Dr. Roman Bek Profile

Dr. Roman Bek

at Twenty-One Semiconductors GmbH

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Author

Publications (19)

Proceedings Article | 13 March 2024 Presentation

Membrane external cavity lasers (MEXLs) for the green-yellow spectral range

Roman Bek, Michael Scharwaechter, Matthias Seibold, Michael Zimmer, Sergej Vollmer, Norbert Witz-Haszler

Proceedings Volume PC12868, PC128680A (2024) https://doi.org/10.1117/12.3000849

KEYWORDS: Vertical external cavity surface emitting lasers, Semiconductor lasers, Biomedical applications, Visible radiation, Transmittance, Semiconductors, Optical coatings, Modulation, Laser systems engineering, Laser sources

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Proceedings Article | 13 March 2024 Presentation

Membrane quantum well waveguide lasers

Nicholas Klokkou, Stephen Richardson, Jake Daykin, J. R. Woods, J. Gorecki, Roman Bek, Michael Jetter, Vasilis Apostolopoulos

Proceedings Volume PC12868, PC128680E (2024) https://doi.org/10.1117/12.3004996

KEYWORDS: Waveguide lasers, Quantum wells, Waveguides, Waveguide modes, Silicon carbide, Semiconductors, Refractive index, Optical coherence, Laser optics, Design and modelling

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Proceedings Article | 17 March 2023 Presentation

Membrane external-cavity surface-emitting laser emitting in bi-frequency operation through micromachining of cavity mirror

Jake Daykin, Jonathan R. Woods, Daniel Heath, Roman Bek, James Wilkinson, Ben Mills, Michael Jetter, Peter Michler, Vasilis Apostolopoulos

Proceedings Volume 12404, 1240403 (2023) https://doi.org/10.1117/12.2647363

KEYWORDS: Mirrors, Micromachining, Terahertz spectroscopy, Laser ablation, Continuous wave operation, Spectroscopes, Reticles, Reflectivity, Optical sensing, Optical pumping

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Proceedings Article | 17 March 2023 Presentation

Semiconductor quantum well membranes for tunable coherent waveguide laser arrays

Jake Daykin, Nicholas Klokkou, Stephen Richardson, Jonathan R. Woods, Roman Bek, Jon Gorecki, James Wilkinson, Michael Jetter, Peter Michler, Vasilis Apostolopoulos

Proceedings Volume 12404, 1240404 (2023) https://doi.org/10.1117/12.2655948

KEYWORDS: Waveguide lasers, Semiconductors, Quantum wells, Tunable lasers, Laser resonators, Waveguides, Silicon carbide, Semiconductor lasers, Space operations, Silicon photonics

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Proceedings Article | 11 January 2023 Presentation

III-V compound semiconductor membrane quantum well waveguide lasers emitting at 1 μm

Stephen Richardson, Jonathan Woods, Jake Daykin, Jon Gorecki, Roman Bek, Nicholas Klokkou, James Wilkinson, Michael Jetter, Vasileios Apostolopoulos

Proceedings Volume PC12334, PC123340H (2023) https://doi.org/10.1117/12.2647572

KEYWORDS: Quantum wells, Waveguide lasers, Compound semiconductors, Waveguides, Silicon carbide, Laser development, Semiconductors, Semiconductor lasers, Resonators, Prototyping

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Proceedings Article | 1 April 2022 Presentation

Wafer-scale production of membrane-external-cavity surface-emitting laser (MECSEL) gain chips

Garrett Cole, David Follman, Catherine Nguyen, Roman Bek, Michael Zimmer, Norbert Witz

Proceedings Volume PC11984, PC1198404 (2022) https://doi.org/10.1117/12.2609904

KEYWORDS: Wafer-level optics, Laser optics, Wafer bonding, Visible radiation, Solid state lasers, Semiconductor lasers, Quantum dots, Mirrors, Microfabrication, Manufacturing

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Proceedings Article | 9 March 2022 Presentation

Semiconductor in-plane membrane quantum-well lasers

Jonathan R. Woods, Jon Gorecki, Jake Daykin, Stephen Richardson, Michael Jetter, Roman Bek, Emelia Branagan-Harris, Grace Hooper, James Wilkinson, Anne Tropper, Vasilis Apostolopoulos

Proceedings Volume PC12021, PC1202105 (2022) https://doi.org/10.1117/12.2613328

KEYWORDS: Semiconductor lasers, Quantum wells, Semiconductors, Waveguides, Silicon photonics, Silicon carbide, Semiconducting wafers, Resonators, Planar waveguides, Optical simulations

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Proceedings Article | 4 March 2019 Paper

Investigations on the origins of self-mode-locking in vertical-external-cavity surface-emitting-lasers: nonlinear lensing and the role of the microcavity

Christian Kriso, Sascha Kress, Tasnim Munshi, Marius Großmann, Roman Bek, Michael Jetter, Peter Michler, Wolfgang Stolz, Martin Koch, Arash Rahimi-Iman

Proceedings Volume 10901, 109010H (2019) https://doi.org/10.1117/12.2510373

KEYWORDS: Mode locking, Refractive index, Optical microcavities, Nonlinear optics, Semiconductors, Ultrafast phenomena, Kerr effect, Absorption, Refraction

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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 | 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

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 | 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 | 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 | 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 | 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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Showing 5 of 19 publications

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