Terahertz frequency comb by multifrequency-heterodyning photoconductive detection for high-accuracy, high-resolution terahertz spectroscopy

We report a terahertz spectroscopy technique based on a stable terahertz frequency comb from a photoconductive terahertz emitter driven by a stabilized femtosecond laser. To this end, a photocurrent frequency comb is induced in a photoconductive terahertz detector by instantaneous photogating with another detuned femtosecond laser and is applied to read out the terahertz frequency comb. The detailed structure of the terahertz frequency comb was clearly observed with frequency accuracy of 2.5x10(-7) and resolution of 81.8 MHz using multifrequency-heterodyning photoconductive detection, which in turn is caused by the slightly mismatched frequency spacing between terahertz and photocurrent frequency combs.