修车大队一品楼qm论坛51一品茶楼论坛,栖凤楼品茶全国楼凤app软件 ,栖凤阁全国论坛入口,广州百花丛bhc论坛杭州百花坊妃子阁

oe1(光电查) - 科学论文

过滤筛选

出版时间
  • 2019
研究主题
  • Mach Zehnder Interferometer
  • Convolution code
  • Lithium Niobate
  • Parity
  • Electro-optic
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • DIT University
166 条数据
?? 中文（中国） ▾

  • Lithium Distribution in Structured Graphite Anodes Investigated by Laser-Induced Breakdown Spectroscopy

    摘要： For the development of thick film graphite electrodes, a 3D battery concept is applied, which significantly improves lithium-ion diffusion kinetics, high-rate capability, and cell lifetime and reduces mechanical tensions. Our current research indicates that 3D architectures of anode materials can prevent cells from capacity fading at high C-rates and improve cell lifespan. For the further research and development of 3D battery concepts, it is important to scientifically understand the influence of laser-generated 3D anode architectures on lithium distribution during charging and discharging at elevated C-rates. Laser-induced breakdown spectroscopy (LIBS) is applied post-mortem for quantitatively studying the lithium concentration profiles within the entire structured and unstructured graphite electrodes. Space-resolved LIBS measurements revealed that less lithium-ion content could be detected in structured electrodes at delithiated state in comparison to unstructured electrodes. This result indicates that 3D architectures established on anode electrodes can accelerate the lithium-ion extraction process and reduce the formation of inactive materials during electrochemical cycling. Furthermore, LIBS measurements showed that at high C-rates, lithium-ion concentration is increased along the contour of laser-generated structures indicating enhanced lithium-ion diffusion kinetics for 3D anode materials. This result is correlated with significantly increased capacity retention. Moreover, the lithium-ion distribution profiles provide meaningful information about optimizing the electrode architecture with respect to film thickness, pitch distance, and battery usage scenario.

    关键词： laser-induced breakdown spectroscopy,3D battery,lithium-ion battery,ultrafast laser ablation,graphite anode

    更新于2025-09-12 10:27:22

  • Interfacial Lattice‐Strain‐Driven Generation of Oxygen Vacancies in an Aerobic‐Annealed TiO <sub/>2</sub> (B) Electrode

    摘要： Oxygen vacancies play crucial roles in defining physical and chemical properties of materials to enhance the performances in electronics, solar cells, catalysis, sensors, and energy conversion and storage. Conventional approaches to incorporate oxygen defects mainly rely on reducing the oxygen partial pressure for the removal of product to change the equilibrium position. However, directly affecting reactants to shift the reaction toward generating oxygen vacancies is lacking and to fill this blank in synthetic methodology is very challenging. Here, a strategy is demonstrated to create oxygen vacancies through making the reaction energetically more favorable via applying interfacial strain on reactants by coating, using TiO2(B) as a model system. Geometrical phase analysis and density functional theory simulations verify that the formation energy of oxygen vacancies is largely decreased under external strain. Benefiting from these, the obtained oxygen-deficient TiO2(B) exhibits impressively high level of capacitive charge storage, e.g., ≈53% at 0.5 mV s?1, far surpassing the ≈31% of the unmodified counterpart. Meanwhile, the modified electrode shows significantly enhanced rate capability delivering a capacity of 112 mAh g?1 at 20 C (≈6.7 A g?1), ≈30% higher than air-annealed TiO2 and comparable to vacuum-calcined TiO2. This work heralds a new paradigm of mechanical manipulation of materials through interfacial control for rational defect engineering.

    关键词： aerobic-annealing,oxygen vacancy,pseudocapacitive charge storage,lithium-ion batteries,interfacial lattice strain

    更新于2025-09-12 10:27:22

  • Proceedings of Meetings on Acoustics [Acoustical Society of America 172nd Meeting of the Acoustical Society of America - Honolulu, Hawaii (28 November – 2 December 2016)] - Distribution of point defects in phononic periodically poled lithium niobate

    摘要： The concentration of point defects is investigated along the neighboring domains in a ZX-cut periodically poled lithium niobate (PPLN) plate. PPLN is a ferroelectric phononic crystal (FPC) in which the inversion of polarization occurs across the interdomain wall. The spectra of photoluminescence (PL) are recorded along the domain structure parallel to the x-axis, at room temperature. The PL spectra reveal a nonuniform distribution of defects along the PPLN. The striking result is that some defects have narrow extrema in PL-intensity right in the interdomain wall location. The spread in PL intensity from the average is higher in PPLN when compared to single crystal lithium niobate. Engineering application of these findings may be new non-destructive characterization method of ferroelectric phononic crystals.

    关键词： photoluminescence,phononic periodically poled lithium niobate,point defects,ferroelectric phononic crystals

    更新于2025-09-12 10:27:22

  • All-Fiber Erbium-doped Q-Switched Laser with Recycled Graphite Oxide

    摘要： This work demonstrates a passively Q-Switched fiber laser employing graphite oxide as a saturable absorber, generating tunable microsecond pulses with kHz repetition rates, pulse energies of up to 15.54 nJ and the pulse-to-pulse timing jitter of 46.14 fs. The graphite oxide samples were obtained by recycling the graphite present in Li-ion batteries utilized in cell phone devices through a chemical separation and subsequent oxidation process. Sample characterization employing X-ray diffraction, solid-state nuclear magnetic resonance and Raman spectroscopy showed that the produced graphite oxide exhibited a homogeneously oxidized structure. These results indicate that applications in the physics of pulsed lasers can benefit from the recycling of lithium batteries, directing the process of discarding spent batteries.

    关键词： Recycled Graphite Oxide,Lithium Batteries,Erbium-Doped Fiber Laser,Saturable Absorber,Q-Switched

    更新于2025-09-12 10:27:22

  • There Is a Future for N-Heterocyclic Carbene Iron(II) Dyes in Dye-Sensitized Solar Cells: Improving Performance through Changes in the Electrolyte

    摘要： By systematic tuning of the components of the electrolyte, the performances of dye-sensitized solar cells (DSCs) with an N-heterocyclic carbene iron(II) dye have been significantly improved. The beneficial effects of an increased Li+ ion concentration in the electrolyte lead to photoconversion efficiencies (PCEs) up to 0.66% for fully masked cells (representing 11.8% relative to 100% set for N719) and an external quantum efficiency maximum (EQEmax) up to approximately 25% due to an increased short-circuit current density (JSC). A study of the effects of varying the length of the alkyl chain in 1-alkyl-3-methylimidazolium iodide ionic liquids (ILs) shows that a longer chain results in an increase in JSC with an overall efficiency up to 0.61% (10.9% relative to N719 set at 100%) on going from n-methyl to n-butyl chain, although an n-hexyl chain leads to no further gain in PCE. The results of electrochemical impedance spectroscopy (EIS) support the trends in JSC and open-circuit voltage (VOC) parameters. A change in the counterion from I? to [BF4]? for 1-propyl-3-methylimidazolium iodide ionic liquid leads to DSCs with a remarkably high JSC value for an N-heterocyclic carbene iron(II) dye of 4.90 mA cm?2, but a low VOC of 244 mV. Our investigations have shown that an increased concentration of Li+ in combination with an optimized alkyl chain length in the 1-alkyl-3-methylimidazolium iodide IL in the electrolyte leads to iron(II)-sensitized DSC performances comparable with those of containing some copper(I)-based dyes.

    关键词： N-heterocyclic carbene,iron,dye-sensitized solar cell,ionic liquid,lithium ion,electrolyte

    更新于2025-09-12 10:27:22

  • Silicon photodetector for integrated lithium niobate photonics

    摘要： We demonstrate the integration of an amorphous silicon photodetector with a thin film lithium niobate photonic platform operating in the visible wavelength range. We present the details of the design, fabrication, integration, and experimental characterization of this metal-semiconductor-metal photodetector that features a responsivity of 22 mA/W to 37 mA/W over the wide optical bandwidth spanning in the 635 nm–850 nm wavelength range.

    关键词： lithium niobate,visible wavelength range,integration,photonics,silicon photodetector

    更新于2025-09-12 10:27:22

  • Second harmonic microscopy of poled x-cut thin film lithium niobate: Understanding the contrast mechanism

    摘要： Thin film lithium niobate has been of great interest recently, and an understanding of periodically poled thin films is crucial for both fundamental physics and device developments. Second-harmonic (SH) microscopy allows for the noninvasive visualization and analysis of ferroelectric domain structures and walls. While the technique is well understood in bulk lithium niobate, SH microscopy in thin films is largely influenced by interfacial reflections and resonant enhancements, which depend on film thicknesses and substrate materials. We present a comprehensive analysis of SH microscopy in x-cut lithium niobate thin films, based on a full three-dimensional focus calculation and accounting for interface reflections. We show that the dominant signal in backreflection originates from a copropagating phase-matched process observed through reflections, rather than direct detection of the counterpropagating signal as in bulk samples. We simulate the SH signatures of domain structures by a simple model of the domain wall as an extensionless transition from a ?χ(2) to a +χ(2) region. This allows us to explain the main observation of domain structures in the thin-film geometry, and, in particular, we show that the SH signal from thin poled films allows to unambiguously distinguish areas, which are completely or only partly inverted in depth.

    关键词： lithium niobate,thin films,ferroelectric domain structures,Second-harmonic microscopy,nonlinear optics

    更新于2025-09-12 10:27:22

  • Mechanistic insights into the phenomena of increasing capacity with cycle number: using pulsed-laser deposited MoO <sub/>2</sub> thin film electrodes

    摘要： Lithium ion batteries typically lose capacity or energy storage density (i.e. capacity fading) over the course of extended cycling which can be problematic for applications and appears to be exaggerated when high current rates are used. However, in some cases fluctuations in capacity with cycle number and even increases in capacity with cycle number are noted with predominantly thin film based electrodes. Here we demonstrate the synthesis and in-depth characterisation of laser deposited MoO2 thin film anodes and its unconventional mechanism. A MoO2 electrode shows an initial capacity of 79 mA h g?1 which increases to capacities of 600 mA h g?1 at 15.8 A g?1 after 90 000 cycles. A maximum capacity of 1714 mA h g?1 was achieved in an electrode cycled at 1.5 A g?1 for over 3800 cycles, the highest recorded capacity in MoOx anodes to date. The most intriguing aspects of this work is the fact that capacity is shown to fluctuate and typically increase well above the theoretical capacity of MoO2. A combination of electrochemical cycling, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, focused ion beam milling and transmission electron microscopy at various states of cycling is used to illustrate a proposed mechanism. The mechanism illustrated is based on exfoliation of layers of MoO2 off the pulsed laser deposition (PLD) grown MoO2 electrodes during cycling that creates additional surface area and easier access for Li-ions to both adsorb to the surface and insert/react with the host material. Further features in the capacity evolution are rationalised by this mechanism and methods to control the capacity evolution are detailed. These results present a rational explanation for when an electrode undergoes a substantial increase in capacity over its extended cycling life.

    关键词： pulsed laser deposition,MoO2 thin film anodes,exfoliation mechanism,Lithium ion batteries,capacity increase

    更新于2025-09-12 10:27:22

  • High-Performance Perovskite Light-Emitting Diode with Enhanced Operational Stability Using Lithium Halide Passivation

    摘要： Defect passivation has been demonstrated to be effective in improving the radiative recombination of charge carriers in perovskites, and consequently device performance of the resultant perovskite light-emitting diodes (LEDs). State-of-the-art useful passivation agents in perovskite LEDs are mostly organic chelating molecules, which, however, simultaneously sacrifice the charge transport properties and thermal stability of the resultant perovskite emissive layers, deteriorating the performance especially the operational stability of the devices. In this work, we demonstrate that lithium halides can efficiently passivate defects of halide vacancies and reduce trap state density, suppressing ion migration in perovskite films. Efficient green perovskite LEDs based on all inorganic CsPbBr3 perovskite with a peak external quantum efficiency of 16.2% as well as a high maximum brightness of 50278 cd m-2 are achieved. In addtion, the device shows decent stability even under a brightness of 104 cd m-2. We highlight the universal applicability of defect passivation using lithium halides, which enable us to improve the efficiency and stability of blue and red perovskite LEDs.

    关键词： passivation,lithium halide,surface defects,stability,non-radiative

    更新于2025-09-12 10:27:22

  • [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) - Additive Fiber Optic Probe Technology for Precise Trimming of High-Performance Lithium Niobate Photonic Integrated Circuits

    摘要： Lithium Niobate (LN) is a basic material of integrated optics, for example for electro and acousto-optical modulators, switches, diffraction gratings, nonlinear optical wavelength converters and others [1]. LN based ion exchange or Ti-indiffused contact photolithographic techniques are established technologies, however, finite tolerance of optical elements could not respond some modern applications. For example, high-purity suppressed carrier synthesis or high extinction ratio pulse generation for precision measurement systems require additional active trimming electrodes [2] at the device and corresponding servo loop. Recently developed direct laser writing (DLW) of femtosecond/ultrafast laser pulses [3] can be employed to address the problem, but this method is problematic for mass production and suffer from high insertion loss in optical waveguides (typically ~1 dB/cm compared to <0.1 dB/cm for Ti in-diffused waveguides). We have proposed a method that combines low loss of Ti in-diffused technology and passive permanent trimming of DLW. Moreover, the implementation of the proposed technique is based on very cheap commercially available equipment that makes it very attractive. This is a micro-machining of a thin loading metal film on the top of a waveguide. It is based on dependence of plazmon polariton excitation efficiency on the thickness of metal film. Titanium loading film by thickness of 10 nm adds addition insertion losses (~ 1 dB/mm) and changes effective refractive index of the waveguide (~ 10-6(cid:121)10-5). The loading film was deposited in zones of the integrated optical chip which were most sensitive to its influence such as X-type direction coupler and Y-branch. The film thickness of several nanometres allows rather low laser intensity could be used for local ablation. The simple semiconductor pump laser (978 nm) for erbium doped fiber optic amplifier was used. The output fiber was exploited as a probe. The tip of the fiber was positioned close to the integrated optical chip surface. For laser power of 500 mW the intensity on the tip of the output single mode fiber was about 1 kW/mm2. The integrated optical chip was attached to a precise 3-axis translation stage that allowed flexible manipulation of the loading film micro-machining. Monitoring of optical signals (1550 nm) on the output of integrated optical chip provided possibilities on-line control of the trimming. To demonstrate the efficiency of the proposed method the adjustment of extinction ratio ER (relation of maximum transmitted optical power to its minimum) of Mach-Zehnder modulator was performed. ER is critically dependent on precise power balance in both arms of the interferometers. We demonstrate increase in ER in 17 dB (from 30 to 47 dB). Our findings can potentially be applied in modulators for quantum key distribution, precise sensing, high fidelity signal processing and others.

    关键词： trimming,photonic integrated circuits,integrated optics,fiber optic probe,Lithium Niobate

    更新于2025-09-12 10:27:22