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- DIT University
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3D polarization-dependent waveguide arrays in LiNbO3 crystal produced by femtosecond laser writing
摘要： Waveguide arrays are basic photonic elements in integrated optics. We propose a 3D hybrid-integrated waveguide array based on the femtosecond laser writing of lithium niobate (LiNbO3) crystals by engineering the layout of laser-induced tracks. The cross section of the structure is a cross-shaped geometry. The light propagation through this waveguide array shows polarization-dependent behaviors, which enables mode-coupling along either the vertical or the horizontal direction under excitation of linearly polarized light. This work opens new way to produce polarization-dependent optical devices in photonic systems by using femtosecond laser writing of LiNbO3.
关键词： Femtosecond laser writing,waveguide arrays,polarization-dependent devices,lithium niobate (LiNbO3)
更新于2025-09-19 17:13:59
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Synthesis and Luminescence properties of Lithium Aluminium Phosphate Glasses Doped with Nd <sup>3+</sup> Ion for Laser Medium
摘要： Nd3+ ion doped lithium aluminium phosphate glasses were synthesized and studied their properties for laser medium application. The density and the refractive index of the glass samples were carried out at the room temperature. The optical and luminescence properties were studied by investigating absorption and NIR emission spectra of the glass samples. The glasses absorbed photons in ultraviolet (UV), visible light (VIS) and near-infrared (NIR) regions are clearly observed from absorption spectra. For the photoluminescence properties, the glass samples showed the strongest emission at 1063 nm when it were excited by 581 nm which assigned to the energy transitions of Nd3+. The three phenomenological Judd-Ofelt parameters (?2, ?4, ?6) were determined from the spectral intensities of absorption band in order to calculate the radiative transition possibility (AR), stimulated emission cross section (σ(?p)) and branching ratio (?R) of the 4F3/2?4I9/2, 4I11/2 and 4I13/2 transitions. From the obtained results the conclusions made about the possibility of using these glasses as laser material.
关键词： luminescence properties,laser medium,lithium aluminium phosphate glasses,Nd3+ ion,Judd-Ofelt parameters
更新于2025-09-19 17:13:59
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N-Doped Graphene Quantum Dots Supported by Carbon Nanotubes Grown on Carbon Clothes for Lithium Storage
摘要： Graphite has been widely used as an anode material for commercial lithium-ion battery applications because of its excellent stability and low cost. However, graphite-based anodes need to improve the energy storage capacities to meet the increasing power demands of next-generation technologies. Here, we have developed a class of novel and ?exible electrode materials that consist of N-doped graphene quantum dots supported by carbon nanotubes grown on carbon cloth (denoted as CC/CNT@N-GQD). Such architecture synergistically combines the advantages of three dimensions/one dimension substrates and zero dimension N-GQDs. It greatly improves the electron/ion transport kinetics of N-GQDs, resulting in attractive electrochemical performance in terms of high reversible capacity and excellent rate capability. Moreover, the annealing temperature plays an important role in the control of N-doping types of CC/CNT@N-GQD. CC/CNT@N-GQD anodes annealed at 500 °C have a high content of pyridinic N, exhibiting a very excellent rate capability and cycling stability, as exempli?ed by a capacity of 2.88 mAh cm?2 at 4 mA cm?2 and a reversible capacity of 3.63 mAh cm?2 after 150 cycles at 0.19 mA cm?2.
关键词： carbon nanotubes,carbon cloth,lithium storage,annealing temperature,pyridinic N,N-doped graphene quantum dots
更新于2025-09-19 17:13:59
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[IEEE 2019 Joint Conference of the IEEE International Frequency Control Symposium anEuropean Frequency and Time Forum (EFTF/IFC) - Orlando, FL, USA (2019.4.14-2019.4.18)] 2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum (EFTF/IFC) - Numerical Simulation on Periodically Poled Lithium Niobate Transducers on Rotated Cuts
摘要： Rotated cut Periodically Poled Structures (PPS) are a promising technology allowing to generate bulk acoustic waves from ferroelectric domains periodicity. In this work, evolution of frequency-period product and k2 is investigated in function of the substrate orientation. Numerical computation points out Periodically Poled Lithium Niobate (PPLN) transducers with k2 up to 15% as well as frequency-period factor up to 12600m.s-1. Experimental comparison with the numerical computation for a (YXl)/64° PPLN transducer shows a relative difference of the frequency-period product less than 5%.
关键词： Lithium Niobate,Periodically Poled Structures,Rotated cuts,Electro-acoustic transducers,Bulk Structure
更新于2025-09-19 17:13:59
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Investigation of anomalous behaviour in J-V and Suns-Voc characteristics of carrier-selective contact silicon solar cells
摘要： Process and configuration dependent carrier-selective Ag/ITO/MoOx/n-Si/LiFx/Al silicon solar cells having conversion efficiencies from 6.5% to 14.5% are investigated. Some of the cells’ anomalous characteristics in light J-V and Suns-VOC graphs are analysed by photo-induced capacitance-voltage (C-V), impedance spectroscopy (IS), and voltage- plus light-biased (white, blue and infrared) quantum efficiency (QE). Correlated analysis of cells revealed the physical origin of S-shape in light J-V and turnaround in Suns-VOC graphs. After air exposure of the MoOx film, the charge carrier accumulation at the front interface and inefficient transport through the MoOx layer have led to the anomalous features in light J-V and Suns-VOC graphs of the cell. This is reflected as an additional peak and arc in C-V and IS graphs, respectively. In the absence of the LiFx layer, the cell has shown the only turnaround in Suns-VOC graph due to the Schottky barrier. The IS analysis resolved carrier transport issues at the front junction and back contact of the cells with a distinguished response. The light-bias dependent QE analysis has confirmed the presence of carrier collection barrier at the MoOx/c-Si interface, and the Schottky contact at the back with a different response in EQE spectra.
关键词： Silicon,Turnaround,S-shape,Heterojunction,Molybdenum oxide,Solar cells,Lithium Fluoride,Carrier-selective contacts
更新于2025-09-19 17:13:59
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Stability enhancement of inverted perovskite solar cells using LiF in electron transport layer
摘要： Stability is of great importance to the commercialization of perovskite solar cells (PVSCs). Interface materials are crucial to achieve stable PVSCs. Herein, we report on a strategy of incorporating lithium fluoride (LiF) as part of the buffer layer in inverted PVSCs to suppress the decomposition of perovskite layer and eliminate the corresponding negative effects. The device with C60/LiF buffer layer maintains 87% of its initial efficiency after aging in N2 for 26 days, exhibiting much improved stability compared to the control device with C60/BCP. Our work suggests a viable approach to enhance the device stability for the commercialization of PVSCs.
关键词： Perovskite solar cells,Electron transport layer,Lithium fluoride,Buffer layer,Stability
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) - Quadratic Solitons and their Interaction with Dispersive Waves in Lithium Niobate Nano-Waveguides
摘要： Lithium Niobate (LN) nano-waveguides combine the high nonlinearity and broadband transparency of LN with the sensitive tunability of geometric group velocity dispersion (GVD) and the strong field enhancement of subwavelength waveguides. Together these properties make the newly emerging LN nano-waveguides a compelling candidate for research into dynamics of quadratic temporal solitons, and frequency conversion processes driven by solitons interacting with dispersive waves. Emission of resonant radiation (RR) by temporal solitons due to cubic nonlinearity is known to be one of the key mechanism behind supercontinuum generation. Recent research into cubic solitons interacting with quadratic nonlinearities has found new mechanisms for tunable RR. In this work we analyse theoretically bright temporal quadratic solitons in LN nano-waveguides. Quadratic solitons consist of two co-propagating pulses at fundamental harmonic (FH) and second harmonic (SH) frequencies. The interaction between these two pulses mediated by a nonlinear material allows for the self-phase modulation crucial for soliton formation. Using the slowly varying envelope approximation the normalised fields of the FH, and SH, are described by the coupled nonlinear equations. Structures in which both harmonics experience the same sign of group velocity dispersion (GVD) are predicted to support quadratic solitons. Sub-picosecond solitons with peak powers below 100W can be excited in LN nano-waveguides. We analyse different regimes of RR emission due to non-constant GVD in FH and SH, as well as three wave mixing (TWM) radiation driven by soliton interaction with dispersive waves. Our simulations show RR in agreement with our theoretical predictions. These results suggest the possibility of temporal quadratic soliton excitation and novel mechanisms for RR relevant to frequency conversion and supercontinuum generation in LN nano-waveguides.
关键词： dispersive waves,frequency conversion,resonant radiation,nano-waveguides,supercontinuum generation,Lithium Niobate,quadratic solitons
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) - Second-Harmonic Generation in Monolithic Lithium Niobate Metasurfaces
摘要： Second harmonic generation (SHG) in nonlinear metasurfaces has proven as a versatile tool for novel ultra-thin light sources with engineered spatial wavefronts. However, the availability of second-order nonlinear materials suitable for fabrication of such metasurfaces has so far been mainly limited to III-V semiconductors (e.g. GaAs, AlGaAs, GaP). Such systems have a limited transparency range and unusual off-diagonal second-order susceptibility tensors. These constraints have driven the search for new material platforms, including lithium niobate as one of the most promising nonlinear materials. Various approaches, such as plasmonic cavities [1], bottom-up techniques [2] and lithium niobate on insulator [3], have been recently explored, however with limited applicability. Here we propose a new design concept for second-order nonlinear metasurfaces on a monolithic substrate, which is not limited by the availability of thin crystalline films and can be applied to any non-centrosymmetric material. Our approach enables blue SHG from a monolithic lithium niobate metasurface with a conversion efficiency above 10?5 using 1 GW/cm2 pump intensity, opening new opportunities for practical designs of nonlinear metasurfaces.
关键词： second harmonic generation,monolithic substrate,Mie-type resonances,lithium niobate,nonlinear metasurfaces
更新于2025-09-16 10:30:52
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Determination of Electro-Optical Coefficients of Lithium Niobate Crystals
摘要： The electro-optical coefficients r22, rе of doped lithium niobate crystals were determined by the interference-polarization method, depending on the zinc concentration in the range 0.018-0.88 wt. %. The dependence of the electro-optical coefficient on the zinc concentration is nonlinear. The values r22, rе are determined.
关键词： conoscopic figures,electro-optic coefficient,electro-optical effect,lithium niobate crystal
更新于2025-09-16 10:30:52
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AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS WITH HIERARCHICAL STRUCTURE FOR NEW TECHNOLOGIES AND RELIABLE STRUCTURES 2019 - Tomsk, Russia (1–5 October 2019)] PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS WITH HIERARCHICAL STRUCTURE FOR NEW TECHNOLOGIES AND RELIABLE STRUCTURES 2019 - Cutting of aluminum alloys with a Q-switched repetitively pulsed CO2 laser under conditions of intense material evaporation
摘要： The results of an experimental study of laser cutting of aluminum-lithium alloys using a repetitively pulsed CO2 laser with Q-switching under conditions of intense material evaporation are presented. The dependence of cut quality on the assisted gas pressure is determined. It is shown that a high-quality cut with a sheet thickness of 1.5 mm can be obtained at a gas pressure of 0.5–0.6 bar, which is significantly less compared to cutting with a continuous laser power. This makes it possible to reduce the assisted gas consumption. The dependence of cut surface roughness on the pulse repetition rate is measured.
关键词： laser cutting,aluminum-lithium alloys,material evaporation,Q-switched CO2 laser,cut quality,pulse repetition rate,gas pressure
更新于2025-09-16 10:30:52