Optical frequency comb offers a convenient way to generate elusive terahertz frequencies

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.