Quantum-cascade lasers (QCLs) are a special kind of semiconductor laser. They emit in the mid- and long-wave infrared bands and, instead of operating on laser transitions between different electronic bands, they operate on intersubband transitions of a semiconductor structure. Their potential has piqued the interest of researchers, with possible applications in a number of areas, including precision sensing, military applications and spectroscopy. As they have a wide tuning range and fast response time, their use allows for precision in devices, such as element detectors and gas analysers. A team of researchers based at the THz Quantum Device Laboratory Center for Advanced Photonics RIKEN in Japan is working on designing and fabricating high output power operation and high temperature operation terahertz (THz) QCLs with a variety of potential uses.