Bridging the terahertz gap

Optical frequency combs are widely-used, high-precision tools for measuring and detecting different frequencies - a.k.a. colors - of light. Unlike conventional lasers, which emit a single frequency, these lasers emit multiple frequencies simultaneously. The equally spaced frequencies resemble the teeth of a comb. Optical frequency combs are used for everything from measuring the fingerprints of specific molecules to detecting distant exoplanets. Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) are exploring the possibility of using an infrared frequency comb to generate elusive terahertz frequencies. These frequencies - which lie in the electromagnetic spectrum between radio waves and infrared light - have long promised to transform communications and sensing but are very challenging to source.