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- 2019
- Mach Zehnder Interferometer
- Convolution code
- Lithium Niobate
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- Electro-optic
- Optoelectronic Information Science and Engineering
- DIT University
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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) - Electro-Optic Frequency Comb Generation in Lithium Niobate Whispering Gallery Mode Resonators
摘要： Optical frequency combs (OFCs) are light sources whose spectra consists of equally spaced frequency lines in the optical domain [1]. They have great potential for improving high-capacity data transfer, all-optical atomic clocks, spectroscopy, and high-precision measurements [2]. In contrast to the traditional third-order nonlinearity based OFC generation methods, we present a new approach which is based on second-order non-linear effects in a whispering gallery mode (WGM) resonator made of lithium niobate (LN) [3,4]. Our system is composed of a resonant hybrid structure comprising an optical LN disk resonator and a microwave copper cavity. The hybrid structure enables highly efficient nonlinear mixing of photons. In this scheme, two continuous waves, one in the optical domain ((cid:2033) = 193 THz) and another in the microwave region (Ω = 8.9 GHz) couple within a LN WGM resonator [5]. The second-order non-linearity of LN leads to frequency comb generation via cascaded symmetric sum and difference frequency generation [6]. In our experiment, the optical pump power is coupled into the WGM by using a standard prism coupling method that is based on frustrated total internal reflection (Fig. 1 (a)). The microwave power is coupled using a coaxial probe coupled attached to the 3-D copper cavity specifically designed to have the microwave cavity resonance to be equal to the optical free spectral range of the LN resonator, required for efficient phase matching. In addition, the cavity design also provides a very good spatial overlap between the microwave and optical modes by confining the microwave field to the rim of the LN disk. In our proof-of-concept experimental demonstration we observe a 1.6 THz long frequency comb centred around 193.5 THz more than180 comb lines by using only 20 dBm of microwave power. Compared to previously reported OFCs generation schemes, this method has two major advantages: inherent phase stability, and better power efficiency. The power efficiency when measured in terms of pi-voltage of the modulator is 25 times better than a commercial Thorlabs modulator.
关键词： second-order non-linearity,whispering gallery mode resonators,electro-optic frequency comb generation,Optical frequency combs,lithium niobate
更新于2025-09-12 10:27:22
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Microscale Generation of Entangled Photons without Momentum Conservation
摘要： We report, for the first time, the observation of spontaneous parametric down-conversion (SPDC) free of phase matching (momentum conservation). We alleviate the need to conserve momentum by exploiting the position-momentum uncertainty relation and using a planar geometry source, a 6 μm thick layer of lithium niobate. Nonphase-matched SPDC opens up a new platform on which to investigate fundamental quantum effects but it also has practical applications. The ultrasmall thickness leads to a frequency spectrum an order of magnitude broader than that of phase-matched SPDC. The strong two-photon correlations are still preserved due to energy conservation. This results in ultrashort temporal correlation widths and huge frequency entanglement. The studies we make here can be considered as the initial steps into the emerging field of nonlinear quantum optics on the microscale and nanoscale.
关键词： quantum optics,spontaneous parametric down-conversion,phase matching,lithium niobate,frequency entanglement,momentum conservation
更新于2025-09-12 10:27:22
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Polymer Pre‐Aggregation Enables Optimal Morphology and High Performance in All‐Polymer Solar Cells
摘要： The preparation technology and limited performance of ion conducting (IC) layers are the two main obstacles for electrochromic devices (ECDs) toward commercial application. In this work, the LixAlOz films were fabricated by direct current (DC) magnetron sputtering with a Li?Al alloy target and show promising potential as an IC layer in ECDs owing to their high transparency, ultrahigh stability, and good ionic conductivity. The integrated all-solid-state ECDs, with the structure of ITO/NiOx/LixAlOz/WO3/ITO, manifest less leakage current density (<10 mA/cm2), high optical regulation (ΔT = 74.4%), excellent cyclic stability (changing less than 10% after 104 cycles), and short response time (5.7 s for coloring time, 2.2 s for bleaching time). A large-scale ECD with the area of 10 × 10 cm2 was fabricated and displayed remarkable potential as a commercial application for dynamic windows.
关键词： energy saving materials,lithium ion conductor,aluminate?lithium alloy,electrochromic
更新于2025-09-11 14:15:04
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Selective Laser Melting Titanium with nanonet topography inhibits osteoclast differentiation through MAPK signaling pathway
摘要： Penetrating into the inner surface of porous metal-oxide nanostructures to encapsulate the conductive layer is an efficient but challenging route to exploit high-performance lithium-ion battery electrodes. Furthermore, if the bonding force on the interface between the core and shell was enhanced, the structure and cyclic performance of the electrodes will be greatly improved. Here, vertically aligned interpenetrating encapsulation composite nanoframeworks were assembled from Cl?/SO3 2?-codoped poly(3,4-ethylenedioxythiophene) (PEDOT) that interpenetrated and coated on porous Fe2O3 nanoframeworks (PEDOT-IE-Fe2O3) via a one-step Fe3+-induced in situ growth strategy. Compared with conventional wrapped structures and methods, the special PEDOT-IE-Fe2O3 encapsulation structure has many advantages. First, the codoped PEDOT shell ensures a high conductive network in the composites (100.6 S cm?1) and provides interpenetrating fast ion/electron transport pathways on the inner and outer surface of a single composite unit. Additionally, the pores inside offer void space to buffer the volume expansion of the nanoscale frameworks in cycling processes. In particular, the formation of Fe?S bonds on the organic?inorganic interface (between PEDOT shell and Fe2O3 core) enhances the structural stability and further extends the cell cycle life. The PEDOT-IE-Fe2O3 was applied as lithium-ion battery anodes, which exhibit excellent lithium storage capability and cycling stability. The capacity was as high as 1096 mA h g?1 at 0.05 A g?1, excellent rate capability, and a long and stable cycle process with a capacity retention of 89% (791 mA h g?1) after 1000 cycles (2 A g?1). We demonstrate a novel interpenetrating encapsulation structure to highly enhance the electrochemical performance of metal-oxide nanostructures, especially the cycling stability, and provide new insights for designing electrochemical energy storage materials.
关键词： porous Fe2O3,lithium-ion battery,PEDOT,organic?inorganic interface,interpenetrating encapsulation
更新于2025-09-11 14:15:04
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Preparation of multifunctional porous carbon electrodes through direct laser writing on a phenolic resin film
摘要： In this study, CuO@ZnO core-shell composite materials were successfully reported by chemical processes of depositing ZnO on the CuO surface. When evaluated as a lithium-ion battery anode, the CuO@ZnO composite shows a higher specific capacity of 300 mAh g-1 at 0.2 C after 100 cycles, especially CuO@ZnO-6.5% (the molar ratio of CuO to ZnSO4·7H2O of 1:0.065) composite material electrode still holds 459.5 mAh g-1 discharge capacity after 500 cycles. The test results show that the excellent coating on the CuO@ZnO composites improves the stability performance as electrodes for lithium-ion batteries due to the mechanism of ZnO. Therefore, the certain coverage of the CuO@ZnO composite electrode results in a valuable material for anodes in future batteries.
关键词： Lithium-ion battery,Anode material,CuO@ZnO composites
更新于2025-09-11 14:15:04
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Dispatch optimization of concentrating solar power with utility-scale photovoltaics
摘要： Concentrating solar power (CSP) tower technologies capture thermal radiation from the sun utilizing a field of solar-tracking heliostats. When paired with inexpensive thermal energy storage (TES), CSP technologies can dispatch electricity during peak-market-priced hours, day or night. The cost of utility-scale photovoltaic (PV) systems has dropped significantly in the last decade, resulting in inexpensive energy production during daylight hours. The hybridization of PV and CSP with TES systems has the potential to provide continuous and stable energy production at a lower cost than a PV or CSP system alone. Hybrid systems are gaining popularity in international markets as a means to increase renewable energy portfolios across the world. Historically, CSP-PV hybrid systems have been evaluated using either monthly averages of hourly PV production or scheduling algorithms that neglect the time-of-production value of electricity in the market. To more accurately evaluate a CSP-PV-battery hybrid design, we develop a profit-maximizing mixed-integer linear program (H) that determines a dispatch schedule for the individual sub-systems with a sub-hourly time fidelity. We present the mathematical formulation of such a model and show that it is computationally expensive to solve. To improve model tractability and reduce solution times, we offer techniques that: (1) reduce the problem size, (2) tighten the linear programming relaxation of (H) via reformulation and the introduction of cuts, and (3) implement an optimization-based heuristic (that can yield initial feasible solutions for (H) and, at any rate, yields near-optimal solutions). Applying these solution techniques results in a 79% improvement in solve time, on average, for our 48-h instances of (H); corresponding solution times for an annual model run decrease by as much as 93%, where such a run consists of solving 365 instances of (H), retaining only the first 24 h’ worth of the solution, and sliding the time window forward 24 h. We present annual system metrics for two locations and two markets that inform design practices for hybrid systems and lay the groundwork for a more exhaustive policy analysis. A comparison of alternative hybrid systems to the CSP-only system demonstrates that hybrid models can almost double capacity factors while resulting in a 30% improvement related to various economic metrics.
关键词： Grid integration,CSP-PV hybrid systems,Mixed-integer linear programming (MILP),System analysis,Photovoltaics (PV),Concentrating solar power (CSP),Dispatch optimization,Lithium-ion battery
更新于2025-09-11 14:15:04
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Effect of post heat treatment on the phase composition and strength of laser welded joints of an Al–Mg–Li alloy
摘要： In the present work, the effects of laser beam welding and post-weld heat treatment on the phase composition and mechanical properties of the 1424 alloy (Al–Mg–Li) joints were investigated. Holding the joints at a certain temperature was followed by quenching and artificial aging. The structural studies were carried out using electron microscopy, conventional X-ray diffractometry, and synchrotron radiation diffractometry. The heat treatment conditions were optimized to favor the formation of strengthening phases in the welds, the presence of which imparted mechanical strength to the joints. For the first time, 1424 Al alloy joints with a weld strength of σuts = 500 MPa have been obtained; this value of strength was achieved by applying post-weld annealing followed by quenching and artificial aging.
关键词： X-ray diffraction,Aluminum-lithium alloy,Laser welding,Electron microscopy,Synchrotron radiation,Mechanical properties
更新于2025-09-11 14:15:04
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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) - Efficient Er and Nd:Ti:LiNbO <sub/>3</sub> Ridge Waveguide Lasers for the Development of Mid Infrared Sources
摘要： The ferroelectric crystal lithium niobate (LiNbO3) is an attractive material for a variety of photonics applications due to its excellent electro-optic and nonlinear properties. Another benefit of rare-earth doped LiNbO3 is the easy implementation of low-loss waveguides leading to the development of waveguide amplifiers as well as waveguide lasers. In the past, a great deal of attention was attracted to the development of optically pumped Er3+- and Nd3+-doped LiNbO3 waveguide lasers emitting around the 1.5 μm telecom wavelength range and 1.08 μm, respectively. Up to date, Er- and Nd-doped LiNbO3 channel waveguide lasers with slope efficiencies up to 30 % [1] and 40 % [2], respectively, have been reported. However, a further improvement of the laser performance can be achieved by using a ridge waveguide geometry due to the smaller mode fields and improved overlap of modes at different wavelengths as well as the reduction of photorefractive damage. In this work, we report on our novel fabrication method for the development of highly efficient Er: and Nd:Ti:LiNbO3 ridge waveguide amplifiers and lasers [3,4]. To improve the amplifier/laser performance a fabrication technique comprised of ridge definition by diamond blade dicing followed by three-side Er/Nd/Ti deposition and in-diffusion (Fig. 1a) was developed and refined allowing higher Er/Nd doping concentrations and overlap of Er/Nd diffusion profiles with guided modes. An internal gain of 3.0 dB/cm has been measured in 4.6 cm long Er:Ti:LiNbO3 ridge waveguides for a coupled pump power of 200 mW at 1486 nm [3]. Utilizing this high internal gain, we achieved efficient lasing with a slope efficiency of 33 % at 1561 nm (see Fig. 1b) [3]. Furthermore, we demonstrated a Nd:Ti:LiNbO3 ridge waveguide laser with a slope efficiency of 34 % at a wavelength of 1084.7 nm pumped by a Ti:Sapphire laser emitting at 814 nm (see Fig. 1b) [4]. Due to improved photorefractive damage resistance by indium tin oxide (ITO) coating we achieved stable laser operation with a maximum output power of 108 mW for a coupled pump power of 402 mW corresponding to an intensity of ~490 kW/cm2 [4]. Recently, a novel method to achieve local periodic poling of Ti-diffused ridge waveguides in zx-cut LiNbO3 has been demonstrated [5]. In contrast to previous approaches, this method for periodic poling allows an optimization of the ridge waveguide geometry for nonlinear optics applications such as quasi-phase-matched (QPM) difference frequency generation (DFG). The ability to develop highly efficient Er- and Nd-doped ridge waveguide lasers in LiNbO3 and to achieve local QPM allows for the development of efficient hybrid optical devices in the same ridge waveguide emitting in the mid-infrared suitable for applications such as gas sensing.
关键词： Nd-doped,ridge waveguide lasers,lithium niobate,photonics applications,Er-doped
更新于2025-09-11 14:15:04
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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) - Spatial Akhmediev Breathers in Slab Waveguides
摘要： The analytical breather-solutions of the Nonlinear Schr¨odinger Equation (NLS) have been intensively studied and veri?ed experimentally in the time-space system of optical pulse propagation in ?bers. In space-space systems, i.e. in optical beam propagation breathers in ultra-fast nonlinear media have not been observed due to the breather’s in?nite background and a resulting extremely large power. In a lithium niobate slab waveguide with two second-harmonic (SH) resonances the resulting quasi-cubic cascaded quadratic nonlinearity provided together with the intrinsic cubic susceptibility enough nonlinearity for breather excitation at experimentally reachable powers. We could characterize the ?rst ultra-fast spatial-spatial optical breathers in a 5-cm-long titanium in diffused lithium niobate slab waveguide at power levels down to tens of kW. The guided fundamental wave (FW) TM0 ?lm mode at l=1.32mm is phase-matched for type-I SH generation to TE0 and TE1 SH modes at temperatures near 295 and 344C. With temperature tuning the phase-mismatch and the two effective cascaded nonlinearities were adjusted. For breather observation, we aimed for a large phase-mismatch with low SH levels such that the cascaded nonlinearity is quasi-cubic and the propagation is well approximated by the NLS and its breather solutions. A frequency-doubled Nd:YAG-pumped OPA with CW-seeding delivered 5-ps long pulses with up to 200kW peak power in the waveguide. With a cylindrical telescope the beam was transformed into a very wide elliptical beam to approximate the breather background. The beam was end-?re coupled into the FW TM0 mode. A variable few% of the beam were separated and coupled with a tilt and good overlap to the main beam into the waveguide to produce a spatial modulation of the input with adjustable period and modulation depth. A beam width of 1.5mm was large enough in the compromise between available beam power and in?nite beam width. A beam with a transverse modulation with periods between 130 to 300mm approximates a constant background with modulation well enough to trigger modulation instability that develops eventually into the breather. The FW and the SH output of the waveguide were imaged into cameras. By changing the power the breather moves along the waveguide and the whole breather can be sampled at the waveguide end during a power scan. Each sample is normalized to its total power. An example is shown in Fig.1. Fig.1(left) Measured breather, scanned at the waveguide output dependent on power. (right) Simulation of the measurement. The in?uence of deviations from ideal theory and real world conditions like ?nite beam width, damping, non-uniform phase-mismatch, pulsed input, and cascading instead of an exact cubic nonlinearity was investigated in simulations describing the experiment very well (see example in Fig.1). The new platform is very versatile. A wide parameter space of different nonlinearity, varying transverse breather period and input modulation depth was investigated. Higher-order breathers were observed (see the grow-ing maxima between the main peaks in Fig.1). The drastic temperature-dependent reduction of the power level for breather formation due to cascading was observed. The expected speci?c details of quadratic breathers like a SH following the FW was documented. The spatial breather spectra showed the expected triangular shape.
关键词： modulation instability,lithium niobate slab waveguide,Nonlinear Schr¨odinger Equation,cascaded quadratic nonlinearity,optical breathers
更新于2025-09-11 14:15:04
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Generation of a Few Cycle Terahertz Pulse in Aperiodically Poled Lithium Niobate by Sequence of Pump Pulses
摘要： It is shown that chirped aperiodically poled lithium niobate crystal is capable to generate powerful THz pulses with controllable number of THz field oscillations (from nearly single- to multi-cycles), when it is pumped by sequence of femtosecond laser pulses with chirped delays between adjacent pulses. The peak electric field strength of about 0.3 MV/cm (for non-focused THz beam) is predicted if intensity of each pump pulse in the sequence is 20 GW/cm2.
关键词： Optical rectification,Aperiodically poled lithium niobate,Terahertz pulse,Femtosecond laser pulses
更新于2025-09-11 14:15:04