Intersubband Emitters
The research comprises the detailed investigation of the conditions for the lasing process and of the lasing properties of intersubband emitters, in particular of GaAs-based quantum-cascade lasers (QCLs). The GaAs-based materials system is used as a model system for mid-infrared QCLs, since the barrier height can be varied without introducing any significant strain into the system. On the one hand, we design, grow, process, and characterize QCL structures with a systematic parameter variation, for example of the doping density. On the other hand, we are developing a numerical model to correlate the results calculated for a large number of parameters with experimental investigations of the transport, optical, and lasing properties. By varying the internal physical properties such as population inversion and field distribution, the threshold current density and the lasing energy are optimized as a function of device parameters (e. g. design, doping profile) and operation conditions (e. g. operating field strength). We have recently started to investigate GaAs-based THz QCLs, which is the materials system of choice for the THz spectral range.
We are currently investigating GaAs/(Al,Ga)As quantum-cascade lasers (QCLs) for the far-infrared (FIR) or THz spectral range. Previously, we also studied the lasing properties of mid-infrared (MIR) QCLs based on the GaAs/(Al,Ga)As materials system.
