Technical University of Darmstadt

The Terahertz Devices and Systems Laboratory (Prof. Sascha Preu) and the Chair of Photonics (Prof. Thomas Kusserow) work on laser systems for communication-, Terahertz-, and Optical Coherence Tomography (OCT) applications. A key element are micromechanically tuned vertical surface emitting lasers (MEMS-VCSEL) with unprecedented tuning range of more than 100 nm. A typical structure of a MEMS-VCSEL is illustrated in Fig.1. It consists of a half-VCSEL containing the active medium, the contact structure, a buried tunnel junction and the bottom Bragg mirror. The top mirror is composed of a thermally tuned Bragg mirror (DBR). Advantages of the VCSEL structure besides huge tuning range are compactness and a circular beam that can comparatively easily be coupled into an optical fiber. VCSELs as well as MEMS filters with even larger bandwidth will be tailored to OCT applications in NETLAS.

Further research interests of the TU Darmstadt groups comprise Terahertz sources, -receivers and -systems that may also find applications in THz OCT

Fig. 1: Typical structure of a MEMS-VCSEL. Reproduced with permission from: “Mohammad Tanvir Haidar, Sascha Preu, Sujoy Paul, Christian Gierl, Julijan Cesar, Ali Emsia, and Franko Küppers, “Widely tunable telecom MEMS-VCSEL for terahertz photomixing”, Opt. Lett. 40, 4428-4431 (2015) © The Optical Society OSA


Prof. Sascha Preu

Prof. Thomas Kusserow


  • ‘Surface micromachined tunable 1.55 μm-VCSEL with 102 nm continuous single-mode tuning’, C. Gierl, T. Gruendl, P. Debernardi, K. Zogal, C. Grasse, H. A. Davani, G. Böhm, S. Jatta, F. Küppers, P. Meißner, and M.-C. Amann, Optics Express, Vol. 19, Issue 18, pp. 17336-17343, (2011),
  • 26-Gb/s DMT Transmission Using Full C -Band Tunable VCSEL for Converged PONs’, Christoph Wagner, Annika Dochhan, Michael H. Eiselt  at all. IEEE Photonics Technology Letters, Vol 29, Issue 17, (2017) 10.1109/LPT.2017.2710323
  • ‘Widely tunable telecom MEMS-VCSEL for terahertz photomixing’  Mohammad Tanvir Haidar, Sascha Preu, Sujoy Paul, Christian Gierl, Julijan Cesar, Ali Emsia, and Franko Küppers Optics Letters, Vol. 40, Issue 19, pp. 4428-4431, (2015),
  • ‘Systematic characterization of a 1550 nm microelectromechanical (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) with 7.92 THz tuning range for terahertz photomixing systems’, M. T. Haidar, S. Preu, J. Cesar, S. Paul, A. S. Hajo, C. Neumeyr, H. Maune, and F. Küppers,  Journal of Applied Physics 123, 023106 (2018);
  • Narrowband optical thin-film filters with distributed cavity modes’, Muhammad Taimoor, Sabrina Reuter, Hartmut Hillmer & Thomas Kusserow, Applied Physics A volume 122, Article number: 538 (2016),