Third-order Nonlinear Properties Research Articles

Third-harmonic generation performance of organic polymer films doped with triphenylmethane derivative dyes

We report on third-order nonlinear properties of triphenylmethane derivative dyes by measuring third-harmonic generation (THG) for fundamental wavelengths within the range 1100–1800 nm. Our studies show that the triphenylmethane dyes Crystal Violet and Ethyl Violet, with a multidirectional charge transfer in their three-fold symmetry structure (octupolar dimensionality), exhibit a third-order nonlinear susceptibility of the order χ (3) ∼ 10 −12 esu when are used as dopants in polymer films. These films, with low residual absorption and anomalous refractive index dispersion for harmonic wavelengths, exhibit efficient THG as a bulk effect. The films are good candidates for ultra-fast optical correlators.

Hydrothermal synthesis, crystal structure and characterization of [Zn(H 2O) 4] 2 [H 2As 6V 15O 42(H 2O)]·2H 2O

The compound [Zn(H 2O) 4] 2[H 2As 6V 15O 42(H 2O)]·2H 2O ( 1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a= b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å 3, Z=3 and R1( wR2)=0.0512 (0.1171). The crystal structure is constructed from [H 2As 6V 15O 42(H 2O)] 4− anions and [Zn(H 2O) 4] 2+ cations linked through hydrogen bonds into a network. The [H 2As 6V 15O 42(H 2O)] 6− cluster consists of 15 VO 5 square pyramids linked by three As 2O 5 handle-like units.

Sulfur-bridged iron and manganese carbonyl clusters: synthesis, structure and nonlinear optical properties of [(μ-SPh) 2Fe 2(CO) 6] 2(μ 4-S) and [PPN][(μ 3-S) 2Mn 3(CO) 9

Two sulfur-bridged carbonyl clusters [(μ-SPh) 2Fe 2(CO) 6] 2(μ 4-S) 1 and [PPN][(μ 3-S) 2Mn 3(CO) 9] 2 were synthesized for study of the third-order nonlinear properties. Cluster 1 consists of two doubly bridged Fe 2(CO) 6 fragments bonded for a center μ 4-sulfur atom of the distorted tetrahedron. Each fragments is also bridged with the sulfur from a thiophenol group. Cluster 2 exhibits a D 3 h equilateral triangular frame with three Mn(CO) 3 units apically bicapped by the two μ 3-sulfur atoms. The moderate third-order optical nonlinear absorption and refraction effects of clusters 1 and 2 in CH 2Cl 2 solution were observed at 532 nm by using of the z-scan measurements of an 8-ns pulsed laser. The third-order nonlinear optical susceptibilities, χ (3), were detected with 5.4×10 −13 and 1.2×10 −13 esu for 1 and 2, respectively, in solution. The structure–property relationship in clusters is also discussed in the paper.

Third-order optical nonlinearities of oligomers, dendrimers and polymers derived from solution Z-scan studies

Z-scan measurements provide a simple way of determining and comparing the third-order nonlinear properties of chemical compounds, especially if measurements can be done on solutions in common solvents. We discuss advantages of the solution Z-scan technique, e.g. the possibility of in situ studies of electrochemical switching of third-order nonlinearity, and problems encountered on the interpretation of the results, such as those due to thermal nonlinearity and solvent effects.

Synthesis and third-order optical nonlinear properties of organic polyheterocyclic materials

A series of three 1,4-bis(naphthothiazol-2-yl)benzene and bis(1,4-dialkoxylnaphthalene) tetrathiafulvalene materials were synthesized and the third-order nonlinear optical properties of the materials were studied with three-dimensional degenerate four-wave mixing (3D DFWM) geometry. The third-order nonlinear optical susceptibilities | χ (3)| of the materials were measured to be 4.32–5.05×10 −13 esu and the third-order hyperpolorizabilities γ of the molecules were calculated to be 4.38–9.95×10 −31 esu.

Electronic spectra and third-order nonlinear properties of new structures in carbon family

New molecular chains of the carbon family were constructed with sym-tribenzotridehydro annulene. The UV/Vis absorption spectra and the second hyperpolarizabilities were investigated through the semiempirical INDO/S and AM1 molecular orbital methods. The transition wavelengths were estimated to be shorter than 350 nm for long enough molecular chains and the increase of second hyperpolarizabilities with the addition of molecular units manifest nonlinear effects. These results imply that these materials are promising third-order nonlinear optical materials with high hyperpolarizability and good transparency.

Near-Field Optical Study of the Third-Order Nonlinear Properties of Polycrystalline Silicon

Near-Field Optical Study of the Third-Order Nonlinear Properties of Polycrystalline Silicon

Properties of zirconia films dispersed with PbS nanoparticles

PbS/ZrO2 optical films were prepared by the dip-coating method from a mixed sol containing two precursors, Zr(OC3H7)4 and Pb(CH3COO)2. The phase structure and size of PbS nanoparticles were characterized by x-ray diffraction and transmission electron microscopy, respectively. Optical absorption and fluorescence spectra were taken on the PbS/ZrO2 films. Larger blue shifts of band edge and weak fluorescence emission of PbS were observed. The third-order nonlinear properties of PbS/ZrO2 films were studied. The calculated values of nonlinear refractive indexes n2 varied between 10−8 and 10−9 cm2/W.

Third-order optical nonlinear properties of amorphous Si/SiO 2 superlattices fabricated by magnetron sputtering

The nonlinear optical response of amorphous Si/SiO 2 superlattices fabricated by magnetron sputtering are studied using the Z-scan technique. The real and imaginary parts of the third-order optical nonlinearity χ (3) have been measured at 532 nm and found to be 6.392×10 −7 esu and −9.814×10 −7 esu, respectively. The results indicate an enhancement over crystalline silicon and porous silicon, which may be attractive for potential application in electro-optic devices.

Nonlinear materials for information processing and communications

The current state-of-the-art of nonlinear optical materials suitable for ultrafast all-optical applications is discussed. This survey will include progress in the third-order nonlinear properties of semiconductors, polymers and glasses and examples of their applications to devices. Also discussed will be `cascading', a second-order nonlinearity-based approach to all-optical effects.

Synthesis and properties of multifunctional poly(2-trimethylsilyl-1,4-phenylenevinylene): a novel, silicon-substituted, soluble PPV derivative

The novel, silicon-substituted, soluble PPV derivative, poly(2-trimethylsilyl-1,4-phenylenevinylene)(TMS–PPV), is prepared in a solution elimination process and shows high electrical conductivity after I2 doping, high third-order nonlinear susceptibility and green light-emitting properties.

Characterization by guided wave of instabilities of optical coatings submitted to high-power flux: thermal and third-order nonlinear properties of dielectric thin films

We study the reversible refractive index variations of optical thin films submitted to a high-power light flux. As a preliminary step, we study the thermorefractive coefficient ?n/?T and the laser damage threshold of our materials. From the hypothesis of a localized optical Kerr-type effect, we use the m-line technique to estimate the nonlinear refractive-index coefficients n(2) of TiO(2), Ta(2)O(5), and ZnS films with continuous illumination. Very large values of n(2) are found for the films obtained by conventional evaporation condensation. On the other hand, the study of the change in the decoupling direction of a low-power light guided in a layer disturbed by a pulsed YAG laser gives a first analysis of the phenomena versus time.

Third-order nonlinear optical properties of polyazine derivatives

Experimental and theoretical results on third-order nonlinear optical susceptibility χ (3) and molecular hyperpolarizability (γ) of oligomeric and polymeric azines are reported for the first time. Molecular hyperpolarizabilities (γ) of well-defined conjugation length polyazines containing terminal electron-donating amino groups were calculated by employing the ab initio Coupled Perturbed Hartee-Fock with the 6-31G basis set. An azine monomer showed a molecular hyperpolarizability of the order of 14.7×10 −36 esu, which is the largest γ value ever reported for such a short π-electron conjugation length. Molecular hyperpolarizability increases significantly as the length of the π-electron delocalization increases. The γ values for the dimer, trimer, tetramer, and pentamer azine derivatives were 79.0×10 −36, 228.3×10 −36, 575.9×10 −36, and 903.0×10 −36 esu, respectively. Third-order nonlinear optical susceptibilities χ (3) of polyazine derivatives were determined by third-harmonic generation (THG) measurements. The χ (3)(-3ω; ω, ω, ω, ω) values of an azine monomer and a pentamer were 1.39×10 −13 and 15.3×10 −13 esu, respectively. On the other hand, the χ (3) of a polyazine possessing statistically alternating methyl and propyl substituents on the carbon atoms along the chain was found to be 8.0×10 −12 esu at 1.5 μm. The interesting third-order nonlinear properties of polyazines presumably originate from the multiple quantum-well structure of the main π-electron conjugated backbone.

Quantum fluctuations of field sources and optical energy transfer near a surface

The use of a probe tip of subwavelength size can convert evanescent waves lying near a surface into homogeneous ones and makes their detection possible. The author shows that the quantum fluctuations introduce an extra contribution giving rise to a supplementary term in the expression of the detected intensity. A whole quantum calculation of the energy transfer is proposed by including spontaneously fluctuating polarization inside the surface. Analytical results indicate that the change in the intensity depends on the third-order non-linear properties of the detector.

Degenerate four-wave mixing in azo-dye-doped polymer films

We report experimental results for the third-order nonlinear properties of thin polymer films doped with azo dyes, which have long-lived triplet states and can undergo reversible photochromic reactions. Cast films of Disperse Red 1 and Methyl Red in polystyrene and polymethyl methacrylate were investigated by degenerate four-wave mixing with a low-power cw mode-locked laser. Polarization properties and the time dependence of the laser-induced gratings were investigated, and results were compared with those obtained for liquid solutions of the dye in the respective monomers. A phase-conjugate reflectivity of 1% was observed for Disperse Red 1 in polystyrene, with no long-term degradation under laser irradiation.