Physics World November 25, 2019 The terahertz region of the electromagnetic spectrum has been the least utilized owing to inadequacies of available sources. A team of researchers in the US (Harvard University, MIT, Duke University) has created a compact, widely frequency-tunable, extremely bright source of terahertz radiation: a gas-phase molecular laser based on rotational population inversions optically pumped by a quantum cascade laser. By identifying the essential parameters that determine the suitability of a molecule for a terahertz laser, almost any rotational transition of almost any molecular gas can be made to lase. Nitrous oxide is used to illustrate the […]