High-power semiconductor lasers are the most efficient man-made light sources, and can convert more than 80% electric energy into light. Currently emission powers of one kW continuous-wave powers are extracted from a single monolithic semiconductor chip. We are interested in the intrinsic limitations of such optoelectronic devices in terms of output power, beam quality (brightness) and lifetime (reliability). For this purpose, we analyze devices, but also their components such as surfaces and interfaces or gain materials such as quantum wells, superlattices and quantum dots.
For our experiments, we use optical tools, in particular transient spectroscopy that represents a generic competence of MBI. Such work is naturally carried out as collaborative work with device vendors, who provide us with high-quality industry-grade devices and structures. The use of such devices ensures high reproducibility and the chance to get general results, which not depend on the particular device structure that was studied. In BMBF-projects such as BlauLas, we work together with Osram OS (Regensburg), Dilas GmbH (Maiz) and Laserline GmbH (Mülheim) or in the frame of bilateral research contracts with Lumentum (Santa Clara) and 3S-Photonics (Nozay).
The material basis of the investigated devices is now focused to GaN-based wide-bandgap devices emitting in the ultraviolet to blue spectral regions. The figure shows damage patterns as observed in 450-nm emitting high power diode lasers after it experienced the so-called catastrophic optical damage in short-pulse operation.
Subfigure (a) shows the damage patterns at the font facet, where the light leaves the device (red circle), while (b) shows the same region from the side. A channel is visible which burned into the device and ends ~80 µm underneath the front facet; see (c). Subfigure (d) shows the end of this channel in higher resolution. The quantum wells, i.e. the gain medium are well resolved.
2018 East China Normal University as ECNU High-End Expert, China
1999 Visitor at the RIKEN-Institute Sendai, Japan
1995 - present: Senior researcher at MBI
1993-1995: Visiting professor at Georgia Tech Atlanta, USA
1986-1989: R&D group leader in a subcontract "Optical characterization of II-VI materials for IR quantum detector fabrication".
1984-1986: R&D work in a subcontract to "Carl Zeiss Jena" company to develop diode lasers for an IR diode laser spectrometer.
1981-1984: PhD student, Dr. rer. nat. in Physics, summa cum laude, Humboldt University, Berlin 1984 Dissertation: Study of the optical properties of n-Pb1-xSnxTe/p-Pb1-xSnxTe/p-PbTe-heterostructures by means of photoluminescence and injection-luminescence.
1977-1982: Physics studies, Diploma in Physics summa cum laude, Humboldt University, Berlin 1982 Thesis: Luminescence properties of lead salts for optical and electrical excitation.
- Light-emitting tunneling nanostructures based on quantum dots in a Si and GaAs matrix Semiconductors 46 (2012) 1460 - 1470
- Light-emitting tunnel nanostructures based on quantum dots in the Si and GaAs matrix Fizika I Technika Poluprovodnikov 46 (2012) 1492-1503
- Relaxation pathways of excitation in the tunnel-injection structures with quantum dots Vestnik of St. Petersburg University 4 (2012) 34-35
- Near-field dynamics of broad area diode laser at very high pump levels AIP Advances 1 (2011) 042148/1-6
- Defect evolution during catastrophic optical damage of diode lasers Semiconductor Science and Technology 26 (2011) 075020/1-10
- The impact of temperature and strain-induced band gap variations on current competition and emitter power in laser bars Applied Physics Letters 98 (2011) 241108/1-3
- Mechanisms and fast kinetics of the catastrophic optical damage (COD) in GaAs-based diode lasers Laser & Photonics Reviews 5 (2011) 422-441
- Tunnel injection emitter structures with barriers comprising nanobridges Physica Status Solidi-Rapid Research Letters 5 (2011) 385-387
- Two-dimensional carrier density distribution inside a high power tapered laser diode Applied Physics Letters 98 (2011) 221110/1-3
- Emission properties of diode laser bars during pulsed high-power operation Semiconductor Science and Technology 26 (2011) 092001/1-4
Juan Jiménez and Jens W. Tomm, "Spectroscopic Analysis of Optoelectronic Semiconductors", Springer Series in Optical Sciences Vol. 202 (Springer, 2016).
Jens W. Tomm and Juan Jiménez, "Quantum-Well Laser Array Packaging", Nanoscience and Technology Series (McGraw-Hill, 2007).