PROF. DR. RALF HELLMANN

Hellman, Ralf | Materials, Intelligent Systems

Research Area:
Materials, Intelligent Systems

Aschaffenburg University of Applied Sciences, Germany
Faculty: Engineering

E-Mail: Ralf.Hellmannth-abde
Phone: +49 6021/4206-874



Areas of Expertise

Research fields
Modern Production Technologies (Innovative Material Processing)

  • Laser micro-nano processing
  • Processing of transparent materials
  • Processing of electronic materials
  • Robotics and automation
  • Additive and Hybrid Manufacturing
     

Laseroptical systems (Material Testing & Sensor Technology)

  • Process monitoring
  • Beam-shaping tools
     

Digitalization (Intelligent Sensors & Signals, Material Testing & Sensor Technology)

  • Sensing and process monitoring and conditioning
  • Development of algorithms for Artificial Intelligence
     

Photonics (Innovative Material Processing, Material Testing & Sensor Technology)

  • Integrated optofluidics
  • Planar polymer optical sensing
  • Surface functionalization
  • Laser Direct Writing


Research Labs & Institutes


Current Research Projects

Mr. Professor Hellmann's research group has conducted more than 70 research projects funded by the EU, German Research Foundation (DFG), German Federal Ministry of Education and Research (BMBF), German Federal Ministery of Economic Affairs and Energy (BMWI), German Federal Office for Radiation Protection (BFS). The following research descriptions are examples that outline the recent scopes of this research.
 

OpenLaserLathe

OpenLaserLathe

MaterialTestingSensorTechnology   InnovativeMaterialProcessing  

Development of an optical engine for femtosecond laser based micro lathe, adapted to high precision needs for 3D processing.

More
 

MOEBIUS Lab-on-a-Chip

MOEBIUS

ElectronicElectricDrives   IntelligentSensorsSignals   MaterialTestingSensorTechnology

Development of a multi-adaptive micro-opto-electronic sensor system for liquid analysis (Lab-on-a-Chip-System).

More

Ultrashort pulsed laser optics module for generating multi-Bessel beams for high aspect ratio drilling

Ultrashort pulsed laser optics module for generating multi-Bessel beams for high aspect ratio drilling

InnovativeMaterialProcessing

Optical simulation for laser drilling with multi-Bessel beams and process development for semiconductor ceramic processing.

More

Laser micromachining for the electronics of the future (LEZ)

Laser micromachining for the electronics of the future (LEZ)

ElectronicsElectricDrives   IntelligentSystemsCleanTech   MaterialTestingSensorTechnology   MaterialsCleanTech   InnovativeMaterialProcessing

Today, laser micro machining is a key and versatile tool in modern electronics production.

More

BFS Hot Bragg

BFS Hot Bragg

IntelligentSensorsSignals   MaterialTestingSensorTechnology    InnovativeMaterialProcessing  

Development of a laser-based manufacturing process for sapphire fiber-based optical high-temperature sensors based on integrated Bragg gratings.
More

Manufacturing of microfluidic 3D structures

Manufacturing of microfluidic 3D structures in transparent polymers by laser-induced inverse 3D printing (Mikrofluidic)
IntelligentSensorsSignals   InnovativeMaterialProcessing 

In this project, an ultra-short pulsed laser is used to create an internal, freely positionable material modification
More

LOTUS 2: Innovations in Laser-Optic Technology for Ultraviolet Ultra-Short pulsed Lasers

LOTUS 2: Innovations in Laser-Optic Technology for Ultraviolet Ultra-Short pulsed Lasers

InnovativeMaterialProcessing

The ongoing trend of miniaturization into the micrometre range demands for innovative machining tools to cope with the associated requirements in terms of precision and quality.

More

SKZ: Optimization of thermal joining quality of hybrid metal

SKZ

RoboticsAutomation   IntelligentSensorsSignals   IntelligentSystemsCleanTech    MaterialTestingSensorTechnology   MaterialsCleanTech   InnovativeMaterialProcessing

Optimization of thermal joining quality of hybrid metal - fibre reinforced plastic composites using additive manufactured surface structured metal parts.
More



Curriculum Vitae

Since 2002 Aschaffenburg UAS Professorship

Faculty of Engineering

  • Professorship for Physics, Laser Technology, Photonics
  • Head of alp (Applied Laser and Photonics Group)
  • Head of OIL (Open Innovation Lab)
     

2001 – 2002    Siemens AG
1998 – 2000    TDK Electronics Europe
1996 – 1998    Philips Components
1996                Philipps-Universität Marburg (Doctorate Dr. rer. nat. in Physics)

 


Awards

  • 2019     Honour „Ausgezeichneter Ort Deutschland, Im Land der Ideen“, by Federal Minister of Labour Hubertus Heil (Berlin)
  • 2019     Honoured by the Bavarian Minister of State Florian Hermann (Munich)
  • 2019     Work on optical CFC-sensing awarded as most influencial research on Global Recycling Day (Wiley)
  • 2008     Awarded with the E.on Environmental Prize (Munich)
  • 2000     International Development Prize by TDK Corporation (Tokyo), multiple international awards as best paper or best presentation, multiple cover  stories in international journals

 


Memberships

  • Modular ultrashort pulse laser technology
  • Optence / Photonics Hub
  • Hybrid Additive Manufacturing
  • LocaSenz Network




Publications

  • Lutz, Christian, Roth, Gian-Luca, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2021. Efficient Ultrashort Pulsed Laser Processing by Dynamic Spatial Light Modulator Beam Shaping for Industrial Use. In: Journal of Laser Micro/Nanoengineering. 16(1), S. 1 – 6. Abstract
  • Roth, Gian-Luca, Kefer, Stefan, Hessler, Steffen, Esen, Cemal, Hellmann, Ralf, 2021. Integration of Microfluidic and Photonic Components within Transparent Cyclic Olefin Copolymers by Using fs Laser. In: Journal of Laser Micro/Nanoengineering. 16(1), S. 1 – 6. Abstract
  • Kefer, Stefan, Roth, Frederick, Kaloudis, Michael, Schmauss, Bernhard, Hellmann, Ralf, 2021. Monitoring of Composite Bicycle Components using Polymer Planar Bragg Gratings. In: SMSI 2021 - Sensors and Instrumentation. Wunstorf, Germany: AMA Service GmbH. S. 161 – 162. ISBN 978-3-9819376-4-0. Abstract
  • Kefer, Stefan, Rosenberger, Manuel, Hessler, Steffen, Girschikofsky, Maiko, Belle, Stefan, Roth, Gian-Luca, Schmauß, Bernhard, Hellmann, Ralf, 2020. Fabrication and Applications of Polymer Planar Bragg Grating Sensors based on Cyclic Olefin Copolymers. In: 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall). Institute of Electrical and Electronics Engineers, S. 647 – 655. ISBN 978-1-7281-5304-9. Abstract
  • Kefer, Stefan, Sauer, Theresia, Hessler, Steffen, Kaloudis, Michael, Schmauß, Bernhard, Hellmann, Ralf, 2020. Robust Polymer Planar Bragg Grating Sensors Embedded in Commercial-Grade Composites. In: Polymers. 12(3), S. 715 – 715. Abstract Fulltext
  • Schwarz, Simon, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2020. Manufacturing of optical elements by non-contact laser processing. In: Seventh European Seminar on Precision Optics Manufacturing, Proceedings.
  • Zettl, Julian, Klar, Maximilian, Esen, Cemal, Hellmann, Ralf, 2020. Generation of Rotationally Symmetric Micro Tools using Ultrashort Laser Pulses. In: Journal of Laser Micro/Nanoengeneering. 15(2), S. 118 – 122. Abstract
  • Roth, Gian-Luca, Hessler, Steffen, Kefer, Stefan, Girschikofsky, Maiko, Esen, Cemal, Hellmann, Ralf, 2020. Femtosecond laser inscription of waveguides and Bragg gratings in transparent cyclic olefin copolymers. In: Optics Express. 28(12), S. 18077 – 18084. Abstract
  • Roth, Gian-Luca, Haubner, Julian, Kefer, Stefan, Esen, Cemal, Hellmann, Ralf, 2020. Fs-laser based hybrid micromachining for polymer micro-opto electrical systems. In: Optics and Lasers in Engineering. 137(10362), S. 1 – 8. Abstract
  • Kefer, Stefan, Sauer, Theresia, Hessler, Steffen, Kaloudis, Michael, Hellmann, Ralf, 2020. Microstructure-Based Fiber-to-Chip Coupling of Polymer Planar Bragg Gratings for Harsh Environment Applications. In: Sensors (Basel). 20(19), S. 5452 – 5452. Abstract Fulltext
  • Schwarz, Simon, Roth, Gian-Luca, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2020. Fabrication and evaluation of negative axicons for ultrashort pulsed laser applications. In: Optics Express. Optics Express(28), S. 26207 – 26217.
  • Kefer, Stefan, Dai, Jixiang, Yang, Minghong, Schmauss, Bernhard, Hellmann, Ralf, 2020. Hypersensitive H2 sensor based on polymer planar Bragg gratings coated with Pt-loaded WO3-SiO2. In: Optics Letters. 45(13), S. 3601 – 3604. Abstract
  • Rung, Stefan, Bokan, Kevin, Schwarz, Simon, Esen, Cemal, Hellmann, Ralf, 2020. Influence of laser wavelength on the modification of friction between 100Cr6 steel and polytetrafluoroethylene by femtosecond laser-induced periodic surface structures. In: Journal of Laser Applications. 32(3), S. 032017-1 – 032017-6.
  • Roth, Gian-Luca, Esen, Cemal, Hellmann, Ralf, 2020. Internal micro structuring of transparent optical polymers by fs laser. In: Laser-based Micro-and Nanoprocessing XIV 2020. International Society for Optics and Photonics, S. 112681L. Abstract
  • Roth, Gian-Luca, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2020. Microchannels inside bulk PMMA generated by femtosecond laser using adaptive beam shaping. In: Optics Express. 28(4), S. 5801 – 5811. Abstract
  • Kefer, Stefan, Dai, Jixiang, Yang, Minghong, Schmauss, Bernhard, Hellmann, Ralf, 2020. Hypersensitive H2 sensor based on polymer planar Bragg gratings coated with Pt-loaded WO3–SiO2: erratum. S. 4498 – 4498. Abstract
  • Schwarz, Simon, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2020. All laser-based fabrication of optical elements. In: Proceedings of SPIE 11270, Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XX.
  • Schwarz, Simon, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2020. Rapid fabrication of precise glass axicon arrays by an all laser-based manufacturing technology. In: Journal of Laser Applications. 32(1), S. 012001 – 012001.
  • Dudutis, Juozas, Pipiras, Jokūbas, Schwarz, Simon, Rung, Stefan, Hellmann, Ralf, Račiukaitis, Gediminas, Gečys, Paulius, 2020. Laser-fabricated axicons challenging the conventional optics in glass processing applications. In: Optics Express. 28(4), S. 5715 – 5730.
  • Sauer, Theresia, Kefer, Stefan, Ruppert, Wolfgang, Hellmann, Ralf, Kaloudis, Michael, 2019. Integration of Bragg grating sensors in components made of carbon fiber reinforced polymers. In: Tagungsband der 20. GMA/ITG-Fachtagung Sensoren und Messsysteme 2019, 25.06.2019 - 26.06.2019, Nürnberg, Deutschland. S. 806 – 810. ISBN 978-3-9819376-0-2. Abstract Fulltext
  • Flachs, Dennis, Emmerich, Florian, Roth, Gian-Luca, Hellmann, Ralf, Thielemann, Christiane, 2019. Laser-bonding of FEP/FEP interfaces for a flexiblemanufacturing process of ferroelectrets. In: Journal of Physics: Conference Series. 1407(012107), S. 1 – 5. Abstract
  • Trautmann, Anika, Roth, Gian-Luca, Nujiqi, Benedikt, Walter, Thomas, Hellmann, Ralf, 2019. Towards a versatile point-of-care system combining femtosecond laser generated microfluidic channels and direct laser written microneedle arrays. In: Microsystems & Nanoengineering. 5(6), S. 1 – 9. Abstract
  • Roth, Gian-Luca, Esen, Cemal, Hellmann, Ralf, 2019. Circular microchannels inside bulk polymethylmethacrylate generated by femtosecond laser using slit beam shaping. In: Journal of Laser Applications. 31(2), S. 022603-1 – 022603-5. Abstract
  • Roth, Gian-Luca, Esen, Cemal, Hellmann, Ralf, 2019. A New Approach to Seal Polymer Microfluidic Devices Using Ultrashort Laser Pulses. In: Journal of Laser Micro/Nanoengineering. 14(1), S. 49 – 53. Abstract
  • Roth, Gian-Luca, Wolf, Bastian, Esen, Cemal, Hellmann, Ralf, 2019. Generation of internal 3D microfluidic architectures in polymers by fs laser processing. In: Lasers in Manufacturing 2019. Abstract
  • Rung, Stefan, Bokan, Kevin, Kleinwort, Frederick, Schwarz, Simon, Simon, Peter, Klein-Wiele, Jan-Hendrik, Esen, Cemal, Hellmann, Ralf, 2019. Possibilities of Dry and Lubricated Friction Modification Enabled by Different Ultrashort Laser-Based Surface Structuring Methods. In: Lubricants. 7(43), S. 1 – 13. Abstract Fulltext
  • Dudutis, Juozas, Pipiras, Jokūbas, Schwarz, Simon, Rung, Stefan, Hellmann, Ralf, Gečys, Paulius, 2019. Bessel beam formation with all laser fabricated axicon - case of glass dicing applications. In: COLA 2019, 15th International Conference on Laser Ablation.
  • Dudutis, Juozas, Pipiras, Jokūbas, Schwarz, Simon, Rung, Stefan, Hellmann, Ralf, Račiukaitis, Gediminas, Gečys, Paulius, 2019. Glass cutting by oblate-tip axicon-generated Bessel-Gaussian beams. In: Open Readings, 63rd International Conference for Students of Physics and Natural Sciences.
  • Roth, Gian-Luca, Esen, Cemal, Hellmann, Ralf, 2018. Control of femtosecond laser generated microfluidic channels inside poly (methyl methacrylate). In: Journal of Laser Applications. 30(3), S. 032016-1 – 032016-6. Abstract
  • Roth, Gian-Luca, Esen, Cemal, Hellmann, Ralf, 2018. Vertical Microchannels for Microfluidic Multilayer Interconnections in PMMA. In: Journal of Laser Micro/Nanoengineering. 13(3), S. 155 – 159. Abstract
  • Roth, Gian-Luca, Esen, Cemal, Hellmann, Ralf, 2018. Laser beam microwelding of transparent plastics. In: Joining Plastics. 12(3/4), S. 2 – 8. Abstract
  • Rung, Stefan, Bokan, Kevin, Rutsch, Kevin, Schwarz, Simon, Esen, Cemal, Hellmann, Ralf, 2018. Laser Induced Periodic Surface Structures on 100Cr6 Steel for Modification of Friction Demonstrated with Stribeck Test. In: Journal of Laser Micro/Nanoengineering. 13(3), S. 160 – 165. Abstract Fulltext
  • Schwarz, Simon, Esen, Cemal, Hellmann, Ralf, 2018. CO2 laser polishing of femtosecond shaped micro-optical components. In: 3rd Conference on Laser Polishing LaP 2018.
  • Schwarz, Simon, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2018. Axicon fabrication with ultrashort and CO2 laser. In: LPM2018 The 19th International Symposium on Laser Precision Microfabrication.
  • Schwarz, Simon, Esen, Cemal, Hellmann, Ralf, 2018. Homogeneous low spatial frequency LIPSS on dielectrics generated by beam-shaped femtosecond pulsed laser irradiation. In: LPM2018 The 19th International Symposium on Laser Precision Microfabrication.
  • Schwarz, Simon, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2018. Fabrication of a high-quality axicon by femtosecond laser ablation and CO2 laser polishing for quasi-Bessel beam generation. In: Optics Express. 26(18), S. 23287 – 23294.
  • Schwarz, Simon, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2018. Influence of pulse duration on high-precision manufacturing of 3D geometries. In: Journal of Laser Micro/Nanoengineering. 13(3), S. 292 – 295.
  • Schwarz, Simon, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2018. Homogeneous low spatial frequency LIPSS on dielectric materials generated by beam-shaped femtosecond pulsed laser irradiation. In: Journal of Laser Micro/Nanoengineering. 13(2), S. 90 – 94.
  • Schwarz, Simon, Rung, Stefan, Esen, Cemal, Hellmann, Ralf, 2018. Surface Plasmon Polariton Triggered Generation of 1D-Low Spatial Frequency LIPSS on Fused Silica. In: Applied Sciences. 8(9), S. 1624 – 1624.
  • Adelmann, Benedikt, Hellmann, Ralf, 2017. Temperature and stress simulation of 4H-SiC during laser-induced silicidation for ohmic contact generation. In: Metals. 2017(7), S. 545 – 553.
  • Adelmann, Benedikt, Hellmann, Ralf, 2017. A study of SiC decomposition under laser irradiation. In: Applied Physics A. 2017(123), S. 454 – 452.
  • Roth, Gian-Luca, Esen, Cemal, Hellmann, Ralf, 2017. Femtosecond laser direct generation of 3D-microfluidic channels inside bulk PMMA. In: Optics Express. 25(15), S. 18442 – 18450. Abstract
  • Roth, Gian-Luca, Rung, Stefan, Hellmann, Ralf, 2017. Ultrashort pulse laser micro-welding of cyclo-olefin copolymers. In: Optics and Lasers in Engineering. S. 178 – 181. Abstract
  • Schleier, Max, Adelmann, Benedikt, Neumeier, Benedikt, Hellmann, Ralf, 2017. Burr formation detector for fiber laser cutting based on a photodiode sensor system. In: Optics & Laser Technology. 96(-), S. 13 – 17.
  • Schleier, Max, Adelmann, Benedikt, Esen, Cemal, Hellmann, Ralf, 2017. Cross-correlation-based algorithm for monitoring laser cutting with high-power fiber lasers. In: IEEE Sensors Journal. 18(4), S. 1585 – 1590.
  • Schwarz, Simon, Rung, Stefan, Hellmann, Ralf, 2017. High quality one-dimensional low spatial frequency LIPSS on sapphire generated by Top-Hat beam shaped ultrashort-pulsed laser. In: MultiScience - XXXI. microCAD International Multidisciplinary Scientific Conference.
  • Schwarz, Simon, Rung, Stefan, Hellmann, Ralf, 2017. One-dimensional low spatial frequency LIPSS with rotating orientation on fused silica. In: Applied Surface Science. 2017(411), S. 113 – 116.
  • Schwarz, Simon, Hellmann, Ralf, 2017. Fabrication of Cylindrical Lenses by Combining Ultrashort Pulsed Laser and CO2 Laser. In: Journal of Laser Micro/Nanoengineering. 12(2), S. 76 – 79.
  • Schwarz, Simon, Rung, Stefan, Hellmann, Ralf, 2017. Two-Dimensional Low Spatial Frequency Laser-Induced Periodic Surface Structuring of Sapphire. In: Journal of Laser Micro/Nanoengineering. 12(2), S. 67 – 71.
  • Preusch, Florian, Rung, Stefan, Hellmann, Ralf, 2016. Influence of Polishing Orientation on the Generation of LIPSS on Stainless Steel. In: Journal of Laser Micro/Nanoengineering. S. 137 – 142.
  • Roth, Gian-Luca, Rung, Stefan, Hellmann, Ralf, 2016. Welding of transparent polymers using femtosecond laser. In: Applied Physics A. 122(2), S. 86 – 90. Abstract
  • Adelmann, Benedikt, Hellmann, Ralf, 2016. Numerical and experimental study on flexural strength of laser microstructured alumina. In: Advances in Ceramic Science and Engineering. 2016(5), S. 28 – 34.
  • Adelmann, Benedikt, Hellmann, Ralf, 2016. SiC absorption of near-infrared laser radiation at high temperatures. In: Applied Physics A. 2016(122), S. 1 – 7.
  • Adelmann, Benedikt, Hellmann, Ralf, 2016. Photodiode-based cutting interruption sensor for near-infrared lasers. In: Applied Optics. 2016(55/7), S. 1772 – 1778.
  • Schwarz, Simon, Rung, Stefan, Hellmann, Ralf, 2016. Simulation of process parameters towards the generation of low spatial frequency LIPSS on dielectric materials. In: MultiScience - XXX. microCAD International Multidisciplinary Scientific Conference.
  • Schwarz, Simon, Rung, Stefan, Hellmann, Ralf, 2016. Generation of laser-induced periodic surface structures on transparent material-fused silica. In: Applied Physics Letters. 108(18), S. 181607 – 181607.
  • Adelmann, Benedikt, Neumeier, Benedikt, Schleier, Max, Wilmann, Eugen, Hellmann, Ralf, 2015. Optical cutting tear detection system for industrial fiber laser based cutting machines. In: Lasers in Manufacturing Conference 2015.
  • Adelmann, Benedikt, Schleier, Max, Neumeier, Benedikt, Wilmann, Eugen, Hellmann, Ralf, 2015. Optical cutting interruption sensor for fiber lasers. In: Applied Sciences. 2015(5/3), S. 544 – 554.
  • Adelmann, Benedikt, Ngo, Chan, Hellmann, Ralf, 2015. High aspect ratio cutting of metals using water jet guided laser. In: The International Journal of Advanced Manufacturing Technology. 2015(80), S. 2053 – 2060.
  • Roth, Gian-Luca, Adelmann, Benedikt, Hellmann, Ralf, 2015. Cutting and Drilling of SiC Semiconductor by Fiber Laser. In: Journal of Laser Micro/Nanoengineering. 10(3), S. 279 – 283. Abstract
  • Adelmann, Benedikt, Hellmann, Ralf, 2015. Comparative study of experimentally determined and simulated mechanical strength of fiber laser cut alumina substrates. In: Proceedings of the 7th International Congress on Laser Advanced Materials Processing. S. 1 – 9.
  • Adelmann, Benedikt, Roth, Gian-Luca, Hellmann, Ralf, 2015. Back side ablation of SiC diodes using a q-switched NIR laser. In: Journal of Laser Micro/Nanoengineering. S. 190 – 194.
  • Adelmann, Benedikt, Hellmann, Ralf, 2015. Rapid micro hole laser drilling in ceramic substrates using single mode fiber laser. In: Journal of Materials Processing Technology. 2015(221), S. 80 – 86.
  • Rung, Stefan, Christiansen, Anne, Hellmann, Ralf, 2014. Influence of film thickness on laser ablation threshold of transparent conducting oxide thin-films. In: Applied Surface Science. S. 347 – 351.
  • Rung, Stefan, Bischoff, Christian, Jäger, Erwin, Umhofer, Udo, Hellmann, Ralf, 2014. Laser thin film ablation with multiple beams and tailored beam profiles. In: Proceedings of SPIE 8967, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XIX.
  • Rung, Stefan, Barth, Johannes, Hellmann, Ralf, 2014. Characterization of Laser Beam Shaping Optics Based on Their Ablation Geometry of Thin Films. In: Micromachines. 5(4), S. 943 – 953. Abstract
  • Jäger, Erwin, Rädel, Ulrich, Bischoff, Christian, Umhofer, Udo, Rung, Stefan, Hellmann, Ralf, 2014. Laser micromachining – parallel processing with multiple top hat beams. In: 8th International Conference on Photonic Technologies LANE 2014.
  • Preusch, Florian, Adelmann, Benedikt, Hellmann, Ralf, 2014. Micromachining of AlN and Al2O3 using fiber laser. In: Micromachines. 2014(5), S. 1051 – 1060.
  • Adelmann, Benedikt, Hellmann, Ralf, 2014. Investigation on flexural strength changes of alumina caused by cutting using fiber laser. In: Journal of Laser Micro/Nanoengineering. S. 153 – 160.
  • Adelmann, Benedikt, Hellmann, Ralf, 2013. Process optimization of laser fusion cutting of multilayer stacks of electrical sheets. In: International Journal of Advanced Manufacturing Technology. S. 2693 – 2701.
  • Hasenstab, Stefan, Adelmann, Benedikt, Hellmann, Ralf, 2013. Laser Cutting of Alumina and Aluminum Nitride with a 500 W Single Mode Fiber Laser. In: XXVII. microCAD International Scientific Conference.
  • Adelmann, Benedikt, Hürner, Andreas, Schlegel, Tobias, Bauer, Anton, Frey, Lothar, Hellmann, Ralf, 2013. Laser Alloying Nickel on 4H-Silicon Carbide Substrate to Generate Ohmic Contacts. In: Journal of Laser Micro/Nanoengineering. 8(1), S. 97 – 101.
  • Hürner, Andreas, Schlegel, Tobias, Adelmann, Benedikt, Mitlehner, Heinz, Hellmann, Ralf, Bauer, Anton, Frey, Lothar, 2013. Alloying of Ohmic Contacts to n-type 4H-SiC via Laser Irradiation. In: Materials Science Forum. S. 773 – 776.
  • Adelmann, Benedikt, Hellmann, Ralf, 2013. Investigation on Flexural Strength during Fiber Laser Cutting of Alumina. In: Physics Procedia. S. 405 – 407.
  • Rung, Stefan, Rexhepi, Mal, Bischoff, Christian, Hellmann, Ralf, 2013. Laserscribing of thin films using top-hat laser beam profiles. In: Journal of Laser Micro/Nanoengineering. 8(3), S. 309 – 314.
  • Rung, Stefan, Rexhepi, Mal, Hellmann, Ralf, 2013. Beam shaping for enhanced through-put of laser ablation of transparent conductive films. In: Proceedings of the XXVII MicroCAD International Scientific Conference.
  • Heilmann, Eva-Maria, Kowalski, Thomas, Hellmann, Ralf, Teigelkötter, Johannes, 2013. Water Jet Guided Laser Cutting of High Temperature Superconductors. In: Journal of Laser Micro/Nanoengineering. 8(1), S. 70 – 74.
  • Bischoff, Christian, Rung, Stefan, Hellmann, Ralf, 2012. Efficient micromachining of thin film layers with nanosecond lasers – beam shaping optics improve process quality and enhance throughput. In: Laser Technik Journal. 9(5), S. 15 – 20.
  • Hellmann, Ralf, Gockel, Tilo, 2012. Optische Charakterisierung von Leuchtdioden. In: Zeitschrift ELEKTOR, Sonderheft LED-Special 4 – Leuchtdioden in Theorie und Praxis, 2012. 9, S. 40 – 46.
  • Kalmár, László, Hellmann, Ralf, Régert, Tamás, Varga, Zoltan, 2012. Numerical investigation of unsteady heat transport procedure in high power LED module. In: GEP. S. 43 – 46.
  • Schneider, Johannes, Bochtler, Ulrich, Hellmann, Ralf, Kaloudis, Michael, Gockel, Tilo, 2012. LUVLED III – Optimierung eines Kühlkonzeptes zur Aktivluftkühlung eines Hochleistungs-UV-LED-Moduls. In: Zeitschrift ELEKTOR, Sonderheft LED-Special 4 – Leuchtdioden in Theorie und Praxis, 2012. 9, S. 20 – 29.
  • Hock, Klaus, Adelmann, Benedikt, Hellmann, Ralf, 2012. Comparative study of remote fiber laser and water-jet guided laser cutting of thin film metal sheets. In: Physics procedia. S. 225 – 231.
  • Kalmár, László, Hellmann, Ralf, Régert, Tamás, Varga, Zoltan, 2012. Numerical investigation of heat transport procedure in high power LED modules. In: Proceedings of the XXVI International MicroCAD Conference, Miskolc (Hungary). S. 43 – 46.
  • Bischoff, Christian, Jäger, Erwin, Rung, Stefan, Hellmann, Ralf, 2012. Diffractive beam shaping optics for efficient micromachining. In: Proceedings of the LASYS (Internationale Fachmesse für Laser-Materialbearbeitung) – SLT (Stuttgarter Lasertage) 2012.
  • Koller, Georg, Hessler, Steffen, Rosenberger, Manuel, Belle, Stefan, Hellmann, Ralf, 2012. Micro-structured optical waveguide fabrication in PMMA using low frequency reactive ion etching. In: Proceedings of the XXVI International MicroCAD Conference – Sensing Technologies, Miskolc (Hungary).
  • Girschikofsky, Maiko, Rosenberger, Manuel, Belle, Stefan, Brutschy, Malte, Waldvogel, Siegfried, Hellmann, Ralf, 2012. α-Cyclodextrin functionalized planar Bragg grating sensor for the detection of small arene traces in solvamt vapour. In: 14th international meeting on chemical sensors (IMCS 2012). S. 646 – 648. ISBN 978-3-9813484-2-2.
  • Rung, Stefan, Hellmann, Ralf, 2012. Laser scribing of metallized transparent conductive oxide – A comparative study using top hat and Gaussian beam profiles. In: Proceedings of the XXVI International MicroCAD Conference – Material Processing Technologies.
  • Girschikofsky, Maiko, Rosenberger, Manuel, Belle, Stefan, Hellmann, Ralf, 2012. Surface modifications of planar bragg grating refractive index sensors for gas detection. In: Proceedings of the XXVI International MicroCAD Conference – Sensing Technologies, Miskolc (Hungary).
  • Heilmann, Eva-Maria, Hellmann, Ralf, 2011. High Speed Fibre Laser Material processing of Stainless Steel Tapes Under Tension. In: XXV International MicroCAD Conference - Material Processing Technologies, Miskolc (Hungary), 21-25.
  • Kalmár, László, Hellmann, Ralf, Régert, Tamás, Varga, Zoltan, 2011. Numerical simulation of heat transfer procedure in high power LED modules. In: Proceedings of the 12th technical and scientific meeting. S. 18 – 20.
  • Girschikofsky, Maiko, Rosenberger, Manuel, Belle, Stefan, Brutschy, Malte, Waldvogel, Siegfried, Hellmann, Ralf, 2011. Optical planar bragg grating sensor for real-time detection of benzene, toluene und xylene in solvent vapour. In: Sensors & Actuators, B - Chemical. 171/172(8/9), S. 338 – 342.
  • Girschikofsky, Maiko, Rosenberger, Manuel, Belle, Stefan, Brutschy, Malte, Waldvogel, Siegfried, Hellmann, Ralf, 2011. Highly sensitive detection of naphthalene in solvent vapor using a functionalized PBG refractive index sensor. In: Sensors. 12(2), S. 2018 – 2025.
  • Rosenberger, Manuel, Belle, Stefan, Hellmann, Ralf, 2011. Detection of biochemical reaction and DNA hybridization using a planar bragg grating sensor. In: Proceeding SPIE, Vol. 8073, article id: 80730C.
  • Risch, Anna, Christiansen, Anne, Hellmann, Ralf, Gockel, Tilo, 2011. Laserstrukturierung vonTCOs zur Herstellung organischer Leuchtdioden. In: Elektor, Sonderheft LEDs 3. 9, S. 39 – 41.
  • Amrhein, Frank, Kehrer, Martin, Schreck, Timo, Bochtler, Ulrich, Hellmann, Ralf, Kaloudis, Michael, 2011. More efficient curing of UV sensitive mounting materials. In: Practical metallography. 48(7), S. 356 – 364.
  • Gockel, Tilo, Engel, Michael, Hellmann, Ralf, 2011. 3D Laserscanning mit Linienlaser und Smart Camera – Systemauslegung mit Rasterlinsenoptik und Scheimpflugentzerrung. In: Elektor Sonderheft LEDs 3. 9, S. 79 – 84.
  • Schneider, Johannes, Bochtler, Ulrich, Hellmann, Ralf, Kaloudis, Michael, Gockel, Tilo, 2011. Effiziente Entwärmung eines Hochleistungs-UV-LED-Moduls. In: Elektor, Sonderheft LEDs 3. 2011(9), S. 12 – 17.
  • Heilmann, Eva-Maria, Hellmann, Ralf, 2011. Water jet guided laser cutting using a green disc laser. In: Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies.
  • Rosenberger, Markus, Belle, Stefan, Hellmann, Ralf, 2011. Detection of unlabeled DNA hybridization with a planar Bragg Grating Sensor. In: XXV International MicroCAD Conference – Sensing Technologies, Miskolc (Hungary). S. 67 – 72.
  • Amrhein, Frank, Kehrer, Martin, Schreck, Timo, Bochtler, Ulrich, Hellmann, Ralf, Kaloudis, Michael, 2011. UV-LED-Bestrahlung von Vergussmaterial: Schnelle Aushärtung auch im Schatten. In: adhäsion KLEBEN & DICHTEN. 5, S. 38 – 41.
  • Risch, Anna, Hellmann, Ralf, 2011. Laser Scribing of Gallium Doped Zinc Oxide Thin Films using Picosecond Laser. In: Applied Surface Science. 258(5), S. 1849 – 1853.
  • Hellmann, Ralf, Moorhouse, Colin, 2011. Laser patterning of transparent electrode films, from solar panels through high-end display. In: Industrial Laser Solutions Magazine. 11,
  • Heilmann, Eva-Maria, Hellmann, Ralf, Seidl, Albrecht, 2011. Water Jet Guided Laser Cutting of Silicon Thin Films Using 515nm Disc Laser. In: Journal of Laser Micro/Nanoengineering. 6(2), S. 168.
  • Adelmann, Benedikt, Hellmann, Ralf, 2011. Fast Laser Cutting Optimization Algorithm. In: Physics Procedia 12-1, Elsevier Properties S.A. 12(Part A), S. 591 – 598.
  • Risch, Anna, Hellmann, Ralf, 2011. Picosecond Laser Patterning of ITO Thin Films. In: Physics Procedia 12-1, Elsevier Properties S.A. 12, S. 133 – 140.
  • Adelmann, Benedikt, Hellmann, Ralf, 2011. Different modulation schemes in fibre laser cutting. In: Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies. S. 1 – 6.
  • Adelmann, Benedikt, Hellmann, Ralf, 2011. DOE based optimization of fibre laser cutting of metals. In: Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies. S. 7 – 12.
  • Risch, Anna, Hellmann, Ralf, 2011. Laser induced modification of GZO thin film. In: Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies. S. 69 – 74.
  • Risch, Anna, Hellmann, Ralf, 2011. ITO thin film laser patterning by picosecond laser. In: Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies. S. 63 – 68.
  • Rosenberger, Manuel, Belle, Stefan, Hellmann, Ralf, 2011. Detection of unlabeled DNA hybridization with a planar bragg grating sensor. In: Proceeding XXV microCAD, International scientific conference, 2011, Section R. S. 67 – 72.
  • Rosenberger, Manuel, Belle, Stefan, Hellmann, Ralf, 2011. Optical interrogation of chemical and temperature bragg grating sensors using tunable fiber coupled bandpass filter. In: Proceeding XXV microCAD, International scientific conference, 2011, Section H. S. 25 – 30.
  • Belle, Stefan, Rosenberger, Manuel, Hellmann, Ralf, 2011. Optical fibre sensing in the production process and storage of biofuels. In: Proceeding XXV microCAD, International scientific conference, 2011, Section A. S. 21 – 26.
  • Belle, Stefan, Rosenberger, Manuel, Hellmann, Ralf, 2011. Evanescent wave planar bragg grating sensor for real-time detection of unlabelled biomolecules. In: Optics Express.
  • Belle, Stefan, Scheurich, Steffen, Hellmann, Ralf, So, Sik, Sparrow, Ian, Emmerson, Greg, 2010. Refractive index sensing for online monitoring water and ethanol contents in biofuels. In: Sensors. 7726, ISSN 1424-8220.
  • Glaab, Johannes, Hellmann, Ralf, 2010. Small-scale low-through UV-C LED disinfection device, in waste processing and recycling. In: Proceedings of the XXIV international Scientific conference Miskolc, Ungarn.
  • Kaloumenos, Mareiki, Amrhein, Frank, Glaab, Johannes, Sauer, Michael, Hellmann, Ralf, Kaloudis, Michael, 2010. Development of a UV-Light Source with Highest Power Density Based on Light Emitting Diode Technology for Applications in Production Engineering, in Production Engineering and manufacturing Systems. In: Proceedings of the XXIV International Scientific Conference Miskolc, Ungarn.
  • Hellmann, Ralf, Glaab, Johannes, Gockel, Tilo, 2010. Wasserentkeimung mit UV-Leuchtdioden. In: Elektor Sonderheft, LEDs 2. 2010(2), S. 40 – 45.
  • Bochtler, Ulrich, Hellmann, Ralf, Kaloudis, Michael, Amrhein, Frank, Glaab, Johannes, Kaloumenos, Mareiki, Sauer, Michael, Gockel, Tilo, 2010. LUVLED - UV-Leistungslichtquelle auf Leuchtdiodenbasis. In: Elektor Sonderheft, LEDs 2. 2011(2), S. 57 – 63.
  • Amrhein, Frank, Bochtler, Ulrich, Hellmann, Ralf, Kaloudis, Michael, Kaloumenos, Mareiki, 2010. Vergleich der thermischen Eigenschaften unterschiedlicher insulated metal substrat-Leiterplatten. In: PLUS, Leiterplattentechnik. 8, S. 1758.
  • Hühnlein, Kristof, Tschirpke, Katrin, Hellmann, Ralf, 2010. Optimisation of laser cutting using design of experiment - A comparative study of cutting thin ceramic layers using a fibre laser and a CO2 laser. In: Physics procedia. 6th international conference on laser assisted net shape engineering. S. 243 – 252. ISSN 1875-3892.
  • Risch, Anna, Hühnlein, Kristof, Knöll, Jürgen, Hellmann, Ralf, 2010. Picosecond and nanosecond pulsed laserscribing on transparent conductive indium tin oxide. In: Journal of Material processing technolgies. Proceedings of the XXIV international scientific conference Miskolc, Ungarn. ISSN 0924-0136.
  • Bochtler, Ulrich, Hellmann, Ralf, Kaloudis, Michael, 2010. Neuartige UV-Lichtquelle auf Leuchtdiodenbasis, Packaging und Hybridschaltungen. In: PLUS. 2,
  • Glaab, Johannes, Hellmann, Ralf, 2010. Germicidal potential of ultraviolet-LED emitting different wavelength for the inactivation of indigenous coliform bacteria. In: Water research conference, Lissabon, Portugal.
  • Risch, Anna, Hühnlein, Kristof, Knöll, Jürgen, Hellmann, Ralf, 2009. Laserscribing of transparent conductive oxides - a comparative study using nanosecond and picosecond pulsed solid state lasers. In: Proceedings of the 20st International Scientific Conference, Mittweida, 2009.
  • Rosenberger, Manuel, Belle, Stefan, Hellmann, Ralf, 2009. Optical interrogation of bragg grating sensors using tunable fibre based bandpass filter. In: Proceedings of the 20st international science conference, Mittweida.
  • Belle, Stefan, Scheurich, Steffen, Hellmann, Ralf, 2009. Interrogation water content in organic solvents by planar bragg grating sensors. In: Proceedings SENSOR. S. 324 – 329. ISBN 978-3-9810993-6-2.
  • Scheurich, Steffen, Belle, Stefan, Hellmann, Ralf, So, Sik, Sparrow, Ian, Emmerson, Greg, 2009. Application of a silica-on-silicon planar optical waveguide. Bragg grating sensor for organic liquid compound detection. In: SPIE Optics an optoelectronics conference, Proceedings of SPIE, Vol. 7356, Prag, CR. ISBN 978-0819476302.
  • Scheurich, Steffen, Belle, Stefan, Hellmann, Ralf, So, Sik, Sparrow, Ian, Emmerson, Greg, 2009. Planar optical waveguide bragg grating chemical sensor for online process control. In: 3rd integrated optics - sensors, sensing structures and methodes Korbielow, PL.

zur Übersicht Wissenschaftlerinnen und Wissenschaftler