The development of the terahertz quantum cascade laser (QCL) nearly two decades ago held great promise for applications ranging from explosives detection to skin cancer screening. However, the need for bulky cryogenic cooling equipment to make the QCL work properly limited the use of such devices in the field.
|Left: The tiny terahertz quantum cascade laser compared in size to two coins. Right: The laser chip with a thermoelectric cooler on a block. In the background is a cryocooler. [Image: Khalatpour et al., MIT and University of Waterloo]|
The terahertz allure
Breaking barriers by making them higher
|University of Waterloo scientist Zbig R. Wasilewski with a student in the lab. [Image: University of Waterloo]|
In the current set of experiments, Qing Hu of MIT and Zbig R. Wasilewski of the University of Waterloo, Canada, and their students heightened the semiconductor barriers to reduce carrier leakage inside their QCL system. The team observed that this design required high-precision molecular beam epitaxy to fabricate—an important concern when refining the technology and someday making it commercially available.