共查询到20条相似文献,搜索用时 10 毫秒
1.
Kamil Gradkowski Tomasz J. Ochalski Jun Tatebayashi Ganesh Balakrishnan Guillaume Huyet Larry R. Dawson 《Journal of luminescence》2009,129(5):456-460
We present results of room temperature photoreflectance (PR) and photoluminescence (PL) measurements of molecular-beam epitaxy (MBE)-grown GaAsSb/GaAs quantum dot structures: one with an In0.14Ga0.86As capping quantum well and one without it. PL was used to determine the structures’ ground-state transition energies. This result was employed in an 8-band k·p Hamiltonian to achieve a band structure of the structures, which have different electron confinement. The dot emission energies suggest a large amount of As incorporation into the dots, which is due to enhanced adatom mixing at a higher than normal growth temperature of 510 °C. Our calculations indicate a dot composition of 25-50% Sb gives the best fit to experiment. This uncertainty in composition arises due to the fact that different bowing parameters of the ternary alloy could be applied in the calculations. The theoretical analysis accounts well for the main feature in the PR spectra of both samples. 相似文献
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基于飞秒激光光刻技术,提出了光纤端面光刻制造微型光纤法布里-珀罗干涉传感器的方案.该方案解决了传统飞秒激光制造光纤F-P传感器的平行度差的问题,制造了对比度超过20 dB的高灵敏度和高分辨率的微型F-P光纤传感器件.该制造方法简单、参量可控,制作的器件可应用恶劣温度条件下应变的精确测量. 相似文献
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Received: 20 September 1998 相似文献
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Using tightly focused femtosecond laser pulses, we have drilled micro-holes from the front and rear surface of soda-lime glass in ambient air. The machined holes have small aspect ratio or irregular inner walls. When the drilling is conducted from the rear surface in contact with distilled water, a good quality micro-hole with a high aspect ratio can be obtained. The corresponding formation mechanisms are investigated. 相似文献
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Based on a parameterized electronic many-body theory we calculate the spectrum of optical second-harmonic generation (SHG)
on an antiferromagnetic (AF) surface: NiO (001). The occurrence of AF spectral lines is further exploited for the calculation
of ultra-fast spin dynamics. This spin dynamics is observable in SHG. It is characterized by both a sharp drop of the AF signal
within a few femtoseconds and a long persistence (up to nanoseconds) of the spin coherence. These two features constitute
an ideal system for possible applications in both magnetic recording and quantum computing.
Received: 16 October 2001 / Revised version: 21 March 2002 / Published online: 6 June 2002 相似文献
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Broadband Optical Active Waveguides Written by Femtosecond Laser Pulses in Lithium Fluoride 下载免费PDF全文
Ismael Chiamenti Francesca Bonfigli Anderson S. L. Gomes Rosa Maria Montereali Larissa N. da Costa Hypolito J. Kalinowski 《中国物理快报》2014,(1):72-75
Broadband waveguiding through light-emitting strips directly written in a blank lithium fluoride crystal with a femtosecond laser is reported. Light guiding was observed at several optical wavelengths, from blue, 458 nm, to near-infrared, at 155nm. Visible photoluminescence spectra of the optically active F2 and F33 color centers produced by the fs laser writing process were measured. The wavelength-dependent refractive index increase was estimated to be in the order of 10-3-10-4 in the visible and near-infrared spectral intervals, which is consistent with the stable formation of point defects in LiF. 相似文献
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The ultrafast electron and spin dynamics of Co films was investigated using a femto-second pump-probe technique. The samples were magnetically characterized by means of magnetooptical Kerr effect and non-optical magnetometers, i.e. superconductive quantum interference device and alternating gradient field magnetometer. Time evolution of both, Kerr rotation and ellipticity, was measured at different points of the static hysteresis cycle. This allowed separating magnetic and non-magnetic contributions to the signal. The sample magnetization was found to drop within 200 fs, following the pulse cross-correlation trace, while the magnetization recovery time was found to last few picoseconds. 相似文献
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Laser Mode-Dependent Size of Plasma Zones Induced by Femtosecond Laser Pulses in Fused Silica 下载免费PDF全文
We carry out the numerical simulations of femtosecond laser propagation with TEMoo mode, TEM10 mode and a beam combining both the modes in fused silica. It is found that the transverse size of plasma zones induced by laser pulses with the TEM10 mode is smaller than that induced by the TEM00 mode, while the longitudinal size is almost the same, and the saturated plasma density is higher. The transverse size, the longitudinal size and the ratio of the longitudinal to transverse size, for the beam combining both the modes, all could be reduced at the same time in comparison with the TEM00 mode under the same focusing conditions. 相似文献
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Optical and AFM study of electrostatically assembled films of CdS and ZnS colloid nanoparticles 总被引:1,自引:0,他引:1
CdS and ZnS semiconducting colloid nanoparticles coated with the organic shell, containing either SO3− or NH2+ groups, were prepared using the aqueous phase synthesis. The multilayer films of CdS (or ZnS) were deposited onto glass, quartz and silicon substrates using the technique of electrostatic self-assembly. The films produced were characterized with UV-vis spectroscopy, spectroscopic ellipsometry and atomic force microscopy. A substantial blue shift of the main absorption band with respect to the bulk materials was found for both CdS and ZnS films. The Efros equation in the effective mass approximation (EMA) theoretical model allowed the evaluation of the nanoparticle radius of 1.8 nm, which corresponds well to the ellipsometry results. AFM shows the formation of larger aggregates of nanoparticles on solid surfaces. 相似文献
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Long-period fibre gratings inside standard single-mode optical communication fibres are successfully fabricated with infrared femtosecond laser pulses. The refractive index perturbations are well confined within the fibre core by choosing the proper laser focusing parameters and translation speed of the fibre during the direct laser writing process. With the self-focusing effect considered and at a constant average irradiation dose of 1.62 × 10^3 J/(cm^2μm), the threshold intensity for fabricating long-period gratings with infrared femtosecond laser pulses is determined to be 5.13 × 10^13 W/cm2. 相似文献
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Temperature Insensitivity of Optical Properties of InAs/GaAs Quantum Dots due to a Pregrown InGaAs Quantum Well 下载免费PDF全文
Both the peak position and linewidth in the photoluminescence spectrum of the InAs/GaAs quantum dots usually vary in an anomalous way with increasing temperature. Such anomalous optical behaviour is eliminated by inserting an In0.2Ga0.8As quantum well below the quantum dot layer in molecular beam epitaxy. The insensitivity of the photoluminescence spectra to temperature is explained in terms of the effective carrier redistribution between quantum dots through the In0.2Ga0.8As quantum well. 相似文献
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In this paper, we present a study of photoluminescence (PL) from AlInAs/AlGaAs quantum dots (QDs) structures grown by molecular beam epitaxy. Specifically, we describe the effects of the temperature and of the excitation density on the photoluminescence circular polarization. We have found that the circular polarization degree depends on temperature. On the other hand, the study of the excitation density dependent circular polarization PL degree shows that the last increases in the case of the sample of weak dot density. However, in the case of large dot density, it is almost constant in the excitation density range from 0.116 W cm−2 to 9 W cm−2. 相似文献
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Eugene Kogan Danny Eliyahu Moshe Kaveh 《Zeitschrift für Physik B Condensed Matter》1993,91(4):497-499
We have calculated the time autocorrelation function of the intensity of light multiply scattered in the medium with dynamical properties. A new asimptotic for larget is found. 相似文献
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Transverse Writing of Multimode Interference Waveguides inside Silica Glass by Femtosecond Laser Pulses 下载免费PDF全文
Multi-mode interference waveguides are fabricated inside silica glass by transverse writing geometry with femtosecond laser pulses. The influences of several writing and reading factors on the output mode are systematically studied. The experimental results of straight waveguides are in good agreement with the simulations by the beam propagation method. By integrating a straight waveguide with a bent waveguide, a 1× 2 multi-mode splitter is formed and 2×3 lobes are observed in the output mode. 相似文献