in broadband optical limiting (OL) applications was investigated by the open-aperture Z-scan method. At laser wavelengths of 532 nm and 1064 nm, the effective nonlinear extinction coefficients showed nonmonotonic dependence on the morphology; nanotubes gave the maximum value. The results confirmed that the NLO and OL responses of one-dimensional nanostructured Na₂Ti₃O₇ can be effectively optimized by tailoring the morphology. In addition, the nonlinear extinction coefficients of these three types of one-dimensional nanostructured Na₂Ti₃O₇ are better than those of multi-walled carbon nanotubes, a benchmark one-dimensional OL material, at 532 nm and 1064 nm; they therefore have potential applications in nonlinear optics. Nonlinear scattering and photothermal effect measurements showed that the OL shown by one-dimensional nanostructured Na₂Ti₃O₇ can be mainly attributed to nonlinear scattering and free-carrier absorption at both irradiation wavelengths. The fabrication of one-dimensional nanostructured Na₂Ti₃O₇ with different morphologies via this simple approach paves the way for the synthesis and tuning of new one-dimensional materials with desirable photonic properties for various applications.

Well-crystallized SrBi₂Nb₂O₉ (SBN) thin films with smooth surfaces (the root mean square roughness is about 4.550 nm over an area of 2×2 μm²) are fabricated on MgO (100) substrates by the pulsed laser deposition technique at 750 °C under the oxygen pressure of 30 Pa. The nonlinear optical properties of the films are studied by using a single beam z-scan with ns pulses at 532 nm. SBN thin films exhibit an excellent nonlinear optical response, with the real and imaginary parts of the third-order nonlinear optical susceptibility being 4.139×10⁻⁷ esu and 1.104×10⁻⁷ esu, respectively. These show that SBN ferroelectrics thin films have potential applications in nonlinear optics.

Based on the Z-scan technology, the nonlinear absorption characteristics, the nonlinear refraction characteristics of ZnO nanoparticles dimethylformamide (DMF) solution and ZnO nanoparticles ethanol solution have been studied under the nanosecond (ns) laser pulses and the picosecond (ps) laser pulses. The experimental results show that the third-order nonlinear effect of ZnO nanoparticles ethanol solution is stronger than that of ZnO nanoparticles DMF solution under the ns laser pulses, and the third-order nonlinear susceptibility coefficient of the ZnO nanoparticles DMF and the ethanol solution are |χ⁽³⁾| = 2.15 × 10⁻¹²esu, |χ⁽³⁾| = 8.12 × 10⁻¹²esu respectively. The third-order nonlinear effect of the ZnO nanoparticles ethanol solution is similar to the ZnO nanoparticles DMF solution under the ps laser pulses. The third-order nonlinear susceptibility coefficient of the ZnO nanoparticles DMF and the ethanol solution are |χ⁽³⁾| = 1.16 × 10⁻¹⁴esu, |χ⁽³⁾| = 1.15 × 10⁻¹⁴esu respectively and the optical nonlinearities of ZnO nanoparticles under the ns laser pulses are better than that of the ZnO nanoparticles under the ps laser pulses.