Azobenzenes for photonic network applications: Third-order nonlinear optical properties

We review the third-order nonlinear performance of pseudo-stilbene type azobenzenes with an eye to application in ultrafast optical signal processing. We discuss mechanisms responsible for the nonlinear response of the azobenzenes. By aggregating experimental data and theoretical trends reported in the literature, we identify five characteristic regions of optical nonlinear response. Analyzed with respect to Stegeman figures of merit, pseudo-stilbene type azobenzenes show promise for ultrafast optical signal processing in two spectral regions, one lying between the main and two-photon absorption resonances, and the other for wavelengths longer than the two-photon absorption resonance. © 2001 Kluwer Academic Publishers     

新型双光子聚合引发剂的合成和非线性光学性质的研究

合成了两种新的双光子聚合引发剂反式-二苯基-{{4-[2-(4-吡咯基-1-苯基)-乙烯基]-苯基}胺(简称DPVPA)和反式-9-{4-[2-(4-吡咯基-1-苯基)-乙烯基]-苯基]-9-氢咔唑(简称PPVPA).用1H NMR谱和元素分析进行了表征.测试了紫外吸收光谱、单光子荧光光谱、单光子荧光寿命和双光子荧光光谱.在760 nm的飞秒脉冲激光激发下,DPVPA和PPVPA均发出较强的上转换荧光,荧光峰分别位于468和452 nm.以DPVPA做引发剂,加入丙烯酸酯型齐聚物(CN120C80),用DATACHROOM-5000纳秒激光器辐射出600nm的激光做光源,实现了双光子聚合反应,并定性地解释了其聚合机理.     

A numerical scheme for nonlinear Helmholtz equations with strong nonlinear optical effects

A numerical scheme is presented to solve the nonlinear Helmholtz (NLH) equation modeling second-harmonic generation (SHG) in photonic bandgap material doped with a nonlinear χ((2)) effect and the NLH equation modeling wave propagation in Kerr type gratings with a nonlinear χ((3)) effect in the one-dimensional case. Both of these nonlinear phenomena arise as a result of the combination of high electromagnetic mode density and nonlinear reaction from the medium. When the mode intensity of the incident wave is significantly strong, which makes the nonlinear effect non-negligible, numerical methods based on the linearization of the essentially nonlinear problem will become inadequate. In this work, a robust, stable numerical scheme is designed to simulate the NLH equations with strong nonlinearity.     

Functionalized gold nanoparticles self-assemblies with efficient nonlinear optical properties

Satellite-patterns aggregate structures of gold nanoparticles were fabricated by the inducing pi-pi stacking interactions. The self-assembly process of satellite-patterns was tuned by the controlling ligand exchange on the surface of spherical gold nanoparticles, which provide a novel concept and an efficient method for controlling self-assembly of gold nanoparticles. With increasing the porphyrin alkanethiol ratio (r) of gold nanoparticles, the self-assembly induces to form the larger satellite-structures. The study indicates that exchange process of tetra-n-octylammonium bromide molecules and porphyrin alkanethiol molecules results in the formation of satellite-pattern structures with topological features. Nonlinear optical properties of porphyrin alkanethiol capped gold nanoparticles of toluene solution were measured using the Z-scan technique, and its third-order nonlinear optical susceptibility (chi(3)) is calculated as 0.9 x 10(-13) esu, presented the third-order nonlinear optical properties. The well-ordered assembly of gold nanoparticles exhibits controlled the third-order nonlinear optical properties, which can be enhanced with the increasing of the porphyrin alkanethiol ratio in systems.     

Synthesis and nonlinear optical properties of two new two-photon initiators: Triphenylamine derivatives

Two new two-photon polymerization initiators, 1-{(1E)-2-[4-(diphenylamino)phenyl]vinyl}-4-[4-N,N-di-methylamino]benzene (PVMB) and 1-[(1E)-2-(4-{[4-((1E)-2-{4-[4-N,N-di-methylamino]phenyl}vinyl)phenyl]phenylamino}phenyl)vinyl]-4-[4-N,N-di-methylamino]benzene (DPVMB) have been synthesized with solid phase Wittig reaction. The single-photon fluorescence, quantum yields, lifetimes, solvent effects of the initiators were studied in detail and both compounds exhibited solvent-sensitivity. Two compounds are good two-photon absorbing chromophores and operative two-photon photopolymerization initiators. Two-photon absorption (TPA) cross-sections from 730 nm to 870 nm at intervals of 10 nm have been measured with the two-photon-induced fluorescence method, and the maximal values of the TPA cross-sections of PVMB and DPVMB are 1.6 GM and 19.9 GM (1 GM = 1 × 10⁻⁵⁰ cm⁴ s photon⁻¹ molecule⁻¹) at 800 nm, respectively. A microstructure has been fabricated by using DPVMB as initiator.     

Synthesis and nonlinear optical properties of two new two-photon initiators: Triphenylamine derivatives

Two new two-photon polymerization initiators, 1-{(1E)-2-[4-(diphenylamino)phenyl]vinyl}-4-[4-N,N-di-methylamino]benzene (PVMB) and 1-[(1E)-2-(4-{[4-((1E)-2-{4-[4-N,N-di-methylamino]phenyl}vinyl)phenyl]phenylamino}phenyl)vinyl]-4-[4-N,N-di-methylamino]benzene (DPVMB) have been synthesized with solid phase Wittig reaction. The single-photon fluorescence, quantum yields, lifetimes, solvent effects of the initiators were studied in detail and both compounds exhibited solvent-sensitivity. Two compounds are good two-photon absorbing chromophores and operative two-photon photopolymerization initiators. Two-photon absorption (TPA) cross-sections from 730 nm to 870 nm at intervals of 10 nm have been measured with the two-photon-induced fluorescence method, and the maximal values of the TPA cross-sections of PVMB and DPVMB are 1.6 GM and 19.9 GM (1 GM = 1 × 10⁻⁵⁰ cm⁴ s photon⁻¹ molecule⁻¹) at 800 nm, respectively. A microstructure has been fabricated by using DPVMB as initiator.     

A donor-nanotube paradigm for nonlinear optical materials

Studies of the nonlinear electronic response of donor/acceptor substituted nanotubes suggest a behavior that is both surprising and qualitatively distinct from that in conventional conjugated organic species. We find that the carbon nanotubes serve as both electronic bridges and acceptors, leading to a donor-nanotube paradigm for the effective design of large first hyperpolarizabilities. We also find that tuning the donor orientation, relative to the nanotube, can significantly enhance the first hyperpolarizability.     

An effective-medium approach to the optical properties of heterogeneous materials with nonlinear properties

Abstract

We have derived an analytic approach, based on the hypothesis of the effective-medium theory, to evaluate the effective dielectric magnitudes, including the effective third order nonlinear optical susceptibility α(χ⁽³⁾), of a heterogeneous two-component medium in which one of the components (the host matrix or the embedded particle respectively) presents nonlinear behaviour. Our formulation allows us to solve the full nonlinear problem in the whole range of concentrations without treating the nonlinear effects as a small perturbation to the linear behaviour. Therefore, it can be considered as an upper limit of the commonly used low-field nonlinear approximations for heterogeneous materials. Under certain conditions, these composites can exhibit a bistable regime that the present theory properly describes in wide ranges of the concentration, shape, wavelength, dielectric contants and intrinsic nonlinear optical susceptibility of the nonlinear component as well as in terms of the intensity of the external electric field. The present approach has been used to calculate the nonlinear optical response of Cu—Al₂O₃ nanocomposites.     

Two new asymmetrical two-photon photopolymerization initiators: Synthesis, characterization and nonlinear optical properties

Two new asymmetrically free-radical two-photon photopolymerization initiators, Diphenyl-{4-[2-(4-pyrrolidin-1-yl-phenyl)-vinyl]-phenyl}-amine (abbreviates to DYVPA) and 9-{4-[2-(4-Pyrrolidin-1-yl-phenyl)-vinyl]-phenyl}-9H-carbazole (abbreviates to PPVPA), have been synthesized and characterized. Linear absorption, one-photon fluorescence emission and their lifetimes, and two-photon fluorescence emission have been investigated. The calculated two-photon absorption cross-sections of DYVPA and PPVPA are 70.1 and 28.0 × 10⁻⁵⁰ cm⁴ s photon⁻¹, respectively. Microfabrications via two-photon initiating polymerization have been studied and the possible photopolymerization mechanism is discussed.     

Two-photon pumped upconversion and nonlinear optical properties of a new lasing dye: HMASPS

Abstract

Two-photon pumped frequency upconversion optical properties and two-photon absorption (TPA) induced nonlinear absorption of a new dye, trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium ptoluene sulfonate (abbreviated to HMASPS) have been experimentally investigated. This new dye exhibits strong superradiation properties when the pumping power is above its threshold. The superradiation upconversion efficiency from 900 to 1150 nm and the nonlinear absorption from 720 to 1100 nm have been measured. The largest effective molecular TPA cross-section was measured to be 44.3 × 10^?48 cm⁴·s·photon^?1at 920 nm. At 1064 nm, it was 2.77 × 10^?48 cm⁴·s·photon^?1, much smaller than that at 920 nm. The highest conversion efficiency is 7% at 990 nm, whereas 4.2% at 1064 nm.     

Rh:BaTiO3 thin films with large nonlinear optical properties

We report the fabrication and the nonlinear optical properties of Rh-doped BaTiO3 thin films. The films were deposited on SrTiO3 (100) substrates by pulsed-laser deposition. The deposited Rh:BaTiO3 thin films were single phase and c-axis orientation investigated by x-ray diffraction. The films exhibited large nonlinear optical effects, which were determined using Z-scan technique at a wavelength of 532 nm with a laser duration of 10 ns. The real and imaginary parts of the third-order nonlinear susceptibility chi (3) were 5.71 x 10(-7) esu and 9.59 x 10(-8) esu, respectively. The value of Re chi (3) of Rh:BaTiO3 films is much larger than those of several representative nonlinear optical thin films. The results show that Rh:BaTiO3 thin films have great potential applications for nonlinear optical devices.     

Enhanced third-order nonlinear optical properties in dendrimer-metal nanocomposites

Nonlinear optical (NLO) and time-resolved fluorescence spectroscopic measurements of dendrimer-metal nanocomposites (DNCs) are reported. Third-order NLO effects were investigated by degenerate four-wave mixing (DFWM) measurements for DNCs and DNCs incorporated into thin polymeric films. The results show an enhancement of the third-order nonlinear susceptibility for the chromophore-functionalized dendrimer-metal nanocomposites. Investigations of the mechanism of the enhanced NLO effect suggested a strong contribution because of the metal's local field. These results show the potential usefulness of dendrimer-metal nanocomposites for nonlinear optical effects and biophotonic applications.     

Stability and nonlinear optical properties of ZnO nanoparticles

Photoluminescence (PL) of ZnO nanoparticles of different surface states and sizes grown by several methods has been measured. The origin of luminescence and dependence of the luminescence spectrum shape and intensity on 325 nm excitation laser power are studied. Strong ultraviolet emission at 3.26 eV, weak violet emission around 3.12 eV and weak green emission at 2.40 eV have been observed in 16 nm nanoparticles capped by octylamine grown by non-hydrolytic method. The nanoparticles are stable under high power laser radiation and their PL intensity increases nonlinearly with an increasing laser power. As the nanoparticle size decreases to 12 nm, high power laser produces nonradiative centers which may quench the luminescence in a degree. Nanoparticles of 8 nm capped by PVP and uncapped nanoparticles of 14 nm are unstable and their luminescence depends on the excitation laser power. High power laser can quench O vacancy emission and enhance ultraviolet emission in PVP capped nanoparticles while vacancy emission can not be quenched in uncapped nanoparticles.     

紫外、深紫外非线性光学晶体的最新进展

深紫外相干光源对于光刻技术、光电子能谱仪、激光精密机械加工等均具有十分重要的意义.本文将系统地阐述可产生深紫外谐波光输出的非线性光学晶体是如何被发现的,这些晶体的基本线性、非线性光学性质和使用它们产生深紫外谐波光的方法.最后还简单介绍深紫外谐波光的几个典型例子.     

Oxygen plasma flow properties deduced from laser-induced fluorescence and probe measurements

Estimation of the local dissociation degree and the local mass-specific enthalpy of a pure oxygen plasma flow determined mainly from laser-induced fluorescence measurements are reported. Measurements have been conducted for several generator parameters in an inductively heated plasma wind tunnel. Additional probe measurements of total pressure together with the deduced translational temperature are used to estimate the local mass-specific enthalpy. For a reference condition, full dissociation has been measured. The measured translational temperature of atomic oxygen for this condition is T = 3500 K. Subsequently, the local mass-specific enthalpy has been derived using these local density and temperature measurements. For the reference condition the estimated value of h = 27 MJ/kg is in good agreement with the probe measurements and results from diode laser absorption spectroscopy.     

新型铁离子荧光探针的合成与性质研究

设计、合成了一种基于α-氨基蒽醌和8-羟基喹啉的金属离子荧光探针3。在DMF溶液中该探针本身有荧光,当加入Fe3+后,其在358nm处产生明显的荧光淬灭,而其它金属离子基本上无明显的荧光淬灭现象,该化合物是一种高选择性的Fe3+荧光探针。