Terahertz emission from Bi2Sr2CaCu2O8+x intrinsic Josephson junction stacks

Electromagnetic radiation at frequencies in the terahertz (THz) range is highly interesting for potential applications in biology or medical diagnostics, high-bandwidth communication, security and defence, nondestructive evaluation, and other fields. However, particularly, the frequency range between 0.5 and 1.5 THz has turned out to be difficult to fill with powerful coherent solid-state sources. Suitably patterned structures made of the high critical temperature superconductor Bi 2 Sr 2 CaCu 2 O 8 + δ can operate in this frequency range, and the best devices presently reach an output power around 100 μ W. In this tutorial, we will give an introduction into the basic physics of this type of oscillator and into the challenges that appear. We will explain how the generators are fabricated, which measurement techniques are used for characterization, and which models are used to describe their dynamics. We will also give some examples demonstrating potential applications in the fields of THz imaging and THz spectroscopy.