Terahertz Frequency Combs

Absolute Intensity Measurements of CW GHz and THz Radiation Using Electro-Optic Sampling

“…The experimental technique is based on the concept of THz frequency combs [2], [3], [12], [13] that are obtained from optical frequency combs [14]. Although we employ this technique for the measurement of CW GHz/THz signals, it can also easily be applied to the measurement of pulsed THz signals.…”

“…This signal is obtained from focusing the laser pulses onto a fast photodiode and mixing the resulting signal with the signal from a signal generator acting as a stable local oscillator [2]. A comparison between the two beating signals enables phase measurements of the GHz/THz source [3]. The phase measurements are important for the analysis of the measured amplitude since we need to know the curvature of the emitted wavefront as will be discussed in the following.…”

“…We have performed spatially resolved phase measurements (see [3]) with a distance between the antenna and the EO crystal of 60 mm. In Fig.…”

“…Nowadays National Metrology Institutes throughout the world are working on THz metrology such as frequency measurements [2], [3], radiometry [4]- [6], and spectrometer calibration [7]- [9]. Yet, the quantitative measurement of electric fields and intensities in this frequency range being even traceable to the International System of Units (SI) has so far not been paid much attention.…”

“…In previous studies, we have reported on precision frequency measurements as well as on spatially resolved measurements Manuscript of relative amplitude and phase using a THz frequency comb [2], [3]. Spatial resolution was obtained by moving the gigahertz (GHz) or THz sources [10].…”