MBI-Mitarbeiter - Persönliche Daten

Research

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.

 

Curriculum vitae

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.

MBI Publikationen

  1. Monitoring of aging properties of AlGaAs high-power laser arrays

    J.W. Tomm, A. Bärwolff, U. Menzel, M. Voss, R. Puchert, T. Elsaesser, F.X. Daiminger, S. Heinemann, J. Luft

    Journal of Applied Physics 81 (1997) 2059-2063
  2. Aging behaviour of high-power laser arrays monitored by photocurrent spectroscopy

    J.W. Tomm, A. Bärwolff, U. Menzel, C. Lier, T. Elsaesser, F.X. Daiminger, S. Heinemann

    SPIE Proceedings 3004 (1997) 134-144
  3. Laser-based facet inspection system

    J.W. Tomm, A. Bärwolff, C. Lier, T. Elsaesser, F.X. Daiminger, S. Heinemann

    SPIE Proceedings Series 3000 (1997) 90-98
  4. The use of fourier-transform photo-current spectroscopy for the analysis of aging properties of high power laser diode arrays

    J.W. Tomm, A. Bärwolff, T. Elsaesser, A. Gerhardt, J. Donecker

    Defect Recognition and Image Processing in Semiconductors, INST Phys. Conf. Series 160 (1997) 471-474
  5. Waveguide effect on the image formation process in near-field photocurrent spectroscopy of semiconductor laser diodes

    A. Richter, C. Lienau, J.W. Tomm

    Surf. & Interf. Analysis 25 (1997) 573-582
  6. Near-field photocurrent spectroscopy: A novel technique for studying defects and aging in high-power semiconductor lasers (invited paper)

    C. Lienau, A. Richter, J.W. Tomm

    Applied Physics A 64 (1997) 341-351
  7. Optical near-field photocurrent spectroscopy - a new technique for analyzing microscopic aging processes in optoelectronic devices

    A. Richter, J.W. Tomm, C. Lienau, J. Luft

    Appl. Phys. Lett. 69 (1996) 3981-3983
  8. Fast recombination processes in lead chalcogenide semiconductors studied via transient optical nonlinearities

    R. Klann, T. Höfer, R. Buhleier, T. Elsaesser, J.W. Tomm

    Journal of Applied Physics 77 (1995) 277-286
  9. Stimulated emission in multi-valley lead salts with star degeneracy lifted by strain and magnetic fields

    J.W. Tomm, K.H. Herrmann, S. Haertle, T. Kelz, M. Mocker, T. Elsaesser, R. Klann, V.B. Novikov, V.G. Talalaev, V.E. Todorovskii, H. Böttner

    Inst. Phys. Conf. Ser. 144 (1995) 135-139
  10. Threshold of stimulated emission in multi-valley lead salts

    J.W. Tomm, M. Mocker, T. Kelz, T. Elsaesser, R. Klann, B.V. Novikov, V.G. Talalaev, V.E. Tudorovskii, H. Böttner

    Journal of Applied Physics 78 (1995) 7247-7254

Andere Publikationen

Books

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).