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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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.
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. 相似文献
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. 相似文献
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 IUV/IVIS 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, Eth = 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. 相似文献
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. 相似文献
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. 相似文献