Search

Bismuth-modified lead silicate glasses with composition 20PbO∙(80-x)Bi2O3∙xSiO2 (10 ≤ x ≤ 40 mol%) were fabricated by classical melt-quench technique. The density (D), crystalline volume (VC), and molar volume (VM) values decrease with a decrease in bismuth concentration. FTIR spectra suggest the formation of [BiO3], [BiO6], [SiO4], [PbO3], and [PbO4] structural units. The optical band gap (Eg) values for the studied glass composition are determined to be between 1.93 and 2.12 eV, while their Urbach energy (∆E) values fall between 0.14 and 0.24 eV. A decrease in values of average electronic oxide polarizability (2.84‒1.62 Å3), and optical basicity (1.08‒0.64), predict the increase in the covalence nature of the Bi-O bond with the incorporation of SiO2 in the glass network. The small metallization criterion (0.311 to 0.325) predicts the suitability of the prepared series to be utilized as nonlinear optical materials. The Z-scan approach was utilized to determine the third-order nonlinear optical characteristics, including the nonlinear absorption coefficient (α2), nonlinear susceptibility (χ(3)), and nonlinear refractive index (η2). Optical studies reveal that with the decrease in Bi2O3 content, nonbridging oxygens (NBOs) decrease leads to an increase in bandgap and a drop in the nonlinear refractive index. The dynamic range (DR) and limiting threshold values have also been reported from the optical limiting studies of the prepared glasses. [ABSTRACT FROM AUTHOR]

This research presents the optical limiting properties of a novel axially linked D‐A type compound, LaPc‐C60(OH)n, where lanthanide phthalocyanine serves as the donor and fullerenol as the acceptor. The incorporation of fullerenol expands the π‐conjugated system, decreases the aggregation of the phthalocyanine, and significantly increases the solubility of the compound. The establishment of this D‐A system promotes intramolecular electron transfer, effectively improving both the non‐linear optical (NLO) response and optical limiting properties. In addition, homogeneous poly(methyl methacrylate) (PMMA) composite films (LaPc‐C60(OH)n/PMMA) are prepared using a simple solution casting method. Compared to fullerenol or lanthanum phthalocyanine individually, LaPc‐C60(OH)n exhibited a superior NLO response both in solution and in the solid composite film. In particular, LaPc‐C60(OH)n/PMMA demonstrated an increase in the non‐linear absorption coefficient (2050 cm GW−1) and a larger third‐order magnetization (1.84 × 10−8 esu). In addition to exhibiting an excellent NLO response at 532 nm, LaPc‐C60(OH)n also shows significant NLO enhancement at 1064 nm, extending the limiting range into the near‐infrared region. This behavior is attributed to different nonlinear absorption mechanisms and the synergistic effect that arise from the photo‐induced electron transfer process between the fullerenol and LaPc. [ABSTRACT FROM AUTHOR]

The investigation of nonlinear optical (NLO) properties is crucial for the effective application of CsPbI3/TiO2 nanocomposites in NLO devices. The CsPbI3/TiO2 nanocomposites were synthesized by a hot injection method. Then, the CsPbI3/TiO2 nanocomposites were poured into methyl methacrylate via polymerization to fabricate CsPbI3/TiO2/PMMA organic glasses (OGs). The crystal structure and size morphology of the CsPbI3/TiO2 nanocomposites were examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The nonlinear absorption (NLA), nonlinear refraction (NLR), and optical limiting (OL) properties of the CsPbI3/TiO2/PMMA OGs were investigated by using the Z-scan technique, employing a nanosecond pulse laser operating at a wavelength of 532 nm. The CsPbI3/PMMA and CsPbI3/TiO2/PMMA OGs can be transferred from saturable absorption (SA) to reverse saturable absorption (RSA) by varying the incident energy. In addition, the CsPbI3/TiO2/PMMA OGs exhibit superior NLA, NLR, and OL performances compared to the CsPbI3/PMMA OG and other halide-based perovskites. The enhanced nonlinear optical (NLO) properties of CsPbI3/TiO2/PMMA OGs can be ascribed to the cooperative interaction between CsPbI3 and TiO2. In summary, the results indicate that CsPbI3/TiO2 nanocomposites possess substantial potential for applications in NLO devices such as optical limiters, optical switches, and optical modulators. [ABSTRACT FROM AUTHOR]

Abstract This study discusses the nonlinear optical properties of as-grown and annealed NiO thin films using the Z-scan technique utilizing the femtosecond laser pulses at a repetition rate of 100 kHz of wavelength 1030 nm with a pulse duration of 370 fs. In open aperture measurements, pristine reveal saturable absorption (SA) with a negative sign of nonlinearity, while annealed samples exhibit reverse saturable absorption (RSA) with a positive sign of nonlinearity. In closed aperture conditions, all samples show prefocal minima and postfocal maxima, indicating self-focusing behavior. The observed RSA phenomena are attributed to the indirect two-photon absorption (TPA) process. The influence of surface plasmon resonance on nonlinear absorption is successfully ruled out due to insufficient excitation energy (1.20 eV) to induce resonance in the samples. The increase in bandgap with annealing temperature, associated with indirect TPA, is elucidated with the shifting of Ni- $$d_{x^2-y^2}$$ d x 2 - y 2 and Ni- $$d_{z^2}$$ d z 2 orbitals in the conduction band, under the framework of Density Functional Theory (DFT). The DFT results are correlated with the observed nonlinear SA and RSA processes. The Ni d-d and Ni-d to O-p transitions contribute to the modulation of nonlinearity in the indirect TPA process. The study suggests that the sample annealed at 400 °C exhibits superior optical limiting properties with the highest nonlinear absorption coefficients compared to the other annealed sample, while the as-grown sample is suitable for passive Q-switching applications.

Two Curcumin (Cur) based mixed ligand complexes of Nickel have been investigated for their optical nonlinearity (NLO). Physicochemical characterization of two nickel precursors and their interaction with curcumin produced two molecules, namely Ni(C3S5)(Cur).2H2O (abbreviated as NiThCur) and NiCl(Cur)(PPh3) (abbreviated as NiTppCur). Additionally the Conceptual‐Density‐Functional‐Theory (CDFT) studies were performed. CDFT‐based optimization parameters of both molecules are theoretically interpreted. HOMO‐LUMO energy gap of NiThCur and NiTppCur were calculated 1.474 eV and 2.744 eV respectively. Both molecules demonstrated good NLO activities, studied by a Z‐scan approach and additionally with a Differential Four wave Mixing (DFWM) technique. Preliminarily investigations showed that the molecules can be potential optical limiters (OL). These studies divulge the exhibition of a 3‐photon absorption (3PA) mechanism by the synthesized molecules. NLO absorption 3PA coefficient (γ) value of 1.34×10−24 m3/W2, third‐order optical susceptibility (χ(3)) value of 1.543×10−11 esu, and the figure of merit 6.64×10−14 esu was observed for the NiThCur complex and γ=3.61×10−24 m3/W2, χ(3)=1.521×10−11 esu, and FoM=5.61×10−14 esu for NiTppCur with Z‐scan (γ and χ(3)) and DFWM methods, respectively. Normalized transmittance (NT) exhibited a decrease to 78.5 % from 100 % in NiThCur and to 69.5 % in NiTppCur. Optical limiting calculations are also presented. [ABSTRACT FROM AUTHOR]

The structural dependence of nonlinear optical properties associated with ADP-doped PVA/PVP polymer composites is discussed in this work. Polymer composites are fabricated using the solution casting method. X-ray diffraction (XRD) was used to perform structural analysis on these samples whose average crystallite size increases with an increase in dopant concentration. Results from UV–Vis–NIR spectra show that the samples are transparent in the IR region. The Z-scan technique was established by following the method described by Sheik-Bahae et al. The shape of the open aperture plot suggests that the samples exhibit two-photon absorption. The NLO properties such as nonlinear absorption coefficient (β) , two-photon absorption cross-section ( σ 2) and the imaginary part of third-order nonlinear susceptibility (χ (3)) were investigated at 1064 nm and these values were found to be in the order of ∼ 1 0 − 7 W/cm, ∼ 1 0 − 2 0 cm4/GW and ∼ 1 0 − 1 4 esu, respectively. The open aperture Z-scan method yielded optical limiting data, from which the optical limiting threshold was calculated to be in the order of ∼ 1 0 1 3 W/m2. Functional data analysis uses a suitable basis representation to assess the functional correlation between global and local variables. [ABSTRACT FROM AUTHOR]

Herein, we report the extraction of natural pigment curcumin from curcuma longa and their linear and third-order nonlinear optical (NLO) characteristics. The characterization techniques viz., UV–Visible absorption, FT-IR, Micro Raman and Gas Chromatography Mass Spectrum (GC–MS) are used to study the spectral characteristics of curcumin. Third-order NLO features of curcumin are studied using Z‒scan technique with a semiconductor diode laser working at 405 nm wavelength. The natural pigment exhibits negative nonlinear index of refraction resulting from self-defocusing and positive coefficient of absorption is the consequence of reverse saturable absorption (RSA). The order of nonlinear index of refraction (n2) and nonlinear coefficient of absorption (β) is measured to be 10−7 cm2/W and 10−2 cm/W, respectively. Third-order NLO susceptibility (χ(3)) and second-order hyperpolarizability (γ) of curcumin is measured to be 2.73 × 10‒7 esu and 1.67 × 10‒31 esu, respectively. A low optical limiting (OL) threshold of 0.71 mW is observed in the extracted pigment. The experimental results are supplemented by quantum mechanical calculations of the NLO parameters. The overall result finding is that curcumin extracted from curcuma longa has the potential to be novel optical candidates for photonics and optoelectronics applications. [ABSTRACT FROM AUTHOR]

This article reports the nonlinear refractive index (n2) and nonlinear absorption coefficient (β) of acid blue 129 (AB 129) dye-doped polyvinyl alcohol (PVA) thin film with different dye concentrations using Z-scan technique. The experimental technique consists of a continuous wave laser with 5 mW power working at 635 nm wavelength. The normalized transmittance curve suggests that the dye-doped polymer film exhibits a self-defocusing nonlinear index of refraction and a large nonlinear absorption coefficient ascribed to the behaviour of reverse saturable absorption. The order of third-order NLO susceptibility of the sample is estimated to be 10‒5 esu. The dye-doped polymer films show a low-limiting threshold of 0.15 kW cm–2 at 0.04 mM dye concentration and believed that the prepared thin film is a suitable candidate for application in optical limiting. The self-diffraction pattern is observed at far-field and estimated the nonlinear refractive index of the thin film using this technique. The results of the nonlinear refractive index of the sample obtained from the self-diffraction method are comparable with Z-scan results. [ABSTRACT FROM AUTHOR]

Herein, we report the nonlinear refractive index and nonlinear absorption coefficient of anthraquinone dye (disperse blue 14)-doped polymer film using a facile Z-scan technique. The Z-scan studies were carried out using a semiconductor diode laser with a constant power output of 5 mW at a wavelength of 635 nm as the source of excitation. The Z-scan technique consists of closed and open aperture methods, which revealed the self-defocusing and reverse saturable absorption mechanisms based optical nonlinearity. The third-order nonlinear optical susceptibility (χ(3)) of dye-doped polymer film was estimated to be in the order of 10–5 esu. Optical limiting (OL) behaviour of the polymer film with different dye concentrations was performed under the same experimental conditions and found to be a low OL threshold of 1.45 × 102 W cm–2 at 0.04 mM dye concentration. Self-diffraction ring pattern of the polymer film was also noticed in the far field. The overall results found that the dye-doped polymer film is a potential material for photonics and optoelectronics applications. [ABSTRACT FROM AUTHOR]

Abstract There is a mounting demand for nonlinear optical materials with superior optical limiting performance which has a noticeable impact on protecting the delicate optical components from laser-induced damage. Transition metal molybdates have garnered attention in the nonlinear optics field due to their outstanding optical and luminescent properties, which give rise to widespread applications in next-generation optoelectronics devices. The structural confirmation of the as prepared silver molybdate nanoparticles were made by XRD and Raman spectroscopy analysis. The linear optical properties and the band gap of the synthesized material were studied using UV–Visible and photoluminescence spectroscopy. SEM analysis revealed the pebble like morphology of the silver molybdate nanostructures. The nonlinear responses of the samples were studied using open aperture z-scan approach with Nd:YAG pulsed laser (532 nm, 9 ns, 10 Hz). The sample exhibits reverse saturable absorption pattern attributed to the two photon absorption (2PA) mechanism. The obtained OL threshold value is in the order of 1012 which is suitable for fabricating optical limiters in nano second pulsed laser regime.

There is a mounting demand for nonlinear optical materials with superior optical limiting performance which has a noticeable impact on protecting the delicate optical components from laser-induced damage. Transition metal molybdates have garnered attention in the nonlinear optics field due to their outstanding optical and luminescent properties, which give rise to widespread applications in next-generation optoelectronics devices. The structural confirmation of the as prepared silver molybdate nanoparticles were made by XRD and Raman spectroscopy analysis. The linear optical properties and the band gap of the synthesized material were studied using UV–Visible and photoluminescence spectroscopy. SEM analysis revealed the pebble like morphology of the silver molybdate nanostructures. The nonlinear responses of the samples were studied using open aperture z-scan approach with Nd:YAG pulsed laser (532 nm, 9 ns, 10 Hz). The sample exhibits reverse saturable absorption pattern attributed to the two photon absorption (2PA) mechanism. The obtained OL threshold value is in the order of 1012 which is suitable for fabricating optical limiters in nano second pulsed laser regime. [ABSTRACT FROM AUTHOR]

We investigate the nonlinear optical response of Pb2+-doped ZnMoO4 nanostructures synthesized by chemical precipitation technique. X-ray diffraction (XRD) and Raman spectroscopy results confirm the formation of ZnMoO4 nanostructures with a triclinic structure. High-Resolution Transmission electron microscope (HRTEM) reveals the deformed spherical shape of nanostructures. Further, the successful doping and molecular bonding of Pb2+ with ZnMoO4 was evidenced by FTIR and XPS. UV–Vis absorption spectra reveals the alteration in the electronic band structure of ZnMoO4 nanostructures upon Pb doping, leading to a considerable increase in bandgap and enhanced charge transfer within ZnMoO4: Pb nanostructure. The nonlinear optical absorption and optical limiting characteristics of the nanoparticles is measured via the open aperture Z-scan technique with an Nd: YAG pulsed laser at 532 nm, exhibiting a reverse saturable absorption and a rapid decrease in the commencement of the optical limiting threshold with the increased in Pb concentration. The observed nonlinear absorption can be attributed to the crystal structure, particle size, creation of oxygen vacancies, and defects on the host lattice. These results suggest that Pb2+-doped ZnMoO4 nanoparticles have excellent prospects for optical limiting (OL) applications. This could be useful for applications such as laser protection and optoelectronic device applications. [ABSTRACT FROM AUTHOR]

The sonochemical synthesis, structural analysis, theoretical calculations, and the nonlinear optical (NLO) discovery of benzylidenehydrazono thiazolidin-4-one derivative 8, that is, (Z)-ethyl-2-((Z)-2-((E)-(4-chlorobenzylidene)hydrazono)-4-oxo-3-phenylthiazolidin-5-ylidene) acetate (C20H16ClN3O3S), are detailed. The 1H and 13C NMR data, melting point (m.p), infrared spectrum (IR), mass spectrum, and UV–visible spectrum measurements are used to confirm the authenticity of the synthesized derivative 8. The geometrical structural optimizations and theoretical properties of the synthesized compound are performed using density functional theory (DFT). The NLO properties of the synthesized derivative 8 are studied under continuous wave (cw) 473-nm laser beam via conducting the closed (C)- and open (O)-aperture (A) Z-scan techniques where the nonlinear refractive index (NLRI) and the nonlinear absorption coefficient (NLAC) are obtained, viz. 1.79 × 10−7 cm2/W and 2.72 × 10−3 cm/W, respectively, and an optical limiting (OLg) threshold of 13 mW is obtained. [ABSTRACT FROM AUTHOR]

With the extensive use of lasers for a variety of applications in day-to-day life, the need for optical limiters is driven by the importance of ensuring safety and maintaining the reliability and integrity of sensitive optical systems in various applications. Especially the nanosecond 532 nm laser is widely used in a large number of industrial applications, pertaining to the need of optical limiters for specifically attenuating the wavelength of the nanosecond green laser (typically operating at 532 nm). Advanced photonic materials comprising complex networks of metal–organic–inorganic Ag–rGO–MoS2 systems with varying concentrations of Ag (2.5, 5, 7.5, and 10 wt %) were developed, and their nonlinear absorption (NLA) is explored. Under Q-switched nanopulsed Nd:YAG laser (532 nm, 9 ns, 10 Hz) excitation, the hydrothermally synthesized hybrid system exhibited reverse saturable absorption, arising due to the two-photon absorption (2PA) process. The intensity-dependent Z-scan experiment and optical studies portray the existence of a genuine (simple and fast) 2PA mechanism in the hybrid, affirming the possibility of the utilization of the Ag–rGO–MoS2 hybrid for optical limiting applications. The Ag-(7.5 wt %)–rGO–MoS2 hybrid showed a higher NLA coefficient of 9 × 10–10 m/W and a corresponding lower optical limiting threshold of 1 × 1012 W/m2. The hybrid exhibits strong absorption in the UV region due to the synergistic contribution of all the individual counter parts of the hybrid. The availability of multiple energy states near the 2PA state, the surface plasmon resonance-induced higher local field, and strong structural defects enhance the fast nonlinear response at nanosecond laser excitation. Thus, the exploration of the nonlinear optical behavior of Ag–rGO–MoS2 against 532 nm nanosecond laser pulses for laser safety applications is reported. [ABSTRACT FROM AUTHOR]

The copper oxide nanoparticles (CuO NPs) were synthesized via solution combustion approach with Bengal gram powder as a fuel. The XRD analysis confirms the monoclinic structure of CuO NPs. FT-IR spectrum reveals the formation of CuO NPs. SEM studies show that the NPs are nearly spherical, and the elemental composition was confirmed by EDAX. The absorption spectra revealed a direct optical band gap of 1.50 eV. DFT calculations were performed to determine the HOMO–LUMO energy bandgap and found to be 1.72 eV, which is in good agreement with the experimental value. The Z-scan technique was used to investigate the third-order nonlinear optical (NLO) characteristics using DPSS continuous wave laser (532 nm, 200 mW). A high reverse saturation absorption and negative nonlinear refractions were observed. Third-order NLO parameters β , n 2 and χ (3) were found to be 1 9. 6 × 1 0 − 5 cm/W, − 1. 1 2 × 1 0 − 8 cm2/W and 5. 9 7 × 1 0 − 7 esu, respectively. The CuO NPs also displayed strong optical limiting behavior with a limiting threshold of 2.11 kW/cm2. [ABSTRACT FROM AUTHOR]

Context: In this work, the 4-dimethylaminopyridinium-2,4-dinitrophenolate (4DMAP + 2,4DNP) by slow evaporation solution growth method has been presented. The Fourier transform infrared (FT-IR) (4000–400 cm−1) and FT-Raman (4000–50 cm−1) spectra were recorded for the grown crystal. Methods: The computational calculation has been carried out with density functional theory (DFT) in ground state with Gaussian program package. Optimized geometrical parameters (bond distances, bond angles, and dihedral angles) have been obtained and compared with X-ray crystallography data. The calculated fundamental vibrational frequencies from DFT/B3LYP with 6–311 + + G(d,p) level of theory were scaled so as to agree with the observed results, and the scaling factors were reported. Results: Experimental and computed ultraviolet–visible (UV–Vis) spectra in acetone and methanol solvents were found comparable to each other. Furthermore, the frontier molecular orbitals (FMOs) energies, molecular electrostatic potential (MEP), nonlinear optical (NLO), hirshfeld surface (HS), and global chemical descriptors of the molecule were also calculated. The thermal stability and the melting point of the title compound were analyzed by the thermogravimetric analysis/differential thermal analysis (TGA/DTA) techniques. The mechanical behavior of the organic single crystal was measured by Vickers micro-hardness method. The third-order nonlinear optical properties such as nonlinear refractive index (n2), nonlinear absorption coefficient (β), optical nonlinear susceptibility Reχ(3), and optical nonlinear susceptibility Imχ(3) were calculated by using the open and closed aperture Z-scan technique. Conclusion: The theoretical and experimental NLO values clearly proposed that the nonlinearity of 4DMAP + 2,4DNP molecule could be helped as a potential candidate for optical limiting, frequency doubling, and optical switching applications. [ABSTRACT FROM AUTHOR]

Abstract Tailoring efficient nonlinear optical materials continues to be a topic of great interest in the scientific field. In this paper, we study the nonlinear response of graphene oxide nanosheets GO, gold nanorods AuNRs, and graphene oxide/gold nanorods hybrid nanocomposite GO@AuNRs respectively, GO was prepared by modified Hummer method while AuNRs were prepared by the seed-mediated method and GO@AuNRs prepared by simple ex-situ method. The nonlinear absorption was measured via open aperture Z scan using nanosecond pulses at 532 nm, The nonlinear absorption coefficients were measured for the proposed materials in colloidal and polymeric forms. The results show an enhancement of the nonlinear absorption and optical limiting of GO@AuNRs over GO and AuNRs. Furthermore, enhanced optical nonlinearity and stability are achieved in polymeric form compared to colloidal forms. These materials could potentially be used in optical limiting applications and photonic devices. Graphical abstract

Recently, the preparation of some hematene and magnetene ultrathin non van der Waals (non‐vdW) 2D nanoplatelets was reported starting from hematite and magnetite natural iron ores. The present work reports on the determination and evaluation of the nonlinear optical response and the optical limiting (OL) action of these 2D nanoplatelets dispersed in water under ns laser excitation. The obtained results show that both hematene and magnetene exhibit strong nonlinear absorption and refraction, comparable and even larger than those of other van der Waals (vdW) 2D counterpart materials. In addition, due to their strong nonlinear absorption, both hematene and magnetene show exceptional OL performance from the UV to visible, attaining very low values of optical limiting onset (OLon), comparable and even lower than that of vdW 2D nanomaterials, such as graphene, graphene oxide, other transition metal dichalcogenides like MoS2, WS2 and MoSe2, black phosphorous and antimonene. Moreover, hematene was found to exhibit more efficient OL action than magnetene for all the excitation wavelengths studied, attributed to more efficient ligand to metal charge transfer. The present findings open new possibilities for the potential use of these non‐vdW 2D materials in photonics and optoelectronics, e. g., as optical limiters and optical switchers. [ABSTRACT FROM AUTHOR]

The casting technique is employed to prepare the film from a mixture of sudan brown RR (SBRR) dye and poly methyl methacrylate (PMMA). The surface profile of this film is identified using a scanning probe microscope and image J software. The linear optical (LO) properties of the solid film were studied. The nonlinear optical (NLO) properties of SBRR/PMMA film and sudan brown (RR) solution in dimethylformamide (DMF) as a solvent are evaluated using two methods including diffraction ring patterns and Z-scan. The optical limiting (OLg) property for the SBRR/PMMA film and SBRR solution was extensively investigated. The values of nonlinear refractive index (NRI) and threshold limiting (TH) of the solid film and dye solution were compared. [ABSTRACT FROM AUTHOR]

Tailoring efficient nonlinear optical materials continues to be a topic of great interest in the scientific field. In this paper, we study the nonlinear response of graphene oxide nanosheets GO, gold nanorods AuNRs, and graphene oxide/gold nanorods hybrid nanocomposite GO@AuNRs respectively, GO was prepared by modified Hummer method while AuNRs were prepared by the seed-mediated method and GO@AuNRs prepared by simple ex-situ method. The nonlinear absorption was measured via open aperture Z scan using nanosecond pulses at 532 nm, The nonlinear absorption coefficients were measured for the proposed materials in colloidal and polymeric forms. The results show an enhancement of the nonlinear absorption and optical limiting of GO@AuNRs over GO and AuNRs. Furthermore, enhanced optical nonlinearity and stability are achieved in polymeric form compared to colloidal forms. These materials could potentially be used in optical limiting applications and photonic devices.Article highlights: The nonlinear optical absorption of three different materials—graphene oxide nanosheets (GO), gold nanorods (AuNRs), and a hybrid of the two known as GO@AuNRs—was examined in this study. The findings revealed that GO@AuNRs had better nonlinear absorption and optical limiting properties than GO and AuNRs alone. In addition, the materials' optical nonlinearity and stability were improved in the polymer-based form compared to their colloidal counterparts. These results imply that these materials have a promising future for use in optical limiting and photonic devices. [ABSTRACT FROM AUTHOR]

In the present work, spray pyrolysis method was adopted to synthesis nano thin films of Sn 1-x Nd x O 2 (x = 0.01 to 0.1) possessing tetragonal structure with (1 1 0) plane orientation. Nd doping reduced the overall crystallinity of the films, however Sn 0.92 Nd 0.08 O 2 film showed crystallite size of 18.7 nm, similar to that of the pure film. The morphology changed to distinct grains at lower doping concentration, beyond which a fibrous nature evolved but again changed to smaller grains with further increase in the doping. The oxidation states of the constituent elements were confirmed using XPS. The transmittance of the films reduced due to incorporation of Nd ions. A decrease in the energy band gap was also noticed in the films following dopant addition. The PL emissions corresponding to the Nd ion transitions was found in the NIR region resulting from internal 4f-shell transitions of Nd3+ ions. Other defect related emissions like the one from oxygen vacancies also showed up in the UV and visible wavelength regions, which were responsible for a near white light emission. The third-order optical nonlinearity of the films was confirmed using the Z-scan technique. All the Sn 1-x Nd x O 2 films till 8 at. % of doping showed reverse saturable absorption. The highest and lowest nonlinear absorption coefficient was exhibited by Sn 0.92 Nd 0.08 O 2 and Sn 0.98 Nd 0.02 O 2 films, respectively. Depending on the Nd concentration, the films either showed self-focusing or self-defocusing behavior and influenced the nonlinear refractive indices of the films. The least optical limiting values among the doped films was obtained in the range of 1.73 kJ/cm2 for Sn 0.92 Nd 0.08 O 2 films. [ABSTRACT FROM AUTHOR]

The significance of the anthracene moiety on nonlinear optical (NLO) characteristics is thoroughly examined. The presence of strong electron donor and acceptor groups, large and prolonged conjugation transfer axis, amplifies the push–pull action and increases NLO responses. The values of χ3 obtained for AC derivatives are considerably larger (10−3 esu), indicating that they accurately reflect NLO reactions. According to the optical limiting (OL) investigation, AC has a strong limiting behavior with action beginning at 1.6 KW/cm2. The relationship between transmittance and intensity has demonstrated their potential use in OL applications. Nonlinear optical studies show that all conjugated anthracene chalcones are potential materials for OL devices. [ABSTRACT FROM AUTHOR]

A mixture of polyurethane (PU) and neutral red (NR) dye solution is prepared. The nonlinear optical properties of the mixture of PU with NR dye solution are studied using a 473 nm laser beam of continuous fashion. The nonlinear refraction index of prepared material is determined via diffraction patterns and Z-scan. The diffraction patterns are calculated based on the Fresnel-Kirchhoff integral. Optical limiting of the prepared material is tested. All-optical switching occur in the sample using two low power visible laser beams. [ABSTRACT FROM AUTHOR]

The present work reports on the synthesis and characterization of iridium (Ir)-based nanohybrids with variable chemical compositions. More specifically, highly stable polyvinylpyrrolidone (PVP) nanohybrids of the PVP-IrO2 and PVP-Ir/IrO2 types, as well as non-coated Ir/IrO2 nanoparticles, are synthesized using different synthetic protocols and characterized in terms of their chemical composition and morphology via X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM), respectively. Furthermore, their nonlinear optical (NLO) response and optical limiting (OL) efficiency are studied by means of the Z-scan technique, employing 4 ns laser pulses at 532 and 1064 nm. The results demonstrate that the PVP-Ir/IrO2 and Ir/IrO2 systems exhibit exceptional OL performance, while PVP-IrO2 presents very strong saturable absorption (SA) behavior, indicating that the present Ir-based nanohybrids could be strong competitors to other nanostructured materials for photonic and optoelectronic applications. In addition, the findings denote that the variation in the content of IrO2 nanoparticles by using different synthetic pathways significantly affects the NLO response of the studied Ir-based nanohybrids, suggesting that the choice of the appropriate synthetic method could lead to tailor-made NLO properties for specific applications in photonics and optoelectronics. [ABSTRACT FROM AUTHOR]

Materials exhibiting strong two-photon absorption and low photo-damage threshold are highly desirable owing to their wide application in optoelectronic and photonic devices. Metal molybdates have gained significant attention for optoelectronic applications due to their excellent optical and luminescent properties. Herein, we report the nonlinear properties of the unexplored tin (Sn) doped barium molybdate (BaMoO 4) nanostructures for tunable optical limiting applications. XRD and Raman Spectroscopy extensively studied structural properties. The UV–Vis absorption spectra clearly reveal the strong absorption in the blue region and suggest the bandgap reduction with increased Sn concentration in the host lattice. Open aperture Z scan mode, exhibits strong reverse saturable absorption owing to two-photon absorption. In addition, we observed that the nonlinear absorption coefficient and optical limiting threshold depend extensively on the excitation laser energy and can be altered by varying the concentration of Sn ions. The observed nonlinearity confirms that the synthesized Tin (Sn) doped Barium Molybdate (BaMoO 4) nanostructures are potential for tunable optical limiting applications. [ABSTRACT FROM AUTHOR]

Piperazine (bis) p-toluenesulfonate (PPTSA), an organic single crystal was synthesized and grown at environmental temperature by slow evaporation process using methanol as the solvent. The grown PPTSA crystal is from the triclinic system and belongs to the space group P1-. Powder X-ray diffraction was performed to ensure lattice parameters. Analysis and confirmation of functional groups and bonds were carried out through FT-IR spectral study. The optical characteristics were investigated using the UV-Vis spectrum such as the optical absorption, cut-off wavelength were calculated. The photoluminescence investigation was conducted to assess the luminous characteristics of grown crystal. The calculated NLO parameters like β, n2, and χ(3) were found to be 0.0495×10-4 (cm/W), 8.705×10-10 (cm2/W), 5.316×10-7 (esu) and Optical Limiting threshold value was found to be 3.074×10-3 (Wcm-2). Antibacterial studies were carried out to investigate the biological significance against selected foodborne germs.

Acid green 3 (AG 3) dye-doped poly(vinyl alcohol) (PVA) films were formed on microglass slides via solution casting technique; their structural, morphological, linear, nonlinear optical and power limiting characteristics were studied. AG 3-PVA films were characterized by UV–visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy and scanning electron microscopy methods. The nonlinear optical absorption and refraction properties of AG 3-PVA films were studied by Z-scan technique using a 5 mW diode laser of 635 nm wavelength. AG 3-PVA films were found to exhibit a consistent reverse saturable absorption phenomenon and negative optical nonlinearities; their χ(3) values were measured to be of the order of 10−5 esu and optical power limiting behavior was also observed for these films. Based on the results of the present experimental work, we suggest that AG 3-PVA films may be suitable for optical limiting, photonic and optoelectronic applications in the low-power regime. [ABSTRACT FROM AUTHOR]

In this study, a polyvinyl alcohol–sodium alginate blend, PVA:SA 3:1 (w:w), was doped with different contents of TiO2 nanoparticles (NPs) prepared by aloe vera leaf extract to form the investigated nanocomposites. The nonlinear parameters of third-order susceptibility (χ(3)) and refractive index (n2) were detected by using UV-Vis spectroscopy and Z-scan techniques. Some different optical parameters were also determined, including the refractive index (n), optical dielectric parameters, volume and surface energy loss functions, and some others. The best solar skin protection factor (SSPF) was investigated by 5 wt.% of TiO2 NPs doped in PVA:SA 3:1, which was about 84.6% compared to the corresponding value of the host blend (41%). The studied nanocomposites were examined for their utility in the optical limiting of CUT-OFF laser filters utilizing a continuous He-Ne laser working at 632.2 nm. As a result, our finding demonstrated that TiO2 NPs doped in the host blend of PVA:SA positively influences a laser light blocking for the investigated laser source. Using the estimated gap energies values, different models were used to deduce theoretical values of the linear refractive index (n). The presence of Ti peaks in the EDX spectrum confirmed the doping of TiO2 NPs in the nanocomposites. SEM showed that the TiO2 NPs are homogeneously dispersed through the host blend with some agglomerates. XRD spectra showed that the values of the lattice strain εstr. detected at 2ϴ = 19.78° are 0.058, 0.055, and 0.060, corresponding to 1, 3, and 5 wt.% of TiO2 NPs doped in the PVA:SA blend. [ABSTRACT FROM AUTHOR]

Utilizing plasmonic effects of metal nanostructures on tailoring the properties of semiconducting materials has gained substantial research attention in the past 10 years. Here, we report the plasmon resonance-induced enhanced optical nonlinearity of Au–WS2 nanohybrids prepared via the blending of liquid phase exfoliated few-layer WS2 nanosheets with chemically synthesized spherical gold nanoparticles (NPs). Nonlinear optical properties were studied using the open aperture Z-scan technique with nanosecond laser pulses of wavelength 532 nm, which lie in the plasmonic band of Au NPs (480–550 nm) and B-excitonic transition range of WS2 nanosheets (520–535 nm). Au–WS2 nanohybrids exhibited an enhanced nonlinear absorption and optical limiting activity with an effective nonlinear absorption coefficient of 182 cm/GW at an on-axis input intensity of 0.14 GW/cm2, which is 3.87 times higher than that of bare WS2 nanosheets. The improved NLO response of nanohybrids is due to the plasmon resonance-induced local field effects, which significantly enhance B-excitonic transitions in WS2 nanosheets. The simulated field intensity enhancement profile also confirmed the effect of formation, where a strong interaction of plasmonic fields with WS2 nanosheets is clearly visible. The enhancement observed in simulated absorption density profiles indicated improved B-excitonic transitions in WS2 nanosheets due to the resonant plasmonic field. Au–WS2 nanohybrids exhibited a low limiting threshold of 0.55 J/cm2, which is better than that of many eminent nanohybrids reported so far. The strategy followed in this work for attaining superior nonlinear optical responses in Au–WS2 nanohybrids will be useful to develop novel nonlinear optical materials for photonic device applications. [ABSTRACT FROM AUTHOR]

Pristine NiO and 2% Cr doped NiO nanostructures are successfully synthesized by the modified auto–combustion method for the determination and improvement of linear and nonlinear optical behaviours, and for identifying them as suitable materials for optical limiting applications. Vibrational and linear optical properties of both nanostructures are investigated, and structural and morphological studies are carried out using XRD, FE-SEM, and HR-TEM. From the Kubelka-Munk model, the energy band gaps for pristine and doped samples are found to be 3.52 eV and 3.44 eV, respectively. Both pristine as well as Cr-doped NiO nanostructures reveal substantial nonlinear optical behaviour at the excitation wavelength of 532 nm, arising from the presence of strong reverse saturable absorption. The third order nonlinear absorption coefficients have values of the order of 10−10 m/W and 10−6 m/W, under pulsed (5 ns) and continuous wave laser excitations, respectively. These values confirm the suitability of these nanostructures for fabricating efficient optical limiting devices for safeguarding human eyes and optical sensors from hazardous laser radiation. [ABSTRACT FROM AUTHOR]

Optical nonlinearities of two all-carbon twistacenes, DPyA and DPyN, with the different π-conjugated central bridges were investigated. The nonlinear absorption properties of these compounds were measured using the femtosecond Z-scan with wavelengths between 650 and 900 nm. It has been found that the nonlinear absorption originated from two-photon absorption (TPA) and TPA-induced excited state absorption (ESA), wherein DPyA demonstrates higher performance than DPyN. The TPA cross section of DPyA (4300 GM) is nearly 4.3 times larger than that of DPyN at 650 nm. Moreover, the different central structures modulate the intensity of ESA at 532 nm, and DPyA exhibits an excellent ESA at 532 nm with multi-pulse excitation. Meanwhile, the result of data fitting and quantum chemistry calculation shows that the enhancement of nonlinear absorption in DPyA is due to the extended π- conjugated bridge and improved delocalization of π-electrons. These all-carbon twistacenes could yield potential applications in optical power limiting (OPL) technology. [ABSTRACT FROM AUTHOR]

The standard melt-quenching technique was used to synthesize heavy metal-based PbO·Bi2O3·Ga2O3 glasses. The physical properties such as density and molar volume were calculated, and it is found that these parameters decrease with an increase in the Bi2O3 content of the studied samples. The optical transmittance spectra were recorded in 300–3300 nm wavelength range for all the glasses. The presence of a sharp cutoff and a wide transmission (from 0.43 to 2.5 μm) shows the suitability of these glasses for the IR transmission window. From the absorption analysis cutoff wavelength, the optical bandgap and Urbachʼs energy were estimated. The bandgap values of these glasses range from 2.51 to 2.59 eV. Third-order nonlinear optical properties of PbO·Bi2O3·Ga2O3 glasses were studied using the Z-scan technique. With increasing Bi2O3 concentration in the studied glasses, third-order nonlinear refractive index and third-order nonlinear susceptibility were found to increase while bandgap decreased, which might be related to an increase in the quantity of non-bridging oxygens. IR studies indicate that these glasses are composed of [BiO3], [BiO6], [GaO4], [PbO3] and [PbO4] fundamental structural units. From optical limiting studies, the dynamic range and limiting threshold of the glasses were calculated. Good optical limiting responses and significant values of dynamic range for all the glasses indicate that the investigated glasses can be explored for optical limiting applications. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the laser-induced third-order optical nonlinearity in vanadium pentoxide (V2O5) thin films and doped molybdenum vanadium pentoxide thin films. The work presents the synthesis of V2O5 (100 nm) and MoO3 (8wt. %) doped V2O5 thin films using the standard thermal evaporation technique at a glass substrate with a substrate temperature of 250 °C at two different thicknesses of 100 nm and 200 nm. The XRD shows that films exhibit orthorhombic structure with strong orientation (200) and also with doping, there is variations in lattice parameters as well as with thickness and UV–visible spectra showing the two-photon absorption. A pulsed Nd-YAG laser (532 nm) is used as a source of light to estimate the nonlinear index of refraction (n2), intensity-dependent absorption coefficient (β ), and nonlinear susceptibility ( χ 3 ) by using the z-scan methodology. Optical limiting behavior with a limiting threshold is also reported. The presence of significant third order optical nonlinear susceptibility ( χ 3 ) and a comparatively small limiting threshold (TL) for visible laser beam suggests that MoO3: V2O5 thin films have a lot of potential for photonic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The NLO characteristics of push–pull chalcone derivative were investigated with the aid of density functional theory and z-scan technique. • The structural determination of chalcone was obtained using NMR, FT-IR and FT-Raman spectroscopic techniques. • Ground-state and excited-state dipole moments were quantified using solvatochromic shift method. • Chalcone exhibits significant two-photon absorption with a positive nonlinear absorption coefficient and a positive index of refraction due to self-focusing effect. • The dependency of structure–property relationship on NLO responsiveness have also discussed. In this article, the structural and nonlinear optical behaviour of a chalcone derivative, (2E)-1-(4-ethoxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one have been studied. FT-IR, FT-Raman, and NMR spectroscopy were analyzed to validate the molecular structure. To predict the nonlinear optical characteristics of the chalcone, the DFT approach was used and the experimental results were corroborated by the computations. The bathochromic shift is obtained in linear absorbance spectra and is validated using TD-DFT. Also, the broad emission in the blue region demonstrates the blue light emission property of the sample. Using the finite-field method, the dipole moments, polarizability, first-order and second-order hyperpolarizability parameters have been computed. Ground and excited state dipole moments were quantified by solvatochromism. The third-order nonlinear optical characteristics of chalcone in polar and non-polar solvent media were examined using the open/closed-aperture z-scan technique. The chalcone displayed considerable two-photon absorption with a positive nonlinear absorption coefficient and a positive index of refraction due to the self-focussing effect. Furthermore, the optical limiting study manifests that the investigated chalcone might well be favourable for NLO applications. [ABSTRACT FROM AUTHOR]

Recently, with the continuous progress of nonlinear optics (NLO), the optical limiting (OL) performance of monomer materials has gradually difficult to meet the requirements. In this study, we successfully modified molybdenum disulfide quantum dots (MoS 2 QDs) onto the surface of multi-walled carbon nanotubes(MWCNTs)via an ultrasonic method, therebyobtained MoS 2 QDs@MWCNTs nanocomposites. The morphology, structure, composition and linear optical properties of MoS 2 QDs@MWCNTs were systematically investigated in detail. The NLO and OL responses of MoS 2 QDs@MWCNTs and its constituent materials were investigated at a wavelength of 532 nm by Z-scan technology. The third-order nonlinear polarizability of MoS 2 QDs@MWCNTs is 2.74 times and 4.53 times higher than that of MWCNTs and MoS 2 QDs, respectively, owing to the unique optical properties of MoS 2 QDs. Moreover, the nanocomposite exhibited excellent nonlinear optical limiting properties, with an optical limiting threshold of 0.73 J/cm2, which is 3.08 times higher than MWCNTs. Finally, compared to previous reports, the competitive OL performance of MoS 2 QDs@MWCNTs indicates its promising application prospect in the field of nonlinear optical devices. • MoS 2 QDs were successfully loaded on the surface of MWCNTs by ultrasonic method using van der Waals force. • Compared with single MoS 2 QDs and MWCNTs,The MoS 2 QDs@MWCNTs nanocomposite demonstrates excellent third-order nonlinear polarizability, increased by 4.53 and 2.74 times, respectively. • The OL threshold is derived as F th = 0.73 J/cm2, which is 3.08 times that of MWCNTs and better than other OL materials in previous reports. [ABSTRACT FROM AUTHOR]

• A potential nonlinear organic single crystal was grown by slow evaporation of solvent technique at room temperature. • Vickers microhardness test confirmed that the grown crystal belongs to hard category. • The FTIR spectra were calculated by DFT method and compared experimentally. • The open aperture Z-scan studies revealed the two-photon absorption of the grown material. • The closed aperture Z-scan studies confirms the positive nonlinearity with χ (3) value 2.6763 × 10 − 6 (e s u). By employing methanol as the solvent in slow solvent evaporation method, a new nonlinear optical organic single crystal of 2-cyanopyridinium salicylate (2-CPSC) was grown. The lattice parameters of the 2-CPSC crystals were found out to be a = 7.7764(9) Å, b = 12.3938(17) Å, c = 12.3685(18) Å , and β = 94.44º using single crystal X-ray diffraction (SCXRD) analysis. The confirmation of crystalline nature was done by powder XRD analysis. The 2-CPSC crystal's chemical composition and functional groups were confirmed by Fourier transform infrared (FTIR) spectral analysis. The optical study was done by ultraviolet-visible-near infrared (UV–Vis-NIR) spectral analysis showing a cutoff wavelength of 338 nm. Studies on the grown 2-CPSC crystal's dielectric and Vicker's microhardness were also conducted. The linear dependence of photocurrent with the applied electric field was revealed for the grown crystals. The 2-CPSC crystal's third-order nonlinearity was investigated by the single-beam Z-scan technique using a continuous He-Ne laser. The open aperture Z-scan reveals the two-photo absorption mechanism and the closed aperture Z-scan study reveals the positive nonlinearity of the 2-CPSC crystals with third order susceptibility value of χ 3 = 2.6763 × 10 − 6 (e s u). The density functional theory (DFT) method of B3LYP level with the 6–31++ G (d,p) basis set was used for different quantum chemical calculations like geometry optimization, natural bond orbital (NBO) analysis, mulliken atomic charge, and molecular electrostatic potential (MEP). The higher nonlinearity of the 2-CPSC can be a potential alternative for commercially available potassium dihydrogen phosphate (KDP) and candidate for its application in nonlinear optical devices like optical limiting and optical switching. [ABSTRACT FROM AUTHOR]

• Molecular structural characterization was achieved by 1H & 13C NMR, FT-IR and FT-Raman analyses. • With the aid of density functional theory, the structural, electronic, charge transfer interactions and nonlinear optical properties were predicted. • The ground and excited state dipole moments and nonlinear optical properties were determined experimentally by solvatochromic shift method. • The material can exhibit two photon absorption with reverse saturable absorption behaviour and has a strong nonlinear index of refraction with self-focusing effect and are determined by z-scan technique. • The results reveal that the chalcone derivative can act as a promising candidate for laser assisted applications. The current research reports the nonlinear optical features of a chalcone derivative, (E)-1-(2,4-Dihydroxyphenyl)-3-(3,4-dihydroxyphenyl)-2-propen-1-one which are examined through theoretical and experimental approaches. The spectra from the NMR, FT-IR, FT-Raman, and UV–Vis were retrieved and studied. Density functional theory computations were executed to confirm the experimental findings. Ground-state and excited-state dipole moments were assessed by solvatochromism. Also, the nonlinear optical characteristics were examined using two-level solvatochromic model and theoretically by hybrid functionals - B3LYP and CAM-B3LYP. By employing the z-scan technique, the third-order NLO characteristics as well as the limiting threshold of the chalcone in polar and nonpolar solvent media were studied. The z-scan results demonstrate the chalcone as a desirable candidate for designing optoelectronic and photonic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

2-(1,3-dioxoisoindolin-2-yl)-N-(pyrimidin-2-yl) acetamide is synthesized as a new cyclic amide derivative. The structure of this derivative has been characterized by NMR, FTIR, and Mass spectra. The molecular docking calculations of the prepared cyclic amide against (PDB ID: 3PP0) receptor are performed. The prepared compound has the potential to inhibit breast cancer cells, according to molecular docking results. The DFT/B3LYP via 6–311 G(d,p) level was performed to optimize the geometrical structure and the global and local reactivity descriptors of this compound. The calculated values of polarizability and hyperpolarizability of the prepared cyclic amide equal 30.774 ×10−24 esu and 114.678 ×10−32 esu, respectively. The nonlinear optical (NLO) properties of the prepared compound are studied under irradiation with a visible, cw laser beam. The nonlinear refraction index (NLRI), n 2 , of the compound is estimated using diffraction patterns (DPs) and the Z-scan techniques, where as high as 2.682 ×10−11 m2/W are obtained. The optical limiting property of the prepared compound is studied using the same laser beam. An optical limiting threshold of 15 mW is obtained. [ABSTRACT FROM AUTHOR]

The Bi 2 WO 6 /ZnO (BWO/ZnO) composites were synthesized by using a hydrothermal method. Then, the BWO/ZnO composites were poured into methyl methacrylate through polymerization to make the BWO/ZnO/PMMA organic glasses (OGs) with different amounts. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to investigate the crystal structures and morphology size of BWO/ZnO composites. The nonlinear absorption (NLA), nonlinear refraction (NLR) and optical limiting (OL) properties were systematically investigated by using the Z-scan technique at 532 nm. The BWO/PMMA and BWO/ZnO/PMMA OGs may transform from saturable absorption (SA) to reverse saturable absorption (RSA) by varying the input energy. The NLA, NLR and OL performances of the BWO/ZnO/PMMA OGs are superior to those of the BWO/PMMA OGs and other bismuth-based metal oxides. The synergistic interaction of BWO and ZnO plays a crucial role in the BWO/ZnO/PMMA OGs. The NLA mechanisms were analyzed using an energy-level model. [Display omitted] • The BWO/ZnO composites were synthesized by a hydrothermal method, which can be used in optical limiters and optical switches. • The BWO/PMMA and BWO/ZnO/PMMA OGs both may transform from SA to RSA by varying the input energy. • The BWO/PMMA and BWO/ZnO/PMMA organic glasses exhibit self-focusing and self-defocusing effects. • The enhanced NLA and NLR make the BWO/ZnO/PMMA OGs exhibit excellent OL performance (F th =1.53 J cm−2). [ABSTRACT FROM AUTHOR]

A nonlinear optical single crystal of bis (cytosinium) tartarate monohydrate (BCTM) was grown by slow evaporation method at room temperature. Single crystal X-ray diffraction study revealed their cell parameters and corresponding space group. Different functional groups were identified by using FTIR spectral analysis. Phase purity of the grown crystal was analysed by chemical etching and powder X-ray diffraction studies. The mechanical strength of the grown crystal was estimated using Vickers microhardness test. The thermal stability of the grown crystal was investigated by TGA-DTA studies. The optical absorption study was carried out in the wavelength range of 190–1100 nm. The dielectric response of the grown crystal was studied as a function of frequency at different temperatures. Second harmonic generation efficiency (SHG) was measured by Kurtz and Perry powder technique. The Z-scan pattern clearly evidenced that the BCTM exhibits sequential two photon absorption induced reverse saturable absorption.

In the present work, some MoS2 and WS2 nanosheets were prepared and characterized. Depending on the preparation procedures, trigonal prismatic (2H) or octahedral (1T) coordination of the metal atoms was obtained, exhibiting metallic (1T) or semiconducting (2H) character. Both MoS2 and WS2 nanosheets were found exhibiting large nonlinear optical (NLO) responses, strongly dependent on their metallic (1T) or semiconducting (2H) character. Therefore, the semiconducting character of MoS2 and WS2 exhibits positive nonlinear absorption and strong self-focusing behavior, while their metallic character counterparts exhibit strong negative nonlinear absorption and important self-defocusing behavior. In addition, the semiconducting MoS2 and WS2 were found exhibiting important and very broadband optical limiting (OL) action extending from 450 to 1750 nm. Therefore, by selecting the crystalline phase of the nanosheets, that is, their semiconduction/metallic character, their NLO response can be greatly modulated. The results of the present work demonstrate unambiguously that the control of the crystalline phase of MoS2 and WS2 provides an efficient strategy for 2D nanostructures with custom-made NLO properties for specific optoelectronic and photonic applications such as OL, saturable absorption, and optical switching. [ABSTRACT FROM AUTHOR]

Poly [pyrrole-co-(vinyl acetate)] is prepared via chemical polymerization method. Obtained copolymer is characterized by Fourier transform infrared (FTIR) and thermal gravimetric analysis (TGA). The nonlinear optical properties of this copolymer are studied using the diffraction ring patterns and the Z-scan techniques using 473 nm wavelength laser beam. The total change in the copolymer index of refraction and nonlinear index of refraction are determined via the first technique while the nonlinear refractive index is determined via the second technique. The property of optical limiting of the copolymer is investigated where it is found that this medium possess optical limiting with limiting threshold of 14 mW is obtained. The diffraction rings patterns are simulated numerically via the diffraction integral of Fresnel-Kirchhoff with reasonable agreement compare to the experimental findings. [ABSTRACT FROM AUTHOR]

Long hexagonal Co3(PO4)2·4H2O nanosheets were synthesized using a hydrothermal method, where their nonlinearity was probed via a femtosecond Z-scan system. The results show that the Co3(PO4)2·4H2O nanosheets exhibit saturable absorption when the incident photon energy is greater than the forbidden band width, while optical limiting is found when the incident photon energy is smaller than the forbidden band width. In particular, the obtained Co3(PO4)2·4H2O nanosheets demonstrate the best optical limiting properties at 600 nm. The present study suggests the cobalt phosphates nanosheets as a promising candidate for optical limiters. [ABSTRACT FROM AUTHOR]

In present work, we discovered that nano-crystallization behavior of Ge–S binary chalcogenide glass can be remarkably improved by incorporating trace amount of CsCl as nucleating agent. After implementing an annealing process, the resultant Ge-S-CsCl chalcogenide glass ceramics (GSC ChGCs) possess fine distribution of crystallites belonging to GeS 2 and GeS mixture phase which could enhance mechanical strength and narrow bandgap energy of the original glass. By utilizing femtosecond Z-scan method, nonlinear optical properties of the GSC ChGCs were investigated in a spectral range from 750 to 900 nm. The results showed that the nonlinear absorption attribute of the GSC ChGCs can be enhanced by the crystallinity increase which led to the maximum two-photon absorption coefficient of 19.57 cm/GW at excitation wavelength of 750 nm, increased by 78% as compared to the original glass. This indicates the current GSC ChGCs a promising candidate for the optical limiting devices. [ABSTRACT FROM AUTHOR]

The absorption performance and evolution of the organic dye disperse blue 1 (DB1) in dioxane at different concentrations was investigated. The nonlinear absorption coefficient has been measured through the open aperture Z-scan technique, whose values increased exponentially from 0.997×10-3 to 11.7×10-3 cm/W as the dye concentration increased from 3.7×10-5 to 74.6×10-5 M. Also, DB1 optical power limiting characteristics appeared at high laser light intensities, whereby very dilute solution of the order of ~10-4 M was sufficient to limit the transmitted ‎power of the incident laser light by ~90%.

Thin graphene oxide (GO) films have been widely explored for their outstanding optical properties, especially their large optical nonlinear coefficients, and high tunability of optical nonlinear coefficients under photoreduction. In this work, an experimental observation of giant nonlinear optical response in GO films under two different photoreduction mechanisms is reported. After ultraviolet (UV) light‐induced photochemical reduction and continuous wave (CW) laser‐induced photothermal reduction, the nonlinear optical response of reduced graphene oxide (rGO) via the Z‐scan method using a femtosecond laser beam at a wavelength of 800 nm is characterized. The rGO exhibits a giant optical nonlinearity, especially two‐photon absorption (TPA). A giant TPA coefficient of rGO on the order of ≈105 cm GW−1 is obtained under two photoreduction mechanisms (photochemistry and photothermal). This is the first time that a large enhancement effect of TPA has been observed in graphene‐based materials, and the TPA coefficient is an order of magnitude higher than the highest value previously reported. The versatile optical nonlinear properties imply a huge potential of the GO film in advanced photonic and optoelectronic devices such as broadband ultrafast optical switching and optical limiting. [ABSTRACT FROM AUTHOR]

In the sight of the present demand of scientific exploration in nonlinear optics (NLO), we synthesized a symmetric donor– π –acceptor– π –donor (D– π –A– π –D) type organic chromophore [2-[2,6-di((E)-styryl)]-4H-pyran-4-ylidene]malononitrile (M1) for linear and nonlinear optical studies. The structural character of the compound M1 was confirmed using 1H NMR, 1 3 C NMR, and IR spectroscopy. The intramolecular charge transfer (ICT) in molecule M1 has been analyzed using absorption and fluorescence spectrometry in different nonpolar and polar solvents. The optical bandgap, optical conductivity, and linear refractive index of M1 were also calculated using UV–Vis absorption spectrum in CHCl3. The thermogravimetric analysis (TGA) was also carried out to check the thermal stability of the compound M1 and it was found to be thermally stable up to 200∘C. Furthermore, the third-order optical nonlinearity in M1 has been investigated elaborately using the Z -scan technique with a continuous wave (CW) diode laser at 520 nm. The nonlinear absorption (β), nonlinear refraction ( n 2 ), and nonlinear optical susceptibility ( χ (3) ) were computed for various solution concentrations as well as several laser powers and the magnitude of all the parameters were found to vary linearly with concentration and power. The magnitude of two-photon absorption cross-section ( σ TPA ) was also calculated and found to be of the order of 10 1 0 GM. The optical limiting performance of the compound was also studied in different solution concentrations using the same laser. Furthermore, DFT and TD-DFT theoretical calculations were performed for the support of experimental results. [ABSTRACT FROM AUTHOR]