Dr. Hermann Kahle Profile

Dr. Hermann Kahle

Postdoctoral Researcher / Scientific Employee at Univ Paderborn

SPIE Involvement:

Author

Area of Expertise:

VECSEL , SHG , Laser , MECSEL , Optics , semiconductor

Websites:

Personal Website

Publications (29)

Proceedings Article | 12 March 2024 Presentation + Paper

Membrane external-cavity surface-emitting lasers (MECSELs) optimized for double-side-pumping: a first fundamental single-side pumping characterization

Telsche Mikitta, Ana Ćutuk, Michael Jetter, Peter Michler, Klaus Jöns, Hermann Kahle

Proceedings Volume 12868, 1286803 (2024) https://doi.org/10.1117/12.3002481

KEYWORDS: Quantum wells, Mirrors, Indium gallium phosphide, Vertical external cavity surface emitting lasers, Silicon carbide, Heatsinks, Emission wavelengths, Semiconductor lasers, Absorption

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Proceedings Article | 17 March 2023 Presentation

Latest developments on membrane external-cavity surface-emitting lasers (MECSELs)

Hermann Kahle

Proceedings Volume 12404, 1240402 (2023) https://doi.org/10.1117/12.2657039

KEYWORDS: Semiconductor lasers, Semiconductors, Distributed Bragg reflectors

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Proceedings Article | 25 May 2022 Presentation

Membrane external-cavity surface-emitting lasers (MECSELs): State of the art in broadband (> 25 THz) tuning and antiresonant gain structure design

Hermann Kahle, Philipp Tatar-Mathes, Patrik Rajala, Mircea Guina

Proceedings Volume PC12141, PC1214109 (2022) https://doi.org/10.1117/12.2632734

KEYWORDS: Terahertz radiation, Structural design, Semiconductor lasers, Vertical cavity surface emitting lasers, Quantum wells, Indium gallium phosphide, Distributed Bragg reflectors, Absorption

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Proceedings Article | 6 May 2022 Paper

Towards red-emitting MECSELs for visible-light OCT applications

Philipp Tatar-Mathes, Hoy-My Phung, Aaron Rogers, Patrik Rajala, Sanna Ranta, Hermann Kahle, Mircea Guina

Proceedings Volume 12170, 1217003 (2022) https://doi.org/10.1117/12.2592919

KEYWORDS: Optical coherence tomography, Light sources, Quantum wells, Visible radiation, Silicon carbide, Image processing, Diamond, Semiconductors, Semiconductor lasers, Reflectivity

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Proceedings Article | 1 April 2022 Presentation

Membrane external-cavity surface-emitting lasers (MECSELs): Fundamentals, state of the art, and future perspectives

Hermann Kahle

Proceedings Volume PC11984, PC1198401 (2022) https://doi.org/10.1117/12.2610128

KEYWORDS: Vertical cavity surface emitting lasers, Semiconductor lasers, Semiconductors, Distributed Bragg reflectors

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Proceedings Article | 1 April 2022 Presentation

MECSELs with a non-resonant sub-cavity design

Philipp Tatar-Mathes, Hoy-My Phung, Aaron Rogers, Patrik Rajala, Sanna Ranta, Hermann Kahle, Mircea Guina

Proceedings Volume PC11984, PC1198408 (2022) https://doi.org/10.1117/12.2610633

KEYWORDS: Semiconductors, Heterojunctions, Wavelength tuning, Silicon carbide, Semiconductor lasers, Reflectors, Quantum wells, Optical microcavities, Laser resonators, Indium gallium phosphide

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Proceedings Article | 4 March 2022 Presentation + Paper

Thermal behavior and management of membrane external-cavity surface-emitting lasers (MECSELs)

Hoy-My Phung, Philipp Tatar-Mathes, Aaron Rogers, Patrik Rajala, Sanna Ranta, Hermann Kahle, Mircea Guina

Proceedings Volume 11984, 1198402 (2022) https://doi.org/10.1117/12.2610644

KEYWORDS: Silicon carbide, Diamond, Digital signal processing, Sapphire, Finite element methods, Optical simulations, Absorption, Semiconductor lasers, Quantum wells, Optical pumping

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Proceedings Article | 4 March 2022 Presentation + Paper

Design and characterization of MECSELs for widely tunable (>25 THz) continuous wave operation

Patrik Rajala, Philipp Tatar-Mathes, Hoy-My Phung, Jesse Koskinen, Sanna Ranta, Mircea Guina, Hermann Kahle

Proceedings Volume 11984, 1198404 (2022) https://doi.org/10.1117/12.2610649

KEYWORDS: Quantum wells, Mirrors, Semiconductor lasers, Terahertz radiation, Calibration, Digital signal processing, Silicon carbide, Polarization, Continuous wave operation, Structural design

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Proceedings Article | 5 March 2021 Presentation

Vertical external-cavity surface-emitting lasers in the 700 to 800 nm region for nonlinear frequency generation

Jonathan R. Woods, Hermann Kahle, Alan Gray, Lewis Carpenter, Sam Berry, Jake Daykin, Anne Tropper, Mircea Guina, Corin Gawith, Vasilis Apostolopoulos

Proceedings Volume 11704, 117040F (2021) https://doi.org/10.1117/12.2578152

KEYWORDS: Sum-frequency generation, Second-harmonic generation, Optical filters, Atomic, molecular, and optical physics, Ytterbium, Waveguides, Ultraviolet radiation, Spectroscopy, Solid state physics, Silicon carbide

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Proceedings Article | 5 March 2021 Presentation

Membrane external-cavity surface-emitting lasers (MECSELs) with broadband gain in the 9XX to 10XX nm spectral range

Hermann Kahle, Hoy-My Phung, Philipp Tatar-Mathes, Sanna Ranta, Patrik Rajala, Mircea Guina

Proceedings Volume 11704, 117040E (2021) https://doi.org/10.1117/12.2577563

KEYWORDS: Semiconductor lasers, Semiconductors, Quantum wells, Mirrors, Laser systems engineering, Distributed Bragg reflectors

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Proceedings Article | 2 March 2020 Presentation + Paper

A membrane external-cavity surface-emitting laser (MECSEL) with emission around 825 nm

Hoy-My Phung, Hermann Kahle, Jussi-Pekka Penttinen, Patrik Rajala, Sanna Ranta, Mircea Guina

Proceedings Volume 11263, 112630H (2020) https://doi.org/10.1117/12.2545980

KEYWORDS: Semiconductor lasers, Thermal effects, Semiconductors, Silicon carbide, Mirrors, Resistance, High power lasers

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Proceedings Article | 5 March 2019 Presentation + Paper

MECSELs with direct emission in the 760 nm to 810 nm spectral range: a single- and double-side pumping comparison and high-power continuous-wave operation

Hermann Kahle, Jussi-Pekka Penttinen, Hoy-My Phung, Patrik Rajala, Antti Tukiainen, Sanna Ranta, Mircea Guina

Proceedings Volume 10901, 109010D (2019) https://doi.org/10.1117/12.2512111

KEYWORDS: Digital signal processing, Silicon carbide, Quantum wells, Sapphire, Aluminum, Resistance, Semiconductors, Semiconductor lasers, Gallium arsenide, Absorption

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Proceedings Article | 23 May 2018 Presentation

MECSEL: new concept for optically pumped semiconductor disk lasers with versatile wavelength (Conference Presentation)

Michael Jetter, Roman Bek, Hermann Kahle, Peter Michler

Proceedings Volume 10682, 1068213 (2018) https://doi.org/10.1117/12.2306947

KEYWORDS: Semiconductor lasers, Semiconductors, Optical pumping, Disk lasers, Optical semiconductors, Optical filters, Laser systems engineering, Quantum wells, Frequency doubling crystals, Mirrors

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Semiconductor disk lasers, also called vertical external-cavity surface-emitting lasers (VECSELs) have advantageous properties such as high output power, wavelength flexibility due to bandgap engineering and near-diffraction limited beam quality. The possibility to insert intra-cavity elements – filters, frequency doubling crystals or semiconductor saturable absorber mirrors (SESAMs) – enables wavelength tuning, second harmonic generation or mode locking with ultra-short pulses. A major challenge for these laser sources is the removal of heat which is introduced by optical pumping. The thermal management can improved by placing only the active region directly between two heat spreaders. This membrane external-cavity surface-emitting laser (MECSEL) allows emission in an even larger wavelength range, since the growth is not restricted by a distributed Bragg reflector. We present the fabrication, processing and characterization of MECSELs using different material systems for laser emission at various wavelengths in the visible and in the infrared spectral range. Our semiconductor structures are grown by metal-organic vapor-phase epitaxy and contain quantum wells (QWs) or quantum dots (QDs) in the active regions. We discuss our latest results of the membrane laser concept with investigations of strain effects on the photoluminescence and the laser emission and different pumping schemes. In particular, we show results of a MECSEL placed into a linear cavity and pumped by a 532 nm laser. The system was operated at a heat sink temperature of 10°C and achieved nearly 600 mW at 3.7 W pump power. The slope efficiency achieved here was 22.3 % with a threshold pump power of 1 W. This slope efficiency exceeds any slope efficiency published before with green pumped conventional VECSEL in this emission range at these elevated heatsink temperatures. Including a birefringent filter into the laser cavity allows for a tuning of the emission laser wavelength. The group could demonstrate a tuning range of 24 nm (650 nm – 674 nm), which is the highest value achieved in this spectral range by semiconductor lasers to date. All these achievements come with the expected Gaussian TEM00 mode with a beam quality factor of M2< 1.06[Optica 3(12), 1506-1512 (2016)]. To demonstrate the flexibility and usability of the MECSEL approach, we have created an optically pumped laser with a GaInAsP membrane for emission around 1000 nm, together with a group in Dundee. The set-up of the laser was similar to that of the red spectral range but instead of diamond, SiC was used as heat spreader material. Nevertheless, the achieved output powers could exceed 10 W with a slope efficiency of 27.5% and this with the heat spreader on only one side. This work was as well recently published in Electronic Letters 2017 [DOI:10.1049/el.2017.2689]. Actually, we realized a running membrane laser at a wavelength of 608 nm, a wavelength not accessible so far. The characterization measurements are now ongoing, first results will be presented at the conference.

Proceedings Article | 14 March 2018 Presentation

VECSEL and MECSEL: high power, wavelength versatility and ultra-short pulses (Conference Presentation)

Roman Bek, Hermann Kahle, Michael Jetter, Peter Michler

Proceedings Volume 10515, 105150B (2018) https://doi.org/10.1117/12.2291744

KEYWORDS: Semiconductor lasers, Semiconductors, Optical pumping, Mode locking, Pulsed laser operation, Aluminium gallium indium phosphide, Disk lasers, Optical filters, Frequency doubling crystals, Mirrors

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Proceedings Article | 14 March 2018 Presentation

MECSELs and VECSELs for rubidium spectroscopy with direct emission around 780 nm (Conference Presentation)

Hermann Kahle, Kostiantyn Nechay, Jussi-Pekka Penttinen, Antti Tukiainen, Sanna Ranta, Mircea Guina

Proceedings Volume 10515, 105150A (2018) https://doi.org/10.1117/12.2290307

KEYWORDS: Spectroscopy, Rubidium, Semiconductor lasers, Laser applications, Optical pumping, Semiconductors, Tunable lasers, Emission spectroscopy, Near infrared, Aluminium gallium indium phosphide

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Proceedings Article | 14 March 2018 Presentation

Towards direct emitting MECSELs in the yellow and red-orange spectral range (Conference Presentation)

Hermann Kahle, Kostiantyn Nechay, Jussi-Pekka Penttinen, Jari Lyytikäinen, Mircea Guina

Proceedings Volume 10515, 1051509 (2018) https://doi.org/10.1117/12.2290174

KEYWORDS: Semiconductor lasers, Semiconductors, Indium gallium phosphide, Aluminium gallium indium phosphide, Disk lasers, Laser development, Harmonic generation, Refractive index, Distributed Bragg reflectors, Absorption

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Proceedings Article | 21 April 2017 Presentation

Towards self-mode locking of AlGaInP-VECSELs (Conference Presentation)

Roman Bek, Quynh Duong-Ederer, Max Vaupel, Hermann Kahle, Thomas Schwarzbäck, Arash Rahimi-Iman, Michael Jetter, Martin Koch, Peter Michler

Proceedings Volume 10087, 100870N (2017) https://doi.org/10.1117/12.2252473

KEYWORDS: Indium gallium phosphide, Mode locking, Pulsed laser operation, Semiconductors, Semiconductor lasers, Kerr effect, Mirrors, Femtosecond phenomena, Laser systems engineering, Epitaxy

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Proceedings Article | 28 March 2017 Paper

Improved gain chip holder design for high efficient, high power AlGaInP-VECSEL

Philipp Tatar-Mathes, Hermann Kahle, Cherry M. Mateo, Uwe Brauch, Roman Bek, Michael Jetter, Thomas Graf, Peter Michler

Proceedings Volume 10087, 100870R (2017) https://doi.org/10.1117/12.2253670

KEYWORDS: Heatsinks, Semiconductors, Semiconductor lasers, Disk lasers, Continuous wave operation, Resonators, Distributed Bragg reflectors, Quantum wells, Wavelength tuning, Aluminium gallium indium phosphide, Quantum efficiency, Laser applications, Optical pumping, Free space, Optical components

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Proceedings Article | 27 February 2017 Presentation + Paper

The optically pumped semiconductor membrane external-cavity surface-emitting laser (MECSEL): a concept based on a diamond-sandwiched active region

Hermann Kahle, Cherry May Mateo, Uwe Brauch, Roman Bek, Michael Jetter, Thomas Graf, Peter Michler

Proceedings Volume 10087, 100870J (2017) https://doi.org/10.1117/12.2252182

KEYWORDS: Semiconductors, Semiconductor lasers, Disk lasers, Optical pumping, Heatsinks, Optical semiconductors, Diamond, Wavelength tuning, Solid state lasers, Biomedical optics, Thin film devices, Indium gallium phosphide, Absorption, Quantum wells, Photography, Laser resonators, Resonators, Mirrors

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Proceedings Article | 22 February 2017 Presentation + Paper

Schemes for efficient QW pumping of AlGaInP disk lasers

Uwe Brauch, Cherry May Mateo, Hermann Kahle, Roman Bek, Michael Jetter, Marwan Abdou Ahmed, Peter Michler, Thomas Graf

Proceedings Volume 10087, 1008703 (2017) https://doi.org/10.1117/12.2250901

KEYWORDS: Disk lasers, Diamond, Absorption, Quantum wells, Semiconductors, Semiconductor lasers, Mirrors, Prisms, Reflectivity, Photons

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Proceedings Article | 10 March 2016 Paper

Efficiency and power scaling of in-well and multi-pass pumped AlGaInP VECSELs

Cherry M. Mateo, Uwe Brauch, Hermann Kahle, Roman Bek, Thomas Schwarzbäck, Michael Jetter, Marwan Abdou Ahmed, Peter Michler, Thomas Graf

Proceedings Volume 9734, 973410 (2016) https://doi.org/10.1117/12.2212162

KEYWORDS: Continuous wave operation, Ultraviolet radiation, Mid-IR, Laser sources, Aluminium gallium indium phosphide, Quantum efficiency, Temperature metrology, Numerical modeling, Absorption, Quantum wells, Mirrors, Reflectivity, Semiconductor lasers, Resonators, Heatsinks

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Proceedings Article | 10 March 2016 Paper

Gain chip design, power scaling and intra-cavity frequency doubling with LBO of optically pumped red-emitting AlGaInP-VECSELs

Hermann Kahle, Cherry M. Mateo, Uwe Brauch, Roman Bek, Thomas Schwarzbäck, Michael Jetter, Thomas Graf, Peter Michler

Proceedings Volume 9734, 97340T (2016) https://doi.org/10.1117/12.2209305

KEYWORDS: Second-harmonic generation, Quantum wells, Laser applications, Optical pumping, Absorption, Laser video displays, Laser resonators, Tunable lasers, Aluminium gallium indium phosphide, Quantum dots, Group III-V semiconductors, Semiconductor lasers, Thin film devices, Semiconductors, Heatsinks, Crystals, Ultraviolet radiation

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Proceedings Article | 4 March 2015 Paper

Degradation studies and pump optimization of optically pumped red-emitting AlGaInP-VECSELs

Hermann Kahle, Cherry Mateo, Maren Jäger, Karoline Weinspach, Stefan Baumgärtner, Uwe Brauch, Roman Bek, Thomas Schwarzbäck, Michael Jetter, Thomas Graf, Peter Michler

Proceedings Volume 9349, 93490C (2015) https://doi.org/10.1117/12.2077559

KEYWORDS: Optical pumping, Quantum wells, Heatsinks, Mirrors, Semiconductor lasers, Laser applications, Semiconductors, Luminescence, Tunable lasers

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Proceedings Article | 4 March 2015 Paper

Quantum dot based mode-locked AlGaInP-VECSEL

Roman Bek, Grizelda Kersteen, Hermann Kahle, Thomas Schwarzbäck, Michael Jetter, Peter Michler

Proceedings Volume 9349, 93490G (2015) https://doi.org/10.1117/12.2077164

KEYWORDS: Silica, Mode locking, Picosecond phenomena, Quantum dots, Semiconductors, Mirrors, Pulsed laser operation, Modulation, Semiconductor lasers, Reflectivity

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Proceedings Article | 3 March 2014 Paper

Femtosecond mode-locked red AlGaInP-VECSEL

Roman Bek, Nart Daghestani, Hermann Kahle, Thomas Schwarzbäck, Michael Jetter, Maria Ana Cataluna, Peter Michler

Proceedings Volume 8966, 89660P (2014) https://doi.org/10.1117/12.2037828

KEYWORDS: Quantum wells, Mode locking, Picosecond phenomena, Semiconductors, Femtosecond phenomena, Mirrors, Silica, Diamond, Modes of laser operation, Carrier dynamics

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Proceedings Article | 11 May 2012 Paper

Frequency doubled AlGaInP-VECSEL with high output power at 331 nm and a large wavelength tuning range in the UV

Thomas Schwarzbäck, Hermann Kahle, Michael Jetter, Peter Michler

Proceedings Volume 8432, 84320W (2012) https://doi.org/10.1117/12.922584

KEYWORDS: Ultraviolet radiation, Quantum wells, Optical filters, Second-harmonic generation, Diamond, Mirrors, Heatsinks, Wavelength tuning, Aluminium gallium indium phosphide, Cladding

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Proceedings Article | 11 May 2012 Paper

Red AlGaInP-VECSEL emitting at around 665 nm: strain compensation and performance comparison of different epitaxial designs

Thomas Schwarzbäck, Hermann Kahle, Michael Jetter, Peter Michler

Proceedings Volume 8432, 843209 (2012) https://doi.org/10.1117/12.922593

KEYWORDS: Quantum wells, Absorption, Mirrors, Reflectivity, Cladding, Semiconductor lasers, Diamond, Heatsinks, Aluminium gallium indium phosphide, Copper

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Proceedings Article | 15 February 2012 Paper

UV laser emission around 330 nm via intracavity frequency doubling of a tunable red AlGaInP-VECSEL

Hermann Kahle, Thomas Schwarzbäck, Marcus Eichfelder, Robert Roßbach, Michael Jetter, Peter Michler

Proceedings Volume 8242, 82420M (2012) https://doi.org/10.1117/12.907902

KEYWORDS: Quantum wells, Ultraviolet radiation, Reflectivity, Second-harmonic generation, Heatsinks, Tunable lasers, Optical filters, Mirrors, Laser applications, Absorption

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Proceedings Article | 22 February 2011 Paper

Wavelength tunable red AlGaInP-VECSEL emitting at around 660 nm

Thomas Schwarzbäck, Hermann Kahle, Marcus Eichfelder, Wolfgang-Michael Schulz, Robert Roßbach, Michael Jetter, Peter Michler

Proceedings Volume 7919, 79190B (2011) https://doi.org/10.1117/12.873558

KEYWORDS: Heatsinks, Reflectivity, Mirrors, Quantum wells, Absorption, Diamond, Second-harmonic generation, Ultraviolet radiation, Continuous wave operation, Optical filters

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Showing 5 of 29 publications

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