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Passively Q-switched femtosecond-laser-written thulium waveguide laser based on evanescent field interaction with carbon nanotubes

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Photonics Research 2018年第10期6卷 971-980页

作者： ESROM KIFLE PAVEL LOIKO JAVIER RODRíGUEZ VáZQUEZ DE ALDANA CAROLINA ROMERO AIRáN RóDENAS SUN YUNG CHOI JI EUN BAE fabian rotermund VIKTOR ZAKHAROV ANDREY VENIAMINOV MAGDALENA AGUILó FRANCESC DíAZ UWE GRIEBNER VALENTIN PETROV XAVIER MATEOS Universitat Rovira i Virgili Departament Quimica Fisica i Inorgànica Fisica i Cristal·lografia de Materials i Nanomaterials (FiCMA-FiCNA)-EMaS Campus Sescelades E-43007 Tarragona Spain ITMO University 49 Kronverkskiy pr. 197101 St. Petersburg Russia Aplicaciones del Láser y Fotónica University of Salamanca 37008 Salamanca Spain Istituto di Fotonica e Nanotecnologie Consiglio Nazionale delle Ricerche (IFN-CNR) Piazza Leonardo da Vinci 32 20133 Milano Italy Department of Physics KAIST 291 Daehak-ro Yuseong-gu 34141 Daejeon South Korea Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy Max-Bom-Str. 2a D-12489 Berlin Germany

Surface channel waveguides(WGs) were fabricated in a monoclinic Tm^(3+):KLu(WO_4)_2 crystal by femtosecond direct laser writing(fs-DLW). The WGs consisted of a half-ring cladding with diameters of 50 and 60 μm located just beneath the crystal surface. They were characterized by confocal laser microscopy and μ-Raman spectroscopy,indicating a reduced crystallinity and stress-induced birefringence of the WG cladding. In continuous-wave(CW)mode, under Ti:sapphire laser pumping at 802 nm, the maximum output power reached 171.1 mW at 1847.4 nm,corresponding to a slope efficiency η of 37.8% for the 60 μm diameter WG. The WG propagation loss was0.7 0.3 d B∕cm. The top surface of the WGs was spin-coated by a polymethyl methacrylate film containing randomly oriented(spaghetti-like) arc-discharge single-walled carbon nanotubes serving as a saturable absorber based on evanescent field coupling. Stable passively Q-switched(PQS) operation was achieved. The PQS60 μm diameter WG laser generated a record output power of 150 m W at 1846.8 nm with η = 34.6%. The conversion efficiency with respect to the CW mode was 87.6%. The best pulse characteristics(energy/duration)were 105.6 nJ/98 ns at a repetition rate of 1.42 MHz.

关键词：激光技术波导技术发展现状通讯技术

550 MHz carbon nanotube mode-locked femtosecond Cr:YAG laser

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Chinese Optics Letters 2018年第6期16卷 64-67页

作者： Jun Wan Kim Sun Young Choi Won Tae Kim Bong Joo Kang Won Bae Cho Guang-Hoon Kim fabian rotermund Advanced Medical Device Research Division Korea E1ectrotechnology Research Institute （KERI） Ansan 15588 Korea Department of Physics Korea Advanced Institute of Science and Technology （KAIST） Daejeon 34141 Korea BioMed Research Section Electronics and Telecommunications Research Institute （ETRI） Daejeon 34129 Korea

We demonstrate a femtosecond Cr：YAG laser mode-locked by a carbon nanotube saturable absorber mirror（CNT-SAM） at a repetition rate of 550 MHz. By employing the CNT-SAM, which exhibits a modulation depth of 0.51% and a saturation fluence of 28 μJ∕cm^2 at 1.5 μm, we achieved a compact bulk Cr：YAG laser with selfstarting mode-locked operation near 1.5 μm, delivering an average output power of up to 147 m W and a pulse duration of 110 fs. To our knowledge, this system provides the highest repetition rate among reported CNT-SAM mode-locked Cr：YAG lasers and the shortest pulse duration among saturable absorber mode-locked Cr：YAG lasers with repetition rates above 500 MHz.

关键词： YAG MHz carbon nanotube mode-locked femtosecond Cr:YAG laser Cr

Power-scalable sub-100-fs Tm laser at 2.08μm

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High Power Laser Science and Engineering 2021年第4期9卷 41-45页

作者： Li Wang Weidong Chen Yongguang Zhao Hanlin Yang Wei Jing Zhongben Pan Hui Huang Jiachen Liu Ji Eun Bae fabian rotermund Pavel Loiko Xavier Mateos Zhengping Wang Xinguang Xu Uwe Griebner Valentin Petrov Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy 12489 BerlinGermany Jiangsu Key Laboratory of Advanced Laser Materials and Devices School of Physics and Electronic EngineeringJiangsu Normal UniversityXuzhou 221116China Institute of Chemical Materials China Academy of Engineering PhysicsMianyang 621900China Key Laboratory of Advanced Ceramics and Mechanical Technology of Ministry of Education School of Materials Science and EngineeringTianjin UniversityTianjin 300072China Department of Physics Korea Advanced Institute of Science and Technology(KAIST)34141 DaejeonRepublic of Korea Centre de Recherche sur les Ions les Matériaux et la Photonique(CIMAP)UMR 6252 CEA-CNRS-ENSICAENUniversitéde Caen14050 Caen Cedex 4France Física i Cristal·lografia de Materials i Nanomaterials(FiCMA-FiCNA) Universitat Rovira i Virgili(URV)43007 TarragonaSpain State Key Laboratory of Crystal Materials and Institute of Crystal Materials Shandong UniversityJinan 250100China

We report on a power-scalable sub-100-fs laser in the 2-μm spectral range using a Tm;-doped‘mixed’(Lu,Sc);O;sesquioxide ceramic as an active *** as short as 58 fs at 2076 nm with an average output power of 114 mW at a pulse repetition rate of approximately 82.9 MHz are generated by employing single-walled carbon nanotubes as a saturable absorber.A higher average power of 350 m W at 2075 nm is obtained at the expense of the pulse duration(65 fs).A maximum average power of 486 mW is achieved for a pulse duration of 98 fs and an optical conversion efficiency of 22.3%,representing the highest value ever reported from sub-100-fs mode-locked Tm lasers.

关键词： 2-μm mode-locked laser single-walled carbon nanotubes Tm:(Lu Sc)_(2)O_(3)

Generation of 84-fs pulses from a mode-locked Tm：CNNGG disordered garnet crystal laser

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Photonics Research 2018年第8期6卷 800-804页

作者： ZHONGBEN PAN YICHENG WANG YONGGUANG ZHAO HUALEI YUAN XIAOJUN DAI HUAQIANG CAI JI EUN BAE SUN YOUNG CHOI fabian rotermund XAVIER MATEOS JOSEP MARIA SERRES PAVEL LOIKO UWE GRIEBNER VALENTIN PETROV Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy Max-Bom-Str. 2a D-12489 Berlin Germany Institute of Chemical Materials China Academy of Engineering Physics Mianyang 621900 China Jiangsu Key Laboratory of Advanced Laser Materials and Devices Jiangsu Normal University Xuzhou 221116 China Department of Physics Korea Advanced Institute of Science and Technology (KAIST) 34141 Daejeon South Korea Fisica i Cristal·lografia de Materials i Nanomaterials (FiCMA-FiCNA)-EMaS Departament de Quimica Fisica i Inorganica Universitat Rovira i Virgili (URV) Campus Sescelades E-43007 Tarragona Spain ITMO University 49 Kronverkskiy Pr. 197101 St. Petersburg Russia

A mode-locked laser based on a Tm:CNNGG disordered crystal as an active medium and a single-walled carbon nanotube saturable absorber is demonstrated, operating at a central wavelength of 2018 nm. Transformlimited 84 fs pulses are generated with an average output power of 22 mW at a repetition rate of ~90 MHz.A maximum output power of 98 mW is obtained at a slightly longer pulse duration of 114 fs.

关键词：无序晶体纳米管通讯技术发展现状

A Eulerian population balance/Monte Carlo approach for simulating laminar aluminum dust flames

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Particuology 2024年第5期88卷 323-343页

作者： fabian Sewerin Jannis Finke Emmy Noether Group for Dispersed Multiphase Flows Chair of Mechanical Process EngineeringOtto-von-Guericke-Universität MagdeburgUniversitätsplatz 239106 MagdeburgGermany

Recently,metal powders have been conceptualized as carbon-free recyclable energy carriers that may form a cornerstone of a sustainable energy *** combustion of metal dusts in oxidizing atmospheres is exothermal and yields oxide particles that could,potentially,be retrieved and,subsequently,recharged by conversion to pure metals using green primary energy *** a step towards a predictive tool for designing metal dust combustors,we present a fully Eulerian modelling approach for laminar particle-laden reactive flows that is,conceptually,based on a population balance description of the dispersed particles and relies on a stochastic Eulerian solution *** the population balance equation(PBE)is formulated for the number-weighted distribution of characteristic properties among all particles near a spatial location,it is kinetically informed by the rates at which mass,momentum and heat are exchanged between the carrier gas and the particulate phase on the single particle *** the scope of the Eulerian Monte Carlo solution scheme,the property distribution is discretely represented in terms of the total number density and a finite number of property samples and the computational work is channelled towards the Eulerian estimation of mean particle *** the case of reactive aluminum particles,we combine a kinetic description of the gas-particle heat and mass transfer with a transport-limited continuum formulation to obtain rate expressions that are valid across the entire particle size range from the free molecular through the continuum *** velocity,the particle properties include only the particle mass,temperature and oxide mass *** set of thermochemical degrees of freedom is retained also as phase transitions due to melting occur,drawing on a smooth blend of the solid and liquid thermodynamic and material *** particle-level formulation encompasses aluminum evaporation,surface oxidation,scavenging of oxi

关键词： Metal dust combustion Aluminum Population balance Eulerian Monte Carlo

Freeform imaging systems:Fermat's principle unlocks"first time right"design

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Light(Science & Applications) 2021年第6期10卷 1029-1040页

作者： fabian Duerr Hugo Thienpont Brussels Photonics Department of Applied Physics and Photonics(B-PHOT TONA)Vrije Universiteit BrusselPleinlaan 21050 BrusselsBelgium

For more than 150 years,scientists have advanced aberration theory to describe,analyze and eliminate imperfections that disturb the imaging quality of optical components and ***,they have developed optical design methods for and manufacturing techniques of imaging systems with ever-increasing complexity and performanee up to the point where they are now including optical elements that are unrestricted in their surface *** so-called optical freeform elements offer degrees of freedom that can greatly extend the functionalities and further boost the specifications of state-of-the-art imaging ***,the drastically increased number of surface coefficients of these freeform surfaces poses severe challenges for the optical design process,such that the deployme nt of freeform optics remained limited until *** this paper,we present a deterministic direct optical design method for freeform imaging systems based on differential equations derived from Fermats principle and solved using power *** method allows calculating the optical surface coefficients that ensure minimal image blurring for each individual order of *** demonstrate the systematic,deterministic,scalable,and holistic character of our method with catoptric and catadioptric design *** such we introduce a disruptive methodology to design optical imaging systems from scratch,we largely reduce the "trial-and-error",approach in present-day optical design,and we pave the way to a fast-track uptake of freeform elements to create the nextgeneratio n high-end *** include a user application that allows users to experience this unique design method hands-on.

关键词： optics eliminate design

Investigation of grain mass flow in a mixed flow dryer

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Particuology 2014年第1期12卷 33-39页

作者： fabian Weigler Jochen Mellmann Department of Post-harvest Technology Leibniz Institute for Agricultural Engineering Potsdam-Bornim

The numerical modeling of grain drying is a topic of great relevance to post-harvest engineering. The required type of drying process depends on the quantity of grain to be dried and the required quality of the grain. The choice of the drying system depends on the operating parameters of the drying process. The granular flow pattern of the material exerts a significant influence on the drying process. Post-harvest drying of grain is essential for better storage, handling, and processing. Therefore, it is important to know the material behavior that controls the particle flow patterns of grain in the drying equipment to guarantee the product quality and to optimize the drying process conditions. The discrete element method （DEM） was applied to investigate the particle flow pattern of wheat through a mixed-flow dryer （MFD） without airflow, and the findings were compared with experimental results in this work. The investigations were performed using dry wheat with 14 wb% moisture content.

关键词： Keywords:Mixed-flow dryerGrain mass flowDiscrete element method

Machine-learning assisted design principle search for singlet fission:an example study of cibalackrot

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npj Computational Materials 2022年第1期8卷 1703-1716页

作者： fabian Weber Hirotoshi Mori Department of Applied Chemistry Chuo University112-8551 Tokyo-toBunkyo-kuKasuga1-13-27Japan Department of Theoretical and Computational Molecular Science Institute for Molecular ScienceOkazaki444-8585Japan

This work uses quantum chemistry calculations and machine learning to explore design rules for singlet fission in a chemical space of four million indigoid *** identify~400,000 derivatives of 2,2′-diethenyl cibalackrot,which theoretically fulfil the energy conditions for exoergic singlet fission above the silicon band gap *** this database with a random forest classifier,we observe that small substituents with positive mesomeric effects and weak negative inductive effects reinforce the desired energetic conditions when placed at specific ***,a subset of molecules that reflects the random forest classifier’s rules are investigated for their quantum chemical properties to translate the desirable structural motifs into wavefunction-based design ***,direct correlations between the energetic condition for singlet fission,the biradical character and the charge and triplet spin density in prominent molecular regions are identified,providing insights that may serve as a guide for singlet fission core structure development.

关键词： singlet quantum classifier

Adaptive nonlinear model predictive control design of a flexible-link manipulator with uncertain parameters

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Acta Mechanica Sinica 2017年第3期33卷 529-542页

作者： fabian Schnelle Peter Eberhard Institute of Engineering and Computational Mechanics University of Stuttgart

This paper presents a novel adaptive nonlinear model predictive control design for trajectory tracking of flexible-link manipulators consisting of feedback linearization, linear model predictive control, and unscented Kalman filtering. Reducing the nonlinear system to a linear system by feedback linearization simplifies the optimization problem of the model predictive controller significantly, which, however, is no longer linear in the presence of parameter uncertainties and can potentially lead to an undesired dynamical behaviour. An unscented Kalman filter is used to approximate the dynamics of the prediction model by an online parameter estimation, which leads to an adaptation of the optimization problem in each time step and thus to a better prediction and an improved input action. Finally, a detailed fuzzy-arithmetic analysis is performed in order to quantify the effect of the uncertainties on the control structure and to derive robustness assessments. The control structure is applied to a serial manipulator with two flexible links containing uncertain model parameters and acting in three-dimensional space.

关键词： Model predictive control Feedback linearization Unscented Kalman filter Flexible-link manipulator Fuzzy-arithmetical analysis