抄録
Absolute frequency measurement system in THz region is an indispensable tool for the establishment of
THz frequency standard. We have developed a THz frequency counter based on THz comb using a
photoconductive antenna with a femtosecond-pulse fiber laser. The THz counter has the fractional
frequency uncertainty of 1.7 × 10‒17 at 0.3 THz and an instability of 4.1 × 10‒14/τ up to an averaging time
of 104s.
