Value Of Nonlinear Coefficient Research Articles

Potential use of nonlinearity-induced virtual gain on parabolic pulse formation in highly nonlinear tapered fiber system

The objective of this work is to investigate the effect of nonlinearity-induced virtual gain in parabolic pulse (PP) formation by dispersion varying fibers and utilizing this gain over that of dispersion. As chalcogenides show high values of nonlinear coefficient, a dispersion decreasing fiber, named as nonlinearly tapered chalcogenide fiber (NLTCF), is designed here by optimizing different combinations of chalcogenide materials and core radius profiles such that efficient PP can be generated at considerably shorter optimum lengths with respect to the corresponding constant dispersion fiber. With suitable manoeuvring of the nonlinearity-induced virtual gain, a fiber combination consisting of a dispersion increasing fiber and the NLTCF shows enough efficiency to reduce the optimum length significantly. Although the virtual gain due to dispersion dominates over that due to nonlinearity in silica fibers, the situation is completely reversed in the case of specially designed highly nonlinear fibers. When compared to silica-based fibers, these types of fibers perform remarkably better in PP formation at shorter values of optimum fiber length with a higher amount percentage reduction of length making the higher order dispersive terms ineffective as well.

Zinc oxide encapsulated poly (vinyl alcohol) nanocomposite films as an efficient third-order nonlinear optical material: Structure, microstructure, emission and intense low threshold optical limiting properties

Keeping in view the significant facts on Zinc Oxide (ZnO) and Poly (Vinyl Alcohol) (PVA), we developed nanocomposite films comprising small weight percentage of ZnO content in host polymer PVA, choosing a simple and cost-effective method based on solution-casting. The investigations of its structure, microstructure, linear/luminescence and nonlinear optical properties are presented. This article mainly discusses the intense low threshold nonlinear absorption (NLA) behaviour displayed by the samples, as studied using the standard Z-scan technique. On either increasing the intensity or ZnO content, the samples exhibited a switchover from saturable to reverse saturable absorption, which is rarely observed under 442 nm continuous wave (CW) laser light excitation. The effective values of nonlinear absorption coefficient and imaginary part of third-order nonlinear susceptibility are higher than the recently reported results. The limiting threshold values (obtained from optical limiting curves) are also found to be much better than other reported ones.

A nonlinear photonic crystal fiber for liquid sensing application with high birefringence and low confinement loss

This paper presents a nonlinear Photonic Crystal Fiber (PCF) based sensor to detect liquid analytes. An extensive analysis has been presented at wide range of wavelength (0.6 μm−1.6 μm) in order to investigate the impact of some design parameters. The numerical investigation has been done using the full vector Finite Element Method (FEM). The proposed model provides an outstanding nonlinear coefficient value with high birefringence, high sensitivity, and low confinement loss. The designed model can be used in sensing and bio-sensing research and their applications.

Fabrication of efficient nonlinear optical absorber using Zn phthalocyanine-semiconductor quantum dots conjugates

In this paper, we report on the synthesis of Zn(II) phthalocyanine derivatives and their conjugates with core/shell and core/shell/shell semiconductor quantum dots (SQDs). Zn(II) mono amino-carboxyethylphenoxy phthalocyanine (1), Zn(II) mono 3-carboxyphenoxy-tris(pyridin-2-yloxy) phthalocyanine (2) and Zn(II) mono aminophenoxy-tris(benzothiazole) phthalocyanine (3) were synthesized. The photophysical and optical limiting properties of the phthalocyanine (Pc) complexes and their conjugates with SQDs were investigated in dimethyl sulfoxide. The optical limiting behaviour of the Pc complexes and their conjugates were measured by the open aperture Z-scan technique at laser excitation wavelength of 532 nm with 10 ns pulse. The conjugates outperformed the Pc complexes alone with the conjugates of 2-SQDs affording highest nonlinear absorption coefficient (βeff) value of ∼80 cm/GW and lowest limiting threshold (Ilim) value of ∼0.27 J·cm−2 as compared to other samples while complex 1 gave low βeff and high Ilim values of 42.2 cm/GW and 1.39 J·cm−2, respectively.

Ablated nickel nanoparticles: third harmonic generation and optical nonlinearities

We report the two-photon absorption and nonlinear refraction studies of the nickel nanoparticles (NPs) in deionized water using femtosecond laser pulses at 400 and 800 nm. The laser ablation technique was employed for the synthesis of nickel NPs using nanosecond, picosecond, and femtosecond pulses. The largest values of nonlinear absorption coefficients and nonlinear refractive indices were determined to be 9 × 10−11 cm W−1 and 2 × 10−15 cm2 W−1 for smaller sized nickel NPs suspension. Third harmonic generation from the Ni plasma which contained NPs was analyzed using picosecond and femtosecond pulses as heating radiation and femtosecond probe pulses.

Spectroscopic and nonlinear optical properties of alkyl thio substituted binuclear phthalocyanines

This work presents the spectroscopic and nonlinear optical properties of metal free binuclear and monomeric 4-(pentylthio)phthalocyanine and cobalt 4,5-(bipentylthio)phthalocyanine. Second order nonlinear absorption coefficient (β) values for the complexes were determined and compared.

Continuous wave laser induced nonlinear optical response of nitrogen doped graphene oxide

This study reports the investigations on linear and nonlinear optical (NLO) properties of graphene oxide (GO) and nitrogen doped graphene oxide (N-GO) obtained by a simple pyrolysis method. The third order nonlinear optical properties of GO and N-GO were studied using continuous wave (CW) laser operating at 532 nm wavelength by employing the Z-scan technique. The nature of the curves suggests that the GO and N-GO exhibits reverse saturable absorption (RSA) and negative nonlinear refractive (NLR) index. Further, nitrogen incorporation has significantly enhanced the nonlinear absorption coefficient (β) values. Variation in the localized sp2 cluster size within the sp3 domains are accounted for the optical energy gap which is determined by the Tauc plot. The fluorescence intensity and their relative quantum yields are largely influenced by nitrogen in sp2 sites studied using Light emitting diode (LED) as a source at an excitation wavelength 452 nm. This cost effective N-GO material with giant linear and nonlinear optical properties may become significant in bio-imaging, biosensor, optical switching devices and NLO based applications.

Effect of La2O3 Dopant on Microstructure and Electrical Nonlinearity of ZnO-CaMnO3 Based Varistor Ceramics

In this research, zinc oxide based varistor are produce by using citrate-gel method compared to conventional solid-state method. The zinc oxide based varistor are fabricate using three different wt.% of ZnO-CaMnO3-La2O3 and divided into three system which are 80 mol% ZnO + 20 mol% CaMnO3, 79.5 mol% ZnO + 20 mol% CaMnO3 + 0.5 mol% La2O3 and 78.5 mol% ZnO + 20 mol% CaMnO3 + 1.5 mol% La2O3. ZnO-CaMnO3-La2O3 compound experienced pre-sintering at 500 °C for 2 hours sintering time. In the sintering condition, sintering temperatures are manipulated, which are varied at 1100, 1200 and 1300 °C while, the sintering time is setting at 4.5 hours. X-ray diffraction patterns show this compound is high in crystallinity. The surface morphology with the average grains size between 2.0 ∼ 10.0 μm was observed by Scanning Electron Microscopy. Energy Dispersive Spectroscopy confirmed that distribution of element are homogenous with high purity. Density of the sample product is range between 5.0 ∼ 5.6 g cm−3. J-E characteristic shows the value of non-linearity coefficient in the range of 1.10 to 4.35.

Effect of Sintering Temperature on Zinc Oxide Varistor Ceramics

Zinc oxide (ZnO) varistors is a solid state electronic ceramic component whose function to protect electronic devices against over voltage surges due to their highly nonlinear electrical properties and ability in controlling the energy. In this study, ZnO varistor is prepared via solid state reaction method. The ZnO based varistor ceramics undergoes sintering temperature at 900 °C, 1100 °C and 1300 °C for 45 minutes. The used of sintering temperature from 900 to 1300 °C, has increased the grain size of ZnO and improved their crystallinity as shown from the peaks intensity of X-ray diffraction (XRD). Current-Voltage properties exhibit the value of nonlinear coefficient in the range of 1.44 to 1.76. Different sintering temperature is used to adjust the microstructure and improve the varistor ceramic characteristics where it shows a potential difference in various application of electronic devices. Increasing in sintering temperature would lead to improved grain growth for better electrical properties.

Fluorescent meso-benzyl curcuminoid boron complex: Synthesis, photophysics, DFT and NLO study

Curcumin based fluorescent NLOphore was synthesized. Solvent polarizability (SP) was found to be responsible for the solvatochromic nature of dye as confirmed from the multilinear regression analysis. DFT computations using global hybrid (B3LYP and BHHLYP) and range-separated hybrid (CAM-B3LYP) functionals with the basis set 6-31 + G(d,p) were performed to determine the linear as well as NLO properties. NLO response was measured using Z scan technique. The computed NLO values (βo = 426.64 × 10−30 esu) were found to be superior to that of urea (βo = 0.371 × 10−30 esu). The value of nonlinear absorption coefficient (β) and third-order nonlinear susceptibility (χ)3 were found to be 2.19 × 10−12 (m/W) and is 2.09 × 10−13 (e.s.u) respectively. The result of present work might be useful for the designing of curcumin based NLOphores for industrial applications.

Ultra-stable X9R type CaCu3-xZnxTi4.1O12 ceramics

CaCu3-xZnxTi4.1O12 (x = 0.00, 0.05 and 0.10) precursor powders were prepared by the polymer pyrolysis (PP) solution method. Ultra-stable X9R type capacitor with very low loss tangent (tanδ) ~0.017 varied within a value of less than 0.05 in a wide temperature range of −60 to 150 °C and high dielectric constants (ε′) ~9200 with Δε′ ≤ ± 15% in a wide temperature range of −60 to 210 °C was achieved in CaCu2.95Zn0.05Ti4.1O12 (Zn05-1) ceramic obtained by sintering the precursor powder (x = 0.05) at 1060 °C for 8 h. A major role for the validity of ε′ and tanδ in these wider temperature ranges was suggested to originated from the very high grain boundary resistance (Rgb ~413,190 Ω cm), resulting from the effect of Zn2+ doping and TiO2-rich at grain boundary. With the excellent dielectric properties of (Zn05-1) ceramic, it was suggested to be applied for X8R and X9R capacitors. Interestingly, improvements of nonlinear properties with very high nonlinear coefficient (α ~ 25.94) and breakdown field (Eb~ 3146.25 V.cm−1) values were achieved in (Zn05-1) ceramic, as well.

Effects of the carboxylic acid substituents on the photophysical and nonlinear optical properties of asymmetrical Zn(II) phthalocyanines–quantum dots conjugates

This work reports on three asymmetrical Zn(II) phthalocyanines, namely: zinc(II) 3–(4-phenoxy)propanoic acid) phthalocyanine(1), zinc(II) 3–(4-phenoxy carboxylic acid) phthalocyanine (2) and zinc(II) 3–(4–oxy)phenoxy)acetic acid phthalocyanine (3) when covalently linked to glutathione(GSH) capped CdTe/ZnSe and CdTe/ZnSe/ZnO quantum dots (QDs). Of the Pc complexes alone, 1 afforded the highest triplet quantum yield (ΦT) value of 0.67 with corresponding largest nonlinear absorption coefficient (βeff) value of 14.0 cm/GW compared to 2 and 3. The conjugates afforded improved triplet quantum yield and nonlinear optical behavior in comparison to the Pc complexes alone.

Effect of Temperature and Magnetic Dopants on Particle size and Electrical Properties of ZnO Ceramic Varistor

We report here structural and electrical properties of Zn0.95 M0.05O ceramic, M = Zn, Co and Mn. It is found that addition of magnetic doping did not influence the hexagonal wurtzite structure of ZnO. Furthermore, the lattice parameters ratio c/a for hexagonal distortion and the length of the bond parallel u to the c axis were nearly unaffected. The average crystalline diameters, deduced from XRD analysis are 83.75, 72.86 and 70.97 nm for Zn, Mn and Co, which are 15 times lower than those obtained from FESEM micrographs (1570, 1380 and 1150 nm). The breakdown field EB was decreased as the temperature increased, in the following order: Mn> Zn > Co. The nonlinear region was observed for all samples as the temperature increased up to 400 K and completely disappeared with further increase of temperature up to 500 K. The values of nonlinear coefficient, α were between 1.65 and 56 for all samples, in the following order: Mn> Zn > Co. Moreover, the electrical conductivity σ was gradually increased as the temperature increased up to 500 K, in the following order: Co > Zn > Mn. On the other hand, the activation energies were 0.194, 0.155 eV and 0.231 eV for all samples, in the following order Mn, Zn and Co. These results have been discussed in terms of valence states, magnetic moment and thermo-ionic emission which were produced by the doping, and controlling the potential barrier of ZnO.

Soil microbial communities and glyphosate decay in soils with different herbicide application history

This study evaluates the glyphosate dissipation under field conditions in three types of soil, and aims to determine the importance of the following factors in the environmental persistence of herbicide: i) soil bacterial communities, ii) soil physicochemical properties, iii) previous exposure to the herbicide. A soil without previous record of GP application (P0) and two agricultural soils, with 5 and >10years of GP exposure (A5 and A10) were subjected to the application of glyphosate at doses of 3mg·kg−1. The concentration of GP and AMPA was determined over time and the dynamics of soil bacterial communities was evaluated using 16S ARN ribosomal gene amplicon-sequencing. The GP exposure history affected the rate but not the extent of GP biodegradation. The herbicide was degraded rapidly, but P0 soil showed a dissipation rate significantly lower than soils with agricultural history. In P0 soil, a significant increase in the relative abundance of Bacteroidetes was observed in response to herbicide application. More generally, all soils displayed shifts in bacterial community structure, which nevertheless could not be clearly associated to glyphosate dissipation, suggesting the presence of redundant bacteria populations of potential degraders. Yet the application of the herbicide prompted a partial disruption of the bacterial association network of unexposed soil. On the other hand, higher values of linear (Kd) and nonlinear (Kf) sorption coefficient in P0 point to the relevance of cation exchange capacity (CEC), clay and organic matter to the capacity of soil to adsorb the herbicide, suggesting that bioavailability was a key factor for the persistence of GP and AMPA. These results contribute to understand the relationship between bacterial taxa exposed to the herbicide, and the importance of soil properties as predictors of the possible rate of degradation and persistence of glyphosate in soil.

Role of defect states on nonlinear properties of 8 MeV electrons irradiated zinc oxide thin films under off-resonant regime

In the present work, ZnO thin films were synthesized by sol-gel with subsequent spin coating on corning glass substrates. To understand the variations in the structural, optical, and nonlinear optical properties of ZnO thin films, 8 MeV electron irradiation with different dose rates (0 kGy, 1 kGy, 5 kGy, and 10 kGy) was performed. The XRD spectra showed transition from polar crystal growth orientation to non-polar crystal growth orientation of the films when the irradiation dose rate was increased from 0 kGy to 10 kGy and this was attributed to the reduced thickness of the irradiated films. The generation of localized surface states below the conduction band upon electron irradiation was confirmed by the quantification of the Urbach energy. A large band gap shrinkage was observed in the irradiated films (3.31–3.10 eV) due to the enhanced surface states. The photoluminescence spectra showed reduction in the NBE emission due to the enhanced surface states in the irradiated films. Open aperture and closed aperture Z-scan measurements were performed to extract the nonlinear absorption coefficient (β) and nonlinear refractive index (n2) values using 532 nm Nd:YAG laser having pulse width of 7 ns. The open aperture Z-scan profiles of the films showed the presence of normalized transmittance valley, which was attributed to the two photon absorption (TPA) behaviour. The reduction in the depth of the normalized transmittance valley in irradiated films was ascribed to the bleaching of carriers in the ground states due to their trapping in the defect states. The closed aperture Z-scan curves showed the presence of normalized pre-focal peak, followed by a valley, which is characteristic of the self-defocusing nonlinear refraction behaviour. The electron irradiation with different dose rates provided an opportunity to understand the variations in the optoelectronic properties of the ZnO thin films considering the various defect states generated upon irradiation.

Optical nonlinearity of pentadecylphenoxyl substituted sandwich–type metallophthalocyanines in the presence of Ag–CdSeTe/ZnTeSe nanocrystals: Effects of conjugation and central metals

Novel pentadecylphenoxyl substituted homoleptic sandwich–type metallophthalocyanines: bis (complexes 2 and 4 containing Eu and Dy, respectively) and tris (complexes 3 and 5 containing Eu and Dy, respectively) 2,9,16,23–tetrakis–(3–pentadecylphenoxyl) phthalocyanines and cadmium based (Ag–CdSeTe/ZnTeSe) nanocrystals (NCs) were synthesized. The nonlinear optical (NLO) behavior of the metallophthalocyanines and their composites with NCs were investigated using the open aperture Z–scan technique at excitation wavelength of 532 nm with 10 ns pulse. All of the samples exhibited interesting NLO attributes: among all the sandwich–type complexes, complex 5 afforded the most efficient NLO features accounting for large nonlinear absorption coefficient (βeff) value of 3500 cm/GW and limiting threshold (Ilim) value of 0.43 J cm−2. Overall, the composites of the triple decker sandwich–type complexes with Ag–CdSeTe/ZnTeSe yielded the best NLO characteristics with 3 and 5 accounting for the largest βeff value of 5500 cm/GW and Ilim value of 0.09 J cm−2. The synthesized complexes and their composites with NCs could be viable and efficient NLO absorber due to their interesting NLO activities.

Femtosecond laser writing of a depressed cladding single mode channel waveguide in high-purity tellurite glass

High-purity tungstate-tellurite glasses doped with molybdenum, lanthanum or bismuth oxides were investigated from a point of view promising medium for nonlinear optical devices fabrication. A tubular-like architecture was employed for fabrication of waveguides in the of tellurite glasses, in which refractive index change is negative under femtosecond laser writing at 1028nm. Thermal, nonlinear optical properties and optimal laser writing conditions were determined. The glasses revealed a very high stability against crystallization, high transparency in the visible, near- and mid-IR regions, large values of Kerr nonlinear coefficient that are within the range of (4.3÷5.4)·10−6cm2/GW. The highest values of the nonlinear coefficient were found for bismuth containing glasses. The single mode waveguide with propagation loss of 0.15dB/cm at 1064nm was inscribed in tungstate-tellurite glass.

A method for measuring the continuous dispersion spectrum of nonlinear refraction coefficients of materials

In this paper, a method for measuring the continuous dispersion spectrum of nonlinear refraction coefficients of materials based on complex refractive index dispersion (CRID) measurement is proposed. This method involves measuring internal reflection spectra with a lab-made apparatus. From the determined CRIDs of a material with and without exciting light, the changes in refractive index over a wide spectral range can be obtained, from which the nonlinear refraction coefficients can be deduced. In addition, the RI changes at wavelengths far from the nonlinear range can be used to monitor the thermal effects. In this study, a methyl-red-doped poly(methyl methacrylate) (MR-PMMA) sample was investigated. A large nonlinear refraction coefficient on the order of 10−1cm2/W was observed. The results also show that the absolute value of nonlinear refraction coefficient of the MR-PMMA sample decreases with the increase of excitation intensity. Consequently, this study provides a powerful approach that has the potential to be applied in the study of the nonlinear properties of materials.

Correlation of quadrature amplitude fluctuations during the intracavity generation of second harmonic

For the process of intracavity generation of the second harmonic, the dynamics of correlation of quadrature amplitudes fluctuations of the fundamental and the second harmonic modes is studied depending on the nonlinear coupling coefficient between the modes. It was shown that in this system the entangled states of field related to variables of quadrature amplitudes may be obtained depending on the nonlinear coupling coefficient. It was also shown that the entanglement of the states of field modes related to one quadrature amplitude may vanish depending on the value of nonlinear coupling coefficient, whereas the states of field modes related to the other quadrature amplitude stay entangled.

Dielectric Properties and Nonohmic Behaviors of CaCu3Ti4O12 Ceramics Prepared by Sol-Gel Process

A sol-gel process was used to synthesize gel precursor of CaCu3Ti4O12. The dry gel were calcined at 800℃/10h and 900℃/10h respectively, and then sintered in air at 1050℃ for 8h. The XRD patterns for calcined powder show that the second phases are contained, and the content of second phases for the powder calcined at 900℃ decreases drastically compared with the powder calcined at 800℃. However, all the second phases have disappeared after the sintering process for the pellets at the same conditions (1050℃/8h, air). The SEM results indicate that the existence of second phases is not conductive to the growth of grains and the formation of grain boundaries during the sintering process. The electric properties measurement demonstrates that the ceramics formulated from dry gel calcined at 900℃/h show not only larger permittivity values and lower dielectric loss, but also larger nonlinear coefficient values comparing those formulated from dry gel calcined at 800℃/h. The nonohmic behaviors measurement results suggest that the higher Schottky barrier is the main factor inducing the larger nonlinear coefficient.