Abstract
Femtosecond-laser-based optical frequency comb has received a lot of interest as powerful metrological tools capable of covering the visible to mid-infrared region. However, frequency comb has not been investigated in the long-wavelength terahertz (THz) region. In this paper, the concept of the frequency comb is extended to the THz region. THz frequency comb is suitable for high-accuracy, high-resolution THz spectroscopy, which can be used to identify molecules of interest with fingerprints in the THz region. Multifrequency-heterodyning photoconductive detection was used; it involves using two stabilized Ti: sapphire lasers having slightly mismatched mode-locked frequencies. The detailed structure of a THz frequency comb was clearly observed with a frequency accuracy of 2.5×10-7 and a resolution of 81.8MHz.
