- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[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 Kerr Beam Self-Cleaning in Yb-Doped Multimode Fiber Taper
摘要： Spatial Kerr beam self-cleaning (KBSC), which transforms an output speckled beam in a quasi-single mode beam in graded index (GRIN) multimode optical fibers (MMFs), has been reported recently [1,2]. GRIN MMFs are also interesting waveguides for supercontinuum (SC) generation in the visible and near infrared regions, as successfully demonstrated by launching femtosecond or subnanosecond pulses in the anomalous (1550 nm) or normal (1064 nm) dispersion regime, respectively [1,3]. The spectral broadening features were explained through the interplay between spatiotemporal multimode soliton oscillations and dispersive wave generation in fibers with parabolic index profile. On the other hand, tapered optical fibers are well known to provide a number of useful features, including strong mode confinement capability, small scale diameter and broad SC generation [4,5]. Herein, we report visible-short infrared SC generation in combination with KBSC in long (~10 m) tapered Yb-doped MMFs, with parabolic index profile and parabolic doping concentration.
关键词： supercontinuum generation,Spatial Kerr beam self-cleaning,graded index multimode optical fibers,Yb-doped multimode fiber taper
更新于2025-09-12 10:27:22
-
Random mode coupling assists Kerr beam self-cleaning in a graded-index multimode optical fiber
摘要： In this paper, we numerically investigate the process of beam self-cleaning in a graded-index multimode optical ?ber, by using the coupled-mode model. We introduce various models of random linear coupling between spatial modes, including coupling between all modes, or only between degenerate ones, and investigate the e?ects of random mode coupling on the beam self-cleaning process. The results of numerical investigations are in complete agreement with our experimental data.
关键词： Nonlinear optics,Kerr e?ect,Multimode ?bers,Beam self-cleaning
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) - Random Mode Coupling Assists Kerr Beam Self-Cleaning in a Graded-Index Multimode Optical Fiber
摘要： Spatiotemporal light beam dynamics in multimode ?bers (MMF) recently has attracted renewed interest in both fundamental physics and various ?elds of practical application [1,2]. Recent experiments [2,3] have shown that, owing to the Kerr effect, a process of beam self-cleaning can be observed in graded-index (GRIN) MMFs. As a result, one observes a robust nonlinear beam, which has a size that is close to the fundamental mode at the ?ber output, in contrast to a speckled output beam, which is obtained in the case of the linear regime. In this paper, we numerically investigate the process of beam self-cleaning in GRIN MMFs. Unlike previous approaches [3], where the nonlinear propagation of a spatial beam along the multimode ?ber was described by the generalized 3D nonlinear Schrdinger equation, we use the coupled-mode model, which has the following form: 2i dAp,m dζ = D(n + 1)2Ap,m + p ∑ m+m1=m2+m3 ∑ p+p1=p2+p3 f m,m1,m2,m3 p,p1,p2,p3 Ap1,m1Ap2,m2Ap3,m3 + ∑ m1,p1 Cm,m1 p,p1 Ap1,m1 . These equations separately describe the evolution of the amplitude of each mode Ap,m. The coupled mode approach signi?cantly reduces the computation time, due to the use of a large integration step. To account for the various imperfections of the multimode ?ber, caused by fabrication, bending or tilting, we added a random linear coupling term to the equation. Fig. 1 Dynamics of energy distribution by modes and the output ?eld for the model without random linear coupling (a) and with random linear coupling between degenerate modes (b). In this contribution, we describe various models of random linear coupling between spatial modes, including coupling between all modes, or only between degenerate ones, and investigate the effects of random mode coupling on the beam self-cleaning process. Fig. 1a shows the spatial dynamics of energy distribution among the modes, corresponding to a model without any random linear coupling. In this case, in spite of being in a strong nonlinear regime, the power of the fundamental mode oscillates along the ?ber, and we still obtain a speckled beam at the ?ber output. On the other hand, if we consider a model with random linear coupling between spatial modes with equal mode numbers, one readily observes the appearance of a self-cleaning effect, and the fundamental mode power swiftly stabilizes upon the propagation (see Fig. 1b). The output beam in this case has a size that is close to that of the fundamental mode. The results of numerical investigations are in complete agreement with our experimental data.
关键词： Kerr effect,graded-index multimode optical fiber,beam self-cleaning,random mode coupling
更新于2025-09-11 14:15:04
-
[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) - Disorder-Induced Acceleration of Condensation in Multimode Fibers
摘要： Recent studies on wave turbulence revealed that a purely classical system of random waves can exhibit a process of condensation, whose thermodynamic properties are analogous to those of Bose-Einstein condensation [1-3]. Classical wave condensation finds its origin in the natural thermalization toward the Rayleigh-Jeans equilibrium distribution, whose divergence is responsible for the macroscopic occupation of the fundamental mode of the system. The experimental study of condensation in a conservative (cavity-less) configuration constitutes a major challenge, because of the prohibitive large propagation lengths required to achieve thermalization. In contrast with this commonly accepted opinion, a remarkable phenomenon of spatial beam self-cleaning has been recently discovered in graded-index multimode optical fibers (MMFs) [4-7]. This phenomenon is due to a purely conservative Kerr nonlinearity [7] and its underlying mechanism still remains debated. Light propagation in MMFs is known to be affected by a structural disorder of the material due to inherent imperfections and external perturbations. On the basis of the wave turbulence theory, we formulate a nonequilibrium kinetic description of the random waves that accounts for the impact of disorder. The theory reveals that a structural disorder is responsible for a dramatic acceleration of the process of condensation by several orders of magnitudes. This counterintuitive mechanism of condensation acceleration provides a natural explanation for the effect of spatial beam self-cleaning: As a consequence of the fast condensation process, the beam power rapidly flows toward the fundamental mode of the MMF, which becomes macroscopically populated to the detriment of the other modes that exhibit energy equipartition, as predicted by the Rayleigh-Jeans distribution [1]. The simulations of the nonlinear Schrodinger equation (NLSE) are in quantitative agreement with those of the derived kinetic equation, and thus confirm the validity of the theory and the effect of acceleration of condensation mediated by disorder (see Fig. 1). Furthermore, the derived kinetic equation also explains why spatial beam self-cleaning has not been observed in step-index MMFs. We performed experiments in a MMF to evidence the transition to light condensation by varying the coherence of the input beam (as described in Fig. 1c). When a large number of modes are excited, the output intensity distribution tends to relax toward the thermal Rayleigh-Jeans distribution, i.e., the 'temperature' is above the critical value for condensation (E > Ecrit in Fig. 1c) and spatial beam self-cleaning is not observed. By reducing the excitation of modes (E < Ecrit in Fig. 1c), the power gradually condenses into the fundamental mode of the MMF, leading to a cleaned beam with a measured condensate fraction as large as ～60%.
关键词： multimode fibers,spatial beam self-cleaning,condensation,wave turbulence,disorder
更新于2025-09-11 14:15:04
-
[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) - Kerr Beam Self-Cleaning in the Telecom Band
摘要： Multimode graded index (GRIN) fibers received a renewed interest in recent years, in particular for the development of new laser sources [1]. In many cases, the use of GRIN fibers is limited by multimodal propagation, leading to a spatially modulated intensity distribution (speckles) at the fiber output. Recent studies have found that quasi-single mode propagation can be recovered in GRIN fibers by the so-called Kerr self-cleaning effect [2]. It consists in the spontaneous recovery of the spatial beam quality, without any frequency shift [2] (as opposed to, e.g., Raman beam self-cleaning [3]). This nonlinear process was only observed so far at laser wavelengths around 1 μm, for peak power levels above a certain threshold value. In this communication, we show that Kerr beam self-cleaning also occurs in a GRIN fiber pumped with chirped pulses in the telecom band (1562 nm). At these wavelengths, the power threshold of the self-cleaning process is decreased by one order of magnitude with respect to pumping at 1 μm.
关键词： GRIN fiber,multimode fibers,nonlinear optics,Kerr beam self-cleaning,telecom band
更新于2025-09-11 14:15:04
-
[IEEE 2019 International Conference on Clean Electrical Power (ICCEP) - Otranto, Italy (2019.7.2-2019.7.4)] 2019 International Conference on Clean Electrical Power (ICCEP) - Application of Dust Mitigation Strategies to Single-Axis-Tracking Photovoltaic Modules in the Semi-Arid Areas of South Africa
摘要： This paper provides field generated data for single-axis-tracker (SAT) photo voltaic (PV) modules subjected to the semi-arid Northern Cape environment of South Africa. The research objectives are the investigation of the effects of dust soiling on PV module performance and the application of experimental dust mitigation methods. This includes the use of a hydrophobic anti-soiling coating and also the execution of a self-cleaning manoeuvre by the SAT systems. Two SAT systems were deployed to serve as experimental platform, from which data was obtained for a three month period (97 days). Raw data validation is established with comprehensive weather monitoring (ambient temperature, wind speed, wind direction, rainfall, pressure, and humidity), irradiance and PV module back sheet temperatures recorded, in accordance with the IEC61724 standard. An intelligent device was used to extract Current-Voltage (I-V) curves from individual PV modules. Maximum PV module power output is derived from the measured I-V curves, validated with a single-diode curve fitting routine. The comparative study between the different PV modules is done with a performance ratio (PR), defined as the temperature and irradiance corrected performance factor of a PV module. Contrary to the initial hypothesis, results indicated that the hydrophobic coating actually promoted dust soiling. The applied self-cleaning capability of the SAT system did not yield any conclusive results as a dust mitigation method. Finally, interesting in-field observations are discussed.
关键词： photovoltaic modules,self-cleaning,hydrophobic coating,performance ratio,dust soiling
更新于2025-09-11 14:15:04
-
Reference Module in Materials Science and Materials Engineering || Glass, Self-Cleaning
摘要： In this article, the essential technological and the scientific features of self-cleaning glass coatings based on titanium dioxide have been described. In addition, detailed aspects of the coating process and the functional aspects of the coatings, which provide the dual hydrophilic and photoactive cleaning mechanism, have also been presented.
关键词： Titanium Dioxide,Glass,Hydrophilic,Photocatalytic Activity,Self-Cleaning
更新于2025-09-10 09:29:36
-
A Bioinspired, Highly Transparent Surface with Dry-Style Antifogging, Antifrosting, Antifouling, and Moisture Self-Cleaning Properties
摘要： Transparent coatings with antireflection, antifogging, antifrosting, antifouling, and moisture self-cleaning properties can dramatically improve the efficiency and convenience of optical elements and thus are highly desirable for practical applications. Here, it is demonstrated that a bionic nanocone surface (BNS) fabricated by a facile, low-cost process consisting of template-assisted prepolymer curing followed by surface modification can possess the multiple functions listed above. The polymer coating firmly adheres to a glass substrate due to bonding agents. After SiO2 nanoparticle deposition and low-surface-energy fluorosilane modification, the coating shows low microdroplet adhesion. As a result, the as-prepared BNS exhibits a high transmittance when exposed to fog and good clarity even when the temperature decreases to ?20 °C in a humid environment. Dipping the BNS into exemplified graphite powder has almost no influence on the transparency, and the BNS can realize self-cleaning of moisture when the surface is covered with a thick layer of man-made contaminants.
关键词： dry-style antifogging,bionic nanocone array,antifouling,moisture self-cleaning,antifrosting
更新于2025-09-10 09:29:36
-
A Novel Green Stabilization of TiO2 Nanoparticles onto Cotton
摘要： Facile embedding of TiO2 nanoparticles onto cotton fabric has been successfully attained by ultraviolet light irradiations. The adhesion of nanoparticles with fibre surface, tensile behaviour and physicochemical changes before and after ultraviolet treatment were investigated by scanning electron microscopy, energy dispersive X-ray and inductive couple plasma-atomic emission spectroscopy. Experimental variables i.e. dosage of TiO2 nanoparticles, temperature of the system and time of ultraviolet irradiations were optimised by central composite design and response surface methodology. Moreover, two different mathematical models were developed for incorporated TiO2 onto cotton and tensile strength of cotton after ultraviolet treatment and used further to testify the obtained results. Self-clean fabric through a synergistic combination of cotton with highly photo active TiO2 nanoparticles was produced. Stability against ultraviolet irradiations and self-cleaning properties of the produced fabric were evaluated.
关键词： Nanoparticles,Self-stabilization,Self-cleaning,TiO2,UV fixation
更新于2025-09-09 09:28:46
-
[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI, USA (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Fundamental Characterization of Anti-Soiling Coatings for PV Glass: Application of Small-Angle X-ray Scattering
摘要： When dust and other particulates accumulate on the surface of solar modules, the efficiency of these soiled modules is significantly reduced. Soiling is especially problematic in regions with little rain, where water resources for cleaning modules are scarce. To combat this issue, anti-soiling coatings, on the top-surface of solar modules, are beginning to enter the market. However, limited understanding of anti-soiling mechanisms and uncertainty in their durability has limited their deployment. Porous coatings are anticipated to discourage soiling because their rough surfaces reduce the strength and probability of dirt-to-coating bonds. However, the evolution of this morphology through soiling cycles is largely unknown. Here we present the use of small angle X-ray scattering (SAXS) to monitor the morphology of pristine and soiled, industry-sourced coatings. Initial soiling tests are performed using a standardized soil (AZ road dust) in the lab. This work demonstrates the effectiveness of SAXS in monitoring coating morphology despite the presence of soil surface layers. The capability of SAXS studies to be performed under various temperature, humidity, and soiling conditions sets it apart as a strong characterization tool for developing the understanding of functionality and degradation mechanisms of anti-soiling coatings for PV glass.
关键词： soiling,anti-soiling,materials forensics,small-angle X-ray scattering,anti-reflection,PV glass,coatings,self-cleaning
更新于2025-09-09 09:28:46