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.
- Spectroscopic measurement of mounting-induced strain in optoelectronic devices IEEE Transactions on Advanced Packaging 23 (2000) 170-175
- Optical and photoelectrical properties of oriented ZnO films Journal of Applied Physics 87 (2000) 1844-8
- Photoelectric dichroism of oriented thin film CdS fabricated by pulsed-laser deposition Solid State Communications 116 (2000) 33-5
- Phonon-assisted magnetopolaron effect in diluted magnetic semiconductors Phys. Rev. B 59 (1999) 2731-2736
- Far-infrared reflectivity study of lattice dynamics of narrow-gap HgCdMnTe semiconductors Semic. Sci. & Technol. 14 (1999) 187-197
- Modulation spectroscopic approach to the study of photocurrent spectra in GaAs/GaAlAs QW-GRIN laser structures SPIE Proceedings 3890 (1999) 70-74
- Temperature dependent carrier escape from quantum well states in GaAs/GaAlAs graded index structures Semic. Sci. & Technol. 14 (1999) 293-297
- Vertical transport in GaAs/GaAlAs QW-GRIN structures studied by photocurrent spectroscopy SPIE Proceedings 3890 (1999) 2-9
- Probing diode lasers with light - photocurrent reveals information on defects and strain in optoelectronic devices LEOS Letters 13 (1999) 20-22
- Photoluminescence excitation due to hot excitons in narrow-gap Hg1-x-yCdxMnyTe Semic. Sci. & Technol. 14 (1999) 148-155
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).