LAUSR

The definition for the frequency range of a terahertz wave varies in the literature. Some refer to terahertz as the spectrum between 300 GHz (λ = 1 mm) and 3 THz (λ = 0.1 mm) to distinguish it from its millimeter-wave counterpart (30-300 GHz). Others adopt a decimal pattern and a loosely defined frequency range from 100 GHz to 10 THz. Based on the latter definition, probably the earliest documented endeavor to reach terahertz frequency was published in a paper in Physical Review in 1923 [1]. In this nearly century-old work, authors Nichols and Tear generated a 0.17-THz signal using a spark-gap oscillator, detected it with a radiometer vane, and analyzed the spectrum through a Boltzmann interferometer.