有机-无机复合材料光波导的制备

有机-无机复合光波导在光通信领域具有重要的应用价值,是目前的研究热点之一.采用溶胶-凝胶法分别制备了膜厚达13μm的光滑平整的PMMA膜和具有紫外感光性的膜厚为1.76μm的SiO2/ZrO2凝胶膜,研究了SiO2/ZrO2凝胶膜的感光性及紫外光照对两种薄膜折射率的影响.在此基础上,以PMMA膜为包层膜,SiO2/ZrO2凝胶膜为芯层膜,实现了光波导的包芯层复合.利用SiO2/ZrO2凝胶膜的感光性,结合紫外掩模技术,制备了条形的有机-无机复合光波导,理论分析表明该复合条形光波导能够实现入射波长为1.31μm,模数为0,1的传输.     

Single-mode optical waveguides fabricated from fluorinated polyimides

Buried channel optical waveguides were fabricated from fluorinated polyimides. They operated in single mode and showed an optical loss of less than 0.3 and 0.7 dB/cm for TE and TM polarizations, respectively, at a wavelength of 1.3 mum. Moreover, these waveguides had high heat and moisture resistance; the optical loss did not significantly change after heating at 380 degrees C for 1 h or after exposure to 85% relative humidity at 85 degrees C for over 200 h.     

Hybrid organic-inorganic ZnS-loaded nanocomposite films for stable optical coatings

Nanocomposite films consisting of a sol-gel hybrid organic-inorganic matrix incorporating ZnS nanocrystals (NCs) have been developed. The nanocomposites films have high visible transparency, enhanced refractive index and photochemical stability. Usage of the diphenyldimethoxysilane and of the ZnS NCs at different concentrations allowed tuning the optical characteristics. Hybrid matrix, NCs and nanocomposite films were characterized by X-Ray Diffraction, High Resolution Transmission Microscopy, spectroscopic ellipsometry, UV-visible and Fourier Transform Infrared Spectroscopy. Applications of nanocomposite films are being investigated as a stable coating for optical purposes.     

Self-assembled nanocomposite of organic-inorganic hybrid: 2,4-dichlorophenoxyacetate in Zn-Al hydrotalcite-like layers

Hydrotalcite-like inorganic layers of Zn-Al, a host containing an organic moiety, 2,4-dichlorophenoxy-acetate, as a guest, was prepared by the spontaneous self-assembly method from an aqueous solution for the formation of a new layered organic-inorganic hybrid nanocomposite material. In this synthesis, the host- and guest-forming species were simultaneously included in the mother liquor, aged, and separated. Various Zn/Al ratios (R = 2, 3, and 4), concentrations of 2,4-dichlorophenoxyacetic acid (0.03-0.1 M), and pH (7 and 10) were studied to optimize the formation of the layered nancomposite. It was found that the optimum conditions for the formation of the nanocomposite were R = 4, pH 7, and concentration of 2,4-dichlorophenoxyacetic acid = 0.08 M. X-ray diffraction shows that this sample affords a nanolayered structure with a basal spacing of 24.6 A.     

Preparation and optical limiting properties of a POSS-containing organic-inorganic hybrid nanocomposite

A novel POSS-containing organic-inorganic hybrid nanocomposite (P) was prepared by the Pt-catalyzed hydrosilylation reaction of octahydridosilsesquioxane (T₈^H) with substituted acetylene, CH≡CCH₂O-C₆H₄-COO-C₆H₄-p-NN-C₆H₄-p-OCH₃ (M). The hybrid nanocomposite was soluble in common solvents such as CHCl₃, THF, toluene and C₂H₄Cl₂. Its structure was characterized by FT-IR, ¹H NMR, and ²⁹Si NMR, respectively. Optical limiting property was evaluated by a Q-switched Nd:YAG laser system with a wavelength of 532 nm, 4 ns pulse width and a repetition of 1 Hz. The result shows that the POSS-based organic-inorganic hybrid nanocomposite exhibits novel optical limiting property, well photo and high thermal stability (T_d, temperature for 5% weight loss, as high as 319 °C). The optical limiting property increases with the increase of solution concentration.     

新型POSS基有机/无机纳米杂化材料的制备及光限幅性能研究

以二苯乙烯衍生物4-乙炔基-4′-硝基二苯乙烯(ENS)和POSS(T8H)为原料,通过钯催化硅氢化反应制备了POSS基有机/无机纳米杂化复合材料(POSS-ENS),并用IR、1H NMR、29Si NMR、UV-vis对其结构进行了表征.同时,对材料的光限幅性能和热性能进行了测试,结果表明,纳米杂化复合材料不仅对532nm、4ns脉宽的激光具有良好的光限幅效应,而且具有很好的光学稳定性和热稳定性能.     

UV written waveguides using crosslinkable PMMA-based copolymers

Crosslinkable copolymers poly(methylmethacrylate/2-methacryloylethylmethacrylate) (P(MMA/MAOEMA)) were developed for waveguide applications. P(MMA/MAOEMA) can crosslink under either UV exposure or heating. The UV-induced refractive index change in unreacted P(MMA/MAOEMA) is found to depend on the fluence. UV exposure of thermally crosslinked P(MMA/MAOEMA) can induce further structure change and thus index change, and therefore, was found to be useful for creating the core layers in optical waveguides. The photosensitivity of the thermally crosslinked polymers is sufficient for the fabrication of low loss (<1 dB/cm) channel waveguides in the thermally crosslinked copolymer system.     

Enhanced optical properties of heterostructured ZnO/CeO2 nanocomposite fabricated by one-pot hydrothermal method: Fluorescence and ultraviolet absorption and visible light transparency

Many researchers investigated the properties of either discrete metal oxide CeO₂ or ZnO materials. However, less attention has been paid to the various nanostructure and performances of CeO₂ and ZnO nanocomposite up to now. In this paper, a facile and low cost one-pot hydrothermal synthesis method has been adopted to obtained directly precursors of CeCO₃OH and Zn₅(CO₃)₂(OH)₆ with different Ce atom molar ratios to Zn, which are transformed into their corresponding metal oxide to form the ZnO/CeO₂ heterostructure nanocomposites (HSNCs) by pyrolysis. The heterostructure is composed of ZnO and CeO₂ monocrystals, simultaneously, CeO₂ monocrystals are well dispersed on the surface of ZnO monocrystal for cosmetics. Bing dependent on the analysis results of XRD and TEM for the obtained precursors before and after pyrolysis, the formation mechanism of HSNCs was proposed. To the best of our knowledge, the paper first reported heterostructured ZnO/CeO₂ nanocomposite grown in one-pot mixed aqueous solution of cerium nitrate, zinc acetate and urea without other extra surfactant. Additionally, the influence of various Ce/Zn molar ratios on the heterostructure, fluorescence emission and UV–visible absorption properties of HSNCs was investigated in detail. ZnO/CeO₂ HSNCs display higher fluorescence emission with the increasing Ce/Zn molar ratio. Meanwhile, the larger Ce/Zn molar ratio of ZnO/CeO₂ HSNCs, the stronger transparency in the visible light region and the weaker UV absorption. The results are due to the fact that the band gap of ZnO/CeO₂ HSNCs will decrease from 3.25 to 3.08 eV when Ce/Zn atom molar ratio is increased from 0 to 0.08. By the comprehensive analysis on the optical performances of HSNCs with the different Ce/Zn atom molar ratios, ZnO/CeO₂-0.04 HSNCs could become UV absorber materials and transparent material in the visible region. ZnO/CeO₂-0.04 HSNCs with the UV-filtering and Vis-transparent properties is appropriate for personal-care cosmetics.     

Stable, low-loss optical waveguides and micromirrors fabricated in acrylate polymers

Acrylate-based optical waveguides have been fabricated with optical loss of 0.5 dB/cm at 1300 nm by means of a new material system that ensures stable optical and mechanical properties over a wide temperature range. No increase in loss was measured after 500 h at temperatures up to 150 degrees C, and there was no significant increase in loss during short (<5 min) temperature excursions to 300 degrees C for bonding. Single-mode waveguides were fabricated with refractive indices for core and clad of 1.505 and 1.500, respectively, so that the mode field is very similar to that of single-mode silica fiber. Guides were fabricated on both planar and structured substrates of Si and GaAs as well as on substrates coated with metals and dielectrics. Fabrication involved spin coating and UV exposure to cross-link the polymer, but the substrate temperature did not exceed 180 degrees C. With this method guides could be fabricated on a range of substrates up to 125 cm in diameter, including those with multilayer metallization for multichip modules, providing optical interconnect capability. Microprism reflecting surfaces were fabricated in the waveguides to couple light out normal to the substrate. All the processing was compatible with normal semiconductor fabrication.     

Preparation and optical properties of organic/inorganic nanocomposite materials by UV curing process

In this study, photo-polymerized poly(acrylic)/silica hybrid thin films were prepared from various acrylic monomers and monodispersed colloidal silica with the coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MSMA). The silica content in the hybrid thin films varied from 0 to 50 wt.%. The experimental results show that the particle size of silica in hybrid films could be effectively controlled at 15–20 nm as the weight ratio of MSMA to colloidal silica is higher than 0.68 and 0.60 for the poly(methyl methacrylate)/silica (US) and poly(ethylene glycol dimethacrylate-trimethylolpropane trimethacrylate)/silica (UDT) hybrid materials, respectively. The polymerization conversion for US and UDT hybrid materials could reach to 100% and 94.5%, respectively. The comparison of surface roughness with the film thickness is less than 0.10%, indicating the excellent surface planarity of the prepared hybrid thin films. Besides, the prepared hybrid films from the crosslinked acrylic polymer moiety show much better film uniformity, thermal stability and mechanical properties than those obtained from poly(methyl methacrylate). The refractive index decreases with increasing the silica content in the hybrid films. Excellent optical transparency is obtained in the prepared hybrid films. These results show that the prepared hybrid thin films have potential applications as passive films for optical devices.     

Metalcones: hybrid organic-inorganic films fabricated using atomic and molecular layer deposition techniques

Hybrid organic-inorganic films can be deposited using atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques. A special set of hybrid organic-inorganic films based on metal precursors and various organic alcohols yields metal alkoxide films that can be described as "metalcones." Many metalcone films are possible such as the "alucones" and "zincones" based on the reaction of trimethylaluminum and diethylzinc, respectively, with various organic alcohols such as ethylene glycol (EG). This paper reviews the previous work on metalcone MLD and discusses a variety of new metalcone systems. "Titanicones" are grown using TiCl4 and glycerol or EG and "zircones" are grown using zirconium tetra-tert-butoxide and EG. In addition, the organic alcohol can also be varied to change the properties within one metalcone family. For example, the glycerol triol precursor allows for more cross-linking and higher toughness in alucones than the EG diol precursor. Alloys can also be formed by combining metalcone MLD and metal oxide ALD. By varying the relative number of cycles of MLD and ALD, the composition and properties of the hybrid organic-inorganic films can be tuned from pure metalcone MLD to pure metal oxide ALD.     

Diffusion-engineered single-photon spectrometer for UV/visible detection

We present predictions for a diffusion-engineered, single-photon spectrometer in the UV–visible range using a superconducting tunnel junction. Quasiparticles are created by photoexcitation, with charge Q₀. After tunneling through the junction, the quasiparticles can either backtunnel or diffuse away. With confinement by a higher gap or by narrow leads the quasiparticles in the counterelectrode dwell next to the junction and backtunnel, increasing the collected charge to Q=pQ₀, p>1. For very narrow leads the dwell time is inversely proportional to the lead width, up to the recombination time of Al, 1 ms at 0.2 K. The new aspect of our work is the use of narrow leads to control the charge gain p, while minimizing self-heating. This charge gain will improve the energy resolution compared to the case p=1, where the electronic noise is dominant, and compared to much larger charge gain, p≈50, where large self-heating resulted with extra noise.     

Modal classification in optical waveguides using deep learning

Single-mode operation is crucial in many on-chip integrated photonic devices, and thus the identification of single-mode geometries is an inevitable design requirement. In this article, we develop deep learning (DL) models for ultra-quick classifications of optical waveguide geometries into single- and multi-modal geometries. The DL model accurately predicts the boundary in the parameter space for the geometry of the waveguide that splits the space into single- and multi-modal regions. Using silicon nitride channel waveguide, and targeting both visible and telecommunication wavelengths, we illustrate how DL models can be developed with a minimal number of exact numerical simulations to Maxwell’s equations.     

Optimization of GTAW Al 3003 weld using fabricated nanocomposite filler metal

Novel Al–3 wt.% TiO₂ (fillers) nanocomposite has been successfully fabricated by accumulative roll bonding method to join Al 3003 alloy with the parameters of gas tungsten arc welding process such as the shielding gas flow rate (G), the welding speed (S), and the current (I) identified by response surface methodology. After preparation of weldment, studies involving X-ray diffraction and advanced electron microscopy techniques (scanning electron microscope and transmission electron microscope) have been carried out. FESEM has revealed the presence of second-phase hard ceramic particles which are embedded homogeneously in the matrix material. Energy dispersive spectroscopy analysis indicates the absence of foreign particles other than Al, Ti, and oxides. Further, the results show that the increase in mechanical properties (hardness and ultimate tensile strength) of the weldment is due to grain refinement and uniform distribution of TiO₂ nanoparticles. The analysis of variance test identified the welding speed as a significant parameter on the homogeneous distribution of TiO₂ particles followed by current and gas flow rate in sequential order.     

Ag/PEO nanocomposite fabricated in a planar magnetron sputtering

Thin films of silver (Ag)/polyethylene-oxide (PEO) nanocomposite were fabricated by a co-deposition of Ag sputtering particles and PEO thin film on substrates using a planar magnetron sputtering system. The PEO were polymerized from the monomer ethyl glycol dimethyl ether in the magnetron sputtering (MS) plasma. The nanocomposites were characterized by using UV-visible spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). The correlation was performed between the concentrations of Ag and functional group density in Ag/PEO nanocomposites with the discharge parameters, such as sputtering gas pressure and the distance of target-to-substrate. By using AFM and XRD, it is illustrated that the Ag particles distribute uniformly in the body of nanocomposite and remain in atomic status with preferential growth in facet of (111).     

Planar optical waveguides in Nd:BSO crystals fabricated by He and C ion implantation

Planar optical waveguides in Nd:BSO crystals were fabricated by the implantation of 500 keV He ions and 6.0 MeV C ions at two different substrate temperatures. The guiding modes were measured by the prism-coupling method with a He-Ne beam at 633 nm. The intensity calculation method (ICM) and reflectivity calculation method (RCM) were used for reconstructing refractive index profiles. The near-field intensity distribution of the waveguide, formed by He and C ions implanted after annealing at 300 °C, was measured by the end-face coupling setup. It was in reasonable agreement with the intensity of the waveguide mode simulated by the finite-difference beam propagation method (FD-BPM). The absorption spectra of the sample with He ions implanted at fluences of 3 × 10¹⁶ ions/cm² were measured using a spectrophotometer.     

Enhanced sensitivity of chemical dosimeters using liquid-core optical waveguides

The spectrophotometric sensitivity of chromophoric chemical dosimeters can be enhanced by increasing the optical path length through the light absorbing medium. This approach is used with optical waveguide (OWG) dosimeters, consisting of liquid-phase light-propagating media filling the core of a long, thin flexible polymer tubing. The liquid phase consists of dimethyl sulfoxide, N, N,-dimethylformamide, or triethyl phosphate solutions of hexa (hydroxyethyl) pararosaniline cyanide, a wellknown radiochromic dye precursor, which on irradiation converts from the leucoform into a brightly colored dye chromophore. The experimental design is described, as well as the influences of some experimental parameters: length of the OWG, curvature of the waveguide loops, cross section of the liquid light-guiding core, the temperature and the solvent. It was shown that concentrations of the radiation-generated dye as low as 5 × 10⁻⁸ mol dm⁻³ (corresponding to absorbed doses of about 10 mGy) can be measured on a standard spectrophotometer using a 100 cm long waveguide. It was also shown that sensitivity (optical absorbance increase per unit length per unit dose) was the same whether the light passed on a straight path or through a multiply looped waveguide as long as 150 cm. It is suggested that such long OWG assemblies can be used for enhancing the response of chemical dosimeters for medical and radiation protection applications, as well as in analytical chemistry and for chemical kinetics studies.     

Refractive indices and thicknesses of optical waveguides fabricated by silicon ion implantation into silica glass

Planar optical waveguides formed by Si ion implantation into PECVD SiO₂ have been characterized by the dark mode spectroscopy method at a wavelength of 0.6328 μm. The measured effective index values of the guided modes have been used to investigate the optical properties of the core layers of the waveguides after different pre-implantation treatments. It was found that annealing the specimens before implantation, affected both the refractive index and thickness of the core layers. In the annealed specimens a thicker core layer and a larger relative refractive index difference between the core and the buffer layer resulted.