- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Extent of Shallow/Deep Trap States beyond the Conduction Band Minimum in Defect-Tolerant CsPbBr <sub/>3</sub> Perovskite Quantum Dot: Control over the Degree of Charge Carrier Recombination
摘要： Perovskite quantum dots (PQDs) are known to be defect tolerant possessing clean band-gap with optically inactive benign defect states. However, we show that there exists significant deep trap states beyond conduction band minimum, although the extent of shallow trap states is observed to be minimal. Extent of deep trap states beyond conduction band minimum seem to significant in PQD, however the extent is less than even optically robust CdSe and InP based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQD which are quite important for energy applications.
关键词： Perovskite quantum dots,ultrafast transient absorption,defect tolerant,single particle spectroscopy,charge carrier recombination,trap states
更新于2025-09-19 17:13:59
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Impact of the Plasmonic Metal Oxide-Induced Photocatalytic Processes on the Interaction of Quantum Dots with Metallic Nanoparticles
摘要： We study plasmonic control of photocatalytic properties of metal oxides and the ways they influence interaction of quantum dots with metallic nanostructures. For this, gold nanostructures are coated with ultrathin layers of metal oxides (Al, Cu, Cr, or Ti oxide) and then covered with CdSe/ZnS quantum dots. The results show how the photocatalytic properties of such metal oxides are renormalized by plasmon near fields. In the cases of Al, Cr, and Ti oxides, the results mostly indicate the direct impact of plasmon fields via enhancement of optical excitations of the quantum dots. For the case of Cu oxide, however, the outcomes are found to be quite unique. In the absence of the plasmonic structures, such an oxide (CuO) presents highly active photocatalytic processes, leading to complete annihilation of the quantum dot emission. In the presence of the metallic nanostructures, the emission of such quantum dots is revived, offering an ultrafast decay process (～112 ps). These results indicate that in the case of CuO, the plasmonic metal oxide-induced photocatalytic processes include not only direct impact of plasmon near fields on the optical excitations of quantum dots but also the enhancement of interband transitions in CuO nanoparticles. The effects of energy transfer from quantum dots to metallic nanostructures and its equalization with Purcell effects on such processes are discussed.
关键词： ultrafast decay process,photocatalytic properties,plasmonic control,metallic nanostructures,Purcell effects,plasmon near fields,energy transfer,quantum dots,metal oxides
更新于2025-09-19 17:13:59
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High-speed modulation of a terahertz quantum cascade laser by coherent acoustic phonon pulses
摘要： The fast modulation of lasers is a fundamental requirement for applications in optical communications, high-resolution spectroscopy and metrology. In the terahertz-frequency range, the quantum-cascade laser (QCL) is a high-power source with the potential for high-frequency modulation. However, conventional electronic modulation is limited fundamentally by parasitic device impedance, and so alternative physical processes must be exploited to modulate the QCL gain on ultrafast timescales. Here, we demonstrate an alternative mechanism to modulate the emission from a QCL device, whereby optically-generated acoustic phonon pulses are used to perturb the QCL bandstructure, enabling fast amplitude modulation that can be controlled using the QCL drive current or strain pulse amplitude, to a maximum modulation depth of 6% in our experiment. We show that this modulation can be explained using perturbation theory analysis. While the modulation rise-time was limited to ~800 ps by our measurement system, theoretical considerations suggest considerably faster modulation could be possible.
关键词： terahertz,quantum-cascade laser,modulation,acoustic phonon,ultrafast
更新于2025-09-19 17:13:59
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Direct observation of ultrafast electrons generated by high-intensity laser-matter interaction
摘要： High intensity ultrashort laser pulses interacting with thin solid targets are able to produce energetic protons and ions by means of extremely large accelerating fields, generated by escaping electrons. The characterization of such electrons is thus a key factor for the understanding of the accelerating potential temporal evolution. Here, we present temporally resolved measurements of the ultrafast escaping electron component. The charge, electric field, and temporal duration of the emitted ultrafast electron beams are determined using temporal diagnostics with a 100 fs temporal resolution. Experimental evidence of scaling laws for the ultrafast electron beam parameters with respect to the incident laser pulse energy is retrieved and compared with theoretical models, showing an excellent agreement.
关键词： ultrafast electrons,high-intensity laser-matter interaction,scaling laws,temporal diagnostics
更新于2025-09-19 17:13:59
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Novel Composite Substrates for Thin Film AlGaInP-based High Power LEDs
摘要： This paper develops and validates a universally applicable computational comprehensive concept for solving nonlinear differential equations (NDEs) through a neurocomputing concept based on cellular neural networks (CNNs). High-precision, stability, convergence, and lowest-possible memory requirements are ensured by the CNN processor architecture. A significant challenge solved in this paper is that all these cited computing features are ensured in all system-states (regular or chaotic ones) and in all bifurcation conditions that may be experienced by NDEs. One particular quintessence of this paper is to develop and demonstrate a solver concept that shows and ensures that CNN processors (realized either in hardware or in software) are universal solvers of NDE models. The solving logic or algorithm of given NDEs (possible examples are: Duffing, Mathieu, Van der Pol, Jerk, Chua, R?ssler, Lorenz, Burgers, and the transport equations) through a CNN processor system is provided by a set of templates that are computed by our comprehensive templates calculation technique that we call nonlinear adaptive optimization. This paper is therefore a significant contribution and represents a cutting-edge real-time computational engineering approach, especially while considering the various scientific and engineering applications of this ultrafast, energy-and-memory-efficient, and high-precise three NDE NDE solver concept. For illustration purposes, models are demonstratively solved, and related CNN templates are derived and used: the periodically excited Duffing equation, the Mathieu equation, and the transport equation.
关键词： nonlinear adaptive optimization (NAOP),CNN processor concept as a universal solver,Cellular neural networks (CNNs)-based neurocomputing,CNN-based ultrafast solving of nonlinear differential equations (NDEs)
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Low-voltage light beam steering by planar dual-domain nematic liquid crystal deflector
摘要： We present photoemission time-delay measurements between electrons originating from the valence shells of neon and argon obtained by attosecond streaking. After giving a brief review of the different techniques, we focus on more detailed analysis using the attosecond streaking technique. We show that the temporal structure of the ionizing single attosecond pulse may significantly affect the obtained time delays, and we propose a procedure how to take this contribution properly into account. Our analysis reveals a delay of a few tens of attoseconds in a photon energy range between 28 and 40 eV in the emission of electrons ionized from argon with respect to those liberated from neon.
关键词： Atomic physics,ultrafast optics,time measurement,ultraviolet spectroscopy
更新于2025-09-19 17:13:59
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Temporal profile measurements of ultrafast pulsed laser systems
摘要： Ultrafast pulsed lasers can be used to measure the phenomena occurring at femtosecond (fs) (10?15 s) time scale which include photo synthesis, protein collapsing and sub-atomic vibrations. In normal course, the temporal pro?le of the nanosecond (ns) pulsed lasers can be estimated by using the standard detectors because the recombination time of the electron-hole pair is of the order of ns. Nevertheless, the electronic equipment and the standard detectors are insuf?cient to measure the temporal pro?le of the ultrafast pulsed lasers. In the present investigation, we compare various techniques to measure the temporal pro?le of the ultrafast lasers which is followed by the details of the experimental con?guration of an autocorrelation technique. The temporal pro?le of the ultrafast pulsed lasers has shown various pulse width values in the experimental set-up when recorded at different con?gurations.
关键词： Second harmonic generation,Nonlinear optics,Autocorrelation measurement,Ultrafast spectroscopy,Ultrafast pulses
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Dynamics of asymmetric soliton explosions in ultrafast fiber lasers
摘要： Asymmetric soliton explosions are numerically demonstrated in an all-normal-dispersion Yb-doped mode-locked fiber laser based on a lumped model. It is found that the explosion events manifest themselves when the pump strength is tuned to reside between stationary dissipative soliton and noise-like pulse regimes. Remarkably, although the initial conditions and the model itself are symmetric, the explosions occur only at one edge of the soliton, i.e., the pulse leading and trailing edges explode alternately. Our results pave the way for further investigation on the dynamics of soliton explosions in ultrafast fiber lasers.
关键词： Soliton explosions,Ultrafast fiber lasers,Dissipative soliton
更新于2025-09-16 10:30:52
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All-Fiber Bidirectional Mode-Locked Ultrafast Fiber Laser at 2? <i>μ</i> m
摘要： In this paper, we demonstrated an all-?ber bidirectional ultrafast thulium-doped ?ber laser at 2 μm with a single-wall carbon nanotube presented as saturable absorber. We successfully obtained bidirectional mode-locking operations with pulse repetition frequency adjustable from 35 to 122 MHz by shortening the cavity length. Meanwhile, with the reduction of the intracavity dispersion, the number of Kelly sidebands was signi?cantly decreased and the output energy was more concentrated on the soliton pulse. Besides, by manipulating the pump power and polarization controller, the two results of bidirectional mode-locked pulses with the same repetition frequency and differential repetition frequency were observed. We found that the repetition rate difference between the clockwise and counterclockwise pulse trains was adjustable by changing the pump power or controlling the intracavity polarization. When the pulse repetition frequency was 35 MHz and 122 MHz, the adjustment range of repetition rate difference was 764–922 Hz and 540–2000 Hz, respectively. It is believed that this novel laser source can support free-running dual optical comb spectroscopy to detect important air gases like H2O or CO2 in the future.
关键词： infrared and far-infrared lasers,thulium-doped ?ber,?ber optics and oscillators,Ultrafast lasers
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optimisation of Dispersion Flatness in Nanostructured Core Fibres
摘要： Nanostructured optical fibres allow to obtain an arbitrary profile of refraction index in the core. These fibres are composed of several thousands of rods with diameter smaller than incident wavelength. Their optical performance is described with the Maxwell-Garnett effective medium theory. A modification of nanorods distribution or doping level in nanorods allow controlling of chromatic dispersion, polarization and modal properties of the nanostructured fibres. We study an influence of additional microrings in the core on fibre dispersion characteristics. We consider a fibre composed of pure silica nanorods and silica nanorods highly doped with Ge (concentration of GeO2 equals 20% mol). Modification of core internal structure affects electric field distribution in the fundamental mode, and consequently results in changes of its dispersion characteristics. We show that flat, all-normal dispersion characteristics (≈ 2.5 ps/nm/km) in wavelength range from 1.3 up to 2.15 μm can be achieved in the optimized structure. Moreover, within these limits, 1.5 μm to 1.9 μm range was revealed to be ultra-flat (≈ 0.2 ps/nm/km). In contrast to already reported in the literature similar fibres, proposed design is based on fused silica glasses, exhibits spectrally broader and more flat dispersion profile, it is an all-solid construction and it has the effective mode area equal 13μm2 for λ=1.55μm wavelength. Thanks to such characteristics, the fiber allows free from higher order distortions light propagation of highly confined broadband optical pulses, what might find applications in ultrafast optics, or dispersion management systems.
关键词： ultrafast optics,Maxwell-Garnett effective medium theory,chromatic dispersion,nanostructured optical fibres,all-normal dispersion
更新于2025-09-16 10:30:52