Refractive Nonlinear Coefficient Research Articles

Ag2S quantum dots in the fields of picosecond and femtosecond UV and IR pulses: optical limiting, nonlinear absorption and refraction properties

We demonstrate strong optical nonlinearities of silver sulfide (Ag2S) quantum dots (QDs) in the ultraviolet range. The 4-nm Ag2S QDs were prepared by chemical method and analyzed using picosecond (800 nm and 400 nm, 200 ps) and femtosecond (800 nm and 400 nm, 60 fs) laser pulses. Our Z-scan measurements show that these QDs have large nonlinear absorption coefficient (~ 10−3 cm W−1) at 400 nm. We also demonstrate the transient absorption and optical limiting in Ag2S QDs. Variations of the signs of nonlinear refractive indices and nonlinear absorption coefficients of QDs are demonstrated by changing pulse width and wavelength of probe radiation.

Nonlinear absorption and refraction in phthalocyanine-doped polymers

Lead-tetrakis-4(cumylphenoxy)phthalocyanine (PbPc) is dispersed into several common optical polymers at various doping levels. The linear and nonlinear optical properties are measured at 600 nm near the region where the excited state and ground state absorption cross sections are nearly equal. The effective nonlinear refraction coefficients observed at high concentration are as much three orders of magnitude larger than that observed for fused silica.

Impact of ligand rotation: Synthesis, crystal structures and third-order nonlinear optical properties of Mn(II), Cu(II) and Ni(II) complexes with 5‑diethylamino‑2‑((4‑(phenyldiazenyl) phenylimino) methyl) phenol

Three new coordination compounds containing 5‑diethylamino‑2‑((4‑(phenyldiazenyl) phenylimino) methyl) phenol ligand have been synthesized and fully characterized. Single crystal structure showed that the ligand shows multiple coordination mode and the phenyl group next to azo group could rotate during the coordination process. In Mn(HDAPPP)2Cl2·CH3CN (1), the HDAPPP behaved as a mono ligand because of the N of the imine group is protonated in the keto form and does not participate in coordination. While the Cu(DAPPP)2 (2) and Ni(DAPPP)2 (3) are classic complexes containing azo-Schiff base ligand. The fluorescence emission peaks of compounds indicated that the fluorescence of the compounds are mainly derived from the π-π* charge transition of the ligand and affected by the rotation of ligand. The UV–Vis data revealed that the compound 1–3 with the maximum absorption peak at 425 nm, 440 nm and 338 nm, respectively. This clearly confirmed that the compound 1 is mainly based on the keto configuration while the compound 3 is mainly based on the enol configuration. Z-scan experiments showed that all compounds exhibited reverse saturable absorption effect and self-defocusing effect for nonlinear optical materials. The nonlinear absorption coefficients (β) of compound 1–3 are evaluated to be 6 × 10−11 m·W−1, 4.4 × 10−11 m·W−1, and 1.7 × 10−11 m·W−1 respectively, and the nonlinear refraction coefficients (n2) are −1.4 × 10−17 m2·W−1, −1.6 × 10−17 m2·W−1, −7.0 × 10−18 m2·W−1 respectively. The nonlinear optical property of compound 1 and 2 are better than compound 3, which are influenced by ligand rotation after coordination.

Preparation of composite Ag@Au core–shell nanoparticles and their linear and nonlinear optical properties

We herein report the preparation of composite Ag@Au core–shell nanoparticles (NPs) through galvanic replacement reaction and the investigations of linear and nonlinear optical properties. TEM micrographs envisage the formation of core–shell NPs. EDS elemental mapping images demonstrate the homogeneous distribution of the elements and their chemical composition. The powder XRD pattern confirms the formation of highly crystalline composite Ag@Au core–shell NPs. The UV–Vis absorption spectrum shows contribution of Ag and Au characteristic absorption bands and the slight red shift provides the strong evidence for coating of Au shell over the Ag core. Moreover, the linear optical parameters such as the extinction coefficient, reflectance, refractive index, conductivity, susceptibility and polarizability are studied. z-scan analysis reveals the enhanced nonlinear optical properties of the composite Ag@Au core–shell NPs with nonlinear refraction coefficient (n2) being ten times higher than that of Ag NPs and eight times increase in comparison with that of Au NPs.

Effective model for nonlinear refraction and extinction coefficients in the presence of stimulated light scattering

We present in this paper a wave-coupled model (WCM) to describe the effective nonlinear (NL) optical response of transparent materials illuminated by strong light beams in conditions such that stimulated light scattering is relevant. At low intensities, the WCM indicates that the NL scattering behaves similarly to a third- and fifth-order polarization susceptibility. However, at sufficiently high intensities, NL light scattering will lead to highly nonperturbative effective NL refraction and NL absorption coefficients. This is an important remark, given that attempts to explain NL scattering contributions as a perturbative NL response from data obtained at low intensities will become discrepant from the data obtained at high intensities. As an application of the model, we show that the existing divergent interpretations of the carbon disulfide (CS2) NL response in the picosecond and femtosecond regimes by several authors are consistent with the WCM, which indicates a direction for future experiments that may clarify the present controversy.

Crystal Structure and Third Order Nonlinear Optical Studies on 2-Phenylbenzimidazolium-p-Toulenesulphonate

A new third order nonlinear optical single crystal of 2-phenylbenzimidazolium-p-toulenesulphonate is grown by the solvent evaporation technique using methanol as a solvent. The single crystal X-ray diffraction analysis reveals that crystals belong to the triclinic system. A nuclear magnetic resonance and Fourier transform infrared spectroscopic study confirms the formation and vibrational analysis for the compound. UV-visible absorption studies are also carried out for the crystal. Nonlinear refractive index, absorption coefficient, and third order nonlinear optical susceptibility of the crystals are evaluated by Z-Scan studies.

Z-Scan and Absorption Study of Crocin and Rhodamine B Decolorization by Bacterial Laccase.

Dye decolorization is currently measured by the reduction of dye absorption, based on its linear optical properties in solution. However, this method is not suitable for high dye concentrations with linear attributes in the absorption spectra. In this work, nonlinear optical properties are used to study dye decolorization of Crocin and Rhodamine B treated with a bacterial laccase. For this purpose, the Z-scan was used to obtain the nonlinear refractive indices and nonlinear absorption coefficient of Rhodamine B and Crocin in the presence and absence of the bacterial laccase enzyme. The results showed that nonlinear optical properties could be used to study dye decolorization in solutions.

Investigation on optical, thermal, mechanical, dielectric and ferroelectric properties of non linear optical single crystal guanidinium manganese sulphate

Semi organic nonlinear optical crystal of guanidinium manganese sulphate hydrate (GuMnS) was grown from its aqueous solution by slow evaporation solution growth technique. Formation of the crystalline compound was confirmed by powder X-ray diffraction analysis (PXRD).The compound crystallizes in the triclinic crystal system with space group Pī. The functional groups present in the crystal have been identified by FTIR spectroscopic analysis. UV–Vis–NIR spectral study indicates that the grown crystal is transparent in the entire visible region with a lower cut off wavelength 229 nm and the band gap value is found to be 5.06 eV. Nonlinear refractive index (n2), absorption coefficient (β) and third order nonlinear susceptibility (χ(3)) were determined using Z-scan technique. Thermo gravimetric and differential thermo gravimetric analyses (TG-DTG) were performed to analyse the thermal behaviour of the grown crystal. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. The ferroelectric nature of the grown crystal was analysed by P–E hysteresis loop. The mechanical behaviour of the grown crystal was studied by Vickers’s micro hardness test. The laser induced surface damage threshold (LDT) of the grown crystal was found to be 1.157 GW/cm2. The obtained results show that guanidinium manganese sulphate crystals are potential materials in NLO device applications.

Near-infrared third-order optical nonlinearity in CaCu3Ti4O12 thin films

We investigate the optical nonlinearity of CaCu3Ti4O[Formula: see text] (CCTO) thin films on MgO substrates using Z-scan technique at a near-infrared wavelength of 1064[Formula: see text]nm with 25[Formula: see text]ps duration pulses. The near-infrared nonlinear saturable absorption coefficient [Formula: see text] and the nonlinear refraction coefficient [Formula: see text] of the values [Formula: see text][Formula: see text]cm/GW and 0.66[Formula: see text]cm2/GW, respectively, were deduced from the study of the nonlinear response at different excitation intensities. The three-level model is proposed to interpret the large optical nonlinearity in CCTO films in near-infrared spectrum, by considering the intermediate energy levels due to the defects or grain boundaries. The large optical nonlinearity and fast response at picosecond time-domain indicate that CaCu3Ti4O[Formula: see text] thin films are promising candidates for applications in near-infrared nonlinear photonics devices.

Temporal and polarization dependence of the nonlinear optical response of solvents

It has long been known that nonlinear refraction in solvents can depend on pulse width, and this along with experimental uncertainties has led to orders-of-magnitude disagreements in nonlinear refractive coefficients reported in the literature. To resolve this issue, we perform beam-deflection (BD) measurements of the rigorously defined nonlinear impulse response function for 24 commonly used solvents selected from various classes of molecules. Using this polarization-resolved BD, the bound-electronic and the three major nuclear contributions are separately measured by determining the magnitudes, symmetry, and temporal dynamics of each mechanism. This allows us to construct the response functions that we use to accurately establish self-consistent references for predicting and interpreting the outcomes of other experiments performed on these materials over the temporal range from 10 fs to 1 ns. The results also provide insight into relating solvent nonlinearities with their molecular structures and exploring the effects of the Lorentz–Lorenz local field. We find that nonconjugated molecules with small polarizability anisotropy exhibit negligible reorientational response, and hence the nonlinear refraction is almost independent of pulse width. Knowledge of the response functions also allows engineering the transient nonlinear refractive properties of solutions of organic dyes, for example, materials with effectively zero nonlinear refraction.

Crystal growth, spectroscopic, DFT computational and third harmonic generation studies of nicotinic acid

An organic centrosymmetric nicotinic acid (NA) single crystal has been grown employing slow evaporation method in water. NA crystallizes in monoclinic system with centric space group P21/C. The experimental and theoretical investigation includes vibrational spectra based on Hartree – Fock (HF) and density functional theory (DFT) has been applied using different function at B3LYP level of theory using 6-311G++(d,p) basis set. The optical transparency of the title molecule was examined by TD- DFT analysis and for comparison basis experimental UV–Vis spectrum was recorded. The interaction of charge within the molecule was analyzed and the HOMO - LUMO energy gap was evaluated. The value of dipole moment, Mulliken charge and molecular electrostatic potential were estimated at the same level of theory. Also the first order hyper polarizability for NA was calculated. The dielectric behavior of the grown crystal was determined for few selected temperatures. The third order nonlinear response of NA has been examined using Z-scan technique and nonlinear susceptibility (χ3), nonlinear refraction (n2) and nonlinear absorption coefficient (β) has been calculated. The current results clearly indicate that the title compound is an excellent applicant in the domain of opto – electronic applications.

Study of linear and nonlinear optical properties of nickel immobilized on acid-activated montmorillonite and copper ferrite nanocomposites

In this paper, the third-order nonlinear optical properties of nickel immobilized on acid-activated montmorillonite (MMT@Ni) and copper ferrite (CuFe2O4@Ni) nanocomposites were investigated. The mentioned nanomaterials were synthesized and then characterized using FT-IR, SEM, EDX, XRD, VSM, and TEM analyses. The nonlinear absorption and refractive coefficients of these nickel nanocomposites were measured by Z-scan technique through a continuous wave diode-pumped laser at 532 nm wavelength. The values of nonlinear absorption and refractive indexes of samples were obtained in order of 10−4m/w and 10−10m2/w, respectively. In addition, the sign of nonlinear refractive index for MMT@Ni and CuFe2O4@Ni was shown to be positive and negative, respectively. It seems that the difference in activities of nanocomposites was relevance to their structural frameworks. Nickel immobilized on acid-activated montmorillonite has layered structure and this provides the possibility to focus the laser beams, and so self-focusing phenomenon was happened. Whereas, nickel immobilized on copper ferrite has inverse spinel structure and this provides the possibility to diverge the laser beams, and so self-defocusing phenomenon was taken place. The results also showed that the values of nonlinearity for solution of CuFe2O4@Ni and MMT@Ni nanoparticles were respectively increased and decreased by rising of the input intensity. In addition, we found that the support of nickel nanoparticles could change the sign of nonlinear optical behavior.

Temperature dependence of the nonlinear optical response of smectic liquid crystals containing gold nanorods.

The present study is devoted to the investigation of the nonlinear optical properties of a smectic liquid crystal doped with gold nanorods. Using the Z-scan technique, we investigate the changes in the optical birefringence of a homeotropic sample upon laser exposure, considering the configurations of normal and oblique incidence. Our results reveal that the birefringence variations may be governed by distinct physical mechanisms, depending on the relative angle between the far-field director and the wave vector of the excitation laser beam. In particular, we observe that the position dependence of the far-field transmittance exhibits different behaviors as the incidence angle is changed, indicating that distortions in the beam wavefront may be associated with the thermal lens phenomenon or an optically induced reorientation of the nematic director. The temperature dependence of the nonlinear refractive and absorptive coefficients is investigated close to the smectic-A-nematic phase transition. A detailed analysis of the interplay between smectic order and plasmon resonance is performed, thus unveiling the capability of plasmonic liquid crystal to be used in optical devices.

Nonlinear refraction in (5,10,15,20-tetraphenylporphyrinato)-copper(II) doped PMMA thin film at wavelength 1064 nm

(5,10,15,20-Tetraphenylporphyrinato)-copper(II) (TPP-Cu) are synthesized, and characterized by X-ray single crystal diffraction. TPP-Cu doped polymethylmethacrylate (PMMA) thin film on quartz substrate were prepared by spin-coating method. The morphology of the film were investigated by scanning electron microscopy. The nonlinear refractive properties of the film were studied using closed aperture Z-scan technique by picosecond (PS) laser pulses at different irradiance at wavelength 1064nm. The nonlinear refraction coefficient n2I value of the film were determined to be 1.28×10−12m2/W, this making them ideally suited to the applications in the field of all-optical switches.

Effect of concentration of Ag Nanoparticles Prepared by γ-Radiation on Nonlinear Refraction and Absorption Coefficient

Effect of concentration of Ag Nanoparticles Prepared by γ-Radiation on Nonlinear Refraction and Absorption Coefficient

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.

Coherent source interaction, third-order nonlinear response of synthesized PEG coated magnetite nanoparticles in polyethylene glycol and its application

Third-order nonlinear response of synthesized polyethylene glycol coated Fe3O4 nanoparticles dispersed in a suitable solvent, polyethylene glycol has been studied. The structural characterization of the synthesized magnetite nanoparticles were carried out. The linear optical property of the synthesized magnetite nanoparticles was investigated using UV-visible technique. Both closed and open aperture Z-scan techniques have been performed at 532nm with pulse width 5ns and repetition rate 10Hz. It was found that polyethylene glycol coated magnetite exhibits reverse saturable absorption, with significant nonlinear absorption coefficient. Two-photon absorption intensity dependent positive nonlinear refraction coefficients indicate self focusing phenomena. Results show that higher concentration gives better nonlinear and optical limiting properties.

Investigations on the growth, linear, nonlinear, dielectric tensor and thermal properties of an acidic molecule: diphenylacetic acid single crystal

An organic crystal, diphenylacetic acid (DPA) was grown by the slow evaporation solution growth technique. The title compound crystallizes in the monoclinic crystal system with space group, P21/c. UV–vis–NIR spectral study showed that the grown DPA crystal is transparent in the entire visible region with the lower cut-off wavelength of 225 nm. The four independent tensor coefficients of dielectric permittivity were found to be e11 = 29.92, e22 = 28.74, e33 = 27.38 and e13 = 0.81 from the dielectric measurements. The DPA compound is thermally stable up to 148.9 °C assessed by thermogravimetric and differential thermal (TG–DTA) analyses. The laser induced surface damage threshold of the grown DPA crystal was found to be 0.2165 GWcm−2 for 1064 nm Nd:YAG laser radiation. Nonlinear refractive index (n2), absorption coefficient (β) and third order nonlinear susceptibility (χ(3)) were determined by Z-scan technique for the DPA crystal. Optical limiting study revealed that the transmitted output power increases linearly with the input power up to irradiance of around 3.1 mW/cm2.

Synthesis of nanocomposites based on carbon nanotube/smart copolymer with nonlinear optical properties

In this study new nanocompoites based on polyglycidylmethacrylate grafted 4-[(4-methoxyphenyl) diazenyl] phenol (Azo-PGMA) and Carboxylicacid functionalized multi-walled carbon nanotubes (MWCNT-COOH) were prepared. The nanocomposites structure was characterized by FT-IR, TGA and SEM. The Z-scan technique was applied for measuring the nonlinear parameters of nanocomposites. The samples after solving in AWM solution (equal ratio of acetone, deionized water and methanol) were investigated by using closed aperture Z-scan technique and a diode-pumped laser at the line 532 nm. All the nonlinear refractive index of the samples at three concentrations of carbon nanotubes in three different intensities of the laser beam were investigated and the nonlinear optical response of them are compared under the same condition. Because of high order of nonlinear refractive coefficient and good nonlinearity, these compounds are suitable candidate for optical switching, optical limiting and electro-optical devices.

Ultrafast carrier dynamics and third order nonlinear optical properties of aluminum doped zinc oxide (AZO) thin films

Aluminum doped zinc oxide (AZO) thin films were fabricated by simultaneous RF/DC magnetron sputtering technique on sapphire (Al2O3) substrate with different DC sputtering power 2, 6, 8 and 10 W respectively. The sputtered thin films were annealed at 350 °C in order to improve the crystal quality. AZO thin films are systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-VIS spectrometer for structural and optical properties. XRD patterns show that all sputtered thin films are well crystallized with hexagonal wurtzite structure. SEM images reveal the average crystallite sizes are increased after doping Al in ZnO which agreed with the calculated values from XRD. All thin films possess high optical transmittance in visible region and optical band gap values are relatively increased with Al concentration. The ultrafast transient absorption (TA) of AZO was analyzed by femtosecond pump-probe spectroscopy. The kinetic TA curves were fitted by tri-exponential decay function and obtained decay time constants are found to be in few picosecond and nanosecond range for ultrafast and slow processes respectively. Third order nonlinear optical absorption and refraction coefficients were investigated by using Z-scan technique. The observed nonlinear coefficients are enhanced with Al concentration in ZnO.