无催化热蒸发ZnS粉末制备半导体ZnO纳米带

通过无催化物理热蒸发ZnS粉末的方法首次制备了互相平行交叉的纤锌矿ZnO纳米带,X射线衍射分析和扫描电镜检测显示所制得的ZnO纳米带沿着它们的长度是平滑而单一的纤锌矿结构.合成的纳米带长度数十微米,宽度几百纳米.同时对纳米带的生长机制作了详细讨论.     

Electrically pumped waveguide lasing from ZnO nanowires

Ultraviolet semiconductor lasers are widely used for applications in photonics, information storage, biology and medical therapeutics. Although the performance of gallium nitride ultraviolet lasers has improved significantly over the past decade, demand for lower costs, higher powers and shorter wavelengths has motivated interest in zinc oxide (ZnO), which has a wide direct bandgap and a large exciton binding energy. ZnO-based random lasing has been demonstrated with both optical and electrical pumping, but random lasers suffer from reduced output powers, unstable emission spectra and beam divergence. Here, we demonstrate electrically pumped Fabry-Perot type waveguide lasing from laser diodes that consist of Sb-doped p-type ZnO nanowires and n-type ZnO thin films. The diodes exhibit highly stable lasing at room temperature, and can be modelled with finite-difference time-domain methods.     

Luminescence of CVD ZnO nanocrystals of different shapes

The effect of the shape and dimensions of zinc oxide nanocrystals on the threshold and directionality of UV lasing in the nanocrystals has been investigated. The results indicate that hexagonal columnar nanocrystals have the lowest optical threshold pump power at nanoresonator diameters of 100–200 nm, comparable to the absorption path length of the excitation light. The laser radiation is shown to have a mode structure, being directed predominantly along the prism axis. The lasing mechanism in prismatic nanocrystals differs from that in hexagonal-pyramidal nanocrystals. Electron microscopy results show that the ZnO nanocrystals are highly uniform in shape and size and that these parameters depend on the chemical vapor deposition conditions.     

Three-photon absorption induced whispering gallery mode lasing in ZnO twin-rods microstructure

The ZnO twin-rods microstructure synthesized by hydrothermal method was employed as a whispering gallery mode lasing microcavity. The growth mechanism of the ZnO twin-rods single crystal was analyzed. Three-photon absorption induced whispering gallery mode lasing with low threshold was observed under the excitation of femtosecond pulses at 800 nm. The spectra from the individual branch and the connection part were investigated, and the whispering gallery mode lasing mechanism was discussed.     

Phase-correlated nondirectional laser emission from the end facets of a ZnO nanowire

We investigated the laser emission from individual ZnO nanowires and observed an interference pattern due to coherent laser emission from the wire end facets. Comparison with numerical simulations shows that the laser light is emitted nearly spherically from the wire ends. The energy spacing between sharp lasing modes scales with the inverse length of the nanowire; thus, laser emission peaks correspond to Fabry-Pérot modes of the nanowire cavity.     

Plasmon enhancement for Vernier coupled single-mode lasing from ZnO/Pt hybrid microcavities

It is essential to develop a single mode operation and improve the performance of lasing in order to ensure practical applicability of microlasers and nanolasers.In this paper,two hexagonal microteeth with varied nanoscaled air-gaps of a ZnO microcomb are used to construct coupled whispering-gallery cavities.This is done to achieve a stable single mode lasing based on Vernier effect without requiring any complicated or sophisticated manipulation to achieve positioning with nanoscale precision.Optical gain and the corresponding ultraviolet lasing performance were improved greatly through coupling with localized surface plasmons of Pt nanoparticles.The ZnO/Pt hybrid microcavities achieved a seven-fold enhancement of intensity of single mode lasing with higher sidemode suppression ratio and lower threshold.The mechanism that led to this enhancement has been described in detail.     

Lasing in hydrothermally grown ZnO nanocrystals

Micro- and nanocrystalline ZnO powders and films have been prepared under mild hydrothermal conditions, and their spectroscopic and lasing properties have been investigated. The polycrystalline ZnO films showed stimulated emission with a lasing threshold of 0.67 MW/cm². Analysis of their lasing behavior suggests that the stimulated emission is generated by individual crystallites, each acting as a microlaser.     

Facile synthesis, optical and photoconductive properties of novel ZnO nanocones

Large-scale, uniform ZnO nanocones with tips about 200 nm and length about 50 μm have been synthesized by a facile hydrothermal method. The morphology and structures were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and high-resolution transmission electron microscope (HR-TEM). The effects of reaction time and PEG-400 on the morphology of ZnO nanostructures were investigated, also an oriented attachment mechanism has been briefly proposed. The optical properties were investigated by lasing confocal microscope and photoluminescence spectrum, a strong near band edge emission peak centered at 387 nm from the ZnO nanocones was observed in photoluminescence spectrum. Finally, we have fabricated UV photodetector based on single ZnO nanocone, which present good switching properties by turning the UV light on and off.     

Ultraviolet lasing action in ZnO nanosheets

We report room-temperature ultraviolet lasing action in large quantities of uniform multilayer ZnO nanosheets grown by a vapor-transport method via thermal evaporation of Zn powder. An excellent multimode lasing emission at a center wavelength of 390 nm with a mode linewidth less than 0.33 nm occurs above an excitation threshold of 8 mJ pulse(-1) cm(-2). The observed multimode lasing action may be attributed to microcavity effect and low concentration of defects in the nanosheets. We believe that the single-mode lasing emission can be obtained by growing completely uniform nanosheets. ZnO nanosheet is an attractive candidate as gain medium to realize ultraviolet semiconductor diode lasers.     

Blue-shifted stimulated emission from ZnO films deposited on SiO2 by atomic layer deposition

ZnO films were prepared by atomic layer deposition upon a SiO₂ layer on a Si substrate and treated by rapid thermal annealing. The optically-pumped random lasing actions with low threshold values were observed in the ZnO films on SiO₂/Si substrates. With the decrease in ZnO film thickness or the increase in post-annealing duration, the stimulated emission shifted toward the shorter wavelength and the lasing threshold increased. The results can be attributed to the inter-diffusion between ZnO and SiO₂, which causes the modification of bandgap renormalization in ZnO.     

Synergistic graphene/aluminum surface plasmon coupling for zinc oxide lasing improvement

Collective oscillations of free electrons generate plasmons on the surface of a material.A whispering-gallery microcavity effectively confines the light field on its surface based on the total reflection from its internal wall.When these two kinds of electromagnetic waves meet each other,the stimulated emissions from an individual ZnO microrod were enhanced more than 50-fold and the threshold was reduced after the whispering-gallery microcavity was coated with a monolayer of graphene and A1 nanoparticles.The improvement of the lasing performance was attributed to the synergistic energy coupling of the graphene/Al surface plasmons with ZnO excitons.The lasing characteristics and the coupling mechanism were investigated systematically.     

腔长损耗对非本征F-P腔光纤传感器的影响

根据光学法布里-珀罗(F-P)腔基本原理,运用单模光纤能量散射模型分析了腔长损耗对非本征F-P腔输出光强度的影响.实验过程中所用的F-P腔由单模光纤端面和弹性硅片组成.实验结果表明,非本征F-P腔输出光强幅度随腔长增大逐渐衰减,其输出特性曲线中不同部分相同周期的线性工作区间却对应不同的测量量程和灵敏度,所以强度型光纤F-P腔传感器初始腔长应基于传感器的性能指标进行选取.     

Facile preparation of Ag/ZnO nanoparticles via photoreduction

Ag/ZnO nanoparticles can be obtained via photocatalytic reduction of silver nitrate at ZnO nanorods when a solution of AgNO₃ and nanorods ZnO suspended in ethyleneglycol is exposed to daylight. The mean size of the deposited sphere like Ag particles is about 5 nm. However, some of the particles can be as large as 20 nm. The ZnO nanorods were pre-prepared by basic precipitation from zinc acetate di-hydrate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide. They are about 50–300 nm in length and 10–50 nm in width. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDS), X-ray powder diffraction (XRD), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) were used to characterize the resulting Ag/ZnO nanocomposites.     

Lateral composition-graded semiconductor nanoribbons for multi-color nanolasers

Low-dimensional semiconductor nanostructures have attracted much interest for applications in integrated photonic and optoelectronic devices. Band gap engineering within single semiconductor nanoribbons helps to manipulate photon behavior in two different cavities (in the width and length directions) and realize new photonic phenomena and applications. In this work, lateral composition-graded semiconductor nanoribbons were grown for the first time through an improved source-moving vapor phase route. Along the width of the nanoribbon, the material can be gradually tuned from pure CdS to a highly Se-doped CdSSe alloy with a corresponding band gap modulation from 2.42 to 1.94 eV. The achieved alloy ribbons are overall high-quality crystals, and the position-dependent band-edge photoluminescence (PL) emission had a peak wavelength continuously tuned from ~515 to ~640 nm. These ribbons can realize multi-color lasing with three groups of lasing modes centered at 519, 557, and 623 nm. It was confirmed that the red lasing was from optical resonance along the length direction, while the green and yellow lasing was from optical resonance along the width direction. These novel nanoribbon structures may be applied to many integrated photonic and optoelectronic devices.

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Growth of high-aspect ratio horizontally-aligned ZnO nanowire arrays

A method of fabricating horizontally-aligned zinc-oxide (ZnO) nanowire (NW) arrays with full control over the width and length is demonstrated. SEM images reveal the hexagonal structure typical of zinc oxide NWs. Arrays of high-aspect ratio horizontal ZnO NWs are fabricated by making use of the lateral overgrowth from dot patterns created by electron beam lithography (EBL). An array of patterned wires are lifted off and transferred to a flexible PDMS substrate with possible applications in several key nanotechnology areas.     

Recent advances in ZnO materials and devices

Wurtzitic ZnO is a wide-bandgap (3.437 eV at 2 K) semiconductor which has many applications, such as piezoelectric transducers, varistors, phosphors, and transparent conducting films. Most of these applications require only polycrystalline material; however, recent successes in producing large-area single crystals have opened up the possibility of producing blue and UV light emitters, and high-temperature, high-power transistors. The main advantages of ZnO as a light emitter are its large exciton binding energy (60 meV), and the existence of well-developed bulk and epitaxial growth processes; for electronic applications, its attractiveness lies in having high breakdown strength and high saturation velocity. Optical UV lasing, at both low and high temperatures, has already been demonstrated, although efficient electrical lasing must await the further development of good, p-type material. ZnO is also much more resistant to radiation damage than are other common semiconductor materials, such as Si, GaAs, CdS, and even GaN; thus, it should be useful for space applications.     

用于光子器件的ZnO薄膜的分子束外延生长

近年 来，由于蓝绿发光二极管和激光二极管的发展，宽禁带ＩＩＩ－Ｖ族氮化行和ＺｎＳｅ基ＩＩ－ＶＩ族半导体材料成为举世瞩目的研究热点之一，取得这些进展的重要原因是材料质量的不断改善以及创新性的掺杂方法的引入。氧化锌（ＺｎＯ）是具有特殊性质的宽禁囊直接带隙ＩＩ－ＶＩ族半导体材料，具有在半导体材料中最高的激子束缚能（６０ｍｅＶ），将是另一种重要的商用光子器件材料。本文将描述高质量氧化锌单晶薄膜的等离子分子     

ZnO ultra-fine powders and films: hydrothermal synthesis,luminescence and UV lasing at room temperature

Zinc oxide ultra-fine crystalline powders and polycrystalline films of high optical quality were synthesized under soft hydrothermal conditions. The phase composition, crystal morphology, and luminescent properties of submicron ZnO powders and films were studied depending on synthesis conditions (system composition, precursor kind, solvent type and concentration, temperature). For the systems containing metallic zinc, the ZnO growth mechanism was suggested. The most intensive UV luminescence and the highest values of I_UV/I_VIS were observed for polycrystalline films grown on Zn substrates. Low-threshold UV lasing at room temperature was found for ZnO-films, grown in hydrothermal systems with hydroxide or halide solutions as solvents, E _th = 1–5 MW/cm². The lowest threshold was observed on the ZnO films grown using LiOH as a solvent and zinc nitrate as ZnO-precursor. Clear mode structures with line-width 0.3 nm are characteristic of the lasing spectra.     

Line narrowing effects and enhanced back scattering from ZnO colloids

The dependence of the fluorescence emission intensity from nano ZnO colloid as a function of incident laser power is investigated. Emission in the near UV region from ZnO particles in diethylene glycol medium is studied using frequency tripled radiations at 355 nm from Nd-YAG laser. The spectrum, which was broad at lower pump intensities, exhibits an increase in the intensity as well as line narrowing above a threshold. The emission occurs in all directions and varies with pumping area. Results indicate the phenomenon of random lasing action due to multiple scattering inside the highly disordered medium. Coherent back scattering experiments confirm multiple scattering and weak localization effects in these samples. These preliminary studies show that colloidal nano ZnO medium is a promising candidate for random lasers.     

Effects of precursor concentrations and thermal annealing on ZnO nanorods grown by hydrothermal method

ZnO nanorods were grown on spin-coated ZnO seed layers by hydrothermal method. The ZnO nanorods were grown with various precursor concentrations ranging from 0.01 to 0.3 M. Field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out to investigate the structural and optical properties of the ZnO nanorods. The average diameter and length of the ZnO nanorods is increased as the precursor concentration increased from 0.01 to 0.3 M. From XRD, the intensity of ZnO (002) peak is increased and full width at half maximum (FWHM) of ZnO (002) decreased as the precursor concentration increased. The FWHM of near-band-edge emission (NBE) decreased and intensity ratio of the NBE to the deep-level emission (DLE) increased as the precursor concentration increased which indicated the optical property is improved. The DLE is red-shifted from yellow- to red-emission and its intensity is increased as the annealing temperature increased due to thermal diffusion process.