The mid-infrared spectral region is of major importance for applications ranging from sensing, medical diagnostics and security. Just recently the mid-infrared gap between about 3-4 µm wavelength is being covered by competing semiconductor lasers. Innovative semiconductor laser concepts utilizing quantum-engineered semiconductor heterostructures are employed for this purpose. This includes conventional interband diode lasers on GaSb substrate based, which allow one to obtain room temperature continuous wave emission up to ~3.4 µm. Furthermore, interband cascade lasers grown on GaSb are well suited to cover the entire range between 3-5 µm with room temperature continuous wave operating lasers. Finally, unipolar quantum cascade lasers are excellent sources to cover the long wavelength region starting from about 3.4 µm with high performance semiconductor lasers as it will be illustrated within this talk. The basics underlying these semiconductor laser concepts will be summarized, their growth and fabrication discussed, and the current state of the art of development and future prospects will be reviewed. Selected results will be presented, which highlight that the entire mid-infrared spectral range from 2 µm – 16 µm can be covered with these semiconductor heterostructure lasers underlining promise for applications.
Dr. Sven Höfling studied Applied Physics at the University of Applied Science, Coburg, Germany. He received the Diploma from the University of Applied Science Coburg, Coburg, Germany, in 2002, for his investigations of InGaN-based blue, green and white light emitting devices at the Fraunhofer Institute of Applied Solid State Physics (IAF) in Freiburg, Germany. In 2003 he joined the department of Technische Physik at Universität Würzburg, Germany. There he worked on the design, growth, fabrication and characterization of single mode emitting quantum cascade lasers for which he received his doctorate degree. Since 2006, he leads at the Optoelectronic Materials and Devices Group and he supervises the molecular beam epitaxial growth at the Microstructure Laboratory using various machines being customized for the growth of III-V based semiconductors in the GaAs-, InP-, Ga(N)P- and GaSb-based material systems. He was short term visiting scholar ate Stanford University, USA in 2010 and 2012. His current research interests include the design, fabrication, and characterization of low-dimensional electronic and photonic nanostructures, including quantum wells and quantum dots, site-controlled quantum dots, high-electron-mobility structures, high-quality-factor photonic cavities, exciton-polaritons and semiconductor lasers.