Infrared/terahertz applications in physical sciences

Starting with a brief survey on infrared/THz applications and systems, this talk concentrates on specific research opportunities in physics offered by free-electron lasers (FEL) at infrared/THz wavelengths. Unique properties of FEL radiation are (i) continuous spectral tunability at narrow spectral bandwidth, (ii) high power, (ii) spatial coherence, and (iv) short pulse length. Corresponding experimental techniques include linear, nonlinear/high-field, near-field, and time resolved spectroscopy. After describing the free-electron laser facility FELBE at HZDR, a few recent studies in solid-state physics covering these techniques will be reported.