The interaction of mid-infrared (mid-IR) and terahertz (THz) light with matter has gathered considerable interest in fields as diverse as material testing, remote sensing, medical imaging or spectroscopy. The active development of solid-state mid-IR and THz sources, amongst which quantum cascade lasers (QCL) are the most prominent example, provides nowadays compact and convenient generation means. Yet, manipulating mid-IR and THz light remains a hassle. The purpose of project L-BloW is the study of the guiding properties of surface waves occurring on dielectric photonic bandgap structures, also known as Bloch surface waves (BSW), in the long wavelength range.