Third-order nonlinear optical characteristics of bulk film effect on regioregular poly(3-dodecylthiophene) thin films fabricated by the drop-casting method

We report the morphologies and the bulk film effect on regioregular poly(3-dodecylthiophene) [RR-P3DDT] thin films fabricated with different concentrations (0.1, 0.2, 0.4 wt%) by drop-casting method using chloroform as a solvent and fused quartz glass as substrate. The measured thicknesses of the films were 220, 340 and 600 nm. The thin films were characterized by UV–Vis spectra and X-ray diffraction. The surface morphology of the thin film (600 nm) was analyzed using atomic force microscopy. The third order nonlinear susceptibility characteristics of the films were measured using Maker fringes method. These films exhibit efficient THG bulk effect with a maximum χ³ value of 1.41 × 10^?10 esu obtained for 0.4 wt% concentration of RR-P3DDT revealing that this material is potentially suited for fabricating optical limiters.     

One-dimensional silicon nanostructures fabricated by thermal evaporation

One-dimensional silicon nanostructures were fabricated by evaporating silicon monoxide (SiO) powders at 1050 °C and collecting the products on gold-coated silicon substrates. The uniform and dense silicon nanowires with the diameter of about 20–30 nm and the length of tens of microns were observed. However, the tufts of silicon nanowires were found while the silicon substrates without gold coating were used. Moreover, the chain-like silicon nano-structures with obvious core-shell morphology that displays a homojunction structure composed of cylindrical section and the oscillating section was also found. Finally, the biforked silicon nanowires with the same diameter of branches were detected, which is hard to understand on the current growth mechanism of silicon nanowires.     

Ultrafast nonlinear optical properties of TiO2 nanoclusters at 850 nm

We discuss nanoclusters of titanium dioxide, bulk CdTe and CS₂ as characteristic materials to illustrate two main ideas; firstly, it is possible to argue about the origin of the nonlinearity even with a high repetition laser, provided that you have as large a peak power (50 kW) as the one found in femtosecond lasers. Secondly, the search for dimensional confinement to enhance nonlinear optical properties has experienced some difficulties with conflicting results. We show that electronic nonlinear behavior increases from TiO₂, CS₂ to CdTe and the nonlinear thermal effect increases from CS₂, CdTe to TiO₂.     

Characteristics of polymeric optical passive single-mode waveguiding devices fabricated by an argon-ion laser

The fabrication of polymeric single-mode Gaussian profile optical waveguides is described. We used poly(methyl methacrylate) and a mixture of two intermiscible monomers for the cladding and the core, respectively, of the waveguides. The cores of the waveguides were fabricated by with an argon-ion laser beam. The waveguides had single-mode Gaussian refractive-index profiles. By using such waveguides, we fabricated directional couplers for power coupling to the adjacent waveguides and also parallel waveguide arrays for preventing power coupling to adjacent waveguides for use in interconnect chips. We analyzed the characteristics of these couplers by using the coupled-mode theory and compared the results with those obtained with the beam propagation method. Experimental results showed good correlation with the theoretical values. We designed optical bus arrays for interconnect chips, considering the variation of normalized frequency V, the power penalty, and the dimensions of the waveguides and the separation between them. The number of waveguides in the bus array increased with increasing V. For a known value of V, a waveguide's density increases with a decrease of its dimensions. The theoretical maximum number of waveguides is ~1490/cm and ~846/cm for 2 mum x 2 mum and 4 mum x 4 mum single-mode waveguides, respectively, to satisfy a 1-dB power penalty criterion at bit-error rate of 10(-9). We fabricated interconnect bus arrays with fifteen 4 mum x 4 mum waveguides for a 3-cm coupling length, and the experimental results were verified to be in good agreement with the theoretical values.     

Planar waveguides formed by Ag+-Na+ ion exchange in nonlinear optical glasses: diffusion and optical properties

All-optical communication systems are the subject of intense research related to the integration of nonlinear optical materials. In sodiocalcic borophosphate glasses that contain niobium oxide and exhibit high nonlinear optical indices, planar waveguides have been formed by a Ag(+)-Na(+) ion-exchange technique. WKB analysis has been used to characterize the diffusion profiles of silver ions exchanged in glass substrate samples chemically by an electron microprobe technique and optically by an M-line technique. These methods permit the Ag(+) penetration depth and diffusion profile shape and index profiles to be determined. The results are analyzed and discussed in relation to Ca(2+) concentration and exchange conditions in glasses. The Ag(+) diffusion in these glasses can be almost entirely controlled for index-profile engineering.     

Shape memory effect in porous volume NiTi articles fabricated by selective laser sintering

The shape memory effect in porous nickel titanium (NiTi) articles obtained by means of layered synthesis using selective laser sintering (SLS) technology was studied by measuring the temperature dependence of the electric resistivity of the material. For the porous NiTi samples synthesized from Ni and Ti powders, the interval of probable appearance of the shape memory effect falls within the temperature interval from −50 to 0°C. In a porous material synthesized by laser sintering from a commercial NiTi powder of the PV N55T45 grade, this effect falls in the interval from +25 to +50°C. Prospects for the use of porous NiTi articles as medicinal implants are discussed.     

Mesoscale dynamics and cooperativity of networking dendronized nonlinear optical molecular glasses

First, molecular scale insight into the mobility of a novel class of organic materials for photonic applications with electro-optical activities larger than 300 pm/V is presented. A representative second order nonlinear optical (NLO) material of this class of self-assembling molecular glasses involving quadrupolar phenyl-perfluorophenyl (Ph-PhF) interactions is analyzed based on its molecular relaxation phenomena and phase behavior. Thereby, a new and straightforward nanoscale methodology, involving shear modulation force microscopy and intrinsic friction analysis is introduced. It provides both the submolecular enthalpic and entropic dynamics in nanoconstrained systems (e.g., ultrathin films), and thus, insight into local motion of single molecules due to dissociation of Ph-PhF pairs as well as the cooperative dynamics of the assembled network. This nanoscale model-independent thermomechanical methodology is shown to be very effective in fundamentally evaluating appropriate poling conditions of organic NLO materials. It promises to be a straightforward analysis tool to guide organic material synthesis from a molecular mobility perspective, particularly for applications that impose nanoscale constraints on the system.     

一种微型转子的激光加工和光致旋转

利用单束强聚焦激光产生的光学力可以驱动微型器件,具有无机械接触和无需导线等优点,为微型机电系统提供了一种新型的驱动方式。在自行研制的飞秒激光微细加工系统中,采用一种新型的丙烯酸酯紫外光固化树脂,通过双光子聚合加工出直径6μm的万字形微转子。利用光镊装置实现了微转子的俘获,并在激光功率50mW时实现了转速为200rpm的光致旋转。微型转子的光致旋转为实现微机械马达提供了一种有效手段。     

Structural and optical properties of tellurite thin film glasses deposited by pulsed laser deposition

Tellurite (TeO₂-TiO₂-Nb₂O₅) thin film glasses have been produced by pulsed laser deposition at room temperature at laser energy densities in the range of 0.8-1.5 J/cm² and oxygen pressures in the range of 3-11 Pa. The oxygen concentration in the films increases with laser energy density to reach values very close to that of the bulk glass at 1.5 J/cm², while films prepared at 1.5 J/cm² and pressures above 5 Pa show oxygen concentration in excess of 10% comparing to the glass. X-ray photoelectron spectroscopy shows the presence of elementary Te in films deposited at O₂ pressures ≤ 5 Pa that is not detected at higher pressures, while analysis of Raman spectra of the samples suggests a progressive substitution of TeO₃ trigonal pyramids by TeO₄ trigonal bipyramids in the films when increasing their oxygen content. Spectroscopic ellipsometry analysis combined with Cauchy and effective medium modeling demonstrates the influence of these compositional and structural modifications on the optical response of the films. Since the oxygen content determines their optical response through the structural modifications induced in the films, those can be effectively controlled by tuning the deposition conditions, and films having large n (2.08) and reduced k (< 10^− 4) at 1.5 μm have been produced using the optimum deposition conditions.     

Structural and optical quality of binary photonic crystal heterostructures fabricated by the modified self-assembly method

Photonic crystal heterostructures constituting of two photonic crystals with different lattice constants are fabricated using the modified self-assembly method and their structural and optical properties are investigated. The results show that these photonic crystal heterostructures of high quality possess deep photonic band gaps and steep photonic band edges in their transmission spectra. Deep double photonic band gaps, steep photonic band edges and high transmittance in the pass band show good ordering of the heterostructure and may offer a probability for studying late-model ultra-fast all-optical switches.     

激光制备超疏水表面研究进展

由于超疏水表面在防腐、油水分离、流体减阻和液体转移方面的应用潜力,如何制作性能优异的超疏水表面成为研究热点。材料表面的形貌特征是决定其润湿性能的一个重要因素,因此,通常采用表面结构化来获得超疏水性能。在材料表面构织微纳结构方面,基于脉冲激光的微纳加工技术具有得天独厚的优势,尤其是在制作特定图案的复杂结构方面。本文根据激光器的脉冲宽度分类,通过刻蚀后材料表面形貌和润湿性特征对激光制作超疏水表面的基本理论和典型工艺方法进行介绍和总结,并对超疏水表面的发展前景作出展望。

     

Large-mode-area leaky optical fiber fabricated by MCVD

A large-mode-area single-mode optical fiber based on leaky-mode filtering was prepared by a modified chemical vapor deposition (MCVD) technique. The fiber has a leaky cladding that discriminates the fundamental mode from higher-order modes. A preliminary version has a 25 μm core diameter and 0.11 numerical aperture. A Gaussian-like mode with 22 μm mode field diameter was observed after 3 m propagation, in agreement with modeling.     

Ultrafast stretched-pulse fiber laser mode-locked by carbon nanotubes

Ultrafast fiber sources having short pulses, broad bandwidth, high energy, and low amplitude fluctuations have widespread applications. Stretched-pulse fiber lasers, incorporating segments of normal and anomalous dispersion fibers, are a preferred means to generate such pulses. We realize a stretched-pulse fiber laser based on a nanotube saturable absorber, with 113 fs pulses, 33.5 nm spectral width and ?0.07% amplitude fluctuation, outperforming current nanotube-based designs.     

Third order nonlinear optical characterization of new chalcohalogenide glasses containing lead iodine

The vitreous formation in a new chalcohalogenide system based on As, Sb, Bi, S, Pb and I has been studied. Wide vitreous regions have been identified both in the ternary As₂S₃–Sb₂S₃–PbI₂ system and in the quaternary As₂S₃–Sb₂S₃–Bi₂S₃–PbI₂ system. More particularly, in the latter case, the vitreous regions have been investigated and established for the two layers of the system corresponding respectively to 10% and 20% molar of Bi₂S₃. Due to the richness of these new glasses in highly polarizable elements, they are of interest for the implementation of high nonlinear optical properties. To explore the potentialities of chalcogenide glasses for ultra-fast optical applications, the nonlinear refractive indices (real and imaginary part) of different compositions are measured. Nonlinear measurements have been performed through a pump/probe experiment using a Mach-Zehnder interferometer coupled to a CCD camera. The measured values are as high as 16×10⁻¹⁸ m²/W for the nonlinear refractive index and 6 cm/GW for the nonlinear absorption.     

Optical properties of NiO thin films fabricated by electron beam evaporation

Nickel oxide (NiO) thin films were deposited onto quartz substrates by the electron beam deposition technique, and obtained high crystal quality after annealing at 1173 K. The structural and microstructural properties of the films were studied by X-ray diffraction (XRD) and atomic force microscope (AFM), respectively. We focus on the optical characterization of the films, indicating the enhancement of the crystal quality, which was confirmed by the photoluminescence and Raman spectrum. Furthermore, PL studies exhibited room temperature emission at 377 nm, and also shown high ultraviolet/visible rejection ratio (>100).     

Multiwell laser heterostructures fabricated by liquid-phase epitaxy

A methodology has been developed for growing InGaAsP/InP multiwell laser heterostructures by liquid-phase epitaxy. Depth profiling using a secondary ion mass spectrometer was used to investigate the distribution profiles of the composition of multiwell laser heterostructures. Liquid-phase epitaxy was used to fabricate InGaAsP/InP multiwell laser heterostructures with active regions having emission wavelengths of 1.3 and 1.55 μm and their radiative characteristics were studied. Pis’ma Zh. Tekh. Fiz. 24, 61–67 (November 12, 1998)     

Structural and optical characterization of CuInS2 thin films grown by vacuum evaporation method

Structural and optical properties of CuInS₂ thin films grown by the single-source thermal evaporation method have been studied. The films were annealed from 100 to 500 °C after an evaporation in air. The surface morphology was investigated by scanning electron microscopy. The maximum grain size of the samples after annealing at 400 °C was over 500 nm. The EPM analysis concluded that the polycrystalline CuInS₂ thin films after annealing below 100 °C were Cu-rich, and those annealed above 200 °C were In-rich. The bandgap energy of the CuInS₂ films after annealing above 300 °C was about 1.48 eV.     

Ultrafast dynamics of copper nanoparticles embedded in soda-lime silicate glass fabricated by ion exchange

Copper nanoparticles embedded in soda-lime glass were fabricated by ion exchange followed by thermal treatment in hydrogen. The ultrafast dynamics of the embedded Cu nanoparticles formed under different fabrication conditions were investigated by applying femtosecond pump-probe technique. Non-Fermi electrons were suggested to be dominant in the transient behavior of the nanocomposites far from surface plasmon resonance of Cu. The long ion-exchange processing time was found to benefit and improve the ultrafast response of the fabricated nanocomposites.