Optical Limiting Properties Research Articles

Non-alternant Benzodifluoranthene Tetraimides from 7,8,9,10-Fluoranthene Diimides: Synthesis, Structure, and Optical-Limiting Properties.

A novel tetraimide-functionalized non-alternant π-conjugated system, namely, benzodifluoranthene tetraimides (BDFTI), has been designed and synthesized through highly efficient UV-photocyclization of a vinyl-bridged fluoranthene diimide dimer (i.e., FDI-V). The synthesis of FDI-V starts from a straightforward three-step route to produce novel 7,8,9,10-fluoranthene diimide (FDIs) building-blocks, followed by nearly complete bromination and then Stille-coupling reaction to give the desired dimer. The analysis by X-ray crystallography confirms a near-coplanar geometry for FDIs, while BDFTI shows a U-shaped and distorted backbone configuration proven by theoretical optimizations. The tetraimide BDFTI exhibits several advantages over the FDI cores, including an extended absorption band and a red-shift in photoluminescence spectra. This enhancement can be attributed to the presence of additional electron-deficient imide units, which promotes increased intramolecular charge transfer and improved electron affinity. All the imides show a local aromatic characteristic owing to the incorporation of pentagon rings in the π-frameworks. The fully fused BDFTI exhibits nonlinear optical properties as analyzed by the open-aperture Z-scan technique, demonstrating superior optical-limiting performance compared to vinyl-bridged FDI-V. The versatile UV-photocyclization chemistries provide a pathway for developing complex and unique multiimide-functionalized π-conjugated systems, paving the way for creating high-performance optical-limiting materials.

Third-order non-linear optical switching and threshold limiting of NiO thin films

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-dx2-y2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d_{x^2-y^2}$$\\end{document} and Ni-dz2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d_{z^2}$$\\end{document} 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.

Second harmonic generation and reverse saturable absorption in electrospun picric Acid-PMMA nanofibers

Picric acid (PA) – polymethyl methacrylate (PMMA) nanofibers were synthesised using electrospinning technique by optimising all the required parameters. The nonlinear optical behaviour of the synthesised nanofibers was investigated along with their preliminary characterisations like morphological, structural, thermal, mechanical, dielectric and linear optical studies. The nanofibers with average diameter around ∼800 nm, were found to crystallise in Pca21 space group under the orthorhombic crystal system. The incorporation of Picric acid nanocrystals inside the PMMA nanofibers enhanced their tensile strength. Second harmonic generation imaging of picric acid embedded PMMA nanofibers was done by nonlinear microscopy and the emission was confirmed by power dependence as well as Kurtz – Perry powder technique. Nonlinear absorption studies by Z – scan technique were conducted with a Q – switched Nd: YAG laser and the nanofibers exhibited reverse saturable absorption nature at all the input intensities (0.616 × 1012 W/m2, 1.23 × 1012 W/m2 and 2.46 × 1012 W/m2) and the value of the nonlinear absorption coefficient increased corresponding to an increase in input intensity (0.98 × 10−10 m/W, 1.39 × 10−10 m/W and 1.61 × 10−10 m/W) owing to a sequential two photon absorption. Using the transmittance data optical limiting properties of the nanofibers were also analysed and the limiting threshold values (1.92 × 1012 W/m2, 1.80 × 1012 W/m2 and 1.54 × 1012 W/m2) at respective intensities were extracted. The low optical limiting threshold obtained in the present case confirms that picric acid – PMMA nanofibers can be an assured contender as optical limiters in laser safety devices.

Enhanced nonlinear optical properties and optical limiting performance of graphene modified polyaniline composite under pulsed laser regime

Polyaniline (PANI) and its graphene-doped composite (PANI-GNP) were subjected to open-aperture (OA) z-scan studies to investigate their nonlinear optical (NLO) properties and optical limiting (OL) behavior. The z-scan experiments were carried out using a nanosecond pulsed Nd:YAG laser at a wavelength of 532 nm. The z-scan studies revealed that PANI and PANI-GNP composites exhibited a reverse saturable absorption (RSA), and graphene doping modified the NLO behaviour and improved the OL property. The nonlinear absorption coefficient (β), OL threshold, and imaginary part of nonlinear susceptibility ( χi(3) ) of PANI and PANI-GNP were calculated for three different laser input pulse energies and found to be in the order of 10−9 cm W−1, 106 W cm−2, and 10−10 esu, respectively. These results qualify the PANI-GNP composite as having potential applications in OL and optoelectronic devices. The successful incorporation of graphene into PANI in PANI-GNP composite was confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Linear optical properties were analysed using UV–visible absorption spectroscopy. To the best of our knowledge, the present work is the first attempt to explore the intensity-dependent NLO properties, OL behaviour and the calculation of their related NLO parameters of PANI-GNP composites.

Third-order nonlinear optics and optical limiting of phenanthrenone derivatives

Organic nonlinear optical materials have attracted much attention due to their large nonlinear optical coefficients and ultrafast response speeds, as well as their potential applications in optical limiting (OL). Among them, nonlinear optical materials with phenanthrenone as the backbone are consistently understudied. We have successfully realized the transformation of organic small molecules in the nonlinear optical direction by replacing the carbonyl group on the structure of phenanthrenone with a malononitrile group. The nonlinear optical properties of CN-2 were investigated under different excitation conditions at 532 nm and the kinetic process of nonlinear optics was analyzed by transient absorption spectroscopy. In addition, we also investigated the OL properties of CN-2, and the OL experiments showed that CN-2 with a lower OL threshold has superior OL properties than C60.

Tailoring of nonlinear optical and optical limiting performance through morphology: PbTe nanostructures in liquid and solid-state matrice

Advances in nanotechnology have provided opportunities to precisely control the morphology of nanostructures and the ability to explore their structure–property relationships. In this work, well-defined PbTe nanostructures with different morphologies were prepared by a one-step microwave synthesis process. The synthesized PbTe nanostructures were incorporated into solid-state silica gel glass matrices by a facile sol-gel approach for application as optical limiters. Nonlinear optical (NLO) and optical limiting (OL) properties were measured by 532-nm laser pulses with a pulse duration of 35 ps to understand the relationship between the NLO properties and the morphology of six PbTe nanostructures (i.e., nanosheets, nanorods, particle assemblies, hoppercubes, nanocubes, and nanoflowers). The PbTe nanostructures had notably different NLO and OL properties, which strongly correlated with the structural characteristics both in liquid and gel glass matrices. The NLO mechanism was also explored and attributed to excited state absorption, which relates to the size and morphology of the nanostructures. The PbTe particle assemblies had the strongest NLO response under laser irradiation, whereas the PbTe nanocubes had the weakest response, both in liquid and a solid-state gel glass matrices. Importantly, a large OL effect was observed for PbTe particle assemblies doped into silica gel glasses, where the OL threshold surpassed that of previously reported semiconductor nanocrystals. This result suggests these materials can be considered as potential candidate for practical applications in the fields of nonlinear optics. Our work provides insights into the morphology dependence of NLO properties and a strategy to optimize the performance of nanostructures through structural design.

Nonlinear optical and photostability studies of Allamanda Cathartica extract dye

In this work, we report the linear and nonlinear optical properties of a natural dye extracted from the flowers of the tropical plant Allamanda Cathartica. PVA films containing the dye in varying concentrations were prepared using the drop-casting technique. The functional groups of the major pigment in the dye were verified using FTIR spectroscopy. UV–visible spectroscopy was carried out to confirm the presence of various carotenoid pigments in the dye. Nonlinear optical characterization was performed by employing the z-scan technique using Nd: YAG laser with a wavelength of 532 nm and 9 ns pulse duration. The dye exhibited significant optical limiting properties due to reverse saturable absorption, thus making them potential candidates for optical limiting. The photostability of the dye was studied using photodegradation rate kinetics to determine its reliability. The dye provides an environmentally friendly and economical alternative to the standard synthetic materials used as optical limiters.

Comparative analyses of Nonlinear Optical (NLO) properties, structural characterization and density functional theory of chloro-trifluoromethyl moiety chalcone derivatives for optical limiting application

This study focuses on the impact of substitutional positions on the nonlinear optical (NLO) and photophysical properties of four novel chalcone derivatives (I–IV). The grown crystals were characterized using FT-IR, NMR and single crystal X-ray diffraction (SCXRD) techniques, and the intermolecular interactions were studied by examining the unique packing motifs. The linear and 3rd-order NLO properties were experimentally determined using UV–Vis spectrometer and Z-scan setup with 637 nm continuous wave excitation, respectively. Compounds I–IV were studied theoretically using density functional theory (DFT) to support the experimental results. B3LYP functional was used to optimize the geometries, and the molecular properties of the compounds were determined via molecular electrostatic potential (MEP), natural population analysis (NPA), and localized orbital locator-π (LOL-π) analyze. The photophysical properties were analyzed using time-dependent DFT (TDDFT) using both CAM-B3LYP and B3LYP functionals to investigate the impact of the long-range correction. Inter-fragment charge transfer (IFCT) analysis and hole-electron analysis were employed to examine the linear optical properties and charge transfer mechanism. The NLO properties such as dipole moment (μ), polarizability (α), first and second hyperpolarizabilities (β and γ) were examined with the numerically differentiate analytic method using both functionals. Z-scan NLO data shows that the nonlinear refraction (NLR) coefficient of I–IV is significantly influenced by intermolecular interactions, specifically aggregation phenomena. Compound IV exhibits an exceptional nonlinear absorption (NLA) response and superior optical limiting properties compared to others attributed to its para-substituted strong electron-acceptor group (CF3) which results in highest transition dipole moment, lowest excitation energy, and well-defined charge transfer processes within its molecule. As a result, this suggests that it could be a potential candidate for NLO applications.

Nonlinear absorption and optical limiting performance of broad-band multi-branched aniline derivatives in the near-infrared region

A thorough investigation was conducted into the impact of π-linker and acceptor group modifications on the nonlinear absorption coefficient and optical limiting (OL) capabilities of multi-branched aniline derivatives. In the experiment, the femtosecond Z-scan technology and the OL experiment were used to detect the nonlinear optical (NLO) response of the samples dissolved in DMF solution at different wavelengths and energies. The femtosecond Z-scan experiments show that all samples exhibit reverse saturable absorption (RSA) caused by excited state absorption (ESA) induced by two-photon absorption (2PA) at specific wavelengths. NBTT still exhibits strong RSA properties at the near-infrared wavelengths, and the 2PA cross-section can reach 293 GM and 289 GM under the incident laser at the wavelength of 900 nm and 1030 nm, while maintaining strong two-photon-induced ESA. Furthermore, the femtosecond OL experiments reveal the commendable OL property of NBTT, and the limiting thresholds reach 0.0026 J/cm2 (at 800 nm) and 0.0033 J/cm2 (at 1030 nm). Quantum chemistry calculations utilizing density functional theory (DFT) show thatπ electrons contribute differently to the bond order on different branches of multi-branched molecules, and the value of Branch 1 is greater than or equal to that of the other two branches at the same position. This leads to the charge transfer (CT) of the molecules NBC and NBTC predominantly concentrated on Branch 1 during the 2PA process, while the addition of conjugate units and cyano-groups in the acceptor groups makes the CT of NBTT not only concentrated on Branch 1, but also extended to Branches 2 and 3. This research seeks to develop the structural design and practical application of multi-branched aniline derivatives to achieve high nonlinear absorption capacity, while maintain a low OL threshold in the near-infrared spectral range.

Identification of the nonlinear optical properties for a mixture of Sudan yellow 3G and poly methyl methacrylate for optical limiting applications

A mixture of sudan yellow 3G dye and poly methyl methacrylate film is fabricated by casting. The optical constants are determined using measurements of absorbance, transmittance, and reflectance spectra. The indirect optical band gap is obtained from Tauc's formula, which is found to be 2 eV. By excitation of the sample with a continuous wave laser beam, the nonlinear optical and the optical limiting properties are studied. The change in refractive index, Δn, and nonlinear refractive index, n2, for the sample is calculated from the diffraction ring patterns and is found to be 44.10 × 10−3 and 18.29 × 10−6 cm2/W respectively. We employ Z-scan to determine nonlinear refractive index n2 = 0.6 × 10−6 cm2/W and nonlinear absorption coefficient β = 8.79 × 10−3 cm/W. The sample is proven to possess the properties of an optical limiter, as the threshold limiting value of the film is equal to 5.3 mW.

Nonlinear optical absorption and optical limiting of magnetic iron oxide nanomaterials

Integration of nanoparticles into polymeric materials enhances the optical properties and stability of the formed nano-composite materials. In this work, magnetic iron oxide nanoparticles Fe3O4NPs were prepared via chemical coprecipitation. In addition, it is polymerized in a host of polyvinylpyrrolidone PVP. The prepared iron oxide nano-size was about 14.0 nm as confirmed by Transmission Electron Microscopy, A vibrating sample magnetometer VSM studies showed Fe3O4NPs possess superparamagnetic behavior. Energy-dispersive X-ray spectroscopy, and X-ray diffraction confirmed the structure and composition of Fe3O4NPs. Open aperture Z-scan and optical limiting experiments were carried out at nanosecond pulses of wavelength 532 nm. The nonlinear absorption coefficients were calculated for the colloidal and polymeric iron oxide. Fe3O4NPs polymeric film exhibits enhanced nonlinear optical properties NLO, and superior optical limiting properties compared to Fe3O4NPs colloidal solution. That makes Fe3O4 nanocomposites a promising candidate for optical limiting applications.

Iridium-Based Nanohybrids: Synthesis, Characterization, Optical Limiting, and Nonlinear Optical Properties.

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.

Photoluminescence and third-order nonlinear optical limiting properties of Sn1-xNdxO2 thin films deposited via spray pyrolysis

In the present work, spray pyrolysis method was adopted to synthesis nano thin films of Sn1-xNdxO2 (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 Sn0.92Nd0.08O2 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 Sn1-xNdxO2 films till 8 at. % of doping showed reverse saturable absorption. The highest and lowest nonlinear absorption coefficient was exhibited by Sn0.92Nd0.08O2 and Sn0.98Nd0.02O2 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 Sn0.92Nd0.08O2 films.

Nonlinear optical response of polycrystalline GeSe films

GeSe exhibits in-plane optical anisotropy similar to black phosphorus and other two-dimensional materials, so it is believed to have remarkable nonlinear optical (NLO) properties. In this work, amorphous GeSe films were prepared by vacuum thermal evaporation. After annealing at 450 °C, GeSe films exhibited a polycrystalline phase. The NLO properties of these GeSe films were investigated by the Z-scan technique. The results indicated that GeSe films exhibited typical reverse saturable absorption (RSA) and self-focusing phenomenon. It was also found that the nonlinear optical parameters and laser-induced damage threshold of annealed recrystallized GeSe films were significantly improved. The nonlinear absorption and refractive coefficients were β = (2.90 ± 0.06)×10−7 m/W and n2= (1.06 ± 0.07)×10−13 m2/W at the incident laser intensity of 0.4 GW/cm2, respectively. The polycrystalline GeSe film showed remarkable RSA-induced optical limiting properties, which exhibited an optical limiting starting threshold of 0.018 GW/cm2 and an optical limiting threshold of 0.98 GW/cm2. These results strongly indicate that GeSe films have potential applications in solid-state optical limiting devices and laser protection.

Evaluation of surface roughness, linear and nonlinear optical parameters of a mixture of sudan black b and polymer films for optical limiting application

A film of a mixture of sudan black b (SBB) dye and a poly methyl methacrylate (PMMA) is fabricated by casting. X-ray diffraction measurement proves the SBB/PMMA film's structure is amorphous. The scanning probe microscope confirmed that the SBB/PMMA film has a good quality and homogeneous surface. The SBB/PMMA film's optical constants are estimated via the transmittance, absorbance, and reflectance spectra. The indirect optical band gap is calculated and found to be 1.49 eV. The single oscillator energy, Eo, the dispersion energy, Ed, and the static refractive index, no, are computed by using Wemple and DiDomenico model. Semi-empirical relation, Z-scan, and diffraction ring patterns are three methods used to determine the film's nonlinear refractive index value. The SBB/PMMA film exhibited a high nonlinear refractive index (n2 = 7.83 × 10−7 cm2/W) and nonlinear absorption coefficient (β = 9.3 × 10−3 cm/W), calculated by the Z-scan method. Under a continuous wave laser beam, the property of the optical limiting of the film is examined. The film exhibited optical limiting properties with a limiting threshold value of 5 mW.

Three-dimensional flower-like MoS2 strung by multi-wall carbon nanotubes: a versatile alternative for high performance optical limiters

Heterostructures based on transition-metal dichalcogenide layered materials show great potential for various applications in nonlinear photonic devices such as optical switches, mode-locking lasers, and optical limiters. Herein, we report the design and synthesis of a hierarchical heterostructure of multi-wall carbon nanotubes (MWCNTs) decorated by three-dimensional molybdenum disulfide (MoS2). The unique MoS2/MWCNT heterostructure was successfully synthesized by a simple one-pot hydrothermal method, as confirmed by field emission scanning and transmission electron microscopies, X-ray diffraction, Raman spectrum, and X-ray photoelectron spectroscopy. The nonlinear optical (NLO) and optical limiting (OL) responses of the heterostructured MoS2/MWCNT and those of its individual components were investigated by the Z-scan technique at 532-nm with nano- and picosecond pulsed-laser sources. The NLO and OL properties of the MoS2/MWCNT heterostructure were improved compared with those of MoS2 and MWCNTs individually. The OL threshold of the heterostructured MoS2/MWCNT was 0.53 J/cm2, which is lower than or comparable to those of either common transition-metal dichalcogenides or graphene-like compounds. The NLO mechanisms are attributed to nonlinear absorption and nonlinear refraction at a picosecond timescale combined with nonlinear scattering induced by the MWCNTs at a nanosecond timescale. The improvements in NLO and OL performance are also attributed to photo-induced interfacial charge transfer between MoS2 and MWCNTs in the unique heterostructured MoS2/MWCNT. We report an efficient method of fabricating novel heterostructures with controllable NLO response. The unique morphology and excellent NLO properties obtained from these MoS2/MWCNT heterostructures show great potential for future optical and photonic applications.

Structural characteristics and effective two photon absorption induced optical limiting behavior of Co2+ doped monoclinic LaPO4 nanostructures

The Nonlinear optical limiting properties of pure and Co2+ doped monoclinic LaPO4 nanostructures synthesized by co-precipitation technique is reported. The Structural confirmation of Co2+ doped LaPO4 nanostructures is studied by X-ray diffraction (XRD) and Raman spectra. The replacement of larger La3+ ion by smaller Co2+ ion is confirmed by the shift of XRD and Raman scattering lines. X ray photoelectron spectroscopy (XPS) survey spectrum of 0.3 % Co2+ doped sample confirms the presence of lanthanum (La). Phosphor (P), oxygen (O) and Cobalt (Co) elements. Transmission electron microscopy (TEM) image portrays the formation of nearly mono-dispersed spherical particle with diameter of 48 nm. The absorption spectra reveals a blue shift in absorption edge with additional peak at 580 nm upon Co2+ doping. Photoluminescence emission spectra shows blue green emission with major peak at 440 nm. Open aperture (OA) Z-scan technique excited at 532 nm with a nanopulsed Nd: YAG laser revealed pure and Co2+ doped LaPO4 exhibits reverse saturable absorption ascribed due to two photon absorption (2PA). Intensity dependent OA measurements shows that the nonlinear absorption coefficient remains constant with varying input on-axis intensity, ensuring genuine 2PA for pure sample. While for Co doped sample, the nonlinear absorption coefficient varies with input on-axis intensity, assuring the occurrence of sequential 2PA. Co doped samples exhibit enhanced nonlinear absorption due to synergistic influence of Co2+ in LaPO4 crystal structure. Optical limiting action induced by 2PA in LaPO4 with lower onset limiting ensures the potentiality of the chosen material for photonic applications.

Synergic effects of Sn4+ doping on the nonlinear optical limiting properties of SnxCd1-xMoO4 nanostructures for optoelectronic applications

There is a rising demand in the development of novel nonlinear optical materials comprised out of transition metal molybdates owing to their fascinating optical and luminescent properties, resulting in wide application in future optoelectronic and optical limiting devices. Herein, we report non linear optical properties of novel tin (Sn4+) doped Cadmium molybdate (CdMoO4) nanostructures synthesized via chemical precipitation technique. The X-ray diffraction (XRD) pattern confirms that pristine as well as tin (Sn4+) doped Cadmium molybdate (CdMoO4) are highly crystalline with a tetragonal structure. Raman spectroscopy further confirms the structure and phase formation of SnxCd1-xMoO4 nanostructures. From the UV–Visible absorption spectra, it is observed that the ground state absorption increases in the UV region after the addition of the Sn4+, and the bandgap is found to be decreased. The morphology and particle size was analysed using Transmission electron microscopy (TEM). The surface binding energy and oxidation state was analysed by X-ray photo electron spectroscopy. The non-linear optical properties was studied by z scan technique using Q switched pulsed Nd YAG laser. Experimental results suggests, that two photon absorption mechanism is responsible for the observed nonlinearity. It is found that two photon absorption (β) is increased from 2.51 to 955.5×10−11 and third order susceptibility (χ(3)) enhances from 10.36 to 1480×10−13esu on Sn doping. The optical limiting threshold of pure and SnxCd1-xMoO4 nanostructures was also studied and found to be in the range of 41.45 to 11.92 J/cm2. These results clearly show that SnxCd1-xMoO4 nanostructures as a potential candidate for photonic, optical limi,ting and optoelectronic devices.

Effect of pyrrole substitution on the optical limiting properties of 3,5-distyrylBODIPYdyes

The optical limiting properties of three meso-pyridyl-distyrylBODIPY dyes with differing alkyl substitution patterns at the 2,6- and 1,7-positions on the pyrrole moieties are investigated. Styryl groups are introduced at the 3,5-positions to form dyes with strong donor-[Formula: see text]-acceptor (D-[Formula: see text]-A) properties. Favorable optical limiting properties are obtained for all three dyes, with the highest second-order hyperpolarizability obtained for a dye that is unsubstituted at both the 2,6- and 1,7-positions suggesting that the optical limiting properties are enhanced when the meso-aryl ring can freely rotate into the plane of the BODIPY core.

Pulse-width-dependent optical limiting properties of a novel twist-acene compound

Organic materials with large nonlinear optical coefficient and ultrafast response speed have attracted considerable attention due to their potential applications in optical limiting (OL). However, it is a challenging obstacle to develop a candidate material with optimal nonlinear absorption response while avoiding undesirable low transmittance. Here, a novel symmetrical heteroacenes compound 4,4'-(buta-1,3-diyne-1,4-diylbis(2,7-di-tert-butyl-9,14-diphenyldibenzo[de,qr]tetracene-12,11-diyl))bis(N,N-diphenylaniline)(abbreviated as JPC-42) was synthesized and its nonlinear optical properties were investigated under different pulse-width excitation conditions at 532 nm. Results show that the compound with twisted structure displays superior optical limiting response in which extremely high transmittance (91% in 532 nm) and low OL threshold (3 × 10−3 J/cm2 in femtosecond regime, 130 × 10−3 J/cm2 in picosecond regime) are obtained. Our results demonstrate that this twist-acene compound is a promising candidate in laser protection fields.