Patent ID: 7876423

Claim:
A process for measuring the velocity of terahertz electromagnetic radiation in a material sample without prior knowledge of the thickness of said sample, said terahertz electromagnetic radiation produced by a source, namely, a transceiver, spaced apart from said sample under test and propagated at the speed of light, c, in a medium located between said source, namely, said transceiver, and said sample, said sample residing on a substrate, comprising the steps of: emitting terahertz electromagnetic radiation from said source; measuring the travel time of said terahertz electromagnetic radiation to and from said substrate without said sample present, t″; placing said sample on said substrate; measuring the travel time of said terahertz electromagnetic radiation to and from said substrate with the sample present, t′; subtracting t″ from t′ to determine the transmission time difference with said sample present and without said sample present, Δt; measuring the travel time of said terahertz electromagnetic radiation to and from said sample, 2t 1 ; determining the time difference between t′ and the 2t 1 , 2τ; dividing Δt by 2τ and determining the quotient; subtracting said quotient from 1 to obtain a factor; and multiplying said factor by, c, to determine the velocity of said terahertz electromagnetic radiation in said sample.