The Mid-InfraRed (MIR) and TeraHertz (THz) regions of the electromagnetic spectrum have a vast range of potential applications. These include security (surveillance, detection of explosives), safety (gas sensing, detection of hazardous compounds) as well as a variety of scientific and industrial applications, such as chemical analysis, thermography, medical imaging, and non-destructive testing. The key to entering these potential applications is the ability to design optoelectronic devices specifically tailored to the particular application at hand. The design of such devices turns out to be a challenging task because it involves several physical systems that have to be grasped, modeled and simulated simultaneously, the two most prominent being the electronic and the optical system.
The trend in modern optoelectronics is to exploit the same mechanisms for both carriers and light, such as spatial confinement or superlattices. Thus it seems a natural approach to treat optics and carrier dynamics on equal grounds. By doing so we gain a clearer picture of the structural similarities of seemingly unrelated physical phenomena, which in turn allows us to exploit synergies. Effects that are well known in one particular field may be found and used in another, potentially leading to the discovery of new devices.
One famous example of the synergistic approach is photonic crystals. Well known principles from solid state physics, such as Bloch theorem or the Kronig-Penney model, serve as a basis for novel optical devices, featuring nonlinear dispersion, photonic bandgaps, etc. Another example is the use of absorbing boundary conditions (perfectly matched layers) to simulate quasi-open quantum systems, a concept borrowed from electromagnetic simulation.
Our simulation framework embeds this way of thinking. One can simply change the governing equation from the Schrödinger equation to the Maxwell equations and vice versa, or even investigate a different domain under the same conditions, e.g. lattice vibrations. Thus, the governing equation appears merely as one degree of freedom in the modeling process. This makes our framework a particularly useful tool in basic research where rapid model prototyping in conjunction with experimental efforts helps unveil new physical phenomena. By providing unified model components, such as governing equations, boundary conditions, or numerical solution procedures, we can cover a broad range of problems encountered in research on optoelectronic nanostructures and even anticipate new problems that have yet to appear.