Third-order Nonlinear Optical Coefficients Research Articles

Investigation of the femtosecond optical limiting properties of monoclinic copper niobate

Investigation of the third-order nonlinear optical properties and optical limiting behaviour of microstructured monoclinic phase copper niobate (CuNb2O6) was performed by the Z-scan technique using femtosecond laser pulses (800 nm, 150 fs, 80 MHz). CuNb2O6 was synthesized by solid-state reaction at a sintering temperature of 700 °C maintained at different times of 3, 6, 9 and 12 h. Formation of rods at higher reaction time of 12 h was observed and is attributed to the mass transport and coalescence processes. From the absorption tail of UV–Vis spectrum, the optical band gap was estimated to be 3.5 eV. In the fluorescence spectra, blue emission was observed near 430 nm and was assigned to the charge transfer from oxygen to central niobium of Nb-O6 octahedra. Open-aperture Z-scan data demonstrated the presence of nonlinear absorption in copper niobate and are ascribed to two-photon absorption process. Closed-aperture data indicated a sign reversal in nonlinear refraction as the sintering time increased. Third-order nonlinear optical coefficients were estimated, and the largest coefficient was observed for the rod-structured CuNb2O6. Copper niobate exhibited optical limiting behaviour, and the limiting threshold was found to be lowest for microrod structures (~0.21 µJ/cm2). Due to the top-notch third-order nonlinear optical coefficients and excellent limiting behaviour, monoclinic copper niobate microrods can be used as a potential material for utilization as an optical limiter for femtosecond pulses.

Notable Third-Order Optical Nonlinearities Realized in Layer-by-Layer Assembled Composite Films by Intercalation of Porphyrin/Polyoxometalate into Layered Double Hydroxide

A series of uniform and smooth (TCPP/LDH)n films and (TCPP/P5W30/LDH)n films were fabricated with meso-tetrakis(p-carboxyphenyl)porphyrin (TCPP), Preyssler-type polyoxometalate K12.5Na1.5[NaP5W30O110]·15H2O (P5W30), and exfoliated Mg2Al–NO3 layered double hydroxide (LDH) monolayer nanaosheets by layer-by-layer assembly technique. The resulting films were characterized by UV–visible spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and fluorescence spectroscopy. Their third-order nonlinear optical properties were studied by Z-scan measurement with laser pulse duration of 6–7 ns at a wavelength of 532 nm. The (TCPP/LDH)n films exhibit notable self-defocusing effect and saturated absorption effect which is different from TCPP solution. The optical nonlinearity of films becomes larger with the increase of the number of bilayers. The third-order nonlinear optical coefficient χ(3) of (LDH/TCPP)50/LDH is calculated to be (6.4 ± 0.18) × 10–11 esu. Remarkably, experimental results sh...

Synthesis, characterization and optical properties of poly(aryleneethynylene)s Containing BODIPY

Poly(aryleneethynylene)s containing BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) (P1) were prepared by palladium-catalyzed Sonogashira polymerization of 2,6-diiodo-functionalized BODIPY monomer (M1) with 1,4-diethynyl-2,5-didodecyl-oxybenzene monomer (M2). The structures of the monomer (M1) and copolymer (P1) were confirmed by 1H-NMR and Fourier transform infrared (FTIR) spectroscopies; their optical properties were characterized by UV-Vis absorption, photoluminescence (PL) spectroscopy and the Z-scan technique. Both UV-Vis absorption and fluorescence emission of copolymer P1 red-shifted to longer wavelengths (λabs: from 502 nm to 542 nm; λem: from 511 nm to 631 nm) relative to those of the monomer M1 due to the π-conjugation extension of the copolymer. The third-order nonlinear optical coefficient (χ(3)) of copolymer P1 was 1.94 × 10−10 esu, which is almost two or three orders of magnitude greater than that of common conjugated polymers without BODPIY moiety.

Self-diffraction and high nonlinear optical properties of carbon nanotubes under CW and pulsed laser illumination

In this work, self-diffraction effect in carbon nanotubes (CNTs) that were dispersed on N,N-dimethylformamide (DMF) solvent is studied. Third-order nonlinear optical coefficients of this nano-suspension are measured using z-scan technique and high nonlinearity is observed. Nonlinear refraction index of the order −10−6cm2W is obtained due to the thermal effect and the nonlinear interaction of the light and the surface plasmonic electrons. Optical diffraction rings of the sample under He–Ne laser illumination at a wavelength of 632.8nm were observed and intensity distribution of the rings is explored. At last, optical limiting performance of CNTs is investigated under irradiation by a continuous wave (CW) He–Ne laser. The optical limiting behavior is investigated by using transmission measurement through the sample and our studies indicate that this material is a potential candidate for optical limiting applications in low power CW regime.

Computations of absorption spectra and nonlinear optical properties of molecules based on anthocyanidin structure

Simulation of UV–VIS spectra and microscopic third-order nonlinear optical (NLO) coefficients at 532 nm wavelength of molecules based of anthocyanidin structure in gas phase environment using semi-empirical PM3 method was calculated. One-photon absorption characterizations of the investigated molecules have been theoretically obtained by configuration interaction method with doubly occupied molecular orbitals. Estimated theoretical spectra shows a sensibility to the different functional groups such as hydroxyl and methoxyl substitution in radicals. These groups causes red shift in absorption spectra in comparison to the other samples what agree well with the experimental data. Adjunction of such functional donor character group in the investigated molecule slightly decreases the HOMO–LUMO energy splitting gap but increases the ground state dipole moment resulting the substantial increase of NLO coefficient in this system comparing to the other samples. According to presented investigations the tested molecules have large nonlinear optical properties.

Synthesis and third-order optical nonlinearities of hyperbranched metal phthalocyanines

A series of novel organic hyperbranched metal phthalocyanines (HMePcs) oligomers were synthesized for investigating their third-order nonlinear optical (NLO) properties. The third-order NLO coefficient was measured by Z-scan technique with a pulsed Q-switched Nd:YAG nanosecond laser at 532nm. The HMePcs showed large molecular cubic hyperpolarizabilities (γ) whose values were of the order of 10−29esu. The variation of substituent groups of and center metal of HMePcs influenced the third-order optical nonlinearity. The presence of electron-withdrawing substituents-fluoro in the phthalocyanine brings about a noticeable improvement of the third-order nonlinear susceptibility χ(3) in these systems and the third-order nonlinear susceptibility χ(3) values of different metal hyperbranched metal (Cu, Ni, Co) phthalocanines oligomers were found to decrease in the order HCuPc>HNiPc>HCoPc.

Polyacetylenes containing BODIPY pendants with different connectivities: synthesis, characterization and opto-electronic properties

A group of novel polyacetylenes containing BODIPY pendants have been synthesized in satisfactory yield using a [Rh(nbd)Cl]2–Et3N catalyst. The pendant BODIPY unit has been directly conjugated to the polyacetylene backbone either through the 8 position of the BODIPY cores in P1, or through the 3 position in P2 and P3. Their optoelectronic properties have been investigated by UV-vis, FL, CV and Z-scan techniques. Interestingly, the spectroscopy results show that little electronic interaction exists between the BODIPY chromophoric units and the polyacetylene main chain for P1. However, the electronic interaction between the side pendant and the main chain becomes notable for P2 and P3, resulting in a significant broadening and red-shift of their UV-vis absorption and fluorescence emission wavelengths in comparison with those of their respective monomers. The polymers display thermal stabilities and nonlinear optical properties that are dependent on the connectivities of the BODIPY pendants and the polyacetylene backbones. P1 exhibits relatively better thermal stability and poorer nonlinear optical properties than P1 and P2. The third-order nonlinear optical coefficient (χ(3)) of P1 is 8.5 × 10−12 esu, which is shown to be ∼15 times smaller than those of P2 and P3.

Na2O–B2O3–SiO2 glass doped with In and Cu2In nanoparticles prepared by sol–gel method

Na2O–B2O3–SiO2 glass doped with In and Cu2In nanoparticles are fabricated through sol–gel technique. The morphology and structure of the samples are investigated by X-ray diffraction (XRD) technique, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The results show that the tetragonal phase of In particles with an average size about 50.0nm and hexagonal phase of Cu2In particles about 31.5nm are formed in the glass matrix. The absorption optical properties of the as-prepared glass are also characterized. Furthermore, the glasses are measured by Z-scan technique to investigate the third-order nonlinear optical properties. The results display that the In and Cu2In nanoparticles have the behaviors of both nonlinear optical saturable absorption and refraction with self-defocusing effect. The third-order nonlinear optical coefficient χ(3) of In and Cu2In nanoparticles are calculated to be 1.64×10−10esu and 2.77×10−10esu, respectively.

Preparation and nonlinear optical properties of indium nanocrystals in sodium borosilicate glass by the sol–gel route

The sodium borosilicate glass doped with indium nanocrystals have been successfully prepared by sol–gel route. The thermal stability behavior of the stiff gel is investigated by thermogravimetric (TG) and differential thermal (DTA) analysis. The crystal structure of the glass is characterized by X-ray powder diffraction (XRD). Particle composition is determined by X-ray photoelectron spectroscopy (XPS). Size and distribution of the nanocrystals are characterized by transmission electron microscopy (TEM) as well as high-resolution transmission electron microscopy (HRTEM). Results show that the indium nanocrystals in tetragonal crystal structure have formed in glass, and the average diameter is about 30nm. Further, the glass is measured by Z-scan technique to investigate the nonlinear optical (NLO) properties. The third-order NLO coefficient χ(3) of the glass is determined to be 2.81×10−10esu. The glass with large third-order NLO coefficient is promising materials for applications in optical devices.

The third-order nonlinear optical coefficients of Si, Ge, and Si1−xGex in the midwave and longwave infrared

Using a combination of semiconductor theory and experimental results from the scientific literature, we have compiled and plotted the key third-order nonlinear optical coefficients of bulk crystalline Si and Ge as a function of wavelength (1.5−6.7 μm for Si and 2–14.7 μm for Ge). The real part of third-order nonlinear dielectric susceptibility (χ(3)′), the two-photon absorption coefficient (βTPA), and the Raman gain coefficient (gR), have been investigated. Theoretical predictions were used to curve-fit the experimental data. For a spectral range in which no experimental data exists, we estimate and fill in the missing knowledge. Generally, these coefficient-values appear quite useful for a host of device applications, both Si and Ge offer large χ(3)′ and gR with Ge offering the stronger nonlinearity. In addition, we use the same theory to predict the third-order nonlinear optical coefficients of Si1−xGex alloy. By alloying Si and Ge, device designers can gain flexibility in tuning desired optical coefficients in between the two fundamental components based upon their application requirements.

Controllable space selective precipitation of copper nanoparticles in borosilicate glasses using ultrafast laser irradiation

Transparent glasses containing copper nanoparticles are promising materials for ultrafast all-optical switches in the THz region due to their wide range of resonant absorption frequencies, ultrafast time response, as well as large third-order nonlinear optical coefficients associated with the surface plasmon resonance (SPR) in the visible region. In this paper, three dimension controllable precipitation of copper nanoparticles inside a borosilicate glass by irradiation of femtosecond laser pulses is studied. According to the designed program, different patterns made up of copper nanoparticles can be induced inside the glass sample. Absorption spectra are used to confirm the precipitation of copper nanoparticles. The precipitated nanoparticles can be space-selectively “dissolved” by the second time femtosecond laser irradiation. The involved mechanisms are discussed.

Electronic Spectra and Nonlinear Optical Properties of 8-Hydroxyquinolinolate-Ag (Pt) Metal Complexes

运用密度泛函理论B3LYP方法对8-羟基喹啉（银、铂）（AgQ、PtQ2）金属配合物及其衍生物的非线性光学性质进行理论计算研究.结果表明：引入取代基使铂配合物的最强吸收波长产生较大红移.最低能量跃迁吸收来自最高占据分子轨道（HOMO）到最低空分子轨道（LUMO）的d→π＊和π→π＊跃迁,属于金属配体电荷转移（MLCT）与配体配体电荷转移（LLCT）.金属银和铂掺杂8-羟基喹啉使其三阶非线性光学系数γ值明显增大,并且在配合物上引入―Ph,―PhOCH3,―PhF2,―PhF5基团将进一步增大γ值.引入基团的供电子性越强,γ值增大的幅度越大,引入基团的吸电子性越强,γ值增大的幅度越小.

长链β-二酮环金属铂配合物的紫外可见吸收光谱和三阶非线性光学系数的理论研究

长链β-二酮环金属铂配合物的紫外可见吸收光谱和三阶非线性光学系数的理论研究

长链β-二酮环金属铂配合物的紫外可见吸收光谱和三阶非线性光学系数的理论研究

长链β-二酮环金属铂配合物的紫外可见吸收光谱和三阶非线性光学系数的理论研究

长链β-二酮环金属铂配合物的紫外可见吸收光谱和三阶非线性光学系数的理论研究

长链β-二酮环金属铂配合物的紫外可见吸收光谱和三阶非线性光学系数的理论研究

The synthesis and third-order nonlinear optical properties of resonance Benzo[a]phenoxazinium salts

The third-order nonlinear optical properties of a series of resonance benzo[a]phenoxazinium salts in acetic acid solution were studied using the Z-scan technique employing a Nd:YAG nanosecond laser at 532 nm. The compounds displayed strong reverse absorption with third-order nonlinear optical coefficients of 0.42–1.20 × 10 −11 esu and second hyperpolarizabilities of 2.75–7.29 × 10 −29 esu, respectively. Quantum chemical calculations showed that the compound with more stable highest occupied molecular orbital energy also displayed highest second hyperpolarizability.

Theoretical investigation on structures, electronic spectra and nonlinear optical properties of gold compounds [X-“Au(PMe3)”2

The structures, electronic spectra, polarizability and third-order nonlinear optical properties of six gold compounds [X-“Au(PMe3)”2] were investigated by density functional theory (DFT) B3LYP and BhandHLYP methods. It was found that the calculation methods and basis set are rational for the object of study, and molecular structures change slightly when PPh3 is replaced by PMe3. The spatial effects of the bridging section have a significant influence on the polarizability, but indistinctive to the third-order nonlinear optical (NLO) coefficient. As a result of the conjugated effect in different compounds, the third-order polarizability of molecule 1a is the smallest, while that of molecule 2a is the largest. Au has donor ability in molecule 1a but acceptor ability in molecules 2a–6a by analyzing the electronic spectra and frontier molecular orbitals constitute maximal absorption, which indicates the contribution of Au to NLO properties in the six molecules is different.

聚氨酯-酰亚胺的合成及三阶非线性光学性能研究

The poly(urethane-imide) (PUI) which uses isophorone diisocyanate, dispersed red 19 (DR-19), and pyromellitic dianhydride is synthesized. The PUI is characterized by Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The results of DSC and TGA indicate that the PUI exhibits high thermal stability up to its glass-transition temperature of 209 C and 5% heat weight loss temperature of 296 C. The fluorescence spectra of PUI and DR-19 are measured, showing that the fluorescence effect of PUI is very similar to that of DR-19 except for the light decrease of fluorescence intensity, which indicates that the fluorescence effect of PUI is generated by the azobenzene groups in its macromolecular chains. The maximum molar absorption coefficient, absorption wavelength, and chromophores density are measured and used to calculate the third-order nonlinear optical coefficient \chi^{(3)} to be 3.96times10^{-13} esu. The nonlinear refractive index coefficient and molecular hyperpolarizability of PUI are also obtained. PUI is proved to have an excellent optical performance.

Optical Properties of Poly(3-hexylthiophene)/ZnS Nanocomposites

Nanocomposites comprised of poly(3-alkyl thiophenes)(P3ATs)/semiconductor nanoparticles exhibited excellent photoelectricity performance due to contributions from both the P3ATs and the semiconductor nanoparticles. In this study, poly(3-hexylthiophene) (P3HT) was synthesized and P3HT/ZnS nanocomposites were prepared using an in-situ method. The ZnS nanoparticles exhibited strong quantum effect on the photoluminescence (PL) properties of P3HT/ZnS and the nanocomposites exhibit an enhanced PL and red-shifted emission with increasing ZnS content. The PL quenched at ZnS-to-3HT ratio of 9.92 1 10-2 mol mol-1. The charge-transfer process between P3HT and ZnS particles is discussed. The P3HT/ZnS composites also exhibited excellent nonlinear optical (NLO) properties. The third-order NLO coefficient of P3HT/ZnS ( χ(3 ) = —6.76 1 10-12 esu) is higher than that of P3HT. The P3HT/ZnS nanocomposites have potential optical applications.

Third-order nonlinear optical properties of Bi 2S 3 and Sb 2S 3 nanorods studied by the Z-scan technique

Bismuth sulfide (Bi 2S 3) and antimony sulfide (Sb 2S 3) nanorods were synthesized by hydrothermal method. The products were characterized by UV–vis spectrophotometer, X-ray powder diffraction (XRD) and transmission electron microscope (TEM). Bi 2S 3 and Sb 2S 3 nanorods were measured by Z-scan technique to investigate the third-order nonlinear optical (NLO) properties. The result of NLO measurements shows that the Bi 2S 3 and Sb 2S 3 nanorods have the behaviors of the third-order NLO properties of both NLO absorption and NLO refraction with self-focusing effects. The third-order NLO coefficient χ (3) of the Bi 2S 3 and Sb 2S 3 nanorods are 6.25×10 −11 esu and 4.55×10 −11 esu, respectively. The Sb 2S 3 and Bi 2S 3 nanorods with large third-order NLO coefficient are promising materials for applications in optical devices.